HomeMy WebLinkAbout6 - Update on the evaluation of source water protection for Boulder Reservoir including additional t
CITY OF BOULDER
WATER RESOURCES ADVISORY BOARD
AGENDA ITEM
MEETING DATE:
March 19, 2007
AGENDA TITLE
: Update on the Integrated Evaluation of Boulder Reservoir Water
Treatment Plant (BRWTP) Source Water Protection and Treatment Improvements
PREPARING DEPARTMENT:
Robert E. Williams – Director of Public Work for Utilities
Anne Noble – Utilities Project Manager
Bob Harberg – Utilities Planning and Project Management Coordinator
Bret Linenfelser – Water Quality and Environmental Services Coordinator
Randy Crittenden – Water Treatment Coordinator
Carol Ellinghouse – Water Resources Coordinator
BOARD ACTION REQUESTED:
None at this time
FISCAL IMPACT:
The 2007-2012 CIP includes $250,000 in 2007 to evaluate, $500,000 in
2008 to design and $25,000,000 to construct a pipeline from Carter Lake to the BRWTP
and/or provide long term treatment facility improvements.
Also included in the six-year CIP is funding to evaluate, design and construct ($100,000 in
2007, $300,000 in 2008 and $3,000,000 in 2009) mid-term treatment plant improvements. In
2007, $250,000 was budgeted to provide source water protection improvements along the
Boulder Feeder Canal.
PURPOSE:
This memorandum provides information to the Water Resources Advisory Board
(WRAB) on the status of source water protection and treatment improvements for the BRWTP.
Attachment A
A previous update was provided on October 17, 2005 () with an information item
provided about the Carter Lake Pipeline Feasibility Study done by the Northern Colorado Water
Attachment B
Conservancy District (NCWCD) on February 27, 2006 ().
EXECUTIVE SUMMARY:
City staff has worked with Black & Veatch Consulting Engineers (B&V) to develop a draft
report on the Integrated Evaluation of Boulder Reservoir Water Treatment Plant (BRWTP)
Attachment C
Source Water Protection and Treatment Improvements (see ). This study
evaluates recommendations from two previous reports, the Source Water Quality Planning Study
AGENDA ITEM # VI Page 1
– Phase I dated 2003 and the Pre-design Report for Near Term Improvements for the Boulder
Reservoir Water Treatment Plant dated 2003. The study develops and evaluates alternatives for
source water protection and treatment and proposes a long term capital improvement plan for the
BRWTP.
Seven alternatives were identified for detailed evaluation. All of the alternatives assumed
construction of the mid-term improvements recommended in the 2003 Pre-design Report. A
baseline alternative, which included no additional treatment improvements, was evaluated. Five
of the alternatives included long-term treatment plant improvements and one alternative included
the construction of a pipeline from Carter Lake to the Boulder Reservoir Water Treatment Plant.
Each alternative was evaluated based on performance, as well as total present worth cost. The
expected performance of each alternative was ranked based on a set of criteria. Performance of
each alternative was also evaluated based on the number of barriers it would provide for six key
groups of contaminants. Based on consideration of both long term performance and cost,
construction of the Carter Lake Pipeline is being recommended as the preferred alternative.
Although the capital cost of constructing a pipeline is relatively high, the total present worth cost
is comparable to other alternatives.
BACKGROUND:
Attachment A
On October 17, 2005 staff presented an update on the status of two studies (), the
Source Water Quality Planning Study – Phase I Report dated 2003 and the Pre-design Report for
Near Term Improvements for the Boulder Reservoir Water Treatment Plant dated 2003.
Background information was provided on the quality of the source water and the history of the
facility. Source water protection and treatment plant improvement recommendations were made.
The primary long-term recommendation of the Source Water Study was the construction of a
pipeline from Carter Lake to the Boulder Reservoir Water Treatment Plant. The 2003 Pre-design
Report listed costs for near-term, mid-term and long term improvements at the treatment plant,
but made no long-term recommendations. Membranes, ultraviolet (UV) disinfection and ozone
were proposed as possible long-term treatment improvements. During this same time period, the
city of Boulder participated in a feasibility study performed by the NCWCD to evaluate a
pipeline from Carter Lake to the BRWTP. Information on the status of the Carter Lake Pipeline
was provided in the October 27, 2005 memo and a subsequent update was presented to WRAB
Attachment B
on February 27, 2006 ().
Information was presented in the October 27, 2005 memo on the status of drinking water
regulations. At that time the Long-term 2 Enhanced Surface Water Treatment Rule
(LT2ESWTR) had not yet been promulgated. This regulation has since been put into effect.
Based on current source water quality data, it appears that the Boulder Reservoir WTP source
water falls into a Bin 1 category, indicating that no further treatment is required from a
regulatory perspective. However, on-going monitoring has indicated both acute and chronic
degradation of the BFC and Boulder Reservoir water supplies. Given the increased reliance on
this facility and the concern that the current treatment processes may not adequately address the
potential contaminant loading, further evaluation was given to long-term capital improvements
for the Boulder Reservoir Water Treatment facility that included both source water protection
and treatment.
AGENDA ITEM # VI Page 2
While the city is currently meeting all regulatory requirements, the water quality in areas served
by the Boulder Reservoir Water Treatment Plant is vulnerable to degradation as a result of
seasonal variation of the water quality in the Boulder Reservoir and acute contamination
episodes in the BFC and the reservoir. Of particular concern are microbial contamination,
disinfection by-product (DBP) formation, contamination by organic micro-pollutants,
manganese, taste and odor concerns and high total dissolved solids and sulfate concentrations.
Because these factors pose a potential threat to drinking water quality, the city has established
drinking water quality goals that are in some instances more stringent than regulatory
requirements. These goals are outlined in Chapter 3 of the attached draft report.
ANALYSIS
In May 2006, the city contracted with B&V to complete the second phase of the source water
planning study in which long-term improvements to the treatment process were evaluated in
conjunction with the construction of a pipeline in order to develop a long term capital
improvement plan for the Boulder Reservoir Water Treatment facility. Alternatives were
developed assuming three source water options: seasonal use of the BFC with the Boulder
Reservoir utilized during the winter; year-round use of the Boulder Reservoir, eliminating the
use of the BFC; and the Carter Lake pipeline. Treatment processes were paired with each
source water option based on the water quality limitations of each source. The following seven
alternatives were evaluated:
Alternative 1A: Continue to utilize both the Boulder Feeder Canal and Boulder Reservoir
with no additional long term treatment plant improvements.
Alternative 1B: Continue to utilize both the Boulder Feeder Canal and Boulder Reservoir
with UV disinfection.
Alternative 1C: Continue to utilize both the Boulder Feeder Canal and Boulder Reservoir
with UV disinfection and Granular Activated Carbon (GAC) adsorption.
Alternative 2A: Year-round use of the Boulder Reservoir, eliminating the use of the BFC
with no additional long term treatment plant improvements.
Alternative 2B: Year-round use of the Boulder Reservoir, eliminating the use of the BFC
with UV disinfection.
Alternative 2C: Year-round use of the Boulder Reservoir, eliminating the use of the BFC
with ozone.
Alternative 3: Carter Lake Pipeline.
All of these alternatives assume the construction of the proposed mid-term improvements
recommended in the 2003 Pre-design Report.
Process Selection
The proposed treatment processes were selected based on several factors including: integration
with the existing treatment process, expected performance and cost. During the evaluation,
water contaminants were grouped into seven categories as follows: microbial pathogens;
disinfection byproducts; organic micro-pollutants; manganese; taste & odor and total dissolved
solids & sulfate. Potential improvements were evaluated based on their ability to address one or
more of these seven categories of contaminants. The alternatives were screened to give greater
AGENDA ITEM # VI Page 3
consideration to those that addressed more than one contaminant, thereby reducing the number
and complexity of the treatment process. The Carter Lake Pipeline was the only source water
protection improvement considered. Source protection strategies for Boulder Reservoir and the
BFC would never achieve the level of protection and security of the Carter Lake Pipeline.
Treatment processes that provide low inactivation/removal of Cryptosporidium were not
considered. Filtration technologies including membrane filtration, second stage granular media
filtration, and slow sand filtration were not evaluated in this study as they generally only provide
inactivation/removal of Cryptosporidium, and provide little in the way of additional barriers for
other contaminant categories. Chemical oxidation can potentially provide additional barriers for
microbial pathogens, DBPs, organic micro-pollutants, manganese, and objectionable tastes and
odors, depending on the oxidant used and its point of application. Addition of chlorine dioxide
for DBP, manganese, and taste and odor control is included in the city’s mid-term improvements
plan, and is therefore assumed as part of the baseline treatment for the long-term improvements
evaluated. Ozone was also evaluated in this study because of its superior performance for taste
and odor control, ability to oxidize many organic micro-pollutants, and additional pathogen
inactivation. UV disinfection was also evaluated due to its superior disinfection performance for
bacteria, viruses, and protozoan pathogens. GAC was evaluated in this study based on additional
barriers for DBPs, organic micro-pollutants, and objectionable tastes and odors that it may
provide.
Performance Evaluation
A decision process for evaluating the alternatives was developed that utilized a performance
ranking as well as a net present cost. Criteria were developed to rank each of these alternatives.
Each criterion was weighted based on the consensus of its relative importance. The seven
alternatives were then numerically rated based on their ability to meet each criterion. The
criteria, relative weighting and performance score for each alternative are shown in Table 6.1 of
the draft report. Each of the alternatives was also evaluated for the number of barriers it would
provide against the seven water quality contaminant categories.
The first three alternatives would not meet the city’s water quality goals with respect to TDS and
sulfates when raw water is provided from the reservoir. Alternative 1A, the baseline alternative,
would not meet the city’s water quality goals with respect to pathogens and does not provide an
effective organic micro-pollutant barrier. With the addition of UV disinfection, Alternative 1B
provides adequate pathogen inactivation, but this alternative would not provide an effective
barrier for organic micro-pollutants. With the addition of GAC the concern of organic micro-
pollutants would be addressed. Alternatives 1A, 1B and 1C ranked 0.51, 0.56 and 0.61
respectively.
Alternatives 2A, 2B and 2C propose eliminating the use of the BFC. These alternatives provide
some potential settling of Cryptosporidium. However, water quality data from the reservoir
indicates similar, if not higher, levels of bacteria in the reservoir as the BFC. Aside from the
potential of settling Cryptosporidium, these alternatives have the same advantages and
limitations as Alternatives 1A, 1B and 1C respectively. Alternatives 2A, 2B and 2C ranked 0.51,
0.57 and 0.61 respectively. Alternative 3, the Carter Lake Pipeline meets all of the city’s water
AGENDA ITEM # VI Page 4
quality goals and provides at least one barrier for each contaminant category evaluated. It
ranked 0.94.
A net present cost was calculated for each alternative, taking into account both capital and
operations and maintenance costs. A 30 year life cycle was assumed for treatment plant
processes, with a 70 year life cycle for the pipeline. The remaining value of the pipeline was
credited back in the net present cost evaluation. Operations and maintenance costs included
power, chemicals and consumables. The cost of staffing the facility was not included as it was
assumed to be constant for all of the alternatives. Capital costs were not included for the mid-
term treatment plant improvements. However, maintenance costs for the mid-term
improvements were included in all of the alternatives. The present worth cost, capital cost and
operations and maintenance (O&M) costs (in $million) are described in chapter 7 of the draft
report and are shown below:
Alternative Description Present Worth Cost Capital Cost O&M Costs
1A BFC $5.2 $0 $0.17
2A BFC & UV $9.3 $2.4 $0.21
3A BFC & UV & GAC $53.4 $21.9 $0.86
2A BR $5.5 $0 $0.18
2B BR & UV $9.6 $2.4 $0.22
2C BR & Ozone $26.9 $13.6 $0.33
3 Carter Lake Pipeline $16.6 $20 $0.19
While the capital cost of the Carter Lake Pipe line is relatively high, the net present cost is not
significantly higher than installing UV and it is significantly less expensive than adding GAC or
Ozone.
The 2007-2012 CIP included $36,000,000 for bonded projects. These projects are as follows:
2009 - $25,000,000 Carter Lake Pipeline
2009 - $3,000,000 BRWTP Improvements
2009 - $3,000,000 Barker Dam
2012 - $5,000,000 Betasso Improvements
The 2007 annual average water bill for a single family home was estimated to be $345.10. The
city Utilities Division has projected a need for a 3 percent increase in water rates due to inflation.
Based on the 2007-2012 CIP bonded projects, the required rate increases (including 3 percent for
inflation) and the associated annual average water bill was projected as follows:
Inflationary Increase Annual bill Bond Rate Increase Annual bill
2008 3% $355.45 10% $379.61
2009 3% $366.11 10% $417.57
2010 3% $377.09 6% $442.62
2011 3% $388.40 4% $460.32
Based on these assumptions, the average annual single family water bill in 2011 would increase
$71.92 in order to fund all of these projects.
AGENDA ITEM # VI Page 5
There are several reasons to consider improvements to the Boulder Reservoir Water Treatment
facility (BRWTP), and specifically the protection of its source water, that will provide long-term
benefits to the city. The city is placing a greater reliance on this facility than in the past due to
continued planned growth in the city’s water service area. Even though currently regulatory
requirements are being met, the risk of contaminants entering the source water and passing
through the treatment process still exists. The Silver Lake Watershed land was acquired
beginning in 1096 and has been protected from public access since 1921. As a result, it
consistently and reliably provides high-quality source water for the Betasso WTP. Investing in a
pipeline that will protect the source water for the BRWTP far into the future is a worthwhile
investment similar to that undertaken by prior generations with the Silver Lake Watershed. The
cost of this investment is somewhat reduced because there is currently an opportunity to share
costs in constructing the Carter Lake pipeline with other communities.
The BRWTP was originally operated as a summer peaking plant. For the first 10 years of its
existence, the treatment plant relied entirely on water taken directly from the Boulder Feeder Canal
which only operates in the non-winter months. The ability to pump water from Boulder Reservoir in
the winter, when the canal is not in operation, was added later and improvements were made to the
treatment plant process in 1993 to allow year-round operation. The BRWTP can be operated year-
round, 24 hours a day and has a nominal capacity of 16 MGD. Currently, the plant typically operates
during 10 to 11 months of the year with about 3 of those months operating for only 12 hours per day.
The amount of time that the plant is operated will increase in the future because the water supplies
planned for meeting Boulder’s future growth will be delivered through the CBT system. The
capacity of this facility was increased in 2005 from 8 to 16 MGD in order to meet the essential
indoor demand level of the city, thereby providing redundancy to the Betasso WTP for that portion
of the city’s water supply that can’t be foregone without dire consequences. The BRWTP production
has increased from treating 10 percent of the city’s total water demand in 1991 to approximately 30
percent in 2005 and is anticipated to provide 40 percent of the total supply on average in the future.
Monitoring beginning in 1997 and continuing until the present has demonstrated an increased
level (chronic) of bacteriological contamination in both the canal and the reservoir (Chapter 2).
Spiking events have also been observed. 24 hour e-coli monitoring at the BFC facility intake
showed spiking events sometimes greater than 2000 colony forming units (cfu’s) per 100 mls.
E-coli is the best indicator available for the presence of disease causing organisms (pathogens).
Spiking events on the canal are probably not limited to microbiological. There are many
unmonitored contaminant possibilities from activity and land use along the canal.
A Source Water Assessment and Protection Plan (SWAP) was developed by city staff in
conjunction with the Colorado Department of Public Health and Environment as part of the
city’s regulatory requirements. A SWAP delineates the watershed for each source water and
identifies potential sources of contamination. This is followed by an assessment of vulnerability
for each potential contaminant. Protection procedures and protocols are then developed. The
SWAP assessment of the BFC indicated that the BFC is susceptible to all categories of
contaminants. A vulnerability Study was also completed in 2003 by Brown and Caldwell and
Versar Inc. This study also documented the BFC as the city’s most vulnerable supply.
AGENDA ITEM # VI Page 6
In the early 1890’s, the city of Boulder recognized water quality concerns associated with taking
water directly from Boulder Creek near the mouth of Boulder Canyon. Through City Council’s
direction, a pipeline was built which moved the point of diversion further upstream to an un-
impacted watershed above Nederland. In 1906 the city made its first purchase of land and water
storage reserviors in the Silver Lake Watershed. City ownership in this area was later expanded
and public access was closed. Because the Silver Lake Watershed is protected, the quality of the
water is very high and the vulnerability to degradation is low.
The quality of water in Carter Lake is also excellent. It is a deep reservoir with a small natural
runoff area and is filled mostly with high quality water imported from the Western Slope.
However, as a result of surface runoff into the Boulder Feeder Canal, degradation of the water
occurs as it is conveyed from Carter Lake to Boulder Reservoir. Boulder Reservoir is a shallow,
low volume reservoir, which is used for recreation and storage for later irrigation use, as well as
a water supply. Water that is stored in Boulder Reservoir is further susceptible to increases in
TDS including sodium, sulfate, hardness, turbidity and manganese, as well as recreational
impacts. The conveyance of Carter Lake water in a pipeline directly into Boulder Reservoir
WTP would prevent water quality degradation.
The city of Boulder is currently participating in the development of right-of-way acquisition plans
and permit applications for the Southern Water Supply Project II (Carter Lake Pipeline). Other
participants include Little Thompson Water District, the town of Frederick and Left Hand Water.
The pipeline is estimated to cost $33 million. Depending upon the number of participants, the city
of Boulder’s share of the cost can range from $20 to $25 million. A previous pipeline project was
completed in 1997 and supplied water to the cities of Broomfield, Louisville, Longmont, Superior
and eight other water providers.
While the city is currently meeting the LT2ESWTR, an important aspect of the regulation is the
recognition of the importance of a multi-barrier approach for treating drinking water. A multi-
barrier treatment process provides a number of protective “layers” against contamination by
using more than one method of prevention and treatment to remove/inactivate pathogens and
minimize disinfection byproducts (DBPs). Cryptosporidium are of particular concern because
they are resistant to conventional disinfection methods. TheLT2 acknowledges source water
protection as important component to providing safe drinking water. The Carter Lake Pipeline
will address both the near-term and potential increase in degradation to water quality of the
BRWTP. Although water treatment technology has advanced, treatment processes do fail.
Preventing source water contamination provides a more robust barrier than subsequent treatment.
The Carter Lake Pipeline would also provide a much more uniform water quality, substantially
simplifying the treatment optimization and increasing treatment process reliability.
PUBLIC COMMENT AND PROCESS:
The public process has not been initiated.
NEXT STEPS:
Staff will respond to WRAB questions and comments regarding the draft report. It is anticipated the
final report will be presented to the WRAB in May along with other information as part of the city’s
AGENDA ITEM # VI Page 7
Community and Environmental Assessment Process (CEAP).
The report recommendations for the Carter Lake Pipeline will be incorporated in the city’s six-year
Capital Improvement Program (CIP). It is anticipated that design of the Carter Lake pipeline will
begin in 2008 and construction in 2009, although the schedule is subject to approval by not only the
city but also other participating water providers and permit review agencies.
The NCWCD should complete right-of-way acquisition plans and permit applications for the
pipeline by the end of 2007. This will include an application to Boulder County for 1041J – Matters
of State Interest review.
ATTACHMENTS:
Attachment A: WRAB Information Item - Update on Boulder Reservoir Source Water
Protection and Facility Improvements for the Boulder Reservoir Water
Treatment Plant dated October 17, 2005
Attachment B: WRAB Agenda Item – Update on Carter Lake Pipeline Feasibility Study
dated February 27, 2006
Attachment C: Integrated Evaluation of Boulder Reservoir Water Treatment Plant (BRWTP)
Source Water Protection and Treatment Improvements Draft Report
AGENDA ITEM # Page 8
Attachment A
CITY OF BOULDER
WATER RESOURCES ADVISORY BOARD INFORMATION ITEM
MEETING DATE:
October 17, 2005
AGENDA TITLE
: Update on the Boulder Reservoir Source Water Protection and Facility
Improvements for the Boulder Reservoir Water Treatment Plant
PREPARING DEPARTMENT:
Robert E. Williams – Director of Public Work for Utilities
Anne Noble – Utilities Project Manager
Bob Harberg – Utilities Planning and Project Management
Coordinator
Chris Rudkin – Water Quality Coordinator
Randy Crittenden – Water Treatment Coordinator
FISCAL IMPACT:
The 2006-2011 CIP includes $250,000 in 2005 and 2006 and $500,000
in 2007 and 2008 for source water protection. As a place holder, $20 million (bond
proceeds) is shown in 2009 for construction of a pipeline from Carter Lake to the Boulder
Reservoir Water Treatment Plant (BRWTP).
Also included in the six-year CIP is $400,000 in 2008 for design of the next phase of
improvements at the BRWTP, with $3 million for construction in 2009. In addition,
$500,000 was included for the design of long-term improvements at the treatment plant in
2011. Funding has not yet been included in the CIP for construction of the long-term
improvements.
PURPOSE:
This memorandum provides information to the Water Resources Advisory Board on
the status of source water protection and facility improvements for the BRWTP.
EXECUTIVE SUMMARY:
Source water protection has become a critical component of providing safe and reliable drinking
water due to a greater understanding of the limits of treatment processes in removing contaminants.
Most water utilities institute a multiple barrier approach which includes preventing contaminants
from entering the water supply, in addition to providing multiple water treatment processes.
Increased loading of contaminants in source waters causes a greater potential for contaminants to
pass through the treatment facility. Over the past decade, water utilities have increased reliance on
source water protection to provide a complete overall prevention and treatment barrier for public
health safety.
AGENDA ITEM # Page 1
Attachment A
A Source Water Quality Planning Study – Phase I (Phase I Study) was completed by Black &
Veatch Consulting Engineers (B&V) in April 2003 to provide the city with an overview of
alternative approaches available to improve and protect the source water quality for the Boulder
Reservoir Water Treatment Plant (BRWTP.) Attachment A is the Executive Summary from that
study. Recommendations from the Phase I Study included further consideration of the
management of Boulder Reservoir and the construction of a pipeline from Carter Lake to the
BRWTP. The Phase I study provided an overview of the range of source water alternatives
available to the city and evaluated the relative merits of each.
At the same time that the Phase I Study was being developed, a BRWTP Facility Plan was
completed by MWH Engineers as part of the Predesign Report for Near-term Improvements.
This plan presented near-term, mid-term and long-term improvements for the BRWTP based on
upcoming regulatory requirements as well as internal city-established goals. Near-term
improvements at the water treatment plant were completed in July 2005.
A second phase of the Source Water Quality study (Phase II Study) will consider the source
water protection alternatives proposed for evaluation in the Phase I Study in conjunction with
options for enhancing treatment processes in order to meet regulatory requirements and internal
city goals.
BACKGROUND:
Source Water
Raw water is primarily delivered to the BRWTP through the Colorado-Big Thompson (CBT)
project, which is operated by the Northern Colorado Water Conservancy District (NCWCD). The
CBT project diverts water from the Colorado River (western slope) and the Big Thompson River
(eastern slope) to be stored and delivered for irrigation and water supplies on the eastern slope of
Colorado. The city of Boulder’s portion of the CBT project water is delivered from Carter Lake in a
21-mile-long open channel known as the Boulder Feeder Canal (BFC). The BRWTP can either
receive water directly from the canal, or canal water can be delivered into Boulder Reservoir and
then pumped into the treatment plant. Water is typically delivered in the canal only during the
irrigation season, which is usually April through October. Historically, the BRWTP has often
operated using water from the BFC in the summer and the Boulder Reservoir in the winter.
Both the canal and the reservoir sources of water have unique challenges. Boulder Reservoir is a
low volume, shallow, multi-purpose reservoir. During the summer, the reservoir stratifies, causing a
low dissolved oxygen layer near the bottom. This results in the release of soluble manganese from
the sediment in the reservoir causing taste, odor and other treatment issues. The water in the
reservoir is also high in total dissolved solids including sodium, sulfate and hardness. The turbidity
of the water in the reservoir is generally low, but high winds can cause the turbidity to increase
significantly over short periods of time. Reservoir water quality is also impacted by recreational
uses including swimming and boating. High flows into the reservoir from the BFC help improve the
quality of the water by keeping it mixed; however, the city has limited control over the amount of
water entering or leaving the reservoir. The reservoir provides dilution, settling and natural
processes that break down contaminants before entering the treatment plant.
AGENDA ITEM # Page 2
Attachment A
The BFC is a 21-mile-long open canal. While the quality of water in Carter Lake, where the canal
originates, is high, a significant degradation of water quality generally occurs along the length of the
canal as a result of surface runoff into the canal.Copper sulfate and herbicides are routinely applied
to the canal to control algae and native vegetation. There are 51 outfalls emptying into the canal that
drain a variety of adjacent land uses. There are 11 street crossings that provide potential for release
of contaminants into the canal.
BRWTP
The BRWTP was built in 1969 with a nominal treatment capacity of 8 million gallons a day.
The current treatment process at the BRWTP includes: rapid mix, flocculation, solids removal,
filtration and disinfection. Until 1994, the plant had primarily been used as a peaking plant to
meet summer water demands. During 1994 it became necessary to operate the facility on a year-
round basis to eliminate staffing and maintenance problems, and to maximize use of the city's
raw water resources. During 1993 a masonry building was constructed to cover the existing
flocculator-clarifier, and a cover was installed over the backwash recovery basin to facilitate
winter operations.
In 1995 the existing filter building was modified to house new chemical feed and storage
equipment, and two new filters were installed. The new chemical feed and storage equipment
was designed for system redundancy and increased storage capacity. The existing chemical
building was converted to administrative and laboratory space. During 2001, the existing
chlorine gas disinfection system was converted to a Mixed Oxidant System (MIOX) in order to
eliminate the use of chlorine gas. The most recent improvements to the facility were completed
in July 2005 and addressed “pretreatment” and residuals handling and are described below under
BRWTP Facility Plan as “near-term” improvements.
Regulatory Requirements
The Safe Drinking Water Act addresses a wide range of water quality issues including microbial
contamination, disinfection byproducts, metals, arsenic, radionuclides as well as biological and
chemical contaminants. The United States Environmental Protection Agency (EPA) has focused
special attention on reducing the potential for the occurrence of certain microbial pathogens,
most importantly Cryptosporidium, because they are resistant to traditional disinfection methods.
In recent years, the EPA has issued the Interim Enhanced Surface Treatment Rule (IESWTR)
and proposed a new regulation called the Long-term 2 Enhanced Surface Water Treatment Rule
.
(LT2ESWTR)This regulation would require certain public water systems to provide additional
treatment for Cryptosporidium by implementing one or more source water protection or
treatment options.
The proposed LT2ESWTR requirements for each system are based on the vulnerability of the
source water to contamination, as measured by the occurrence of Cryptosporidium. This strategy
stems from recognition that only some systems may need to provide additional protection from
Cryptosporidium and that such decisions should be made on a system-specific basis. The
AGENDA ITEM # Page 3
Attachment A
regulations specify categories (bins) based on the quality of the source water and corresponding
additional source water protection or treatment from a “toolbox” of options. Based on current
source water quality data, it appears that the Boulder Reservoir WTP source water falls into a
Bin 1 category when pumped directly from Boulder Reservoir, indicating that no further
treatment is required from a regulatory perspective. However, water delivered from the BFC
exceeds the threshold for Cryptosporidium; therefore, additional source water protection or
treatment will be required once the regulation is enacted.
Another important aspect of the proposed LT2ESWTR is promoting a multi-barrier approach for
treating drinking water. A multi-barrier treatment process provides a number of protective
“layers” against contamination by using more than one method of prevention and treatment to
remove/inactivate pathogens and minimize disinfection byproducts (DBPs).
ANALYSIS:
Source Water Quality Phase I Study Results
The Phase I Study evaluated five source water protection alternatives:
Boulder Reservoir as a year-round terminal reservoir
Pipeline from Carter Lake to the BRWTP
Pipeline from Nelson Road to the BRWTP
New terminal reservoir
Forebay upstream of the Boulder Reservoir
These alternatives were evaluated based on their predicted water quality, treatability issues,
capital cost, operational impacts, water rights impacts, community impacts, impacts on meeting
the city’s goals and the implementation timeframe. The Phase I Study recommends further
evaluation of two alternatives: management of water quality in Boulder Reservoir and full
containment of the BFC in a pipeline. The Phase I Study suggests the full time use of Boulder
Reservoir as a terminal reservoir and eliminating direct use of water from the canal in order to
reduce microbial pathogen risk and gain compliance with the LT2ESWTR. Management
strategies were suggested to enhance the source water quality of the reservoir along with
physical improvements to reduce the uptake of manganese. Additional studies were also
performed by Dr. Bill Lewis that evaluated travel time in the feeder canal, as well as mixing,
short circuiting and optimal withdrawal depth from Boulder Reservoir.
In an effort to improve the quality of the water coming from Boulder Reservoir, the city decided
to move forward with modifications to the Boulder Reservoir Water Treatment Plant intake
structure as recommended by B&V and Dr. Lewis. In order to reduce the turbidity and
concentration of manganese in the plant influent, the elevation of the intake structure was raised
ten feet from the bottom of the reservoir. This work was completed in March 2005 and cost
$235,000. While these improvements reduced the turbidity and concentrations of manganese
entering the treatment plant, treating water from the reservoir continues to present challenges to
the treatment plant. Fine clay silt sediment, high hardness and alkalinity, and low dissolved
oxygen do not allow for optimal coagulation. This has resulted in finished water particle counts
AGENDA ITEM # Page 4
Attachment A
exceeding internal city goals; poor total organic carbon removal which can cause disinfection
byproducts; and problems with dirty taste. These problems were exacerbated by warm
temperatures typical of the reservoir in the summer. Sodium levels also continue to be high.
BRWTP Facility Plan
The Predesign Report for Near-Term Improvements for the Boulder Reservoir Water Treatment
Plant prepared by MWH Engineers in July 2003 included a Facility Plan for the BRWTP. The
Facility Plan evaluated improvements to address deficiencies that were identified in the Treated
Water Master Plan (Integra Engineering, 2000) as well as in a follow-up study conducted by
McGuire Environmental Consultants, Inc. (Assessment of the Boulder Reservoir Water Treatment
Plant, 2001). Improvements were categorized into near-term, mid-term and long-term based on
upcoming regulatory requirements as well as internal city goals. In addition to addressing treatment
deficiencies, it became apparent that the capacity of the facility needed to increase.
The importance of the BRWTP was emphasized during the summer of 2002 when drought
conditions restricted raw water availability to the Betasso Water Treatment Plant (WTP). During
that period, the BRWTP was treating 12 million gallons per day (MGD) although the facility was
designed to treat 8 MGD. Also, in September 2002, an industrial wastewater discharge permit
was issued to the BRWTP restricting the daily maximum iron level allowed to be discharged into
the sanitary sewer resulting in limits on the capacity and operational flexibility of the facility.
The BRWTP Facility Plan recommended that the plant capacity be increased to 16 MGD to be
capable of independently meeting the city’s winter water demand. The plan also recommended
facilities be constructed for on-site handling of the BRWTP treatment residuals so that the water
plant could operate without negative effect on the wastewater treatment plant.
The BRWTP Facility Plan recommended the following near-term improvements to the treatment
plant:
replacing the existing flocculator/clarifier with two Dissolved Air Flotation (DAF)
thickeners
installing baffling in the clearwell
providing increased pumping capacity from the treatment plant
providing on site treatment residual lagoons
These improvements were completed in July 2005. In addition to enhancing the performance of
the treatment plant, the maximum effective capacity of the BRWTP increased from 8.5 million
gallons per day (MGD) to 16 MGD. Previous pretreatment processes (rapid mix, flocculation
and sedimentation) limited the plant capacity at which treatment standards could reliably be met
to 8.5 MGD. Compliance with the Interim Surface Water Treatment Rule for Giardia
inactivation was achieved through baffling the clearwell. The residual lagoons were designed to
handle a 10 MGD annual average flow. By constructing on-site handling of the water treatment
residuals, impacts to the wastewater treatment plant were eliminated and operational flexibility
of the BRWTP increased.
Future Source Water Protection Efforts
Staff continues to evaluate source water protection for both the canal and reservoir water sources, as
AGENDA ITEM # Page 5
Attachment A
well as improvements to the treatment plant. The 2006-2011 CIP for Source Water Protection
includes the following:
20052006200720082009
$250,000$250,000$500,000$500,000$20,000,000
A place holder of $2 million (from bond proceeds) is shown in 2009 for potential construction of a
pipeline from Carter Lake to the BRWTP. The $250,000 budgeted in 2005 is anticipated to be spent
as follows:
$100,000-$120,000 for a Carter Lake pipeline feasibility study to be completed by
Northern Colorado Water Conservancy District
$5,000 for buoys around the Boulder Reservoir intake structure
$65,000-$75,000 for toilet facilities for recreational users north of Boulder Reservoir
$50,000 for monitoring and rerouting outfalls into the BFC
Status of the Carter Lake Pipeline Project
Several water providers, including the city of Boulder, the town of Erie and the Left Hand Water
District, have requested that the NCWCD investigate the possibility of constructing a second
water supply pipeline running from Carter Lake to the southern portions of the district. Boulder
might participate in the pipeline project to gain a flow capacity of 25 cubic feet per second (cfs)
out of what may be up to a 96 cfs pipeline running from Carter Lake through Boulder County.
The pipeline project was initiated in late 2004 with the official request by the water providers
that NCWCD take the management lead in developing the project. A consultant has been hired
to do a project feasibility study with each project participant paying its pro-rata share of the
project costs. The city of Boulder has paid its portion of the feasibility study costs in 2005. The
study is expected to be completed by early 2006. The project schedule calls for obtaining any
necessary county or federal permits in 2006, obtaining rights-of-way in 2007 and 2008, and
constructing the pipeline in 2009 and 2010. Achieving this schedule depends on many variables
and the cooperation of several different entities, this schedule may or may not prove to be
optimistic.
If Boulder elects to continue participation in the Carter Lake Pipeline project, Boulder will seek
sufficient pipeline capacity (25 cfs) to carry the portion of its CBT and Windy Gap Projects
water that is delivered directly for treatment at the BRWTP. The remainder of Boulder’s CBT
and Windy Gap water that is used to drive the exchange of water into Barker Reservoir and the
Silver Lake Watershed reservoirs will continue to be carried in the Boulder Feeder Canal. If
Boulder continues to participate, it is estimated that Boulder’s share of the pipeline project costs
following the feasibility study stage could be in the range of $20 million to $30 million.
Future Water Treatment Facility Improvements
In addition to the near-term improvements at the BRWTP, the BRWTP Facility Plan
recommends the following mid-term improvements:
AGENDA ITEM # Page 6
Attachment A
addition of chlorine dioxide
improved instrumentation
new raw water pump
treatment of discharged washwater
pre-sedimentation
pH adjustment
These improvements continue to strengthen the reliability of the treatment process in meeting
regulatory requirements, as well as internal water quality and quantity goals. Chlorine dioxide will
help oxidize organics, thereby reducing disinfection byproducts and reducing taste and odor issues in
the treated water. It will also help oxidize manganese and reduce the burden on the mixed oxidant
(MIOX) disinfection system which at times has problems meeting chlorine demands. Providing
pretreatment of the discharged washwater will help reduce the recycling of contaminants removed in
the filtration process. Pre-sedimentation will help remove fine particles and reduce the load to the
DAF units. Better pH adjustment will allow improve coagulation.
The 2006-2011 BRWTP CIP includes:
20072008200920102011
0$400,000$3,000,0000$500,000
The CIP includes $400,000 for design of the mid-term improvements in 2008, with $3 million
for construction in 2009. It also includes $500,000 for the design of long-term improvements in
2011. Funding has not yet been included in the CIP for construction of the long-term
improvements to the BRWTP.
The recommended long-term improvements are projected to include:
New treated water storage tank
Third DAF unit
Emergency power
Granular activated carbon
UV or membranes
The long-term improvements at the BRWTP are not firmly established at this time. The final
combination of long-term improvements will be determined by future regulatory requirements
for Cryptosporidium removal/inactivation, the city’s internal goals and the feasibility of source
water protection improvements. The installation of a third DAF unit and a new treated water
storage tank will be driven by a need to increase the capacity of the BRWTP.
Some of the long-term improvements are mutually exclusive. For example, construction of a
new UV disinfection system would make a new reservoir for Giardia inactivation unnecessary.
The need for ozone, UV or membranes will be driven by the need for additional
AGENDA ITEM # Page 7
Attachment A
Cryptosporidium removal/inactivation required by the LT2ESWTR.
Future Analysis
In order to maintain a multiple barrier approach to drinking water protection and treatment, the
city plans to complete a Phase II Water Source Protection study in which the potential long-term
improvements to the treatment process can be evaluated in conjunction with the
recommendations for source water protection. This approach will identify the most cost-
effective means of meeting regulatory requirements and achieving the city’s water quality goals
prior to large investments in either treatment facilities or the Carter Lake Pipeline.
PUBLIC COMMENT AND PROCESS:
The public process has not been initiated. It is anticipated the pipeline from Carter Lake will be
subject to County 1041J review.
ATTACHMENTS:
Attachment A: Source Water Planning Study Phase I Executive Summary (Phase I Study)
AGENDA ITEM # Page 8
Attachment B
C I T Y O F B O U L D E R
WATER RESOURCES ADVISORY BOARD
AGENDA ITEM
MEETING DATE: February 27, 2006
AGENDA TITLE:Update on Carter Lake Pipeline Feasibility Study
PRESENTER: Carol Ellinghouse, Water Resources Coordinator
EXECUTIVE SUMMARY:
The city of Boulder has participated with other area water providers in a feasibility study of
a potential pipeline to carry water from Carter Lake to Boulder Reservoir. This memo
provides WRAB with information developed through the feasibility study on potential
alignments of a Carter Lake Pipeline, its estimated cost and possible timeline. The process
by which the city will evaluate the costs and benefits to Boulder of participating in the
construction of the pipeline as compared to other options for addressing issues at the
Boulder Reservoir Water Treatment Plant (BRWTP) is also described.
The proposed Carter Lake Pipeline, known as the Southern Water Supply Project II (SWSP
II), is a collaborative project between the Northern Colorado Water Conservancy District
(NCWCD) and five northeastern Colorado municipal water providers, including Boulder.
The proposed pipeline would carry Colorado-Big Thompson Project and Windy Gap Project
water from Carter Lake to project participants. The pipeline route is likely to follow
portions of the same alignment used by a previous pipeline project (SWSP I) that was
completed in 1997 to carry Carter Lake water to the cities of Broomfield, Louisville,
Longmont, Superior and eight other municipalwater providers.
This memo is an information item only. No action is requested of WRAB at this time and
staff is making no recommendation at this time. A Community and Environmental
Assessment Process (CEAP) evaluation of options for meeting water supply needs at
BRWTP will be completed and brought to WRAB for comment in the future.
Fiscal Impacts:
Budgetary: No additional funding is required in addition to current budget resources
at this time. Work to date on the pipeline feasibility study and evaluation of
permitting requirements has been paid from existing budgets and has totaled
$211,685. Should it be decided to proceed with the construction of a Carter Lake
pipeline as a SWSP II participant, funds will need to be allocated within the Water
Utility Capital Improvement Project budget.The cost for Boulder’s share of pipeline
design and construction costs is estimated to be $20,148,000.
AGENDA ITEM#________PAGE________
Attachment B
Staff Time: All activities at this time are a part of the normal work plan for staff.
Gathering further information and preparing a CEAP may require use of a consultant
at an estimated cost of $8,000, to be paid out of existing budgets.
Other Impacts:
None at this time.
Environmental: Should the SWSP II project proceed, there will be temporary
construction impacts within the selected pipeline corridor.
Economic: The Carter Lake pipeline would allow the BRWTP to treat higher quality
water directly from Carter Lake, instead of the highly mineralized supply in Boulder
Reservoir or the microbial-laden water from the Boulder Feeder Canal. This may
reduce costs for industries that require very pure water supplies and/or have on-site
treatment facilities.
Community: If the portion of Boulder’s CBT and Windy Gap water that is delivered
for direct treatment at BRWTP is delivered in a Carter Lake pipeline, the flows in the
Boulder Feeder Canal will be reduced to just the portion of Boulder’s water that will
be exchanged to upper Boulder Creek reservoirs and the water used by other CBT
allottees. Some members of the community have expressed concerns about aesthetics
if the canal flows are reduced.
Recreational: The availability of a Carter Lake pipeline could allow for a reduction
in the mitigations necessary for water quality protection that are to be included in the
proposed Boulder Feeder Canal trail management. This could make trail
management enforcement less stringent and reduce mitigation costs.
Other Board and Commission feedback:
None at this time.
Public feedback:
None at this time. Public input will be sought during a CEAP process
evaluating BRWTP options as well as through a 1041 permit process with Boulder County
and a Location and Extent review with Larimer County.
Staff recommendation:
There is no recommendation at this time.
Analysis:
Boulder Reservoir studies
A Community and Environmental Assessment Process (CEAP) study will be completed that
incorporates information that has been developed in the Carter Lake pipeline feasibility
study, the Boulder Reservoir Source Water Quality Planning Study, and other studies of
water supply and facilities for the BRWTP.The CEAP will evaluate options for addressing
water supply and treatment needs at the BRWTP that include construction of the Carter
Lake Pipeline, construction of a new terminal reservoir or water treatment plant
improvements. Staff anticipates presenting the CEAP to WRAB for comment in early 2007.
Boulder’s participation in the feasibility study for the Carter Lake pipeline resulted from
recommendations developed through four separate studies of the BRWTP water supplies
and facilities. These studies were the Treated Water Master Plan (2000), Assessment of the
BRWTP (2001), Source Water Quality Planning Study—Phase I (2003) and the BRWTP
Facility Plan (2003). Information on these studies was presented to the WRAB on October
AGENDA ITEM#________PAGE________
Attachment B
17, 2005. The city has recently issued a Request for Proposals for the Source Water
Planning Study—Phase II in which improvements to the treatment process will be evaluated
in conjunction with source water protection options. This approach will identify the most
cost effective means of meeting regulatoryrequirements and achieving the city’s water
quality goals prior to large investments in either treatment facilities or the Carter Lake
pipeline. In order to accurately perform this evaluation, it was necessary to have the detailed
cost information on the Carter Lake pipeline that was developed through the feasibility
study. The Source Water Planning Study—Phase II is expected to be completed in late 2006
and will provide important information for the CEAP.
The United States Environmental Protection Agency (EPA), through the Safe Drinking
Water Act, has focused special attention on reducing the presence of microbial pathogens,
most importantly Cryptosporidium, because they are resistant to traditional disinfection
methods. The EPA has proposed a new regulation called the Long-term 2 Enhanced Surface
.
Water Treatment Rule (LT2ESWTR)This regulation would require some public water
systems to provide additional treatment for Cryptosporidium by implementing one or more
source water protection or treatment options. An important aspect of the proposed
LT2ESWTR is promoting a multi-barrier approach for treating drinking water. A multi-
barrier treatment process provides a number of protective “layers” against contamination by
using more than one method of prevention and treatment to remove/inactivate pathogens and
minimize disinfection byproducts (DBPs).
The proposed LT2ESWTR requirements for Cryptosporidium for a particular water system
are based on the vulnerability of its source water to contamination and are made on a
system-specific basis. The regulations specify categories (bins) based on the quality of the
source water and corresponding additional source water protection or treatment from a
“toolbox” of options. A water supply can experience additional contamination up to a
specified threshold before it is reclassified into another bin.
Based on current water quality data, water taken directly from the Boulder Feeder Canal into
the BRWTP exceeds a threshold level for Cryptosporidium. Therefore, additional source
water protection or treatment will be requiredonce the LT2ESWTR regulation is enacted. It
is unknown how much future water quality in the Boulder Feeder Canal will degrade due to
land use changes or what future treatment standards will be, so pursuing source water
protection options could give some protection against the need to add expensive treatment
processes in the future such as UV, ozone or membranes.
Long-term improvements at the BRWTP are not firmly established at this time. The final
combination of long-term improvements will be determined by future regulatory
requirements for Cryptosporidium removal/inactivation, the city’s internal goals and the
feasibility of source water protection improvements.
Carter Lake Pipeline Feasibility Study
Integra Engineering performed the feasibility study of the Carter Lake pipeline for SWSP II
project participants. A Final Report was issued on January 6, 2006. (A copy of the report
may be reviewed by contacting Carol Ellinghouse at 303-441-3118.) Information on
participants in the Carter Lake feasibility study is summarized in the table below. The Town
of Erie was initially a project participant but has elected not to continue.
AGENDA ITEM#________PAGE________
Attachment B
PipelineDelivery Pt.
ParticipantCost
Capacity (cfs) Elevation (ft MSL)
City of Boulder 255200$ 20,148,000
Left Hand Water District 115130$ 7,641,000
Little Thompson Water District 35400$ 856,000
Central Weld Water District 105400$ 2,853,000
Town of Frederick65400$ 1,712,000
Total55$33,210,000
The feasibility study evaluated pipeline hydraulic criteria, feasible alignments, and projected
costs. The consultant obtained information from GIS databases, aerial photography,
geologic data, property information, existing utility mapping, original SWSP project data
and environmental/cultural studies. Several pipeline alignments were evaluated based on
adjacent land use, existing easements, proximityto residential structures, avoidance of open
space areas, stream crossings, floodplains, stormdrainage, groundwater, visual resources,
natural landmarks, difficult restoration areas, transportation impacts, biological resources,
wetlands, rare plant communities, critical wildlife habitat, cultural resources, extreme slopes,
underground mines, permitting requirements, and cost.
The proposed pipeline would connect to the existing St.Vrain Supply Canal diversion
structure just below the Carter Lake dam. The pipeline will likely be constructed with steel
pipe that is tape-coated and cement mortar-lined, although ductile iron pipe was also
evaluated. If steel pipe is selected, the pipeline diameterwould range from 28 inches to 42
inches, and steel thickness would be from 0.145 to 0.22 inches. If the project proceeds,
construction might begin in mid-2008, and the pipeline might be operational in mid-2010.
Several preliminary pipeline alignments were evaluated based on initial screening criteria to
arrive at four alternatives. System hydraulics for each alternative was studied in greater
detail. Each alternative was then reevaluated to select a preferred alternative. Two of the
alternatives have no high impact areas and will result in lower impacts to residential
properties, riparian habitats, trees, and transportation than the other alternatives. One of
these two alternatives is less expensive and was selected as thepreferred alternative
The preferred alternative for the pipeline alignment parallels the existing Carter Lake
pipeline for much of its length. The existing easement for the original pipeline is 80 to 90
feet in width, so no new easements would need to be acquired to place a second Carter Lake
pipeline in these locations.Construction widths may be narrowed for short distances to
reduce impacts to environmentally sensitive areas. New easements would be acquired in
areas where the second pipeline does not parallel the first pipeline.
Attachments:
Attachment A – Map of the Preferred Pipeline Alignment
Attachment B – Cost Estimates for Preferred Alignment
Attachment C – Proposed Project Schedule
AGENDA ITEM#________PAGE________
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 1
INTRODUCTION
This chapter describes the purpose, background, and approach of the Boulder
Reservoir Water Treatment Facility (BRWTF) Multi-Barrier Approach Study (Multi-
Barrier Study). In addition, this chapter briefly describes recent regulatory changes that
may affect drinking water treatment at BRWTF.
A. Purpose
The purpose of the Multi-Barrier Approach Study (Study) is to evaluate source
water protection alternatives from the Source Water Quality Planning Study (Phase I
Study) and treatment alternatives from the Predesign Report for Near-Term
Improvements (Predesign Report) and develop a long-term plan for meeting regulatory
and City of Boulder (City) water quality goals at the Boulder Reservoir Water Treatment
Facility (BRWTF). Multi-barrier alternatives have been evaluated based on a set of
performance criteria developed by City staff, and consideration of life cycle costs
associated with each alternative.
The Multi-Barrier Study was performed within the context of an ongoing effort by
the City to establish definitive drinking water quality and quantity goals as a framework
for planning and implementing future improvements throughout the City’s drinking water
system. One central strategy for achieving the City’s water quality goals is to implement
a multi-barrier approach to protecting the City’s drinking water supply from both
biological and chemical contaminants. Barriers may include source water protection
activities that either reduce or prevent introduction of contaminants, or minimize their
passage throughout the drinking water system through treatment. A multi-barrier
strategy to control drinking water contaminants affords superior public health protection.
B. Project Background
Raw water is conveyed to BRWTF from Carter Lake through a 21-mile long,
open, earthen canal, referred to as the Boulder Feeder Canal (BFC), which ultimately
discharges into Boulder Reservoir (Figure 1-1). Between April and October, the City
diverts raw water from BFC just upstream of Boulder Reservoir and delivers it through a
pipeline directly to BRWTF. During the remaining months, when BFC is not in
operation, raw water is pumped from Boulder Reservoir to BRWTF for treatment. Both
BFC and Boulder Reservoir have several features that make them vulnerable to source
water quality degradation, as listed in Table 1-1 and shown in Figures 1-2 and 1-3.
Chapter 1 – Introduction1-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Table 1-1
Boulder Feeder Canal and Boulder Reservoir
Vulnerabilities to Water Quality Degradation
BFCBoulderReservoir
Open channel Open to recreational uses including swimming
and motorized boating
51 outfalls discharge into BFC
Overland flow drainage
11 street crossings
Naturally occurring manganese
Uncontrolled access
Algal blooms leading to T & O episodes
Neighboring land uses
Higher TDS due to mineral dissolution
Herbicides routinely applied
High turbidity from wind action and BFC flows
Bank scouring during storm events
Reduced treatability due to higher temperature
In 2003, the Source Water Quality Protection Study (Phase 1 Study) was
completed by Black & Veatch (B&V) to identify and evaluate alternative approaches to
improve and protect source water quality for the BRWTF, based on forecasted
regulatory requirements as well as internal City-established goals. It was recommended
that the following alternatives be carried forward for further investigation:
Near-Term – Boulder Reservoir Management – Utilize Boulder Reservoir as a
year-round terminal reservoir rather than divert raw water directly
from the BFC. Raw water will then be pumped from Boulder
Reservoir to the BRWTF.
Long-Term – Pipeline from Carter Lake to the BRWTF – Construct a 21-mile raw
water pipeline from Carter Lake that would deliver water year-round
to the BRWTF by gravity flow.
Since that time, the City has modified the intake structure at the Boulder
Reservoir to reduce the manganese load to the BRWTF. In addition, the City recently
participated with other drinking water providers in a study to further explore the
feasibility of a pipeline from Carter Lake to the BRWTF. The study evaluated potential
pipeline alignments and refined capital cost opinions for each of the participants.
Chapter 1 – Introduction1-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
However, some of the entities included in the study may not participate in the pipeline,
which would potentially increase the City’s share of the cost.
At the same time the Phase 1 Study was being developed, the Predesign Report
for Near-Term Improvements for the Boulder Reservoir Water Treatment Plant
(Predesign Report) was completed by MWH. This plan presented near-term, mid-term
and long-term recommendations for improvements at the BRWTF. Near-term
improvements were completed in 2005 and included the installation of dissolved air
flotation (DAF) facilities, baffling the clearwell, and providing on-site residuals lagoons.
Recommended mid-term and long-term improvements included:
Mid-Term – Chlorine dioxide
Pre-sedimentation
Filter backwash water treatment
pH adjustment
Long-Term – Ultraviolet (UV) disinfection
Membranes
Ozone
Granular activated carbon (GAC) caps on existing filters
The mid-term treatment process improvements listed above have not yet been
implemented, but the City has begun the budget planning process for their addition at
BRWTF. For the purposes of this assessment mid-term improvements are assumed to
be included in the BRWTF treatment process train, and addition of long-term
improvements was evaluated based on this updated baseline treatment capability.
The City has requested that B&V utilize the findings of the two reports to develop
a multiple-barrier approach that combines the most cost effective means of meeting the
City’s water quality and quantity goals. This study is especially timely in light of the City
Council’s recent endorsement of the development of an 11-mile recreational trail along
the BFC from U.S. 36, southeast of Lyons, to the Boulder Reservoir. A city and county
staff team assessed the potential impacts of the trail and identified mitigation measures
through a community and environmental assessment process (CEAP). The primary
issue identified in the CEAP was the potential impacts of the proposed trail on the city's
drinking water supply for the BRWTF.
Chapter 1 – Introduction1-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
C. Regulatory Environment and City Water Quality Goals
This study is also timely due to the recently promulgated Long-Term 2 Enhanced
Surface Water Treatment Rule (LT2ESWTR). Based on an improved understanding of
Cryptosporidium occurrence in surface waters and treatment process limitations, the
LT2ESWTR has established risk-targeted log-removal/inactivation levels for
Cryptosporidium, in addition to those specified in earlier rules, based on average source
waterCryptosporidium concentrations.
The primary purposes of this rule are to protect
public health from illness due to Cryptosporidium and other microbial pathogens in drinking
Because
water and to address risk-risk trade-offs with the control of disinfection byproducts.
this regulation links the required level of drinking water treatment with source water
quality, a careful evaluation of source water protection and treatment options is required
to ensure public health protection and regulatory compliance. Furthermore, an
assessment is necessary to determine if the requirements of the LT2ESWTR are
sufficient to ensure public health in Boulder, based on unique source protection
challenges faced by the City.
LT2ESWTR classifies source water quality into four bins based on average
Cryptosporidium concentration and treatment type, and specifies associated levels of
additional treatment required. Table 1-2 lists the required levels of additional treatment
for WTPs that utilize conventional treatment consisting of chemical coagulation,
flocculation, clarification, and granular media filtration.
Table 1-2
LT2ESWTR Cryptosporidium Treatment Requirements for Conventional WTPs
BinCryptosporidium Concentration Additional Removal/Inactivation
Designation (oocysts/L) Treatment Required
1Less than 0.075 None
20.075 or higher, but less than 1.0 1-log
31.0 or higher, but less than 3.0 2-log
43.0 or higher 2.5-log
As a public water system serving a population greater than 100,000, the City is
required to conduct 24 months of initial source water monitoring beginning in October
2006, or submit grandfathered existing monitoring data to establish average
Cryptosporidium concentrations for LT2ESWTR bin determination at BRWTF. Historical
Chapter 1 – Introduction1-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Cryptosporidium monitoring data for Carter Lake, BFC, and Boulder Reservoir collected
between 1997 and 2006 indicate that these source waters would be classified in Bin 1
with respect to LT2ESWTR compliance, requiring no additional treatment for
Cryptosporidium. However, if grandfathered existing data are not accepted by the
regulatory primacy agency, then LT2ESWTR bin classification would be based on the
results of source water monitoring beginning in October 2006. While these results are
not expected to vary significantly from historical data, they could potentially result in
additionalCryptosporidium treatment regulatory requirements.
As part of its water quality goal setting process, the City has determined that a
minimum of one additional log-removal/inactivation of microbial pathogens above
regulatory requirements is prudent to protect public health. Table 1-3 lists the required
and target log-removal/inactivation for regulated microbial pathogens based on meeting
federal regulations and City water quality goals.
Table 1-3
Required and Target Log-Removal/Inactivation for Regulated Microbial Pathogens
Pathogen
Regulation/Goal
Viruses
GiardiaCryptosporidium
Regulatory Requirement 433*
CityGoal545
*Assumes LT2ESWTR Bin 1 classification.
D. Contaminant Barrier Requirements
The barrier requirements for BRWTF, based on current state and federal
regulatory requirements and City water quality goals, were identified through review of
source water quality data for Carter Lake, BFC, and operational data from BRWTF.
Barriers for microbial pathogens, disinfection byproducts (DBPs), organic micro-
pollutants, manganese, taste and odor, and inorganic contaminant control were
evaluated. The potential impacts of both long-term average water quality and short-
term acute contamination episodes were considered.
Chapter 1 – Introduction1-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
E. Multi-Barrier Alternatives Performance Evaluation
The relative performance of multi-barrier water delivery alternatives developed in
this study was evaluated using the Kepner-Tregoe (K-T) decision analysis procedure.
K-T Decision Analysis is a systematic procedure that encompasses the fundamental
thought pattern people use to make choices. The specific techniques that define the
systematic procedure used in K-T Decision Analysis expand and refine the elements of
this thought pattern:
We appreciate that there is a choice to be made.
We consider the specific factors that should be satisfied for the choice to
succeed.
We decide what course of action best satisfies these factors.
We consider the risks associated with the chosen course of action that could
jeopardize its success.
The following sections describe the 9 steps that constitute the K-T Decision Analysis
process
1. State the Decision
The decision statement describes the “choice dilemma” that is to be resolved in a
decision-making process, indicates an intended result, and sets limits on the choice
being made. A decision statement is a short and concise description of the choice to be
made that includes a choice word (select, choose, pick, etc.), an intended result, and
one or two key modifiers that broaden or narrow the range of the choice. The decision
statement also specifies the level at which the current choice is to be made based on
implied prior decisions. The decision statement for this project is:
“Select a multi-barrier water delivery approach for the BRWTF.”
2. Develop the Objectives
The second step in K-T Decision Analysis is to develop the decision objectives,
which consists of the set of criteria that will influence the decision. This set of decision
criteria forms a basis to help evaluate BRWTF water delivery alternatives fairly. City
staff developed criteria in 5 categories including finished water quality, source water,
treatment operations, risk, and environmental and public acceptance, as outlined in
Chapter 4.
Chapter 1 – Introduction1-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
3. Classify the Objectives Into MUSTs and WANTs
Each of the criteria that form the set of decision objectives is classified based on
its role in the decision:those criteria that are mandatory for any acceptable decision
alternative are classified MUSTs, whereas those criteria that are desirable for any
acceptable decision alternative are classified as WANTs. The set of decision criteria
developed in Chapter 4 are also classified in that chapter.
4. Weigh the WANTs
The relative importance of WANT criteria in the decision at hand is established
by assigning numerical weights between 1 and 10 to each. City staff assigned relative
weights to the WANT decision criteria as described in Chapter 6.
5. Generate Alternatives
Candidate solutions for the decision statement are developed based on review of
the decision criteria set, regulatory requirements, industry standards, and decision
group experience and judgment.Conceptual improvements previously identified in the
Phase 1 Study and Pre-design Report, as well as those in the LT2ESWTR Microbial
Toolbox (Table 3-4), were reviewed for applicability to either source water conveyance
to or treatment at BRWTF. Conceptual improvements that were determined to be
potentially feasible were grouped into candidate water delivery alternatives based on
meeting the barrier requirements identified in Chapter 3.
6. Screen the Alternatives Through the MUSTs
Each alternative developed in step 5 is screen against the minimum set of
requirements defined by mandatory MUST criteria. Only those alternatives that
completely satisfy all MUST criteria are considered further in the decision process. The
BRWTF multi-barrier water delivery alternatives developed in Chapter 5 satisfy the
MUST criteria as classified in Chapter 4.
7. Compare the Alternatives Against the Wants
The performance of each decision alternative against the set of WANT criteria is
evaluated in comparison to all other alternatives to establish a relative ranking of
alternatives. The relative performance ranking of BRWTF water delivery alternatives is
described in Chapter 6.
Chapter 1 – Introduction1-7
City of Boulder BRWTF Multi-Barrier Approach Study Draft
8. Consider the Adverse Consequences
Adverse consequences associated with selection of each alternative are
identified and reviewed to understand the risks associated with each.
9. Make the Best Balanced Decision
A balanced decision regarding the most appropriate alternative solution to the
decision statement requires collective consideration of relative alternative ranking and
potential adverse consequences of each alternative. For this study, an economic
evaluation of capital and operation and maintenance costs was also conducted, as
described in Chapter 7. Both non-economic performance and economic life-cycle value
of BRWTF water delivery alternatives were considered in selection of a recommended
BRWTF water delivery alternative, as described in Chapter 8.
Chapter 1 – Introduction1-8
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 2
BRWTF SOURCE WATER QUALITY
This chapter provides a brief overview of the existing BRWTF source water
system and its historical operation. An evaluation of water quality for the potential
sources that could be used to supply BRWTF, including Carter Lake, BFC, and Boulder
Reservoir, is also provided. The quality of raw water delivered to BRWTF by the BFC
and Boulder Reservoir systems was evaluated for their current configurations with no
additional source water protection features added, and with full containment from Carter
Lake to BRWTF as recommended in the Phase I Source Water Protection Study.
A. Existing BRWTF Source Water System
Historically, operation of BRWTF has ultimately relied on delivering raw water
through BFC, either directly to BRWTF or to Boulder Reservoir for subsequent use.
During canal operation, raw water is typically diverted from BFC at a location upstream
of Boulder Reservoir and delivered through a pipeline to BRWTF for treatment and
distribution. Any remaining flow continues in BFC for a short distance and discharges to
Boulder Reservoir where it is stored for water exchanges, downstream irrigation or as a
reserve raw water supply for treatment at BRWTF. When the canal is not in operation,
raw water is pumped from Boulder Reservoir to BRWTF.
1. Boulder Feeder Canal
The open channel BFC generally follows a north to south route traversing the
lower slopes of the foothills. As such, it tends to capture a significant amount of surface
runoff that originates uphill and to the west. Although a riparian habitat along the canal
could, to some extent, naturally attenuate contamination, the channel bottom and banks
are regularly maintained by Northern Colorado Water Conservancy District (NCWCD) to
prevent growth of vegetation. Therefore, although the raw water at its source in Carter
Lake is of a very high quality, significant degradation generally occurs as the water
travels the length of the BFC.
The resulting variable water quality delivered to BRWTF and/or Boulder
Reservoir can pose significant treatment challenges to the City. The BRWTF staff must
frequently adjust treatment operations in response to raw water quality changes due to
weather and human or animal activities. Unfortunately, existing BRWTF monitoring and
treatment technologies have not always provided the ability to respond quickly enough
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
to rapid water quality changes and there have been occasions when the facility has
been taken off-line to avoid the possibility of violating treated water quality standards.
Operational changes in treatment are also required each time the raw water supply is
switched between BFC and Boulder Reservoir.
2. Boulder Reservoir
Boulder Reservoir is a low volume, shallow, Class 1 warm water fishery owned
by the City of Boulder and operated by NCWCD. The reservoir has a surface area of
approximately 700 acres and a capacity of about 13,270 acre-feet. Historically,
BRWTF has primarily used the Boulder Reservoir supply only during the winter months
when BFC is not in service. Water from Boulder Reservoir must be delivered by
pumping from RWTF Raw Water Pumping Station.
Boulder Reservoir is a multipurpose reservoir that is used year round for a variety
of recreational activities including special events that bring in large numbers of people
for short durations. As a result, the reservoir is subject to water quality degradation
resulting from both body contact recreation and non-body recreational activities such as
fishing and boating. These activities contribute to general water quality degradation and
an increase in BRWTF raw water supply contaminant load.
Flows from BFC have in the past been as high as 2.5 times the reservoir volume.
These flows are significant in that high flows tend to improve water quality by keeping
the reservoir water mixed and fresh, which helps reduce stratification that occurs in the
summer. However, the City has no control over these flows, which can vary
significantly from year to year. In addition, the reservoir provides a degree of dilution,
settling, and natural processes to break down contaminants before raw water reaches
BRWTF.
During the late summer, natural temperature stratification occurs in the reservoir
and a hypolimnetic layer low in dissolved oxygen forms in the deeper regions of the
reservoir. This condition results in the release of soluble manganese from reservoir
sediment into the water column and causes taste and odor treatment concerns at
BRWTF.
The water in the reservoir has higher total dissolved solids (TDS) including
sodium, sulfate, and hardness compared with water entering from BFC. Turbidity in the
reservoir is typically less than 10 nephelometric turbidity units (NTU), but wind action
and high canal flows can increase turbidity to as high as 150 NTU. Additional water
quality concerns include objectionable tastes and odors, which may be a byproduct of
hypolimnetic anoxia.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
B. Water Quality Data Sources
Source water quality data for Carter Lake, BFC, and Boulder Reservoir were
reviewed. Water quality data were collected from previous reports prepared for the City
as well as supplemental data supplied by the City. Data obtained from United States
Environmental Protection Agency (USEPA) and United States Geologic Survey (USGS)
online databases were also reviewed.Table 2-1 lists source water data reviewed for
this study. Not all analyses cover the entire sampling period or all three source waters.
Table 2-1
Water Quality Data Sources
ParameterData Source Time Period
Microbiological
(1)
Giardia, Crypto, FC Phase I StudyPre 2004
(2)
Giardia, Crypto Predesign Report1992-2000
(3)
Giardia, Crypto, TC, FC, HPC Water Treatment Evaluation StudyPre 1999
(4)
Giardia, Crypto, FC Boulder Reservoir WTP Assessment1994-2000
(5)
Giardia, Crypto, TC, FC, EC City of Boulder1995-2005
(6)
Giardia, Crypto BFC Proposed Trail Study1997-2000
(7)
TC, FC, EC, FS USGS National Water Information System1970-2004
Physical Parameters
pH, turbidity, temperature, DO, SC Phase I Study Pre 2004
pH, turbidity, temperature, DO, SC Predesign Report1992-2000
pH, turbidity, color, odor Water Treatment Evaluation Study Pre 1999
pH, turbidity, temperature, DO, SC Boulder Reservoir WTP Assessment1994-2000
(8)
pH, temperature, DO, SC USGS Water-Resources Report 99-40911997-1998
pH, turbidity, temperature, DO, SC, true
City of Boulder1995-2005
color, ORP, flow
pH, transparency, temperature, DO, SC USGS National Water Information System 1970-2004
Chemical Parameters
Cations, anions, alkalinity, Fe, Mn Phase I Study Pre 2004
Cations, anions, alkalinity, Fe, Mn Predesign Report1992-2000
Cations, anions, alkalinity, metals Water Treatment Evaluation Study Pre 1999
Cations, anions, alkalinity, Fe, Mn Boulder Reservoir WTP Assessment1994-2000
Fe, Mn, Se, U, N, P, trace metals USGS Water-Resources Report 99-4091 1997-1998
Cations, anions, alkalinity, Fe, Mn, P,
City of Boulder1995-2005
NO, NO
32
Cations, anions, alkalinity, metals USGS National Water Information System 1970-2004
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Table 2-1
Water Quality Data Sources (continued)
ParameterData Source Time Period
Organic Parameters
Chlorophyll a, TOC, UVAPhase I Study Pre 2004
254
Chlorophyll a, TOC, SUVA Predesign Report1992-2000
TOC, DBPs Water Treatment Evaluation Study Pre 1999
Chlorophyll a, TOC, UVABoulder Reservoir WTP Assessment1994-2000
254
Chlorophyll a, TOC, UVACity of Boulder 1995-2005
254
Chlorophyll a/b, TOC USGS National Water Information System 1970-2004
(9)
TOC Bureau of Reclamation2005
Abbreviations:
'%3V±GLVLQIHFWLRQE\SURGXFWV'2±GLVVROYHGR[\JHQ(&±Escherichia coli)&±IHFDOFROLIRUPV
)6±IHFDOVWUHSWRFRFFL+3&±KHWHURWURSKLFSODWHFRXQW253±R[idation-reduction potential,
6&±VSHFLILFFRQGXFWDQFH689$±specific ultraviolet absorbance (UVA72&
7&±WRWDOFROLIRUPV
254
72&±WRWDORUJDQLFFDUERQ89$±XOWUDYLROHWDEVRUEDQFHDWQP
254
(1)
Source Water Quality Planning Study, Black & Veatch, April, 2003.
(2)
Predesign Report for Near-Term Improvements for the Boulder Reservoir Water Treatment Plant,
MWH, June 20, 2003.
(3)
:DWHU7UHDWPHQW3ODQW(YDOXDWLRQ6WXG\ :736±(Uie, CO), HDR Engineering Inc., February, 2006.
(4)
Assessment of the Boulder Reservoir Water Treatment Plant, McGuire Environmental Consultants
Inc., May 2001.
(5)
City of Boulder Drinking Water Program, various data provided by the City of Boulder
(6)
Assessment of Pathogen Risk of a Proposed Trail on the Boulder Feeder Canal (BFC), Boulder
County Colorado, CH Diagnostic & Consulting Service, Inc., October 10, 2000.
(7)
United States Geological Survey, National Water Information System: USGS 06742500 Carter Lake
near Berthoud, CO, http://nwis.waterdata.usgs.gov/usa/, accessed June 09, 2006.
(8)
Water-Quality Conditions, Hydrologic Budget, and Sources and Fate of Selected Trace Elements and
Nutrients in Boulder Reservoir, Boulder, Colorado, 1997-98. USGS Water-Resources Investigations
Report 99-4091.
(9)
1RUWKHUQ&RORUDGR:DWHU&RQVHUYDQF\'DWDEDVH%XUHDXRI5HFODPDWLRQ±&DUWHU/DNH6WDWLRQ&/
DAM1, 2005.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
C. Source Water Quality Data Summary
Water quality data reviewed for this study were evaluated for both spatial and
temporal coverage of the associated source waters. Table 2-2 lists the average water
quality data for each raw water source and the following sections provide a summary of
the data evaluation by source water.
1. Carter Lake
Carter Lake is a relatively deep (140 feet) upland reservoir. Upland reservoirs
receive imported water by utilizing hydraulic structures and typically very small runoff
areas. Carter Lake is surrounded by Bureau of Land Management lands and has no
natural tributaries. The lake is open to motorized boating, but has historically had
excellent water quality with only slight seasonal variations.
a. Microbial Characteristics
The microbial quality of Carter Lake has historically been excellent, due in large
part to its location, small runoff area, and limited human impact. Sample data for total
E. coli
coliforms, fecal coliforms, , and fecal streptococci are consistent with surface
water that is minimally impacted by human and animal wastes. The following
summarizes the historic microbial quality of Carter Lake.
Fecal coliform measurements collected between 1970 and 2001 averaged less
than 1 colony forming unit per 100 milliliters (CFU/100 mL), with a maximum
concentration of 17 CFU/100 mL. Only three percent of the samples reviewed
had concentrations greater than 1 CFU/mL.
E. coli
All monitoring results reviewed between 2001 and 2004 were less than or
equal to 1 CFU/100 mL.
No data on protozoan levels in Carter Lake was reviewed; however, between
GiardiaCryptosporidium
1998 and 2003, neither nor was detected in raw water
conveyed through a pipeline from Carter Lake to the City of Erie, Colorado.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Table 2-2
Average Water Quality Data for Carter Lake,
Boulder Feeder Canal, and Boulder Reservoir
(1)(2)(3)
Water Quality Parameter Carter LakeBoulder Feeder CanalBoulder Reservoir
Monitoring Period 19702005 19972005 19972005
10.2 11.5 14.2/16.8
Temperature (C)
pH (s.u.) 7.6 8.2 7.6/8.2
DO (mg/L) 7.9 10.1 4.9/8.2
Turbidity (NTU) N/A5.4 25/9
Specific conductance (µmho/cm) 71 109 284/295
(4)
Total dissolved solids (mg/L)43 66 172/180
Total suspended solids (mg/L) N/A 7 18/6
Hardness (mg/L as CaCO) 40 48 120/122
3
Alkalinity (mg/L as CaCO) 31 39 66/66
3
Sodium (mg/L) 2.2 3.4 10.3/9.6
Sulfate (mg/L) 3 14 77/78
Iron, dissolved (µg/L) 9 10 4/3
Manganese, dissolved (µg/L) 3 < 10 88/8
Phosphorous, dissolved (µg/L) 12 15 22/14
Nitrate + nitrite (mg/L) 0.07 0.03 0.02/0.01
Total organic carbon (mg/L) 3.6 3.5 3.5/3.6
E. coli (CFU/100 mL) 1 66 58/8
Fecal coliform (CFU/100 mL) < 1 38 20/7
3
Giardia (cysts/L) ND0.32 to 0.49 < 0.001
Cryptosporidium (oocysts/L) ND 0.02 to 0.16 0.01
(1)
Samples collected from Carter Lake when ice cover was not present.
(2)
Samples collected during periods of canal operation only, typically April through October.
(3)
Samples collected 0.5 m above the bottom/composite epilimnion samples.
(4)
TDS = 0.61×Specific conductance
1$±1RWDYDLODEOH
1'±1RWGHWHFWHG
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
b. Physical Characteristics
Physical water quality parameters in Carter Lake are typical of relatively deep
lakes with small catchments, as summarized below.
Raw water pH is neutral to slightly alkaline.
Turbidity and specific conductance are low.
The average temperature of water in Carter Lake between 1970 and 2004 was
10.2 degrees Celsius (C), with maximum and minimum recorded values of 24C
and 0.5C, respectively. Temperature stratification with depth was observed in
summer months, with seasonal overturn events in the spring and fall.
Dissolved oxygen in the hypolimnion is below saturation during summer months;
however, generally remains above 3 milligrams per liter (mg/L).
c. Chemical Characteristics
The following provides a summary of the chemical characteristics of Carter Lake.
Carter Lake displays chemical characteristics consistent with highly pristine
mountain waters derived primarily from snowmelt including low alkalinity,
hardness, and TDS. Figure 2-1 shows TDS and sulfate concentrations for the
period 1970 to 2004.
Because Carter Lake is situated in an area with low mineral content soils, there is
little opportunity for metals uptake into the water column.
Both iron and manganese concentrationsKDYHEHHQFRQWLQXRXVO\EHORZ(3$¶V
Secondary Maximum Contaminant Levels (SMCLs) of 0.3 mg/L and 0.05 mg/L,
respectively for data reviewed between 1973 and 2004.
The productivity of Carter Lake is classified as oligotrophic based on chlorophyll
a and total phosphorous concentrations, and TOC concentrations average 3.5
mg/L and vary little with season. Based on these considerations the potential for
serious taste and odor problems related to algal blooms in Carter Lake is low.
2. Boulder Feeder Canal
The BFC is bordered by a variety of public and private lands that have
agricultural, industrial, residential, and recreational usages. Because of its open
construction, BFC experiences surface runoff and has 51 outfalls and 11 street
crossings along its length. Therefore, although water quality in Carter Lake has
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-7
City of Boulder BRWTF Multi-Barrier Approach Study Draft
historically been excellent, significant degradation typically occurs as water flows
through BFC.
a. Microbial Characteristics
The City of Boulder Drinking Water Program has conducted extensive
reconnaissance of water quality in the BFC in recent years, particularly related to
microbial degradation. Data collected between 1995 and 2005 were reviewed and
yearly baseline fecal coliform contamination values were calculated after excluding
anomalously high values associated with acute contamination events. Fecal
contamination in BFC appears to be increasing with time, as shown graphically on
Figure 2-2. Both average monthly (June through October) and maximum monthly fecal
coliform concentrations increased over the time period examined. Because the trends
represented by these data do not include acute contamination events, they represent a
conservative estimate of fecal contamination in BFC.
Review of extensive bacteriological reconnaissance monitoring data collected
during the 1995 through 2005 BFC operating seasons reveal the following:
E. coli
and fecal coliform levels were measured at multiple locations along BFC,
E. coli
with a total of 307 measurements collected on 78 days during the 2002
through 2005 canal operating seasons and a total of 328 fecal coliform
measurements collected on 89 days during the 1995 through 2003 canal
operating seasons, respectively. Samples were not collected at all locations on
every sample date. The cumulative frequencies of bacterial contamination in
BFC based on this data are given in Figure 2-3.
Bacterial water quality varies spatially along the length of BFC, with higher levels
of degradation frequently occurring downstream, as shown in Figure 2-4.
Bacterial water quality varies temporally in BFC, with positive correlation between
canal flow and rainfall and contamination. Figure 2-5 illustrates the magnitude of
E. coli
an elevated contamination episode in BFC captured in July, 2005.
The bacterial quality of water delivered by BFC to BRWTF is significantly
E. coli
degraded compared with that of the original Carter Lake source water.
and fecal coliforms are typically present in BFC water at the BRWTF intake in
concentrations of tens to thousands of CFU/100mL and tens to hundreds of
CFU/100 mL, respectively, compared to concentrations typically less than
1 CFU/100 mL in Carter Lake.
These data highlight the potential for microbial contamination of BFC water through
surface runoff, outfalls, and scouring of the canal banks.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-8
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Extensive reconnaissance for protozoan contamination in BFC has also been
conducted over the past decade. The following summarizes these findings.
Giardia
has been regularly detected in BFC samples at an average concentration
between 0.32 and 0.49 cysts per liter (cysts/L), with positive occurrence in
Giardia
68 percent of samples. The maximum concentration detected between
1994 and 2004 was 2.00 cysts/L.
Cryptosporidium
has frequently been detected in BFC samples at an average
concentration between 0.02 oocysts per liter (oocysts/L) and 0.16 oocysts/L, with
a maximum reported concentration of 3.04 oocysts/L.
CryptosporidiumGiardia
The frequency of detection was lower than that of , with
positive occurrence in between 11 and 23 percent of BFC samples.
Cryptosporidium
Monte Carlo simulation was used to predict probable
concentrations in BFC resulting from various levels of recreational trail usage
along BFC as a function of canal flowrate. Results from these simulations
indicated potential for significant degradation in BFC water quality due to
Cryptosporidium
contamination from adjacent recreational use.
b. Physical Characteristics
Physical water quality parameters in BFC are similar to those of Carter Lake, with
slight increases in temperature, pH, and dissolved oxygen.
c. Chemical Characteristics
Chemical water quality of BFC was also similar to that of Carter Lake, with only
marginally higher average mineral content, although short-term seasonal increases in
TDS and sulfate do occur, as shown in Figure 2-6. TOC at the BRWTF intake on BFC
is similar to that in Carter Lake.
3. Boulder Reservoir
Boulder Reservoir is located atop mineralized soils that have relatively high
native sulfate and manganese. There are two natural tributaries and several ditches
that drain into Boulder Reservoir, increasing the nutrient loading and potentially
introducing contaminants. Boulder Reservoir is also used year-round for a variety of
recreational purposes including fishing, boating, and swimming, which can also
contribute to pathogen and contaminant loading.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-9
City of Boulder BRWTF Multi-Barrier Approach Study Draft
a. Microbial Characteristics
The microbial water quality of Boulder Reservoir is vulnerable to pathogen
contamination due to operation of Boulder Feeder Canal. The following summarizes the
bacterial characteristics of Boulder Reservoir.
Sampling of Boulder Reservoir by City staff demonstrates a causal link between
fecal contamination in the reservoir and operation of BFC. Fecal coliforms are
present at or below the detection limit during the months when BFC is not in
operation. However, during the months that BFC is in operation fecal coliforms
are typically present at measurable concentrations.
E. coli
Both and fecal coliform concentrations in the hypolimnion (0.5 meters
above the bottom of the reservoir) are slightly less than their respective average
concentrations in BFC.
Fecal contamination in Boulder Reservoir appears to be increasing with time, as
shown graphically on Figure 2-7, based on both seasonal and maximum monthly
average fecal coliform data. Samples collected from the hypolimnion between
1997 and 2003 show similar increasing trends as previously described for BFC
over the same time period.
Although fecal contamination of Boulder Reservoir through surface tributaries
and recreational use have been documented, the relatively low tributary flows
(roughly eight percent of BFC flow) and vertical stratification during warm
weather months of BFC operation make it unlikely that these contaminant
sources account for elevated fecal coliform levels in the reservoir hypolimnion.
Protozoan contamination has been detected less frequently and at lower
concentrations than in BFC. The following summarizes the protozoan characteristics of
Boulder Reservoir.
Giardia
was detected in 8 percent of samples collected from Boulder Reservoir
between 1997 and 2004, with a maximum concentration of 0.3 cysts/L.
CryptosporidiumCryptosporidium
was not detected in these samples. However,
was reported at an 8 percent incidence rate in earlier sampling with a maximum
concentration of 0.2 oocysts/L.
Dilution and natural attenuation processes that occur in the reservoir likely
contribute to the lower protozoan detection rate compared with BFC.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-10
City of Boulder BRWTF Multi-Barrier Approach Study Draft
b. Physical Characteristics
Physical water quality parameters in Boulder Reservoir are moderately different
than those of Carter Lake and BFC; with similar pH, lower dissolved oxygen, and higher
temperature, turbidity, total dissolved solids, and specific conductance (Table 2-2).
Seasonal variation in physical water quality is observed as discussed below.
c. Chemical Characteristics
Chemical water quality in Boulder Reservoir is degraded compared to Carter
Lake and BFC. The following summarizes chemical water quality in Boulder Reservoir.
Dissolution of naturally occurring mineral deposits in Boulder Reservoir
sediments leads to dramatically increased TDS, hardness, alkalinity, sodium,
sulfate, and manganese (Table 2-2).
TDS and sulfate concentrations in Boulder Reservoir vary with season, generally
decreasing when BFC is in service and increasing when BFC is not in service, as
shown in Figure 2-8.
Phosphorous concentration is slightly higher in Boulder reservoir than Carter
Lake and BFC. TOC in Boulder Reservoir is similar to that in BFC and Carter
Lake.
d. Seasonal Water Quality Variation
Physical and chemical water quality in Boulder Reservoir follows a repeating
seasonal pattern that results in vertical stratification in the water column, impacting
treatability at BRWTF when operation is from the reservoir intake. Vertical stratification in
Boulder Reservoir is reinforced by inflow from BFC that is lower in temperature than
either the epilimnion or hypolimnion year-round. During the summer months when
reservoir water temperature increases, the hypolimnion becomes anaerobic, and
manganese is mobilized from native sediments. Manganese mobilization is generally
followed by a dramatic decrease in sulfate concentration throughout the summer and fall,
as illustrated on Figure 2-9. Sulfate concentration is re-established throughout the water
column in the winter when biological activity is reduced.
Comparison of the water temperatures in BFC at BRWTF and the epilimnion
(surface layer) of Boulder Reservoir indicate that water entering the reservoir from BFC is
consistently cooler than the surrounding reservoir, as shown on Figure 2-10. The higher
bacterial contaminant concentrations in the hypolimnion of Boulder Reservoir may be
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-11
City of Boulder BRWTF Multi-Barrier Approach Study Draft
attributed to the settling of the cooler, and thus denser, BFC water into the hypolimnion.
This can cause short-circuiting of much of the reservoir volume, resulting in a reduced
mixing and dilution volume. Because the reservoir intake for BRWTF is located in the
hypolimnion, short-circuiting of potentially pathogen loaded BFC water is particularly
undesirable. Further studies are necessary to quantify the extent of short-circuiting.
The seasonal variation in hypolimnion water quality is characteristic of microbially
mediated activity. Heterotrophic bacteria couple the oxidation of organic matter with the
reduction of inorganic terminal electron acceptors to gain energy for metabolism.
Bacteria preferentially exploit electron acceptors in order of greatest energy generation,
resulting in a temporal sequence of utilization (Figure 2-11). The sequence of oxygen
depletion followed by Mn(II) production and ultimately sulfate reduction observed in the
hypolimnion of Boulder Reservoir is consistent with microbial activity based on low iron
and nitrate concentrations.
Variation in physical water quality parameters also supports seasonal
stratification in Boulder Reservoir. Lower temperature, pH, and dissolved oxygen, as
well as higher turbidity and suspended solids, are all indicative of stratification.
However, several key chemical constituents including hardness, alkalinity, total
dissolved solids, total organic carbon, and sulfate remain relatively constant with
reservoir depth. A scenario that mechanistically explains this apparent inconsistency
may be related to a thermally generated density gradient as BFC water flows into
Boulder Reservoir, as illustrated in Figure 2-12.
In this scenario, BFC water entering Boulder Reservoir sinks to the bottom due to
its lower temperature and higher density, where dissolved oxygen is depleted by
microbial respiration. As anaerobic water flows away from the BFC inlet in the
hypolimnion, manganese dioxide (MnO) in bottom sediment is first microbially reduced
2
2+
releasing soluble manganese (Mn), followed by sulfate reduction. Dissolution of other
soluble minerals in bottom sediment also occurs, increasing TDS. Inflow of water to the
hypolimnion from BFC is balance by withdrawal for BRWTF treatment and upwelling to
2+
the epilimnion. At the interface between the hypolimnion and epilimnion soluble Mn is
oxidized by molecular oxygen, re-precipitating particulate MnO that settles back into
2
the hypolimnion. Thus, mixing from below maintains anaerobic conditions in the
hypolimnion, while promoting otherwise somewhat similar chemical water quality
throughout the water column.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-12
City of Boulder BRWTF Multi-Barrier Approach Study Draft
D. BRWTF Operational Data
Operational water quality data for BRWTF provided by the City was reviewed
with respect to the treatment barriers currently in place for microbial, disinfection
byproduct, organic contaminant, manganese, taste and odor, and inorganic contaminant
control. Data for the years 1997 through 2005 indicate that finished water from BRWTF
generally meets all current Primary and Secondary National Drinking Water Standards.
However, several aspects of finished water quality that may impact the decision on
whether or not to implement mid-term and long-term improvements to BRWTF identified
in previous studies were noted, as described in the following sections.
1. pH
BRWTF finished water pH varied between 7.15 and 8.78 s.u. during the period of
data reviewed, as shown in Figure 2-13.
2. TOC Removal
Historical TOC removal at BRWTF was reviewed as summarized in the following.
BRWTF has consistently met the TOC removal mandated by the Stage 1
Disinfectants and Disinfection Byproducts Rule based on the running annual
average (RAA) of quarterly values, as illustrated in Figure 2-14.
Since mid 2002 the RAA TOC removal at BRWTF has declined, with several
individual monthly values falling below the required RAA.
3. Disinfection Byproduct Formation
Formation of currently regulated disinfection byproducts that result from
chlorination of drinking water was reviewed, as summarized below.
Trihalomethane and haloacetic acid formation in areas served by BRWTF
followed a seasonally recurring pattern with highest concentrations occurring in
mid to late summer, as shown in Figure 2-15 and 2-16, respectively.
Both trihalomethane and haloacetic acid formation show increasing trends in
peak concentration since mid 2002, which correlates with the trend of decreasing
TOC removal previously noted.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-13
City of Boulder BRWTF Multi-Barrier Approach Study Draft
4. Total Dissolved Solids and Sulfate
Review of total dissolved solids and sulfate data for BRWTF finished water reveal
the following:
TDS and sulfate levels in BRWTF finished water vary throughout the year, with
peak concentrations in late winter to early spring, as shown on Figure 2-17.
Because there are no treatment processes for inorganic ion removal currently
installed at BRWTF, TDS and sulfate concentrations in finished drinking water
essentially mirror those of BFC and Boulder Reservoir source waters.
E. Conclusions
Based on a review of the existing data with respect to this Study, B&V does not
see a need for additional water quality testing above and beyond that required for
Cryptosporidium
current regulatory compliance. Either grandfathered existing data or
source monitoring under LT2ESWTR, that would begin in October 2006 for the BRWTF,
will determine what if any level of additional treatment will be required by regulation.
The following summarizes the main findings of the data review.
1. Microbial Source Water Quality Data
The microbial quality of water conveyed directly to the BRWTF through the BFC
is at risk, with potential for high levels of fecal matter as a result of acute contamination
episodes. Routine water quality monitoring of BFC has demonstrated an increasing
Giardia
trend in fecal coliform contamination between 1997 and 2003. has routinely
Cryptosporidium
been detected in BFC water, and has been detected occasionally.
Protozoan contamination in Boulder Reservoir has been detected at much lower
concentrations compared to BFC. Based on samples collected from BFC and Boulder
Reservoir between 1997 and 2004, the BRWTF would fall into bin 1 under the
Cyptosporidium.
LT2ESWTR, requiring no additional treatment for
Caution should always be exercised when interpreting protozoan monitoring
results, particularly in untreated surface waters, where turbidity and suspended solids
may interfere with (oo)cyst recovery. Effective detection of protozoa in natural waters
requires separation from aggregated colloids and particles as well as other particles of
similar size. The filtration technique used in early Information Collection Rule
monitoring was notoriously unreliable for protozoan recovery and results based on this
method are highly suspect. The immunomagnetic separation technique used in EPA
Method 1623 is somewhat more reliable, but protozoan recovery from spiked natural
water samples using this technique is still routinely less than 50 percent. Finally, routine
monitoring samples only a very small fraction of 1 percent of total flow through BFC and
Boulder Reservoir, making the probability of capturing transient protozoan
contamination events unlikely.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-14
City of Boulder BRWTF Multi-Barrier Approach Study Draft
2. Physical and Chemical Source Water Quality Data
Analysis of physical, chemical, and biological source water quality data collected
in Boulder Reservoir between 1997 and 2004 indicates seasonal development of anoxic
conditions at depth in the reservoir. Anoxia in the reservoir hypolimnion can be
correlated with microbially mediated release of soluble manganese from bed sediment,
which is in turn entrained in water supplied to the BRWTF through a submerged intake
structure.
3. BRWTF Operational Water Quality Data
Review of operational data from BRWTF demonstrates trends of decreasing
TOC removal and increasing disinfection byproduct formation since mid 2002. Because
of the forthcoming shift from system-wide running annual average to locational running
annual average calculation of disinfection byproduct concentrations for compliance
purposes, the potential impacts of mid-term and long-term improvements on TOC
removal and DBP formation should be carefully considered.
CHAPTER 2 – BRWTF SOURCE WATER QUALITY2-15
lfate (mg/L)TDS, Su
liforms (cfu/100 mL)oFecal C
equencyrve fimmualtuC
E. coli
/100 mL)# (
/100 mL)#E. coli (
TDS, Sulfate (mg/L)
Fecal coliforms (cfu/100 mL)
TDS, Sulfate (mg/L)
g/L)mnganese (aM
g/L)me (atDO, Sulf
elcius)Cure (Temperat
pH
(Actual/Required)oti RalamovTOC Re
g/L)TTHM (
5
g/L) (HAA
TDS, Sulfate (mg/L)
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 3
BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS
This chapter describes the different categories of contaminant barriers, defined
by regulatory requirements and City finished water quality goals, for drinking water
produced at BRWTF with each of the source waters considered in this study. The three
water sources for BRWTF considered here were 1) seasonal use of the BFC and
Boulder Reservoir, 2) year-round use of Boulder Reservoir, and 3) direct conveyance to
BRWTF through a dedicated pipeline. These three sources provide distinctly different
raw water quality to BRWTF as discussed in Chapter 2, which impacts the combination
of drinking water treatment processes that best addresses contaminant barriers in a
cost-effective multi-barrier water delivery approach.
The BRWTF currently meets or exceeds all National Primary and Secondary
drinking water regulations during routine operation, and based on source water quality
data reviewed in Chapter 2, will likely continue to do so for the foreseeable future.
However, finished water quality in areas served by BRWTF is vulnerable to short-term
degradation due to seasonal variation in Boulder Reservoir water quality and acute
contamination episodes in either BFC or Boulder Reservoir. Of particular concern are
microbial contamination in BFC or Boulder Reservoir, DBP formation during treatment
and distribution, contamination by organic micro-pollutants in BFC and Boulder Reservoir,
seasonal manganese uptake, taste or odor episodes in Boulder Reservoir, and non-
uniform total dissolved solids (TDS) and sulfate concentration across the distribution
system when BRWTF uses Boulder Reservoir as its source.
Because these factors pose a potential threat to drinking water quality, the City has
established drinking water quality goals that are in some instances more stringent than
state or federal regulatory requirements to ensure public health. Appendix 1 lists the
&LW\¶VZDWHUTXDOLW\JRDOV)Rr the purposes of this study, the minimum contaminant
barrier requirements were those specified by enforceable USEPA and CDPHE Primary
Drinking Water Standards. Non-enforceable Secondary Drinking Water Standards were
also generally satisfied by all multi-barrier water delivery alternatives considered (Chapter
6). However, not all of the &LW\¶VGULQNLQJZDWHUTXDOLW\JRDOVwere fully satisfied by all
multi-barrier water delivery alternatives evaluated, primarily due to compelling economic
considerations.
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
A. Barriers for Microbial Pathogen Control
. Overview
1
Over the past two decades the Environmental Protection Agency (EPA) has
issued a series of increasingly stringent Drinking Water Regulations designed to protect
GiardiaCryptosporidium
the public from microbial pathogens such as viruses, , and that
may be present in surface water supplies. Because turbidity is often used as an
indicator of microbial water quality, it is also regulated in drinking water produced from
surface water sources. Relevant regulations include the Surface Water Treatment Rule
(SWTR), Interim Enhanced Surface Water Treatment Rule (IESWTR), Long-Term 1
Enhanced Surface Water Treatment Rule (LT1ESWTR), and most recently the Long-
Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). Each rule specifies
treatment techniques required to achieve specified levels of physical removal or
inactivation of specific microbial pathogens in drinking water.
Turbidity in water is caused by suspended particles that scatter or absorb
incident light, therebyUHGXFLQJWKHZDWHU¶VFODULW\Soil and mineral weathering products
and microorganisms including bacteria, algae, and protozoa are the principal sources of
turbidity in natural waters, either occurring naturally or as the result of agricultural,
municipal or industrial activity. The IESWTR established a combined filter effluent
(CFE) limit for turbidity of less than or equal to0.3 nephelometric turbidity units (NTU) in
at least 95 percent of monthly samples and a limit of 1 NTU for all samples, with
additional limits on individual filter effluent (IFE) turbidity. The City has set internal
water quality goals for turbidity of less than or equal to 0.1 NTU in at least 95 percent of
all IFE samples and less than 0.15 NTU for all CFE samples.
Turbidity removal is perhaps the oldest form of drinking water treatment,
traditionally relying on clarification and granular media filtration. Standard practice now
includes chemical pre-treatment that modifies particle surface chemistry to improve
removal. Enhanced clarification processes such as ballasted flocculation and dissolved
air flotation (DAF), as well as membrane filtration are also now being used to for
turbidity removal. BRWTF utilizes chemical pre-treatment, DAF, and granular media
filtration for turbidity control. Historical operating data indicates that turbidity in finished
water from BRWTF has exceeded 0.1 NTU 14 % of the time.
Cryptosporidium
Based on an improved understanding of occurrence in surface
waters and treatment process limitations, LT2ESWTR has established risk-targeted log-
Cryptosporidium
removal/inactivation levels for in addition to those specified in earlier
rules. The primary purposes of this rule are to protect public health from illness due to
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Cryptosporidium
and other microbial pathogens in drinking water and to address risk-
risk trade-offs with the control of disinfection byproducts. Because this regulation links
the required level of drinking water treatment with source water quality, a careful
evaluation of source water protection and treatment options is required to ensure public
health protection and regulatory compliance.
LT2ESWTR classifies source water quality into four bins based on average
Cryptosporidium
concentration and treatment type, and specifies associated levels of
additional treatment required. Table 3-1 lists the required levels of additional treatment
for WTPs that utilize conventional treatment consisting of chemical coagulation,
flocculation, clarification, and granular media filtration.
Table 3-1
LT2ESWTR Cryptosporidium Treatment Requirements for Conventional WTPs
BinCryptosporidium Concentration Additional Removal/Inactivation
Designation (oocysts/L) Treatment Required
1 Less than 0.075 None
2 0.075 or higher, but less than 1.0 1-log
3 1.0 or higher, but less than 3.0 2-log
4 3.0 or higher 2.5-log
As a public water system serving a population greater than 100,000, the City is
required to conduct 24 months of initial source water monitoring beginning in October
2006, or submit grandfathered existing monitoring data to establish average
Cryptosporidium
concentrations for LT2ESWTR bin determination at BRWTF. Historical
Cryptosporidium
monitoring data for Carter Lake, BFC, and Boulder Reservoir collected
between 1997 and 2006 indicate that these source waters would be classified in Bin 1
with respect to LT2ESWTR compliance, requiring no additional treatment for
Cryptosporidium
. However, if grandfathered existing data are not accepted by the
regulatory primacy agency, then LT2ESWTR bin classification would be based on the
results of source water monitoring beginning in October 2006. While these results are
not expected to vary significantly from historical data, they could potentially result in
Cryptosporidium
additional treatment regulatory requirements.
As part of its water quality goal setting process, the City has determined that a
minimum of one additional log-removal/inactivation of microbial pathogens above
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
regulatory requirements is prudent to protect public health. Table 3-2 lists the required
and target log-removal/inactivation for regulated microbial pathogens based on meeting
federal regulations and City water quality goals.
Table 3-2
Required and Target Log-Removal/Inactivation for Regulated Microbial Pathogens
Pathogen
Regulation/Goal
Viruses
GiardiaCryptosporidium
(1)
Regulatory Requirement 4 3 3
City Goal 5 4 5
(1)
Assumes LT2ESWTR Bin 1 classification.
(2)
Provides for potential BFC and Boulder Reservoir LT2ESWTR bin 2 classification.
2. Existing Barriers for Microbial Pathogen Control
Existing barriers for microbial pathogen control in place at BRWTF include
conventional treatment (coagulation, flocculation, dissolved air floatation, and granular
media filtration) and chemical disinfection with free-chlorine. The presumptive log-
GiardiaCryptosporidium
removal/inactivation of viruses, , and credited to conventional
treatment under the SWTR and IESWTR are listed in Table 3-3. The balance of virus
Giardia
and treatment required under the SWTR is currently provided by chemical
disinfection with free-chlorine.
Table 3-3
Regulatory Requirements and Additional Pathogen Removal/Inactivation
to Meet City Goals at BRWTF
Conventional Regulatory Additional Needed
Pathogen Disinfection
Treatment Requirement to Meet City Goal
Viruses 2 2 4 1
Giardia 2.5 0.5 3 1
**
Cryptosporidium 3 -- 32
*
Assumes LT2ESWTR Bin 1 classification.
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
3. Potential Additional Barriers for Microbial Pathogen Control
The LT2ESWTR Microbial Toolbox is a list of potential treatment options for
Cryptosporidium
additional removal/inactivation, as given in Table 3-4. Table 3-4 also
gives a preliminary evaluation of the potential applicability of these techniques at
BRWTF. Because of the pristine microbial quality of Carter Lake is low (Chapter 2,
section C.1.a), full containment of source water in a dedicated pipeline to BRWTF would
also provide an additional barrier.
Table 3-4
LT2ESWTR Microbial Toolbox
Treatment Removal/Inactivation
Applicability Comments
Technique Credit
Source Water Protection and Management
Watershed Control Program 0.5 Likely Treatment cost avoidance and
direct credit
Prefiltration
Presedimentation and Coagulation 0.5 Possible Reduces acute loading to BRWTF
Two-Stage Lime Softening 0.5 Unlikely Not required by source water
hardness
Bank Filtration ±Possible Boulder Reservoir delivery
alternative
Treatment Performance
Combined Filter Performance 0.5 Likely Presumptive operational credit
Individual Filter Performance 0.5 Likely Presumptive operational credit
Demonstration of Performance Variable Unlikely Requires state approved protocol
Additional Filtration
Bag and Cartridge Filters 2.0 singly, Possible Additional pumping, small footprint
2.5 in series
Membrane Filtration Demonstrated removal Possible Retrofit in existing filter boxes
efficiency
Second Stage Filtration 0.5 Unlikely Additional pumping likely
Slow Sand Filtration ±Unlikely Additional pumping likely
Inactivation
Chlorine Dioxide Based on LikelyManganese and taste & odor
measured CT control
Ozone Based on LikelyManganese and taste & odor
measured CT control
UV Based on validated UV LikelyAdvanced oxidation of EDCs with
dose HO
22
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
B. Barriers for Disinfection Byproduct Control
DBPs are compounds formed during drinking water treatment through reaction of
chemical disinfectants with either organic or inorganic constituents present in the source
water.
1. Overview
The most widespread and well documented class of DBPs is halogenated
organic compounds formed by reaction of free-chlorine and natural organic matter.
Typically, only 30 to 60 percent of halogenated organic DBPs are chemically
identifiable, with trihalomethanes (THMs) and haloacetic acids (HAAs) occurring in the
highest concentrations. The Stage 2 Disinfectants and Disinfection Byproduct Rule
(Stage 2 DBPR) standards for total THMs and five HAAs (HAA) are 80 and 60
5
micrograms per liter (g/L), respectively, measured as locational running annual
averages (LRAAs) at each monitoring site. The City has set internal water quality goals
of 40 g/L and 30 g/L for THMs and HAAs as LRAAs, respectively.
Disinfection of drinking water with ozone leads to formation of low-molecular
weight organic byproducts through oxidation of NOM, and bromate (BrO) by oxidation
3
of bromide (Br). The organic by-products are primarily aldehydes, ketoacids, and
carboxylic acids that are not currently believed to pose a health hazard and are
therefore not regulated in drinking water. Bromate is believed to be a human
carcinogen and is currently regulated by the Stage 1 Disinfectants and Disinfection
Byproduct Rule (Stage 1 DBPR) at 10 g/L, with a future maximum contaminant level
(MCL) of 5 g/L under consideration. The City currently has no internal water quality
goal for bromate.
Chlorine dioxide (ClO) is much less reactive with NOM compared with free-
2
chlorine or ozone, and produces very few halogenated organic DBPs. However, the
reduced inorganic byproducts chlorite (ClO) and chlorate (ClO) may be produced
23
during onsite ClO generation or by ClO oxidation of NOM and reduced iron or
22
manganese. Stage 1 DBPR set an MCL of 1 mg/L for chlorite. Chlorate is currently
not regulated in drinking water due to a lack of conclusive evidence regarding adverse
health effects. The City currently has no internal water quality goals for chlorite or
chlorate.
Combined-chlorine (NH&O±PRQRFKORUDPLQH
LVDOVRPXFKOHVVUHDFWLYHZLWK
2
NOM than free-chlorine, producing on average less than 20 and 50 percent of the THM
and HAA concentrations, respectively, at comparable disinfectant concentrations.
Reaction between combined-chlorine and certain cationic resins and polymers has
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
recently been implicated in the formation of nitrosodimethylamine (NDMA), which is
classified as a probable human carcinogen by USEPA. NDMA is not currently regulated
6
in drinking water, but has an estimated 10 cancer risk at 0.7 nanograms per liter
(ng/L), which is below the level often measured in chloraminated drinking water. The
City currently has no internal water quality goal for NDMA.
2. Existing Barriers for DBP Control
DBP precursor removal at BRWTF relies solely on TOC removal by enhanced
coagulation; alternative oxidants are not currently used, nor is activated carbon
adsorption applied. Although BRWTF has consistently met the treatment technique
requirement for TOC removal (Figure 2-
WKH&LW\¶V7+0DQG+$$ZDWHUTXDOLW\
goals have not been met consistently (Figures 2-15 and 2-16). Between 1998 and
WKH&LW\¶VJRDOVKDYe been exceeded in 56 to 70 percent of THM samples, and 65
to 90 percent of HAA samples, collected from locations served exclusively by the
BRWTF.
3. Potential Additional Barriers for DBP Control
Treatment technologies that seek to minimize DBP formation follow one of three
strategies related to the reactions between chemical disinfectants and organic or
inorganic source water constituents: 1) remove the undesirable byproduct once formed,
2) alter the reaction conditions so as to reduce byproduct formation, or 3) reduce or
remove one of the byproduct precursors. Because DBPs are generally non-volatile,
solid phase adsorption processes have long been viewed as candidates for DBP
removal from finished drinking water. Granular activated carbon (GAC) adsorption and
ion exchange (IX) have been extensively explored as treatment techniques for organic
and inorganic DBP removal, respectively. However, these processes have not been
widely deployed for DBP removal from finished drinking water because of limitations
including insufficient adsorption capacity, lack of specificity for targeted DBPs,
undesirable interactions with residual disinfectants, and operational and economic
considerations.
Controlling DBP formation by altering reaction conditions such as temperature or
contact time is of only limited value or practicality. Utilities have very little if any control
over source and finished water temperatures, and lowering water temperature during
treatment is economically unviable. Although the point(s) of disinfectant application
may sometimes be moved further downstream in the treatment process train,
disinfection contact time requirements and distribution system residence time limit the
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-7
City of Boulder BRWTF Multi-Barrier Approach Study Draft
extent to which contact time can be reduced. For these reasons, minimizing DBP
formation during drinking water treatment has largely focused on reducing or removing
DBP precursors, and has governed development of the interrelated set of microbial and
DBP regulations over the past decade.
Strategies for DBP precursor removal include use of alternative disinfectants,
precipitative NOM removal by enhanced coagulation, and NOM adsorption on activated
carbon. Ozone, chlorine dioxide, chloramines and UV light have been used to either
partially or completely replace free-chlorine, thereby lowering THM and HAA formation.
However, alternative chemical disinfectants do produce other DBPs as previously
discussed. Stage 1 DBPR mandates a treatment technique for NOM removal in
facilities that utilize conventional treatment of surface water based on source water total
organic carbon (TOC) and alkalinity concentrations, as indicated in Table 3-5.
Table 3-5
Percent TOC Removal Required by Enhanced Coagulation for
Surface Water Systems Utilizing Conventional Treatment
Source Water TOC Source Water Alkalinity (mg/L as CaCO)
3
(mg/L)
060>60120>120
> 2.0 to 4.0 35.0 25.0 15.0
> 4.0 to 8.0 45.0 35.0 25.0
> 8.0 50.0 40.0 30.0
Alternative Compliance Criteria:
(1) Source water TOC < 2.0 mg/L
(2) Finished water TOC < 2.0 mg/L
(3) Source water TOC < 4.0 mg/L, alkalinity > 60 mg/L as CaCO, TTHM < 40 g/L, and HAA <
3
30g/L
(4) TTHM < 40 g/L and HAA < 30g/L, and only chlorine used for disinfection and residual
maintenance
(5) Source water SUVA prior to any treatment 2.0 L/mgm
Â
(6) Treated water SUVA 2.0 L/mgm
Â
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-8
City of Boulder BRWTF Multi-Barrier Approach Study Draft
C. Barriers for Organic Micro-Pollutant Control
1. Overview
Organic micro-pollutants enter source waters from industrial and municipal
effluents, agricultural runoff, and unregulated waste discharge. These pollutants
encompass a wide range of chemical compounds with diverse physical and chemical
properties. Historically important classes of synthetic organic compounds (SOCs)
include solvents, plasticizers, propellants, petroleum additives, chemical intermediates,
herbicides, and pesticides. Emerging SOC classes of concern that are not currently
regulated include endocrinologically active compounds (EDCs), pharmaceutically active
compounds (PhACs), and personal care products (PCPs). Although SOCs typically
occur at low concentrations in source waters, and at trace levels in drinking water
supplies, many of these compounds are highly toxic or carcinogenic and therefore pose
a health risk if present in drinking water. There are currently national primary drinking
water standards for 62 SOCs and pending standards for another 38 listed in the
Contaminant Candidate List 2. The City currently has no internal water quality goal for
specific organic micro-pollutants.
2. Existing Barriers for Organic Micropollutant Control
There are currently no known industrial or municipal effluent discharges to Carter
Lake, BFC, or Boulder Reservoir; although, all three water sources for BRWTF are
subject to organic micro-pollutant contamination to varying degrees through surface
runoff and unregulated waste releases. Carter Lake is the least susceptible of BRWTF
sources because of its remote location, small catchment area and lack of natural
tributaries, and restricted adjacent land usage. Boulder Reservoir is somewhat more
vulnerable to organic micro-pollutant contamination due to natural tributaries and
ditches that flow in and extensive recreational use. BFC is highly vulnerable to organic
micro-pollutant contamination because of its extended length with virtually uncontrolled
access, numerous outfalls and street crossings, and adjacent residential, commercial,
agricultural, and recreational land uses. There are no dedicated SOC treatment
processes at BRWTF, and only very limited organic pollutant removal is provided by
DAF and co-precipitation during natural organic matter (NOM) coagulation.
3. Potential Additional Barriers for Organic Micropollutant Control
Organic micro-pollutant control in drinking water supplies utilizes watershed
management to limit effluent discharges, as well as treatment processes including air
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-9
City of Boulder BRWTF Multi-Barrier Approach Study Draft
stripping, chemical oxidation, coagulation, activated carbon adsorption, reverse
osmosis, and advanced oxidation for removal during treatment. Chemical
characteristics such as volatility, polarity, charge, molecular weight, and solubility,
determine which processes are appropriate for SOC removal during drinking water
treatment. Because the potential for introduction of organic micropollutants into Carter
Lake is low (Chapter 2, section C.1), full containment of source water in a dedicated
pipeline to BRWTF would also provide an additional barrier.
D. Barriers for Manganese Control
1. Overview
Manganese may be present in ground and surface waters that are in contact with
2+
manganese containing minerals, occurring as either soluble Mn (reduced form) or
precipitated MnO (oxidized form), depending on pH and oxygen concentration.
2
Aesthetic issues associated with manganese in drinking water include staining of
laundry and fixtures and unpleasant taste. Manganese concentrations of less than 0.5
milligrams per liter (mg/L) may promote bacterial growth in reservoirs and drinking water
distribution systems. Consumer complaints regarding aesthetic issues associated with
manganese in drinking water have been documented at concentrations as low as 0.02
mg/L. There are presently no known adverse health effects of manganese in drinking
water, but the USEPA has set a secondary maximum contaminant level (SMCL) for
manganese at 0.05 mg/L based on aesthetic concerns. The City has set an internal
goal of 0.03 mg/L for manganese in finished drinking water.
2. Existing Barriers for Manganese Control
Manganese concentrations in Carter Lake have historically been very low year-
round. Manganese concentrations increase only slightly as a result of conveying water
to BRWTF through BFC. However, seasonal manganese mobilization is routinely
observed in Boulder Reservoir during late summer and early fall due to hypolimnetic
anoxia produced by thermal stratification. Although the manganese concentration in the
hypolimnion of Boulder Reservoir exceeds tKH&LW\¶VJRDOLQRIVDPSOHVZLWK
levels of 0.5 mg/L to 1.0 mg/L not uncommon, manganese loading in BRWTF influent
has historically been minimized by using the low manganese BFC source almost
exclusively during periods when stratification results in mobilization. Because oxidation
2+
of Mn with oxygen and free-chlorine is relatively slow at pH less than 9.5, the
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-10
City of Boulder BRWTF Multi-Barrier Approach Study Draft
efficiency of manganese removal for the conventional treatment process configuration
currently in place at BRWTF may not be sufficient if Boulder Reservoir was used as the
water source year-round.
3. Potential Additional Barriers for Manganese Control
Manganese control during drinking water treatment most often involves oxidation
2+
of soluble Mn to particulate MnO, with subsequent removal by clarification or filtration.
2
Manganese removal through autocatalytic adsorption and oxidation on MnO coated
2
filter media surfaces is also practiced, and less frequently by ion exchange,
nanofiltration/reverse osmosis or precipitative softening. Because the potential for
soluble manganese release from bed sediments in Carter Lake is low (Chapter 2,
sections C.1.b and C.1.c), full containment of source water in a dedicated pipeline to
BRWTF would also provide an additional barrier.
E. Barriers for Taste and Odor Control
1. Overview
Objectionable tastes and odors in drinking water may occur due to the presence
of microbial metabolites and degradation products, anthropogenic volatile and synthetic
organic compounds, and naturally occurring inorganic compounds. Numerous microbial
species belonging to cyanobacteria, green algae, diatom, and flagellate groups that may
be present in surface waters produce odors variously described as sweet, grassy,
musty, earthy, swampy, fishy, and septic. Geosmin and 2-methylisoborneol (MIB) are
the most well known microbial odor-causing metabolites found in drinking water
supplies, producing earthy and musty odors, respectively. Medicinal and phenolic off-
tastes and odors are often associated with drinking water supplies developed from
source waters that receive organic solvents, pesticides, and petroleum products from
industrial effluent, agricultural runoff, and liquid waste disposal. Often, these chemicals
produce tastes and odors that are not directly attributable to a parent organic
compound, but rather to chlorinated disinfection byproducts that occur in discharged
waste effluents or finished drinking water. Thermal stratification in lakes and reservoirs
often leads to anaerobic conditions at depth, releasing inorganic taste and odor
2+2+
compounds through mobilization of soluble iron and manganese (Fe and Mn) from
insoluble oxide minerals in bottom sediments, as well as sulfide production. There are
currently no national drinking water regulations for taste; however, USEPA has set a
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-11
City of Boulder BRWTF Multi-Barrier Approach Study Draft
SMCL for odor at a threshold odor number of 3. The City has set an internal water
quality goal of no detectable tastes or odors in finished drinking water.
2. Existing Barriers for Taste and Odor Control
BRWTF currently depends largely on source water control strategies for taste
and odor control, as chemical oxidation with free-chlorine is only marginally effective at
controlling algal metabolites and oxidizing soluble manganese. Algicides are
periodically applied in BFC, but not to Carter Lake or Boulder Reservoir. There is no
aeration for volatile organic removal or activated carbon or ion exchange processes for
soluble contaminant removal, nor is there is a routine monitoring program for seasonal
.
formation of algal taste and odor compounds in Carter Lake, BFC, or Boulder Reservoir
3. Potential Additional Barriers for Taste and Odor Control
Taste and odor control in drinking water supplies may rely on source water
management or removal during treatment, or frequently a combination of both
strategies. Source water management strategies include lake and reservoir aeration,
chemical inhibition of algal growth, watershed management to limit nutrient input, and
effluent discharge restrictions. Chemical characteristics of taste and odor compounds
such as volatility, polarity, charge, molecular weight, and solubility, determine which
processes are appropriate for their removal during drinking water treatment. Treatment
processes commonly used for taste and odor control include aeration, chemical
oxidation, activated carbon adsorption, ion exchange, and precipitation. Because the
potential for objectionable taste or odor episodes in Carter Lake is low (Chapter 2,
section C.1.c), full containment of source water in a dedicated pipeline to BRWTF would
also provide an additional barrier.
F. Barriers for Inorganic Contaminant Control
1. Overview
Natural waters contain a variety of inorganic constituents that occur primarily as
the result of mineral weathering and leaching reactions in soil, sediment, and rock
formations; although, industrial, municipal, agricultural, and surface runoff effluents may
in some instances contribute inorganic constituents. Inorganic constituents typically
occur in ionic form in aqueous solution, and may be present as suspended and colloidal
solids or dissolved species. Major cations (positively charged) in natural waters include
sodium, potassium, calcium, magnesium, iron, and manganese; whereas, major anions
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-12
City of Boulder BRWTF Multi-Barrier Approach Study Draft
(negatively charged) include bicarbonate, chloride, sulfate, sulfide, nitrate, nitrite,
fluoride, and silicate. Other trace inorganic constituents that may be present in source
waters are alkali and alkaline metals, other metallic elements, and nonmetals. There
are currently National Primary Drinking Water Standards for 16 inorganic elements and
compounds, and National Secondary Drinking Water Standards for 10 inorganics.
There is also a National Secondary Drinking Water Standard for pH of 6.5 to 8.5
standard units (s.u.), as an indicator of finished water quality and corrosivity. The City
has set internal water quality goals for sodium (5 to 20 mg/L), sulfate (less than 5 mg/L),
TDS (less than 125 mg/L), fluoride (0.9 0.1 mg/L), and pH (7.8 0.2 s.u.) that are
more restrictive than required by state and federal regulations.
2. Existing Barriers for Inorganic Contaminant Control
BRWTF utilizes conventional treatment for suspended and colloidal inorganic
contaminant removal. No dedicated processes for dissolved inorganic contaminant
removal are currently in placHDW%5:7)7KH&LW\¶VZDWHr quality goals for sulfate and
TDS have historically been routinely exceeded (see Figure 2-17). In addition, finished
water pH at the BRWTF has routinely been RXWVLGHWKH&LW\¶VGHVLred range, exceeding
the upper limit and falling below the lower limit 10 percent and 42 percent of the time,
respectively.
3. Potential Additional Barriers for Inorganic Contaminant Control
Suspended and colloidal inorganic constituents may be effectively removed from
source waters by standard treatment methods including coagulation, clarification, and
filtration. However, with the exception of several regulated metals, dissolved inorganic
constituents are typically only poorly removed by these methods, if at all. The
concentrations of multivalent ions may be reduced by precipitative softening or ion
exchange, but reverse osmosis is the only practical treatment method to lower TDS or
remove monovalent ions. Because the potential for naturally-occurring or human-
induced inorganic contamination in Carter Lake is very low (Chapter 2, section C.1.c),
full containment of source water in a dedicated pipeline to BRWTF would also provide
an additional barrier.
CHAPTER 3 – BRWTF DELIVERY ALTERNATIVE CONTAMINANT BARRIERS3-13
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 4
BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA
This chapter describes the criteria developed as part of a structured K-T
decision analysis model used to select a preferred multi-barrier water delivery
alternative for BRWTF. This set of decision criteria forms the basis of a fair and
balanced evaluation of BRWTF multi-barrier water delivery alternatives. City staff
developed decision model criteria in 5 categories including finished water quality,
source water, treatment operations, risk, and environmental and public acceptance.
A set of preliminary decision model performance criteria was presented to City
staff by Black & Veatch in a workshop held on August 16, 2006. Over the next several
months, an ad hoc committee (BRWTF Multi-Barrier Project Working Group)
representing drinking water quality, water resources, operations, and senior
management functions refined the preliminary decision model performance criteria
through a series of scheduled meetings and informal communications. Based on the
collective expertise and experience of the Project Working Group members, the set of
decision model performance criteria ultimately chosen was reviewed and finalized in a
workshop held on December 14, 2006.
A. Mandatory MUST Criteria
As described in Chapter 1, performance criteria in K-T decision analysis are
classified either as MUST criteria that each candidate problem solution must absolutely
satisfy in order to be included in the decision process, or WANT criteria that are
desirable but not mandatory for each candidate problem solution to satisfy. Two MUST
decision criteria were developed by the Project Working Group.
1. Regulatory Compliance
For a candidate decision model alternative to be considered as an acceptable
BRWTF multi-barrier water delivery approach it must be capable of continuously
meeting all enforceable USEPA and CDPHE drinking water regulations and standards.
This MUST criterion assumes that BRWTF will be adequately maintained and operated
in accordance with its design specifications. Furthermore, this MUST criterion assumes
that only raw water delivered through BFC, pumped from Boulder Reservoir, or
conveyed directly from Carter Lake through a dedicated pipeline will be utilized at
BRWTF.
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
2. Water Rights Portfolio Yield
Each candidate BRWTF multi-barrier water delivery alternative must be capable
of maintaining the current expected yield of the City’s water rights portfolio and must not
reduce the current level of flexibility in selecting drinking water sources from its water
rights portfolio.
B. Desirable WANT Criteria
The Project Working Group developed 28 decision model performance criteria in
5 categories including finished water quality, source water, treatment operations, risk,
and environmental and public acceptance, as listed in the following sections. These
criteria are satisfied by the BRWTF multi-barrier water delivery alternatives outlined in
Chapter 5 to varying degrees.
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
1. Finished Water Quality Criteria
Finished water quality WANT criteria related to each of the contaminant barrier
categories detailed in Chapter 3 were incorporated including pathogens, disinfection by-
products, organic micropollutants, manganese, taste and odor, and inorganic
contaminants, as listed in Table 4-1.
Table 4-1
Finished Water Quality Criteria for BRWTF Multi-Barrier Water Delivery Alternatives
CriteriaComments
Pathogens What are the recent trends in microbial water
quality in BFC, Boulder Reservoir, and Carter
Lake? How likely are acute pathogenic
contamination events in these raw water sources?
Are barriers sufficient to prevent pathogens from
passing through BRWTF at levels that could
jeopardize public health?
Disinfection Byproducts Which DBPs will be formed and at what levels?
Can source water as well as treatment controls be
used to minimize DBP formation?
Organic Micro-Pollutants How significant is the potential risk of organic
chemical contamination during source water
conveyance or storage? To what extent can
treatment processes mitigate acute or chronic
organic chemical contamination?
Manganese What is the extent and duration of seasonal
manganese mobilization? Can source water as
well as treatment controls be used to limit
manganese concentrations?
Taste and Odor What is the extent and duration of seasonal taste
and odor episodes associated with algal blooms
or manganese mobilization? Can source water as
well as treatment controls be used to minimize
objectionable tastes and odors?
Inorganic Contaminants What is the potential for inorganic contamination
during source water conveyance or storage? Can
source water as well as treatment controls be
used to mitigate inorganic contamination?
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
2. Source Water Portfolio Criteria
Decision model performance criteria related to management of the City’s source
water portfolio were identified, as listed in Table 4-2.
Table 4-2
Source Water Conveyance Criteria for BRWTF Water Delivery Alternatives
CriteriaComments
Source Water Quality Consistency What is the extent of seasonal and short-term
source water quality fluctuation to BRWTF? Do
these fluctuations impact treatment at BRWTF
and for how long?
Water Rights Yield What is the availability of raw water for direct use?
Is the ability to manage stored reservoir water
throughout the year and during droughts
maximized? Can water rights yield be increased
through enhanced water management or capacity
of facilities?
Portfolio Flexibility How many options are available for delivering raw
water to BRWTF? How difficult is it to switch
water sources in response to changing
conditions? Are there seasonal limitations on use
of raw water sources?
Availability of Raw Water Delivery Facilities What is the expected reliability of infrastructure for
raw water delivery to BRWTF? What are the
capacity limitations of these delivery methods?
Are their restrictions on the use of water delivery
infrastructure due to external factors that affect
operations or water quality?
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
3. Water Treatment and Operations Criteria
Decision model performance criteria related to water treatment and BRWTF
operations were identified, as listed in Table 4-3.
.
Table 4-3
Water Treatment and Operations Criteria for BRWTF Water Delivery Alternatives
CriteriaComments
Worker Safety What types and amounts of treatment or cleaning
chemicals that staff will be exposed to? What are
the durations of these exposures? Will staff be
exposed to high voltage electrical shock hazards?
Are physically intensive maintenance procedures
such as cleaning intake grates required?
Process Flexibility What is the maturity and robustness of treatment
technologies? Is the number of treatment process
technologies required to provide required
contaminant barriers minimized?
Process Reliability Is raw water delivered with consistent quality and
flow? Can consistent year-round treatment be
provided with minimal process failure?
Process Redundancy Are multiple barriers provided for contaminant
categories of concern? Is back-up capability
provided for critical treatment operations?
Maintenance Can all maintenance be performed by City staff or
will an outside contractor be required? Will routine
replacement of consumable items such as lamps
or membranes be required?
StaffingWhat are the levels of staffing and supervision
required? What levels of expertise and
certification are required?
Residuals Processing What are the quantities and characteristics of
residuals produced by new treatment processes?
Will residuals disposal require special
environmental permitting?
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
4. Risk Criteria
Decision model performance criteria associated with risk of source water
contamination, adverse impact of additional regulatory requirements on BRWTF
operations, infrastructure vulnerability, and chemical usage and delivery were identified,
as listed in Table 4-4.
Table 4-4
Risk Criteria for BRWTF Water Delivery Alternatives
CriteriaComments
Acute Contamination What is the potential for acute or “slug-loading” of
contaminants that could disrupt or disable water
delivery from BRWTF either temporarily or long
term? Is there potential for undetected
breakthrough of these contaminants?
Chronic Contamination What is the risk associated with non-point
contaminant sources in BRWTF raw water
supplies that could pose a threat to public health?
Are these contaminants difficult to remove or
inactivate through treatment?
Adaptability to Change What is the risk to public health associated with
potential near- and long-term source water quality
degradation? What is the potential for future
regulatory non-compliance?
Infrastructure Vulnerability Whatis the likelihood that damage to
infrastructure could impede purveyance or
treatment of the potable water supply?
Consumable Delivery/Usage Are there consumables such as process specific
chemicals, membranes, or lamps that would
impede treatment or public health protection if
delivery was interrupted? To what extent are
alternate sources of these critical treatment
consumables available?
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
5. Environmental and Public Acceptance Criteria
Decision model performance criteria associated with environmental and public
acceptance issues specific to BRWTF were identified, as listed in Table 4-4.
Table 4-5
Environmental and Public Acceptance Criteria for BRWTF Water Delivery Alternatives
CriteriaComments
Adjacent Land Use CompatibilityAre there critical wildlife habitats, archeologically
sensitive, or historically significant lands adjacent
to conveyance structures? What impact might
adjacent agricultural, industrial, commercial,
recreational, and residential tracts have on
conveyance?
Finished Water Uniformity How uniform is finished water quality across the
distribution system? Does finished water from
BRWTF meet City water quality goals?
Construction What are the land area footprint and associated
restoration requirements? Will extensive
underground excavation and associated materials
handling be required?
Consumer Confidence What is the level of consumer confidence with
finished water delivered from BRWTF?
PermittingAre there sensitive environmental or public
acceptance issues that would make required
permitting difficult? What measures are available
to mitigate these concerns?
Energy Requirements What are the operational energy requirements
and what are their secondary environmental
effects? Is there potential for renewable energy
generation?
CHAPTER 4 – BRWTF MULTI-BARRIER APPROACH DECISION CRITERIA4-7
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 5
BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT
The integration of source water protection and treatment technologies into multi-
barrier water delivery approaches for BRWTF is detailed in this chapter. Additional
conceptual improvements recommended in the Phase I Source Water Protection Study
and Predesign Report including full containment from Carter Lake to BRWTF, UV light
disinfection, membrane filtration, ozone, and GAC were considered here. Barriers for
microbial pathogen control listed in the LT2ESWTR Microbial Toolbox (Table 3-4) were
also considered in this study.
A. Conceptual Improvement Screening
Conceptual improvements that could be included in a multi-barrier water delivery
alternative at BRWTF were screened for applicability based on several factors including
integration with the existing treatment process train, probable performance, and
economic considerations. Potential conceptual improvements were evaluated based on
their ability to address one or more of the contaminant barriers identified in Chapter 3
including microbial pathogens, DBPs, organic micropollutants, manganese, taste and
odor, and TDS and sulfate. The general strategy of the screening process was to give
greater consideration to conceptual alternatives that where possible addressed more
than one contaminant barrier, thereby minimizing the number of conceptual
improvements and complexity of proposed multi-barrier water deliver alternatives.
1. Source Water Protection
Full containment from Carter Lake to BRWTF was the only source water
protection improvement considered in this study. Other strategies such as large scale
improvements to storm-water diversion along BFC or around Boulder Reservoir, BFC
road crossings, and hydraulic structures were not recommended in the Phase I source
water protection study, and were beyond the scope of this study.
2. Prefiltration
Prefiltration options in the LT2ESWTR Microbial Toolbox, including pre-
sedimentation, two-stage lime softening, and bank filtration, receive low
inactivation/removal credit were not selected for inclusion in multi-barrier alternatives.
These treatment processes could provide an additional minimal barrier for pathogens,
but would not generally provide substantial additional barriers for other contaminant
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
categories. Because of the mineralized soils that contribute to manganese and TDS
increases while raw water is held in Boulder Reservoir, bank filtration could even lead to
raw water quality degradation.
. ,
3. Treatment Performance
Combined filter effluent and individual filter effluent performance credit was
considered an effective component of any multi-barrier treatment alternative. These
Cryptosporidium
options assign additional log-inactivation/removal credit based on
maintaining filter turbidity levels below target values, thus require no additional
treatment processes. BRWTF has a treatment process optimization program in place,
so additional contaminant barrier credit based on demonstration of further enhanced
performance is unlikely, and was not considered in this study.
4. Additional Filtration
Additional filtration technologies including bag or cartridge filters, membrane
filtration, second stage granular media filtration, and slow sand filtration were not
included in multi-barrier water delivery alternatives evaluated in this study. As with the
prefiltration options previously discussed, these additional filtration options would
Cryptosporidium
generally only provide additional log-inactivation/removal credit for ,
and provide little in the way of additional barriers for other contaminant categories. The
hydraulic profile of the existing BRWTF would also not accommodate additional filtration
without substantial supplemental pumping, increasing O&M costs. The limited benefit of
additional filtration to finished water quality of the well designed and operated full-
conventional treatment provided by the existing BRWTF were not viewed as sufficient to
justify the associated large capital cost, increased O&M costs, and additional filter
backwash/cleaning requirements.
5. Oxidation/Inactivation
Chemical oxidation can potentially provide additional barriers for microbial pathogens,
DBPs, organic micropollutants, manganese, and objectionable tastes and odors,
depending on the oxidant used and its point of application. Addition of chlorine dioxide
IRU'%3PDQJDQHVHDQGWDVWHDQGRGRUFRQWUROLVLQFOXGHGLQWKH&LW\¶VPLGWHUP
improvements plan, and is therefore assumed as part of the baseline treatment for the
long-term improvements evaluated here. Ozone was also evaluated in this study
because of its superior performance for taste and odor control, ability to oxidize many
organic micropollutants, and additional pathogen inactivation. UV disinfection was also
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
evaluated due to its superior disinfection performance for bacteria, viruses, and
protozoan pathogens. These treatment processes result in relatively low headloss,
simplifying their integration with the existing hydraulic profile at BRWTF.
6. GAC Adsorption
Granular activated carbon was evaluated in this study based on additional barriers for
DBPs, organic micropollutants, and objectionable tastes and odors that it may provide.
Although GAC adsorption has headloss restrictions similar to the filtration technologies
previously considered, the multiple potential finished water quality benefits that it may
provide were viewed as sufficient to warrant the added complexity and cost of
integrating this process into the existing BRTWF hydraulic profile.
B. Grouping Conceptual Improvements into Delivery Alternatives
Candidate multi-barrier approaches were developed for BRWTF by combining
conceptual improvements that address identified drinking water quality vulnerabilities in
source water conveyance to and treatment at BRWTF. Only those conveyance and
treatment barriers that were selected in the screening process previously described
were included in BRWTF multi-barrier alternatives. The combination of conceptual
improvements selected for each delivery alternative was based on providing process
redundancy and operational continuity at BRWTF.
Not all possible combinations of screened barriers were included in alternative
evaluations, but each screened barrier was incorporated in at least one water delivery
alternative. The multi-barrier delivery alternatives developed for this study would
produce finished water that meets all current state and federal drinking water standards;
however, it is important to note that not all of these alternatives continuously meet the
&LW\¶VGULQNLQJZDWHUJRDOVDVGLVFXVVHGEHORZ
1. BFC and Boulder Reservoir Seasonal Delivery Alternatives
Three water delivery alternatives that provide seasonal raw water delivery to
BRWTF through BFC or by pumping from Boulder Reservoir were developed, as shown
schematically on Figures 5-1 through 5-3. Each of these delivery alternatives is based
on the existing conventional treatment at BRWTF and residual disinfection with free
chlorine. In addition, chlorine dioxide preoxidation added as part of the ongoing mid-
term improvements program was also assumed.
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Alternative 1A: This water delivery alternative incorporates preoxidation
with chlorine dioxide followed by full conventional treatment and free
chlorine disinfection. A centralized contact basin for preoxidation contact
time is included to allow use of both BFC and Boulder reservoir raw water
sources. Presedimentation for turbidity and suspended solids control
would also be provided by the preoxidation contact basin, but because no
coagulant would be added prior to basin contact no credit towards
Cryptosporidium
treatment would be provided. Residual chlorine dioxide
and chlorite would be quenched by ferrous sulfate addition prior to
coagulation.
This barrier combination serves as the baseline BRWTF multi-barrier
This baseline alternative would not meet the
water delivery alternative.
City’s water quality goals with respect to pathogen control, nor would it
meet finished water TDS and sulfate goals when raw water is provided
from Boulder Reservoir. No effective barrier for organic micropollutant
control is provided by this alternative.
Alternative 1B: This alternative incorporates UV disinfection with the
This delivery alternative would not
barriers provided by Alternative 1A.
meet the City’s TDS and sulfate water quality goals when Boulder
Reservoir was online, nor would it provide an effective barrier for organic
micropollutant control.
Alternative 1C: This alternative adds both GAC adsorption and UV
disinfection to the contaminant barriers provided by baseline Alternative
This delivery alternative would not meet the City’s TDS and sulfate
1A.
water quality goals when raw water was supplied from Boulder Reservoir.
2. Boulder Reservoir Year-Round Delivery Alternatives
Three water delivery alternatives that provide year-round raw water delivery to
BRWTF by pumping from Boulder Reservoir were developed, as shown schematically
on Figures 5-4 through 5-6. Each of these delivery alternatives is based on the existing
conventional treatment at BRWTF and residual disinfection with free chlorine. In
addition, chlorine dioxide preoxidation added as part of the ongoing mid-term
improvements program was also assumed.
Alternative 2A: This water delivery alternative incorporates preoxidation
with chlorine dioxide followed by full conventional treatment and free
chlorine disinfection. A centralized contact basin for preoxidation contact
time is included to allow use of both BFC and Boulder reservoir raw water
sources. Presedimentation for turbidity and suspended solids control
would also be provided by the preoxidation contact basin, but because no
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
coagulant would be added prior to basin contact no credit towards
Cryptosporidium
treatment would be provided. Residual chlorine dioxide
and chlorite would be quenched by ferrous sulfate addition prior to
coagulation.
This water delivery alternative provides the same treatment processes as
baseline BRWTF multi-barrier water delivery Alternative 1A, with reservoir
dilution as an additional barrier against acute contamination events that
This water
may occur during raw water conveyance through BFC.
delivery alternative would not meet the City’s water quality goals with
respect to pathogen control, nor does it meet finished water TDS and
sulfate goals. No effective barrier for organic micropollutant control is
provided by this alternative.
Alternative 2B: This alternative incorporates UV disinfection with the
This delivery alternative would not
barriers provided by Alternative 2A.
meet the City’s TDS and sulfate water quality goals, nor would it provide
an effective barrier for organic micropollutant control.
Alternative 2C: This alternative adds ozone oxidation to the contaminant
This water delivery
barriers provided by baseline Alternative 2A.
alternative would not meet the City’s water quality goals with respect to
pathogen control during cold weather operation at BRWTF, nor would it
meet finished water TDS and sulfate goals.
3. Carter Lake Pipeline Delivery Alternative
Because a dedicated pipeline from Carter Lake for raw water delivery to BRWTF
provides barriers for each contaminant category except DBP control, only one water
alternative using this delivery method was developed, as shown schematically on Figure
5-7. This alternative utilizes the existing conventional treatment at BRWTF and residual
disinfection with free chlorine. In addition, chlorine dioxide preoxidation added as part
of the ongoing mid-term improvements program was also assumed.
Alternative 3: Carter Lake pipeline for turbidity, suspended solids,
manganese, taste and odor, organics, DBP, and inorganics control; and
ozone followed by biologically active filtration for pathogen and additional
This water delivery alternative
taste and odor, organics, and DBP control.
meets all the City’s water quality goals, and provides at least one barrier
for each contaminant category evaluated.
4. Water Delivery Alternatives Summary
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
The candidate water delivery alternatives outlined here integrate a range of
conceptual improvements with existing treatment processes to provide multi-barrier
approaches for drinking water treatment at BRWTF. Table 5-1 summarizes the barriers
provided in each alternative for identified water quality vulnerabilities.
Table 5-1
Barriers for Water Quality Vulnerabilities at BRWTF
Alternative Pathogens DBPsOrganicMnTaste & TDS/
Micro-OdorSulfate
pollutants
1A ClOClONB
ClONBClO
222 2
Conv. treat. Conv. treat. Conv. treat.
NaOCl
1B ClOClONBClOClONB
2 22 2
Conv. treat. Conv. treat. Conv. treat.
UV
NaOCl
1C ClOClOGACClOClONB
2 2 2 2
Conv. treat. Conv. treat. Conv. treat. GAC
NaOCl GAC
2A ClOClONBClOClONB
2 2 22
Conv. treat. Conv. treat. Conv. treat.
NaOCl
2B ClOClONB
ClONBClO
2222
Conv. treat. Conv. treat. Conv. treat.
UV
NaOCl
2C ClOClOAOPClOClONB
2222
Conv. treat. Conv. treat. Conv. treat. AOP
AOP AOP AOP
NaOCl
3 Pipeline ClOPipeline Pipeline Pipeline Pipeline
2
ClOConv. treat. ClOClO
222
Conv. treat.
NaOCl
Abbreviations:
ClO±FKORULQHGLR[LGH&RQYWUHDW±FRQYHQWLRQDOWUHDWPHQW1D2&O±IUHHFKORULQH1%±QR
2
EDUULHU89±XOWUDYLROHWOLJKWGLVLQIHFWLRQ*$&±JUDQXODUDFWLYDWHGFDUERQDGVRUSWLRQ$23±
advanced oxidation process (ozone/HO).
22
As indicated in Table 5-1 BRWTF candidate water delivery alternatives 1A, 1B,
2A, and 2B do not provide effective barriers for organic micropollutants and only
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
alternative 3 provides TDS and sulfate in finished water that is consistent with City
drinking water goals. AlternatLYHV$$DQG&DOVRGRQRWVDWLVI\WKH&LW\¶VILQLVKHG
Cryptosporidium
water quality goals for control, as shown in Table 5-2.
Table 5-2
Microbial Pathogen Barriers for BRWTF Delivery Alternatives
BarrierViruses
Cryptosporidium Giardia
Conventional Treatment 3.0 2.5 2.0
(1)
Combined Filter Performance 0.5 0.5
(1)
Individual Filter Performance 0.5 0.5
(2)
Chlorine Dioxide 0.02/0.06 0.67/1.58 0.96/2.39
(3)
Ozone0.52/1.60 12.49/31.55 26.64/66.60
(4)
Free Chlorine 0.54/1.21 12.33/30.15
(5)4.0 4.0 0.5
UV Disinfection
(6)1.5 1.5
Pipeline
Viruses
Cryptosporidium Giardia
Alternative
4.02/4.064.71/6.29 15.29/34.54
1A
8.02/8.06 8.71/10.29 15.79/35.04
1B
8.02/8.06 8.71/10.29 15.79/35.04
1C
4.02/4.064.71/6.29 15.29/34.54
2A
8.02/8.06 8.71/10.29 15.79/35.04
2B
4.54/5.66 17.20/37.84 41.93/101.1
2C
5.52/5.56 6.21/7.79 15.29/34.54
3
City Goal 5.0 4.0 5.0
(1)
Assumes same log-removal as for Cryptosporidium because Giardia is substantially larger.
(2)
LT2ESWTR log-inactivation credit: 1 mg/L chlorine dioxide residual, 10 min. contact.3C and 15C.
(3)
LT2ESWTR log-inactivation credit: 1 mg/L ozone residual, 10 min. contact, 3C and 15C.
(4)
LT2ESWTR log-inactivation credit: 1 mg/L free chlorine residual, 10 min. contact, 3C and 15C.
(5)2
LT2ESWTR log-inactivation credit, UV dose 40 mJ/cm, no temperature dependence.
(6)
Cryptosporidium and Giardia log-removal set equal to equivalent log-removal based on ratio of historical
bacterial concentrations in BFC and Carter Lake.
CHAPTER 5 – BRWTF MULTI-BARRIER ALTERNATIVE DEVELOPMENT5-7
Primary MCLSecondary MCL
Primary MCLSecondary MCL
Primary MCLSecondary MCL
Primary MCLSecondary MCL
Primary MCLSecondary MCL
Primary MCLSecondary MCL
Primary MCLSecondary MCL
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 6
BRWTF MULTI-BARRIER APPROACH PERFORMANCE EVALUATION
The relative performance of multi-barrier water delivery alternatives developed in
Chapter 5 was evaluated using the K-T decision analysis procedure outlined in
Chapter 1. The complete non-economic performance decision model including decision
statement, criteria developed in Chapter 4, and multi-barrier water delivery alternatives
developed in Chapter 5 is shown in Figure 6-1. Each water delivery alternative was
ranked by its ability to satisfy the non-economic performance criteria relative to all other
alternatives.
A. Non-Economic Performance Criteria Weighting
The set of non-economic performance criteria developed in Chapter 4 were
evaluated for their relative importance in selecting a multi-barrier water delivery
alternative for BRWTF. City staff assigned each performance criteria a weight between
1 and 10, with the highest value for the most important criteria. An ad hoc committee
(BRWTF Multi-Barrier Project Working Group) representing drinking water quality, water
resources, operations, and senior management functions held a series of informal
meetings and communications to develop a preliminary set of performance criteria
weights based on the collective expertise and experience of the committee members.
These preliminary criteria weights were formalized based on the dialog of a workshop
held on December 14, 2006 between working group members and Black & Veatch.
Table 6-1 lists the relative weights assigned to each decision criteria.
As part of the K-T decision analysis process, the weight assigned to each
criterion was normalized such that the sum of normalized criteria weights is equal to 1.0.
Normalized criteria weights are termed priorities, as shown in Table 6-1. It should be
noted that this normalization process does not change the relative importance of each
criterion weight in determining water delivery alternative scores.
B. BRWTF Multi-Barrier Alternative Performance Scores
The multi-barrier alternatives developed in Chapter 5 were ranked against the
weighted decision criteria listed in Table 6-1. The project Working Group first
established the relative performance of each water delivery alternative against each
decision criterion in turn by assigning scores between 1 and 10, with the highest value
CHAPTER 6 – MULTI-BARRIER APPROACH PERFORMANCE EVALUATION6-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
for the alternative(s) that best satisfied the intent of the criterion. It is important to note
that assigning a score of 10 to an alternative for any given criterion does not imply that
the alternative satisfies the criterion perfectly, but rather that it most closely satisfies the
intent of the criterion. Remaining alternatives were assigned lower scores based on
their ability to satisfy the given criterion relative to the alternative that best satisfies that
criterion.
The general approach taken in ranking BRWTF water delivery alternatives
against each criterion was that wherever possible prevention of contamination during
raw water delivery to BRWTF is a superior strategy to subsequent treatment at BRWTF.
The working group developed a preliminary set of guidelines for scoring alternatives
against each criterion, as listed in Appendix 2. Minor changes discussed in a workshop
held January 18, 2007 with the project Working Group and Black & Veatch were
incorporated with the preliminary guidelines to formalize the multi-barrier water delivery
scoring process. Worksheets used during BRWTF multi-barrier water delivery
alternative scoring are given in Appendix 2.
In the K-T decision analysis process performance scores for each alternative
are calculated as the sum of the products of decision model criteria priorities and each
set of respective alternative rankings.These performance scores are expressed on a
scale of 0 to 1, with a higher values indicating better alternative performance. As shown
in Table 6-1, non-economic performance scores for the BRWTF water delivery
alternatives evaluated in this study were clustered between 0.5 and 0.6 for all but
Alternative 3, which had a performance score of 0.94
CHAPTER 6 – MULTI-BARRIER APPROACH PERFORMANCE EVALUATION6-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 7
BRWTF MULTI-BARRIER APPROACH ECONOMIC EVALUATION
The relative economic merit of multi-barrier water delivery alternatives developed
in Chapter 5 was evaluated based on a life-cycle cost present value analysis that
included capital, operation and maintenance (O&M), and project financing costs.
A. Economic Evaluation Principles and Parameters
The economic analysis performed in this study was based on applying a common
set of unit process and O&M costs to each BRWTF multi-barrier water delivery
alternative. The level I planning cost opinions presented here reflect use of standard
engineering practices and were prepared without the benefit of detailed engineering
designs. Level I cost opinions of this type are generally considered to have an accuracy
range of plus 40 to minus 10 percent. Any actual project cost would depend on current
labor and material costs, competitive market conditions, final project scope, bid date,
and other variable factors.These cost opinions are perhaps best used to compare
relative multi-barrier water delivery alternative costs, rather than actual project costs.
A 30 year life-cycle was assumed for each water delivery alternative evaluated
consistent with industry standard expected service lives for major drinking water
treatment equipment. Because the expected useful life of large diameter subterranean
transmission mains is considerably longer than 30 years, the residual value of the
Carter Lake Pipeline beyond this time was credited to the net present value cost opinion
for Alternative 3. Useful life for large diameter welded steel pipe of the type proposed
for the Carter Lake Pipeline was conservatively estimated using representative survival
functions to be 70 years (Quantifying Future Rehabilitation and Replacement Needs of
Water Mains, AWWARF, 1998). Other common economic analysis parameters used
include a 2007 baseline, an O&M inflation rate of 4 percent, a loan interest rate of 6
percent, and a present worth factor of 4 percent.
B. Capital Cost Opinions
Capital cost opinions include material and construction estimates for process
equipment and basins, any additional structures needed to house process equipment,
electrical service, instrumentation and control, site work, yard piping, and general
contracting. Engineering, legal, and administrative expenses were estimated to be 20
percent of the material and construction cost subtotal. Similarly, a contingency factor of
CHAPTER 7 – MULTI-BARRIER APPROACH ECONOMIC EVALUATION7-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
25 percent was applied to the material and construction subtotal. Present value life-
cycle capital cost opinions were generated using the economic parameters given above
for a firm capacity of 16 mgd at BRWTF.
The capital cost opinions for BRWTF multi-barrier water delivery alternatives
evaluated as part of this study are given in 2007 dollars as shown in Figure 7-1, and the
associated life-cycle present value of these capital costs are given in Figure 7-2. As
shown in Figure 7-1, the capital costs varied widely between no additional capital
expenditure for alternatives 1A and 2A and $M 22 for alternative 1C. The present value
of these capital costs are slightly higher due to project financing at 6 percent interest
over the 30 year project life-cycle. The present value of alternative 3 is substantially
less than its estimated cost in 2007 dollars because the residual value of the pipeline
beyond 30 years was credited to this alternative. It should be noted that these capital
costs estimates are in addition to any capital costs related to planned mid-term
improvements including chlorine dioxide pre-oxidation and finished water pH
adjustment.
C. Present Value O&M Costs
Present value O&M costs were determined for the 30 year life-cycle used for
economic evaluation purposes. These O&M estimates included treatment chemical,
other consumables such as UV lamp and ballast replacement, GAC replacement,
pumping and other energy costs, and scheduled equipment maintenance. An average
daily flow rate of 5 mgd was used to calculate variable consumable and energy O&M
costs. This production rate was slightly higher than the 4.55 mgd average daily flow in
2006 to account for future growth in the BRWTF service area.
Annual O&M cost opinions for BRWTF multi-barrier water delivery alternatives
evaluated as part of this study are given in 2007 dollars as shown on Figure 7-3, and
the associated life-cycle present value of these O&M costs are given in Figure 7-4.
O&M costs for alternatives 1A, 1B, 2A, 2B, and 3 were clustered between $k 170 and
$k 220, with considerably higher values of $k 860 and $k 330 for alternatives 1C and
2C. The higher O&M estimates for alternatives 1C and 2C reflect costs associated with
semi-annual GAC replacement and precursor chemicals for advanced oxidation,
respectively. The present value of these O&M costs reflects an annual inflation rate of
4 percent, applied each year throughout the project life-cycle.The additional O&M
costs for chlorine dioxide preoxidation and pH adjustment planned as mid-term
improvements were include for all water delivery alternatives.
CHAPTER 7 – MULTI-BARRIER APPROACH ECONOMIC EVALUATION7-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
D. Net Present Value Costs
The total net present value cost opinions for BRWTF multi-barrier water delivery
alternatives were calculated as the sum of net present capital and O&M costs, as shown
on Figure 7-5. Water delivery alternative net present value estimates varied widely
between $M 5 and $M 53, based largely on the number and type of additional
contaminant barriers. The comparatively lower net present values for alternatives 1A,
1B, 2A, and 2B reflect the lack of an effective barrier for organic micropollutants,
whereas the substantially higher net present values for alternatives 1C and 2C
compared with alternative 3 reflect a premium required when organic micropollutant and
taste and odor control are provided by treatment rather than source water protection.
CHAPTER 7 – MULTI-BARRIER APPROACH ECONOMIC EVALUATION7-3
Capital Cost in 2007 ($M)
Present Value of Capital Cost ($M)
nual O&M Cost in 2007 ($M)An
Present Value of O&M Cost ($M)
Net Present Value ($M)
City of Boulder BRWTF Multi-Barrier Approach Study Draft
CHAPTER 8
PREFERRED BRWTF MULTI-BARRIER ALTERNATIVE
The non-economic performance score of each BRWTF multi-barrier water
delivery alternative was determined using the Kepner-Tregoe decision analysis
procedure. Economic evaluation of each water delivery alternative was also performed,
based on the net present value of each alternative, which includes capital costs,
operation and maintenance costs, and project financing. This chapter presents these
non-economic performance and economic evaluations together to provide a cost-
performance comparison of BRWTF multi-barrier water delivery alternatives. Based on
a balanced assessment of source water quality information, regulatory requirements,
City drinking water quality goals, non-economic performance scoring, and net present
cost economic evaluations a preferred BRWTF multi-barrier water delivery alternative is
identified.
A. Cost-Performance Comparison
Non-economic performance scoring and economic evaluations of candidate
multi-barrier BRWTF water delivery alternatives were described in Chapters 6 and 7,
respectively. Because of the large variations in alternative performances and net
present values, these values are shown side-by-side to help assess the relative benefits
for each water delivery alternative, as shown in Figure 8-1.
B. Preferred BRWTF Water Delivery Alternative
Both performance and cost varies widely among the seven BRWTF water
delivery alternatives evaluated. Considering source water quality information, relative
risk of source water contamination, regulatory requirements, City drinking water quality
goals, and operational flexibility Black & Veatch believes that alternative 3, complete
source water containment from Carter Lake to BRWTF with chlorine dioxide
preoxidation, is the most desirable and preferred alternative.
Although alternative 3 does not have the lowest net present value among those
evaluated, it has a number of compelling benefits that are not provided by the other
alternatives including:
CHAPTER 8 – PREFERRED BRWTF MULTI-BARRIER ALTERNATIVE8-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Alternative 3 has the best non-economic performance by a wide margin. This
alternative satisfied 22 of 28 criteria evaluated as well or better than the other
alternatives.
Alternative 3 is unique among those evaluated in that it alone addresses the near
and long term potential for continued degradation of water quality in existing
BRWTF sources due to continued residential development, extensive agricultural
land use, and increasing recreational use. Although notable advances in
treatment technology have been made in recent years, contaminant removal
during drinking water treatment is still an imperfect science. Thus, as has
traditionally been the case, preventing source water contamination provides a
more robust barrier than subsequent treatment as the first line of defense in
protecting public health.
Other regional drinking water providers also desire to use a dedicated pipeline
from Carter Lake for raw water delivery to their facilities. Combining raw water
conveyance to BRWTF with that of other providers allows more efficient use of
scarce regional water resources.
Full containment of raw water conveyance from Carter Lake to BRWTF would
provide additional flexibility in managing the City’s water resources portfolio.
Other water delivery alternatives require seasonal storage of raw water in
Boulder Reservoir for use when BFC in not in service. Year-round storage in
Carter Lake would remove the need to project annual seasonal storage required
in Boulder reservoir, and thus avoid the undesirable consequences that result if
seasonal Boulder Reservoir storage is substantially overestimated.
Conveyance of raw water through a Carter Lake pipeline would be consistent
with the City’s historical policy of protecting source water quality by providing full
containment from its other water sources.
Full containment from Carter Lake to BRWTF would provide a much more
uniform raw water quality, substantially simplifying treatment optimization and
increasing treatment process reliability.
CHAPTER 8 – PREFERRED BRWTF MULTI-BARRIER ALTERNATIVE8-2
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Alternative 3 is the only BRWTF water delivery approach that provides at least
one robust barrier for each contaminant category considered in this study.
CHAPTER 8 – PREFERRED BRWTF MULTI-BARRIER ALTERNATIVE8-3
Decision Score
Net Present Value ($M)
City of Boulder BRWTF Multi-Barrier Approach Study Draft
APPENDIX 2
DECISION MODEL CRITERIA AND ALTERNATIVE SCORING
Changes adopted pursuant to project Working Group workshop held January 18, 2007
1
Finished WaterQuality
-- Corrosion removed -- no significant difference among alternatives
-- Organic micropollutants and emerging contaminants combined
2-
-- Mn, T&O, and TDS/SO added -- significant differenceamong alternatives
4
2
Source Water
-- No changes to Boulder staff draftcriteria of 01/03/07
3
Water Treatment/Ops
-- Monitoring/remote sensing removed -- 0 weight assigned
-- Reliability/redundancy split into 2 criteria
4
Risk
-- Power interruption removed -- no significant difference among alternatives
5
Environ./Public Accept
-- No changes to Boulder staff draftcriteria of 01/03/07
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-1
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Objectives and Criteria for a Multi-Barrier Approach to
Treated Water – Fall 2006
I. Musts for ALL Alternatives:
A. Meet Regulations
B. No loss of water yield
1. The City has a water rights portfolio and raw water system facilities that are
used to provide sufficient raw water to meet the City’s needs in accordance
with adopted reliability criteria. The reliability criteria have been used to
define the level of water use restrictions that might be needed for droughts
with specified recurrence intervals to avoid lowering of reservoirs below safe
levels to the point that delivery of water for essential health and safety needs
is jeopardized. Any alternative for raw water delivery needs to be capable of
maintaining the current expected level of yield of the City’s water rights and
must not reduce the current level of flexibility in selecting water sources.
II. Finished Water Quality Criteria
A. Pathogens
- Health issue.Disease causing organisms.
1. A higher ranking will be given to those alternatives that best address limiting
the potential for public health impacts from pathogens. Alternatives will be
ranked by:
a. Source water vulnerability
1) Pathogen indicator counts
2) Potential for pathogen introduction
b. Treatment
1) Log removal and tool box – use regulatory limits
2) Potential for pathogens to pass through treatment process
2. Factors to consider
a. The intent of this criterion is to address pathogen risk by selecting the best
source water quality and/or treatment techniques
b. See attached source water quality table
B. Disinfection By-Products (DBPs)
- Health issue.Formed when disinfectant
(i.e. chlorine) combines with naturally occurring and/or other compounds in the
water or from the disinfectant itself.
1. A higher ranking will be given to those alternatives that minimize DBP
formation and/or reduce DBP’s. Alternatives will be ranked by
a. Source water
1) Precursors (TOC)
2) Chlorine dosage
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-2
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b. Treatment
1) Removal
2) Oxidation and/or absorption of precursors
2. Factors to consider
a. The intent of this criterion is to address the potential for DBP formation
b. Similar average TOC values (3.5 mg/L) are present in Boulder Reservoir,
BFC and Carter Lake
c. See attached source water quality table
C. Micro-organic Compounds -
Health issue. Man made carbon compounds.
1. A higher ranking will be given to those alternatives that provide the best
protection against the introduction and/or removal of organic compounds (ie.
pesticides, hydrocarbons) and limits the risk of organic compounds passing
on to the consumer in the finished water. Alternatives will be ranked by:
1) Source water vulnerability to organic compounds
b. Treatment
1) Contaminants passing through treatment
2) Absorb organic compounds
2. Factors to consider
a. The intent of this criterion is to evaluate the potential for man made
organic compounds to enter the source water and possibly be passed on
to consumers
b. Potential for organic compounds to enter the source water – intentional,
accidental or due to recreation activities
c. Standard maintenance activities that can introduce organic compounds
d. Potential for non-point source contributions due to precipitation events and
agricultural return inflows
e. Available source water dilution
D. Inorganic Compounds
- Health issue.Non-natural toxic chemicals such as
arsenic and cyanide.
1. A higher ranking will be given to those alternatives that provide the best
protection against the introduction and/or removal of toxic inorganic
compounds. The alternatives will be ranked by:
a. Source water vulnerability to inorganic toxic compounds and chemicals
b. Treatment
2. Factors to consider
a. The intent of this criterion is to evaluate the potential for non-natural and
natural toxic inorganic compounds to enter the source water and possibly
be passed on to consumers in the finished water.
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-3
City of Boulder BRWTF Multi-Barrier Approach Study Draft
E. Emerging Contaminants
- Health issue.Unregulated contaminants that pose a
health risk. Examples are gasoline additives, microbes smaller than
Cryptosporidium that are resistant to chlorine, pharmaceutical drugs, new
disinfection-by-products and new pesticides.
1. A higher ranking will be given to those alternatives that provide the best
protection against the introduction and/or removal of emerging contaminants
to the source water and being passed on to consumers in the finished water.
The alternatives will be ranked by:
a. Source water vulnerability
1) Gasoline additives
2) Microbes smaller than Cryptosporidium that are resistant to chlorine
3) Pharmaceutical drugs
4) New pesticides
5) New disinfection-by-products
b. Treatment-removal and absorption capability for all categories of emerging
contaminants
2. Factors to consider
a. The intent of this criterion is to address the potential for future regulated
constituents and plan ahead in a cost effective and proactive manner
b. Animal activity
c. Non-point sources
d. Wastewater discharges
F. Corrosion
- Health and consumer confidence issue.Aggressive water that will
leach harmful metals from pipes into the water (lead and copper).
1. A higher ranking will be given to those alternatives that create the lowest
potential for aggressive water. The alternatives will be ranked by:
a. Source water
1) Alkalinity
2) pH
3) Sulfate
b. Treatment
1) Corrosion control
2) Match Betasso treated water
2. Factors to consider
a. The intent of this criterion is to provide finished water that is not
considered aggressive
b. A pH below 7.8 is more corrosive
c. Alkalinity around 48 mg/L is less corrosive
d. High alkalinity above 100 mg/L increases copper corrosion potential
e. Low alkalinity increases both lead and copper corrosion potential
f. See attached source water quality table
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-4
City of Boulder BRWTF Multi-Barrier Approach Study Draft
III. Source Water
A. Water Rights Yield
1. Yield of the City’s water rights portfolio is maximized over time by fully using
direct flow water when available and strategic use of available reservoir
storage water. Evaluation of alternatives should consider:
a. Ability to manage stored reservoir water throughout the year
b. Ability to manage stored reservoir water during droughts
c. Access to raw water sources available for direct use
d. Potential for increasing water rights yield through enhanced water
management or capacity of facilities
B. Consistency of quality and quantity 24/7
1. A higher ranking will be given to those alternatives that provide the best
potential for consistent finished water quality. The alternatives will be ranked
by:
2. Source water
a. Operational ease of delivering raw water at a consistent flowrate
a. Operational ease of delivering raw water of a consistent quality
b. Ability to blend raw water sources to improve quality
2. Treatment
a. Reliability: Consistent treatment operation year-round with less process
failure.
b. Efficiency: Minimize chemical usage and operations staff efforts.
3. Facts to consider
a. High quality treated water is more easily attained when raw water sources
feeding the treatment plant are uniform in both quality characteristics and
in flow rate of delivery. The intent of this criterion is to assess the impact
on water treatment from inconsistent source water quality, including
reliability and efficiency and the need for additional treatment process
barriers.
C. Portfolio Flexibility (Flexibility in use of raw water supplies)
1. System reliability improves with flexibility in selection of raw water sources in
response to changes in treated water demands or amount of raw water
available from a source. Evaluation of alternatives should consider:
a. Number of options available for means of delivering raw water
b. Ease of changing water sources in response to changing conditions
c. Seasonal limitations of use on raw water sources
D. Availability of Raw Water Delivery Facilities
1. Management of raw water sources is made more difficult by facilities that are
unavailable for raw water delivery. Evaluation of alternatives should consider:
a. Reliability of facilities
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-5
City of Boulder BRWTF Multi-Barrier Approach Study Draft
b. Capacity limitations
c. Restrictions on facilities use due to external factors affecting operations or
water quality
IV.
Water Treatment / Operations Criteria
A. Worker safety
1. Alternatives will be ranked highest based on least amount of staff interaction
or exposure required. The alternatives will be ranked by:
a. Chemicals
1) Type (degree of hazard)
2) Amount required
b. Processes
1) Type (complexity, hazard)
2) Number (how many processes required)
c. Infrastructure maintenance
1) Cleaning grates/strainers at intakes
2) High power
3) Mechanical complexity
d. Factors to consider
1) The intent of this criterion is to evaluate the potential risk to staff based
on type and amount of chemical required and type and number of
processes required.
B. Process Flexibility
1. Alternatives will receive highest ranking based on the most flexibility in
processes (number and type) required. The alternatives will be ranked by:
a. Maximizing the maturity and robustness of the technology
b. Maximizing the fabrication and engineering design of the various facilities,
unit processes and components.
2. Factors to consider
a. The purpose of this criterion is to compare the need for treatment
processes. The more robust and flexible a process is the broader the
range of treatment concerns addressed will.
b. As source water variability and vulnerability increases the number and/or
complexity of processes will increase.
c. Treatment – add table of data to support
1) Oxidation – manganese, turbidity
2) Caustic and/or acid - pH fluctuations
3) Coagulant - turbidity fluctuations
C. Reliability/Redundancy
1. A higher ranking will be given to those alternatives that provide the best
potential for consistent finished water quality. The alternatives will be ranked
by:
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-6
City of Boulder BRWTF Multi-Barrier Approach Study Draft
a. Source water
1) Operational ease of delivering raw water at a consistent flow rate
2) Operational ease of delivering raw water of a consistent quality
3) Ability to blend raw water sources to improve quality
b. Treatment
1) Reliability: Consistent treatment operation year-round with less
process failure.
2) Efficiency: Minimize chemical usage and operations staff efforts.
3) Minimize need to adjust treatment processes and/or chemical dosage
on regular basis.
c. Factors to consider
1) High quality treated water is more easily attained when raw water
sources feeding the treatment plant are uniform in both quality
characteristics and in flow rate of delivery. The intent of this criterion is
to assess the impact on water treatment from inconsistent source
water quality, including reliability and efficiency and the need for
additional treatment process barriers.
D. Maintenance
1. A higher ranking will be given to alternatives that:
a. Minimize the complexity of facilities, unit processes and components
b. Maximize the expected life of facilities, unit processes and components
c. Maximize the maturity of the technology, fabrication and engineering
design of the various facilities, unit processes and components
E. Monitoring/Remote Operation
1. A higher ranking will be given to those alternatives that exhibit lower
complexity and higher reliability.
a.
2. Facts to consider
a. The intent of this criterion is to compare the complexity and reliability of
the monitoring requirements of each alternative. It does not include the
monetary cost of monitoring since this will be part of the monetary
evaluation.
F. Staffing
1. A higher ranking will be given to those alternatives that minimize the
requirements based on these parameters: include:
a. Total number of staff
b. Expertise of staff
c. Supervision
2. Facts to consider
a. The intent of this criterion is to compare the staffing requirements of each
alternative. It does not include the monetary cost of staffing since this will
be part of the monetary evaluation.
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-7
City of Boulder BRWTF Multi-Barrier Approach Study Draft
G. Residuals disposal
1. Alternatives will be ranked by least volume and best quality of residuals.
a. Source water
b. Treatment
2. Factors to consider
a. Locations for residuals disposal are becoming increasingly difficult to find
so it is important to minimize the production of residuals. (Recent
analyses indicate current residuals may contain low levels of radioactivity
making it even more difficult to dispose of.)
V. Risk
A. Unexpected Acute Contamination
1. A higher ranking will be assigned to those alternatives that best minimize
potential public health impacts from such risk. The alternatives will be
evaluated by
a. Potential for slug-loading of a large amount of harmful contaminant(s) with
potential for treatment breakthrough
b. Potential for slug-loading of contaminant(s) with the capability for disabling
or disrupting water service on a temporary or long-term basis
2. Facts to consider
a. Initial specific risk/contaminant/treatability criteria and assessments for
water supplies addressed in this study have been developed as a part of
the 2003 Water Utility Vulnerability Study. Further development of detailed
source/treatment risk assessment information for these supply/treatment
system, as well as for the entire city of Boulder treatment/source portfolio,
is currently being planned by the city’s utility security work group( with the
goal of incorporating the findings into this and other related long-term
utility planning efforts).
B. Unexpected Chronic Contamination
1. A higher ranking will be assigned to those alternatives that best minimize
potential public health impacts from such risk. Alternatives will be evaluated
by
a. Potential for contamination from bodily contact with the source (wild or
domestic animal and/or human)
b. Potential for contamination from other recreational activities adjacent to
supply
c. Potential for contamination from outfalls emptying into supplies
2. Facts to consider
a. The intent of this criterion is to address day-to-day risks due to existing
non-point-sources in water supplies. Focus is on contaminants that are
difficult to remove or inactivate through treatment and on events that could
cause a moderate to significant waterborne disease.
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-8
City of Boulder BRWTF Multi-Barrier Approach Study Draft
b. Initial specific risk/contaminant/treatability criteria and assessments for
water supplies addressed in this study have been developed as a part of
the 2003 Water Utility Vulnerability Study. Further development of detailed
source/treatment risk assessment information for these supply/treatment
system, as well as for the entire city of Boulder treatment/source portfolio,
is currently being planned by the city’s utility security work group( with the
goal of incorporating the findings into this and other related long-term
utility planning efforts).
C. Adaptability to Unexpected Future Changes -
1. Future changes in source water quality. A higher ranking will be assigned to
those alternatives that best minimize risk of public health impacts from
potential future increases in source WQ risks.
a. The intent of this criterion is to address the tendency toward increased risk
over time from contaminant sources noted in (A.2.) as a function of:
1) Local or regional policy(s) regarding activities allowed or encouraged in
or near drinking water supplies.
2. Facts to consider
a. Increased level of impacting activities over time in popular water supply
corridors.
b. Increased source contamination risks/loading will increase background
public health risks as well as increase the likelihood of peaking events/
waterborne disease outbreak(s). Specific risk information to support this
criterion to be developed in risk assessment efforts noted above.
3. Future changes in regulatory standards. A higher ranking will be assigned to
those alternatives that best minimize risk of non-compliance with future
drinking water standards.
4. Facts to consider
a. The intent of this criterion is to address the risk of drinking water quality
standards (especially those pertaining to source water risks) becoming
significantly more stringent in the future.
b. Potential inability for city to meet future standards to the extent that CIP
and other planning does not anticipate regulatory dynamics/ upcoming
challenges. (See discussion on significant limitations of current standards
which contributes to likelihood of increased future stringency).
D. Infrastructure Vulnerability
1. A higher ranking will be assigned to those alternatives that best minimize risk
of damage to infrastructure that would impede purveyance or treatment of the
potable water supply. The alternatives will be evaluated by
a. Potential for impacts from natural events (i.e. weather-related events)
b. Potential for impacts from accidental or intentional events
2. Facts to consider
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-9
City of Boulder BRWTF Multi-Barrier Approach Study Draft
a. The intent of this criterion is to address risks to facilities in sources and
treatment which would impede delivery of drinking water to the city’s
distribution system.
b. Why it is a problem: Interferes with reliable delivery of water for drinking
and other potable uses and for fire protection.
E. Power interruptions
3. A higher ranking will be assigned to those alternatives that best minimize risk
of power interruptions with potential to impede purveyance or treatment of the
potable water supply. The alternatives will be evaluated by
a. Potential for power interruptions affecting the treatment plant processes
b. Potential for power interruptions affecting the transmission of water to the
distribution system
4. Facts to consider
a. Power interruptions can result in serious consequences for both water
supply and quality. To the extent that an interruption interferes with water
treatment plant processes, tap water quality is at risk (including regulatory
compliance capability). Water transmission may also be compromised by
a power outage to the extent that pumping/ system telemetry are
impacted.
F. Chemical Delivery/Usage
5. A higher ranking will be assigned to those alternatives that best minimize risk
from potential chemical delivery interruptions which would impede treatment
and public health protection capability. The alternatives will be evaluated by
a. Potential for treatment chemical interruption (i.e. distance of source from
plant, mode of transportation, frequency of deliver)
6. Facts to consider
a. The intent of this criterion is to address risks to WQ/public health from
interruption of availability/ delivery of chemicals required to treat water for
potable use.
b. Lack of such chemicals in sufficient quantity could preclude the city’s
ability to treat water to quality or quantity levels needed.
VI. Environmental and Public Acceptance
A. Adjacent land use Compatibility
1. Chemical hazards (us on neighbors)
2. Recreational use (neighbors on us
3. Development
4. Road crossings
B. System-Wide Water Uniformity
1. The desirability of providing equal water quality to all customers
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-10
City of Boulder BRWTF Multi-Barrier Approach Study Draft
a.
b. Quote from Ridge Dorsey re: Industry need to pretreat water “We could go through our
list of permitted industries an give you a count from that select group, but that would not
be representative of the entire city. Many industry types such metal plating, electronics
assembly, food/beverage manufacturing, pharmaceutical, R&D labs, even auto washing
prefer to use de-ionized water, and sometimes ultra pure (reverse osmosis) water.
Potable water for these commercial applications would likely need to be treated to
specific industry standards in any location. I'm not aware of any industry that did not
locate to Boulder due to water quality.”
c.
C. Construction Impacts
1. A higher ranking will be given to those alternatives that exhibit these
characteristics:
a. Minimizing the impacted land area and associated restoration
requirements
b. Minimizing underground excavation and associated materials handling
c. Minimizing the number of subcontractors and suppliers
2. Facts to consider
a. The intent of this criterion is to compare the construction impacts of each
alternative. It does not include the monetary cost of construction since
this will be part of the monetary evaluation.
D. Consumer Confidence
3. A higher ranking will be given to those alternatives that provide the highest
consumer confidence.
a. Source
1) Finished water taste, odor, temperature and appearance.
2) Manganese
3) Hardness.
4) Effects on local business
b. Treatment
1) match Betasso Treated water
c. Facts to consider
1) The intent of this criterion is to evaluate public perception and
acceptance of treated water.
E. Permitting
F. Energy Requirements
3. The intent of this criterion is to compare the energy requirements and the
secondary affects of these requirements. It does not include the monetary
value of the energy requirements since this will be part of the monetary
evaluation. The alternatives will be rated based on minimizing the quantity of
the following:
a. Capacity/load rating (MVA)
b. Net energy consumption (use minus production) (Mw-hr)
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-11
City of Boulder BRWTF Multi-Barrier Approach Study Draft
c. Equivalent amount of coal (tons)
d. Equivalent amount of SO2 (tons)
e. Equivalent amount of NOx (tons)
f. Equivalent amount of CO2 (tons)
VII. Other Criteria
A. Public Acceptance
The intent of this criterion is to compare the anticipated public acceptance of
each alternative. It does not include the monetary cost of any project mitigation
designed for public acceptance since this will be part of the monetary evaluation.
A higher ranking will be given to those alternatives that exhibit these
characteristics:
a. Minimizing the visual impacts of based on the need for above grade
buildings and facilities
b. Minimizing acquisition of land, easements and right-of-way
c. Promoting economic sustainability within the city’s service area
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-12
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Alternative Scoring Worksheets
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-13
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Quality:PathogensCryptoGiardiaViruses
Treatment
Comments: Additional log removal
AlternativeScore
Strategy
ClO
1A2 0.02 0.67 0.96
2
ClO + UV
1B10 4.02 4.67 1.46
2
ClO + GAC + UV
1C10 4.02 4.67 1.46
2
ClO
2A2 0.02 0.67 0.96
2
ClO + UV
2B10 4.02 4.67 1.46
2
ClO + AOP
2C3 0.5413.16 27.60
2
CLP + ClO
36 1.52*2.17* 2.46*
2
*Based on 1.50 log reduction inE.coli by using CLP
Water Quality:DBPs
Treatment
Comments:ClO O, GAC varies, UV -- no effect
AlternativeScore
23
Strategy
ClO
1A9
2
ClO + UV
1B9
2
ClO + GAC + UV
1C9TOC removal varies with GAC life-cycle
2
ClO
2A9
2
ClO + UV
2B9
2
ClO + AOP
2C10
2
CLP + ClO
39Pipeline gives consistent water quality allowing treatment optimization
2
UV -- no contribution to DBP reduction
ClO -- Effective oxidation of NOM
2
AOP -- Effective oxidation of NOM
GAC -- effective adsorption depending on GAC age
Water Quality:Organic Micropollutants
Treatment
Comments:AOP GAC >> UV ClO
AlternativeScore
2
Strategy
ClO
1A2Minimal oxidation
2
ClO + UV
1B3Minimal oxidation and photolytic degradation
2
ClO + GAC + UV
1C7Adsorption varies with contaminant and GAC age
2
ClO
2A2Minimal oxidation
2
ClO + UV
2B3Minimal oxidation and photolytic degradation
2
ClO + AOP
2C10Reservoir dilution + effective oxidation
2
CLP + ClO
38Source water protection + minimal oxidation --EDCs have verylow concentratio
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-14
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Quality:Inorganic Micropollutants
Treatment
Comments: Reduced As, U, Cr, Pb, Cd, Cu
AlternativeScore
Strategy
ClO
1A6Oxidant + conventional treatment
2
+ UV
ClO
6Oxidant + conventional treatment
1B
2
ClO + GAC + UV
1C6Oxidant + conventional treatment
2
ClO
7Oxidant + conventional treatment
2A
2
ClO + UV
2B7Oxidant + conventional treatment
2
ClO + AOP
2C8Optimized oxidation+ conventional treatment
2
CLP + ClO
10Source water protection + reservoir dilution + oxidant +conventional treatment
3
2
Water Quality:Manganese
Treatment
Comments
AlternativeScore
Strategy
ClO
1A8Source water avoidance + effective oxidant
2
ClO + UV
1B8Source water avoidance + effective oxidant
2
ClO + GAC + UV
1C8Source water avoidance + effective oxidant
2
ClO
7Variable Mn -- effective oxidation
2A
2
ClO + UV
2B7Variable Mn -- effective oxidation
2
+ AOP
ClO
8Variable Mn + Two stage optimized oxidation
2C
2
CLP + ClO
310Source water protection + effective oxidation
2
Water Quality:Taste and Odor
Treatment
Comments
AlternativeScore
Strategy
ClO
5
1AModerately effective oxidant
2
ClO + UV
1B5Moderately effective oxidant
2
ClO + GAC + UV
1C7Moderatelty effective oxidant, adsorption varies with contaminant and GAC age
2
ClO
2A5Moderately effective oxidant
2
ClO + UV
2B5Moderately effective oxidant
2
ClO + AOP
2C10Optimized oxidation
2
CLP + ClO
38Source water protection + moderately effective oxidant
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-15
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Quality:TDS and Sulfate
Treatment
Comments
AlternativeScore
Strategy
ClO
1A3Seasonal reservoir usage + no treatment
2
ClO + UV
1B3Seasonal reservoir usage + no treatment
2
ClO + GAC + UV
1C3Seasonal reservoir usage + no treatment
2
ClO
2A2Year-round reservoir use + no treatment
2
+ UV
ClO
2B2Year-round reservoir use + no treatment
2
ClO + AOP
2C2Year-round reservoir use + no treatment
2
CLP + ClO
310Source water protection
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-16
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Source Water:Consistenc
y
Treatment
Comments
AlternativeScore
Strategy
ClO
1A2Seasonal canal usage with low TDS & sulfate
2
+ UV
ClO
2Seasonal canal usage with low TDS & sulfate
1B
2
ClO + GAC + UV
1C2Seasonal canal usage with low TDS & sulfate
2
ClO
2A5Year-round reservoir use with higher TDS & sulfate, seasonal Mn occurance
2
ClO + UV
2B5Year-round reservoir use with higher TDS & sulfate, seasonal Mn occurance
2
ClO + AOP
2C5Year-round reservoir use with higher TDS & sulfate, seasonal Mn occurance
2
CLP + ClO
310Year-round CLP with low TDS&sulfate
2
Source Water:Water Rights Yield
Treatment
Comments
AlternativeScore
Strategy
ClO
Seasonal reservoir usage
1A5
2
ClO + UV
1B5Seasonal reservoir usage
2
ClO + GAC + UV
Seasonal reservoir usage
1C5
2
ClO
2A2Year-round reservoir usage
2
ClO + UV
Year-round reservoir usage
2B2
2
+ AOP
ClO
2C2Year-round reservoir usage
2
CLP + ClO
310Year-round CLP usage
2
Source Water:Portfolio Flexibility
Treatment
Comments: Time limit on reservoir storage(use it or lose it)
Score
Alternative
Strategy
ClO
1A5Requires seasonal reservoir storage
2
ClO + UV
1B5Requires seasonal reservoir storage
2
+ GAC + UV
ClO
1C5Requires seasonal reservoir storage
2
ClO
2A2Requires year-round reservoirstorage
2
ClO + UV
2B2Requires year-round reservoirstorage
2
ClO + AOP
2C2Requires year-round reservoirstorage
2
CLP + ClO
310No reservoir storage required
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-17
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Source Water:Availabilit
y
Treatment
Comments: Both BFC and BR ultimatelyrequire canal use
AlternativeScore
Strategy
ClO
Requires seasonal reservoir storage
1A5
2
ClO + UV
1B5Requires seasonal reservoir storage
2
ClO + GAC + UV
1C5Requires seasonal reservoir storage
2
ClO
2A4Requires year-round reservoirstorage
2
+ UV
ClO
2B4Requires year-round reservoirstorage
2
ClO + AOP
2C4Requires year-round reservoirstorage
2
CLP + ClO
310No limitation on availability
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-18
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Treatment/Operations: Worker Safet
y
Treatment
Comments
AlternativeScore
Strategy
ClO
1A10No additional energized equipment and maintenance
2
ClO + UV
1B7Additional energized equipmentand maintenance
2
ClO + GAC + UV
1C6Additional energized equipment,maintenance, and GAC replacement
2
ClO
2A10No additional energized equipment and maintenance
2
ClO + UV
Additional energized equipment and maintenance
2B7
2
ClO + AOP
2C6Additional energized equipment,maintenance, and chemical handling
2
CLP + ClO
310No additional energized equipment and maintenance
2
ClO
0
2
UV-3
GAC-1
AOP-4
CLP0
Water Treatment/Operations: Process Flexibility
Treatment
Comments
AlternativeScore
Strategy
ClO
1A6Adjustable oxidation
2
ClO + UV
1B8Adjustable oxidation and UV disinfection
2
ClO + GAC + UV
1C8Adsorption varies with contaminant and GAC age, adjustable UV disinfection
2
ClO
2A6Adjustable oxidation
2
ClO + UV
2B8Adjustable oxidation and UV disinfection
2
ClO + AOP
2C10Greatest flexibility for TOC,DBPs, T&O, Mn
2
CLP + ClO
36Adjustable oxidation
2
Water Treatment/Operations: Process Reliabilit
y
Treatment
Comments: Knowledge and operational control of process(es)
Alternative
Score
Strategy
ClO
7 mature (chlorite), source water variability
1AClO
2
2
ClO + UV
1B6ClO mature (chlorite), UV adolescent, source water variability
2
2
ClO + GAC + UV
1C5GAC adolescent, UV adolescent, source water variability
2
ClO
2A8ClO mature (chlorite), source water variability
2
2
ClO + UV
2B7ClO mature (chlorite), UV adolescent, source water variability
2
2
ClO + AOP
2C7ClO mature (chlorite), AOP adolescent, source water variability
2
2
CLP + ClO
310Pipeline mature, ClO mature (chlorite)
2
2
Source water variabilityTechnology
BFC-3Mature0
BR-2Adloescen-1
t
CLP0New-2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-19
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Treatment/Operations: Process Redundanc
Barriers
y
Treatment
Comments: Maximize barriers
AlternativeScore
Strategy
ClO
1A6 8.0
2
+ UV
ClO
1B810.5
2
ClO + GAC + UV
1C911.5
2
ClO
2A6 8.0
2 n= # barriers in alternative
barrier
ClO + UV
2B810.5
N= max # barriers in alternatives
2
barrier
ClO + AOP
2C1013.0
2
CLP + ClO
31013.0
2
Water Treatment/Operations: Maintenance
Treatment
Comments: Deducts for each additional maintenance requirement
AlternativeScore
Strategy
ClO
1A10No additional maintenance
2
+ UVAdditional maintenance for UV
ClO
1B7
2
ClO + GAC + UV
1C4Additional maintenance for GAC (3) and UV
2
ClO
2A10No additional maintenance
2
Additional maintenance and UV
ClO + UV
2B7
2
ClO + AOP
2C6Additional maintenance for AOP
2
CLP + ClO
310No additional maintenance
2
ClO
0
2
UV-3
GAC-3
AOP-4
CLP0
Water Treatment/Operations: Staffing
Treatment
Comments: Effort Expertise Supervision
AlternativeScore
Strategy
ClO
1A8 -1 0 -1
2
ClO + UV
1B7 -1 -1 -1
2
ClO + GAC + UV
1C7 -1 -1 -1
2
ClO
2A8
-1 0 -1
2
ClO + UV
2B7 -1 -1 -1
2
ClO + AOP
2C5 -1 -2 -2
2
CLP + ClO
10
3 0 0 0
2
Base score =10Treatability
BFCWorst-10-1
BRIntermedia-10-1
t
CLPBest000
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-20
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Water Treatment/Operations: Residuals Disposal
Solids:QuantitQualitChemicals
yy
Treatment
Comments
AlternativeScore
Strategy
ClO
1A7 -1 -2 0
2
ClO + UV
1B7 -1 -2 0
2
ClO + GAC + UV
1C5 -3 -2 0
2
ClO
2A6 -1 -3 0
2
ClO + UV
2B6 -1 -3 0
2
ClO + AOP
2C5 -1 -3 -1
2
CLP + ClO
310 0 0 0
2
Base score =10
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-21
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Risk: Acute Contamination
Treatment
Comments: Source water protection only, no treatment
AlternativeScore
Strategy
ClO
1A3Highly vulnerable, BFC
2
ClO + UV
1B3Highly vulnerable, BFC
2
ClO + GAC + UV
1C3Highly vulnerable, BFC
2
ClO
2A5
Moderately vulnerable,reservoir dilution
2
ClO + UV
2B5Moderately vulnerable,reservoir dilution
2
ClO + AOP
5
2CModerately vulnerable,reservoir dilution
2
CLP + ClO
310Minimally vulnerable
2
Risk: Chronic ContaminationPathogensOrganicsInorganics
Treatment
Comments: Micropollutants and emerging contaminants
AlternativeScore
Strategy
ClO
1A2 -3 -3 -2
2
+ UV
ClO
5
1B 0 -3 -2
2
ClO + GAC + UV
1C7 0 -1 -2
2
ClO
2A5 -2 -2 -1
2
ClO + UV
2B7 0 -2 -1
2
ClO + AOP
2C9 0 0 -1
2
CLP + ClO
310
0 0 0
2
Prevention takes precendence over treatment
BFC
Base score =10-3-3-3
BR-2-2-2
CLP
-1-1-1
ClO
00+1
2
UV+300
GAC0+20
AOP+2+3+1
CLP+3+2+2
Risk: Adaptability to Future Regulatory EnvironmentPathogensOrganicsInorganics
Treatment
Comments
AlternativeScore
Strategy
ClO
1A2 0 0 +1
2
ClO + UV
1B5+3 0 +1
2
ClO + GAC + UV
1C7+3 +2 +1
2
ClO
2A2 0 0 +1
2
+ UV
ClO
5
2B+3 0 +1
2
ClO + AOP
2C8+2 +3 +2
2
CLP + ClO
310+4 +2 +3
2
ClO
Base score =100+1
2
UV+300
GAC0+20
AOP+2+3+1
CLP+3+2+2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-22
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Risk: Infrastructure Vulnerability
Treatment
Comments: Source water infrastructure contamination only
AlternativeScore
Strategy
ClO
1A4Highly vulnerable
2
ClO + UV
1B4Highly vulnerable
2
ClO + GAC + UV
1C4Highly vulnerable
2
ClO
2A5Moderately vulnerable,reservoir difficult to decontaminate
2
ClO + UV
2B5Moderately vulnerable,reservoir difficult to decontaminate
2
ClO + AOP
2C5Moderately vulnerable,reservoir difficult to decontaminate
2
CLP + ClO
310Minimally vulnerable
2
Both BFC and BR ultimately rely on canal to deliver waterRiskV. High-4
SourceProbabilitSeveritScoreHigh-3
yy
BFCHighHigh4Mod-2
BRLowV. High5Low-1
CLPV. LowV. Lo10V. Low-0
w
Risk: ConsumableDelivery/Usage
Treatment
Comments
AlternativeScore
Strategy
ClO
1A10No Additional risk
2
ClO + UV
1B8
2
+ GAC + UV
ClO
1C5
2
ClO
2A10No Additional risk
2
+ UV
ClO
2B8
2
ClO + AOP
2C4
2
CLP + ClO
310No Additional risk
2
ChemicalRisk
ClO
-2
2
UV-2
GAC-3
O
-3
3
O
H
-3
22
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-23
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Environmental and Public Acceptance: Adjacent Land Use Compatibilit
y
Treatment
Comments
AlternativeScore
Strategy
ClO
1A4Development, roadcrossings, recreation
2
ClO + UV
1B4Development, roadcrossings, recreation
2
ClO + GAC + UV
1C4Development, roadcrossings, recreation
2
ClO
2A4Development, roadcrossings, recreation
2
ClO + UV
Development, roadcrossings, recreation
2B4
2
Development, roadcrossings, recreation, LOX delivery
ClO + AOP
2C3
2
CLP + ClO
310No incompatibilities
2
Base score =1
LOX delivery1
Development2
Road crossings2
Recreational use2
Environmental and Public Acceptance: System Wide Finished Water Uniformity
Treatment
Comments: Primarily TDS and Sulfate
AlternativeScore
Strategy
ClO
1A3Higherinorganic content during reservoir use
2
ClO + UV
1B3Higherinorganic content during reservoir use
2
ClO + GAC + UV
1C3Higherinorganic content during reservoir use
2
ClO
2A2Continuously higher inorganic content
2
ClO + UV
2B2Continuously higher inorganic content
2
ClO + AOP
2C2Continuously higher inorganic content
2
CLP + ClO
310Source water most closelymatches Betasso source
2
Environmental and Public Acceptance: Construction
Treatment
Comments
AlternativeScore
Strategy
ClO
10
1AClO
2
2
ClO + UV
1B7ClO + UV
2
2
ClO + GAC + UV
1C4GAC + UV
2
ClO
2A10ClO
2
2
ClO + UV
2B7ClO + UV
2
2
ClO + AOP
2C6ClO + AOP
2
2
CLP + ClO
34CLP + ClO
2
2
ClO
0
2
UV3
GAC3
AOP4
CLP6
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-24
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Environmental and Public Acceptance: Permitting/Regulatory Acceptance
Treatment
Comments
AlternativeScore
Strategy
ClO
1A10ClO
2
2
ClO + UV
1B8ClO + UV
2
2
ClO
+ GAC + UV
1C6GAC + UV
2
ClO
2A10ClO
2
2
ClO + UV
2B8ClO + UV
2
2
+ AOP
ClO
2C8 + AOP
ClO
2
2
CLP + ClO
36CLP + ClO
2
2
ClO
0
2
UV2
GAC2
AOP2
CLP4
Environmental and Public Acceptance: Consumer confidence
TDS/SO
T&O
PathogensDBPsOrganicsInorganicsManganese
4
Treatment
Comments: Avoidance takes precedence over treatment
AlternativeScore
Strategy
ClO
1A6 0 +1 0 +1 +2 +2 0
2
ClO + UV
1B7 +1 +1 0 +1 +2 +2 0
2
+ GAC + UV
ClO
1C10
+2 +2 +1 +1 +2 +3 0
2
ClO
2A7 +1 +1 +1 +2 +1 +1 0
2
ClO + UV
2B8 +2 +1 +1 +2 +1 +1 0
2
+ AOP
ClO
2C9
+1 +1 +2 +2 +1 +2 0
2
CLP + ClO
310 +1 +1 +1 +2 +2 +2 +1
2
Base score =0
Avoidance
BFC0000+1+10
BR+10+1+1000
CLP+10+1+1+1+1+1
Treatment
ClO
0+10+1+1+10
2
UV+1000000
GAC0+1+100+10
AOP00+100+10
CLP000000+1
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-25
City of Boulder BRWTF Multi-Barrier Approach Study Draft
Environmental and Public Acceptance: Energy Requirements
Treatment
Comments: Based on relative additional energy usage
AlternativeScore
Strategy
ClO
1A5$22,7505
2
ClO + UV
1B
3$28,6633
2
ClO + GAC + UV
1C3$28,6633
2
ClO
2A2$32,5002
2
ClO + UV
2B1$38,4131
2
ClO + AOP
2C2$32,5002
2
CLP + ClO
310$010
2
APPENDIX 2 – DECISION MODEL CRITERIA AND ALTERNATIVE SCORINGA.2-26