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HomeMy WebLinkAbout7 - Staff presentation and WRAB discussion on Boulder Reservoir source water protection and BoulderCITY 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 - Udliues 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 conswction of a pipeline from Carter Lake to the Boulder Reservoir Water Treatment Plant (BRWTP). Also included in the six-yeaz 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 Boazd 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 safery. AGENDA ITEM # ~. Page 1 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 altemative 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 altematives 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 Neaz-term Improvements. This plan presented neaz-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 (westem slope) and the Big Thompson River (eastern slope) to be stored and delivered for irrigation and water supplies on the eastem 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 urigation 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 neaz 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 hazdness. 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 qualiry is also impacted by recreational uses including swimming and boating. High flows into the reservoir from [he 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 r The BFC is a 21-mile-long open canal. While tbe 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 aze routinely applied to the canal to control algae and native vegetation. There aze 51 outfalls emptying into the canal that drain a vaziety of adjacent land uses. There aze 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, filtrafion and disinfection. Until 1994, the plant had primazily 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 Facilitv Plan as "near-term" improvements. ReQUlatorv Requirements The Safe Drinking Water Act addresses a wide range of water quality issues including microbial contaminauon, 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 yeazs, the EPA has issued the Interim Enhanced Surface Treatment Rule (IESWTR) and proposed a new regulation called the I,ong-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 protecdon or treatment options. The proposed LT2ESWTR requirements for each system aze based on the vulnerability of the source water to contamination, as measured by the occurrence of Cryptosporidium. This suategy stems from recognition that only some systems may need to provide additional protection from Cryptosporidium and that such decisions should be made on a sys[em-specific basis. The regulations specify categories (bins) based on the quality of the source water and corresponding AGENDA ITEM # ~ Page 3 additional source water protection or treatment from a"toolbox" of options. Based on current source water quality data, it appeazs 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 muld-barrier approach for ueating 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 Oualitv Phase I Study Results The Phase I Study evaluated five source water protection alternatives: • Boulder Reservoir as a yeaz-round ternunal reservoir • Pipeline from Cazter Lake to the BRWTP • Pipeline from Nelson Road to the BRWTP • New ternunal reservoir • Forebay upstream of the Boulder Reservoir These altematives 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 dme 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 forwazd with modificaUOns to the Boulder Reservoir Water Treatment Plant intake structure as recommended by B&V and Dr. I.ewis. 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 Mazch 2005 and cost $235,000. While these improvements reduced the turbidity and wncenuations 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 exceeding internal city goals; poor total organic cazbon removal which can cause disinfection AGENDA ITEM # a Page 4 7 byproducts; and problems with dirty taste. These problems were exacerbated by wazm temperatures typical of the reservoir in the summer. Sodium levels also continue to be high. BRWTP Facilitv Plan The Predesign Report for Neaz-Term Improvements for the Boulder Reservoir Water Treatment Plant prepazed 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, Ina (Assessment of the Boulder Reservoir Water Treatment Plant, 2001). ~nprovements 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 appazent that the capacity of the facility needed to increase. The impoRance 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 [reat 8 MGD. Also, in September 2002, an industrial wastewater dischazge permit was issued to the BRWTP restricting the daily maa~imum 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 consuvcted 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 treaUnent plant: • replacing the existing flocculator/clazifier 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. Tn addition to enhancing the performance of the treatment plant, the masimum 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 Giazdia 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 well as improvements to the treatment plant. The 2006-2011 CIP for Source Water Protection AGENDA ITEM # ~ Page 5 includes the following: 2005 2006 2007 2008 2009 $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-$12Q000 for a Carter Lake pipeline feasibility study to be completed by Northern Colorado Water Conservancy District •$5,000 for buoys azound the Boulder Reservoir intake structure •$65,000-$75,000 for toilet facilities for recreauonal 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 I.eft Hand Water District, have requested that the NCWCD investigate the possibility of construcUng 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 eazly 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 vaziables 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 treatrnent at the BRWTP. The remainder of Boulder's CBT and Windy Gap water that is used to drive the exchange of water into Bazker Reservoir and the Silver Lake Watershed reservoirs will continue to be carried in the Boulder Feeder Canal. If Boulder condnues to participate, it is estimated that Boulder's shaze of the pipeline project costs following the feasibility study stage could be in the range of $20 million to $30 million. Future Water Treatrnent Facility Improvements In addition to the neaz-term improvements at the BRWTP, the BRWTP Facility Plan recommends the following mid-term improvements: • addition of chlorine dioxide AGENDA ITEM # ~ Page 6 • improved instrumentation • new raw water pump • treatment of dischazged washwater • pre-sedimentation • pH adjustment These improvements continue to strengthen the reliability of the treatment process in meeting regulatory requirements, as well as intemal water quality and quantity goals. Chlorine dioxide will help oxidize arganics, thereby reducing disinfecGOn 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 dischazged 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: 2007 2008 2009 2010 2011 0 $400,000 $3,000,000 0 $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 Jong-term improvements to the BRWTP. The recommended long-term improvements aze projected to include: • New treated water storage tank • Third DAF unit • Emergency power • Granular activated cazbon • UV or membranes The long-term improvements at the BRWTP aze not firmly established at this time. The final combinaUOn of long-term improvements will be deternuned by future regulatory requirements for Cryptosporidium removaUinactivation, 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 iJV disinfection system would make a new reservoir for Giazdia inactivation unnecessary. The need for ozone, UV or membranes will be driven by the need for additional Cryptosporidium removaUinactivation required by the LT2ESWTR. AGENDA ITEM # ~ Page 7 Future Anal~ 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 protecdon. This approach will identify the most cost- effective means of ineeting regulatory requirements and achieving the city's water quality goals prior to lazge 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. ATTACFIMENTS: Attachment A: Source Water Planning Study Phase I Executive Summary (Phase I Study) AGENDA ITEM # ~ Page 8 ~ CITY OF BOULDER SOURCE WATER QUAL/TY PLANNING STUDY - PHASE 1 EXECUTIVE SUMMARY The purpose of the Phase 1 Source Water Quality Planning Study (Phase 1 Study) is to provide the City of Boulder (City) with an overview of altemative approaches available to improve and protect Boulder Reservoir Water Treatment Facility (BRWTF) source water quality. This Phase 1 Study identifies those altematives that provide the best value to the City for future implementation. The Phase 1 Study was conducted within the context of the City's on- going efforts to establish definitive drinking water quality and quantity goals. As part of the strategy, the City desires to employ a multiple barrier approach to preventing pathogens and other contaminants from reaching the drinking water customer. Source water improvement and protection is the first barrier in this approach. A. Overview The primary source of BRWTF raw water is Carter Lake. Raw water is _~ delivered through a 21 mile open canal known as the Boulder Feeder Canal (BFC). The BFC discharges water either directly to the BRWTF or to Boulder Reservoir for later pumping to the BRWTF. The Phase 1 Study focused on Cryptosporidium as a primary indicator for water quality. Based on historical monitoring of raw water entering the BRWTF, additional removal treatment will be required under the Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) if the City continues its current operational mode. B. Source Water ~uality Management Alternatives The source water quality management altematives investigated as part of the Phase 1 Study were identified through discussions with the City staff during the initial stages of the project. These altematives are briefly described below. • Existing Source Water System. The existing source water delivery system is considered the baseline condition for the alternative evaluation. This altemative represents the current seasonal operation of the BFC and Boulder Reservoir as source water supplies. EXECUTIVE SUMMARY ES-1 ~ CITV OF BOULOER SOURCE WATER QUALITY PLANNING STUDY- PHASE 1 Boulder Reservoir Management. This alternative is based on using Boulder Reservoir as a year-around terminal reservoir. Raw water will be pumped from the reservoir to the BRWTF throughout the year. • Full Containment from Carter Lake to the BRWTF. The full containment altemative is based on the construction of a new 21- mile raw water pipeline that would contain, protect, and deliver CBT source water from Carter Lake directly to the BRWTF on a year- around basis using gravity flow. • Partial Containment from Ne/son Road to the BRWTF. The partial containment alternative is similar to the full containment altemative with a pipeline being constructed through the more highly developed areas to the north of the BRWTF. Above Nelson Road, the BFC would remain in service as an open canal. Under this approach the pipeline would only be in operation during the months when the BFC was in operation. During the remainder of the year, raw water would have to be pumped from Boulder Reservoir, as is the current practice. --~ • New Termina/ Reservoir. This altemative includes the construction of a new earthen terminal reservoir upstream of the Boulder Reservoir and the BRWTF. This approach would avoid the water quality conflicts inherent in using Boulder Reservoir for both recreation activities and a drinking water supply. • New Forebay. Similar to the new terminal reservoir alternative, this altemative is based on the construction of a new earthen forebay upstream of the Boulder Reservoir and the BRWTF. This approach would provide some amount of dilution and settling to reduce the contaminant load entering the BRWTF. C. Alternative Evaluation The altemative evaluation was performed collectively by the study participants. Each alternative was ranked in relation to each of the following criteria: r EXECUT/VE SUMMARY ES-2 CITY OF BOULDER SOURCE WATER OUALITY PLANNING STUDY- PHASE 1 • Predicted water quality with respect to pathogens. • Treatability issues including turbidity, manganese, TDS and algae. • Capital cost to implement each altemative. • Operational impacts including reliability and security. • Potential impacts to water rights or the ability to supply water to the BRWTF. • Community impacts including environmental and public acceptance issues. Potential impacts on the City's water quantity and water quality goals. Implementation timeframe. D. Recommendations As a result of the alternative evaluation, the Boulder Reservoir Management and the Full Containment alternatives were recommended to be carried forward for further investigation. The selection of these two altematives provides the City with both near-term and long-term solutions to their source water quality issues. Facilities are in place to allow the full-time use of Boulder Reservoir as a terminal reservoir for the BRWTF. Based on the historical BRWTF raw water data, this strategy can provide immediate reductions in the occurrence of microbial pathogens in the BRWTF raw water and compliance with the LT2ESWTR. Additional management strategies could be implemented at the reservoir over time to further enhance source water quality. However, to implement this alternative, the City will have to take steps to address the seasonal uptake of manganese. The Full Containment alternative would reliably deliver raw water from Carter Lake and assure that the source water quality will not be degraded in the BFC. Based on historical Cryptosporidium concentrations for other entities that deliver Carter Lake water through a pipeline, no additional treatment would be EXECUTIVE SUMMARY ES-3 CITY OF BOULDER SOURCE WATER QUALITY PLANNING STUDY - PHASE 1 required under the LT2ESWTR if this altemative was implemented. However, implementation of a full containment pipeline will involve a major commitment of capital funds by the Ciry. To date, the Ciry has been engaged in two separate planning efforts; one to investigate altematives for improvements to the BRWTF source water supply system and a second to investigate alternatives for improvements to the BRWTF treatment facilities. It is important for the City to consolidate the findings of these two efforts in a Phase 2 Study to develop a multi-barrier approach that provides the most cost effective means of achieving the City's water quality and quantity goals. The Phase 2 work should encompass the following tasks: • Consider the preferred source water management altematives ident'rfied in this Phase 1 Study in eonjunction with potential BRWTF treatment altematives. • Further define the scope and cost of source water and treatment alternatives as necessary to perform final evaluation. ~~" • Develop recommended long-term plan and prioritize implementation of key elements. • Perform utility cash flow scenarios and develop a capital improvements program (CIP) based on projected financial conditions. • Develop facility planning documents as required to guide the implementation of improvements for both the BRWTF source water supply and treatment facilities. The Phase 2 work will be more comprehensive in nature by considering both source water quality and treatment at the BRWTF. The relationship of source water protection measures in combination with treatment requirements and their overall impact on the requirements of the LT2ESWTR will need to be considered. This analysis will define the scope of combined alternatives, which will include both source water and treatment process elements. EXECUT/VE SUMMARY ES-4