5B - Consideration of Environmental and Engineering Assessment and Feasibility Study (LUR2010-00036) - Hogan-Pancost Property - 5399 Kewanee Dr and 5697 South Boulder Rd
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CITY OF BOULDER
PLANNING BOARD AGENDA ITEM
MEETING DATE: January 6, 2011
AGENDA TITLE:
Public hearing and consideration of Environmental and Engineering Assessment and Feasibility
Study #LUR2010-00036, Hogan-Pancost Property (also known as Boulder Creek Commons),
comprising approximately 22 acres located at 5399 Kewanee Drive and 5697 South Boulder Road.
Applicant I Owner: BCC, LLC
REQUESTING DEPARTMENTS:
Community Planning and Sustainability: Public Works:
David Driskell, Executive Director Maureen Rait, Executive Director
Charles Ferro, Land Use Review Manager Jeff Arthur, Engineering Review Manager
Karl Guiler, Planner II Katie Knapp, Floodplain and Wetland Administrator
Michelle Mahan, Civil Engineer I - Transportation
OBJECTIVE:
Define the steps for Planning Board consideration of this request:
1. Hear applicant and staff presentations
2. Hold Public Hearing
3. Planning Board discussion and recommendation.
STATISTICS:
Proposal: Feasibility study to show that the environmental and engineering constraints of the property can
be mitigated and the site can be reasonably developed.
Project Name: Hogan-Pancost Property (Boulder Creek Commons)
Location: 5399 Kewanee Drive and 5697 South Boulder Road
Zoning: The property is currently located in unincorporated Boulder County and carries a Boulder
County zoning designation of Suburban Residential and Rural Residential.
Comprehensive Plan: Low Density Residential (LR)IEnvironmental Protection (EP)
SUMMARY OF KEY ISSUES:
Staff has identified the following key issue to guide the Planning Board's Discussion:
1) Has the Environmental and Engineering Assessment and Feasibility Study demonstrated that the
environmental and engineering constraints on the property can be sufficiently mitigated so that the
applicant can move forward with a Concept Plan submittal?
BACKGROUND:
Existing Site I Site Context
This discussion item relates to the proposed annexation and development of Boulder County properties at 5399
Kewanee Drive and 5697 South Boulder Road; comprising a roughly 22-acre vacant site in east Boulder in the vicinity of
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the East Boulder Recreation Center more commonly known as the Hogan-Pancost property (see Figures 1 and 2
below). The site can be accessed from 55th Street from South Boulder Road to the south of the site or from 55th Street
from the north by way of the East Boulder Recreation Center.
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Figure 1- Vicinity map and context.
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Figure 2- Immediate site context (Hogan-Pancost properties outlined in red)
The Hogan-Pancost properties are within Boulder County-, however, as shown in Figure 3 below, almost the entirety of the
site is surrounded by city annexed land - namely the single-family residential developments of Keewayden Meadows to
the west, Greenbelt Meadows to the south, and the East Boulder Recreation Center to the northeast.
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OMAHA PL
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Figure 3- Site respective to city limits shown shaded.
Being within the Boulder Valley Comprehensive Plan (BVCP) Planning Area of IIA, the property is eligible to annex to the
city and has a BVCP land use designation of Low Density Residential for a majority of the site as shown in Figure 4 page 5.
The southeast portion of the site has a BVCP land use designation of Environmental Protection. The land use designations
are the result of analyses conducted on the site over the past decade as discussed below. Previous concept plan proposals
have generally been consistent with the Low Density Residential designation with single-family dwelling, senior housing
units, and the intent to preserve the southeast corner.
Since 2000, three requests have been made by the South East Boulder Neighborhood Association to change the BVCP
Planning Area from Area IIA to Area III-Rural Preservation; the most recent of which was made during the Year 2010 Major
Update of the BVCP. As part of the Year 2000 major update to the BVCP, the city and county reviewed a land use
suitability study of undeveloped Area II properties to determine their suitability for urban development as part of the
consideration to change the Planning Area to Area III-Rural Preservation for the Hogan-Pancost site.
As part of that study, it was concluded by council that the west portion of the Hogan-Pancost site was suitable for residential
development while the portion east of 55th Street would be more appropriate for environmental preservation.
Consequently, the city and the county kept the site in Area II, changed the land use designation on the eastern portion of
the site to Environmental Preservation, and retained the existing Low Density Residential designation on the remaining
portion of the site. Staff has recently recommended against a change to Area III-Rural Preservation pending the results of
the environmental study discussed within this memorandum and also to allow the processing of the annexation and initial
zoning application. If it is determined through additional review of the application that the proposal to annex and develop
the site is not supportable, reconsideration of the Planning Area change to Area III-Rural Preservation would be appropriate.
Staff presented this option to City Council this year and the council agreed.
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y
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Figure 4- BVCP land use of the site and surrounding properties.
As the Planning Board is likely aware, previous efforts to annex and develop the property have faced significant
neighborhood opposition related to environmental concerns including wetlands, ground water, flood and wildlife habitat as
well as potential impacts to the surrounding neighborhood from additional density and traffic, resulting in the applicant
withdrawing their application. Controversy also surrounded overlot grading to "contain groundwater seepage from irrigation
ditches in the area" that occurred in 2008.
As part of a previous Concept Plan in 2007, which did not proceed to Planning Board for review and was subsequently
withdrawn, the property owners agreed that prior to the submittal and review of a subsequent Concept Plan application, the
property owners would provide staff with more detailed environmental analyses for the property.
These environmental analyses have been recently completed by the applicant's consultants and have been submitted to the
city and city-contracted third party consultants for analysis. The studies were distributed to the neighborhood as well for their
review. These studies are the subject of the Planning Board discussion at a public hearing and are discussed further in the
`Project Description' and `Analysis' sections that follow.
PROJECT DESCRIPTION:
The land owners of the Hogan-Pancost property have submitted an Environmental and Engineering Assessment and
Feasibility Study to evaluate the site constraints and technical issues associated with developing the subject property. This
study included the following analyses:
• Conceptual Storm Water Management and Floodplain Mitigation
• Groundwater Hydrology Monitoring and Wetland Delineation
• Groundwater Evaluation
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• Preliminary Subsurface Investigation
• Vegetation and Wildlife Habitat Existing Conditions
• Species of Concern
• Wetland Mitigation/Enhancement & Prairie & Riparian Habitat Creations
• Transportation Impact Feasibility Study
A complete copy of the study is available on the city's website at www.boulderplandevelop.net under "Hot Topics and
Current Projects." Below is a summary of the findings of their study:
1. Storm water management facilities designed to support the development of the Hogan-Pancost site will not adversely
affect, and in some cases may improve, conditions on the surrounding properties, irrigation facilities, existing storm
drainage system, and South Boulder Creek
2. The main influence on ground water levels near the Hogan-Pancost site is net recharge (water penetrating the ground
surface). The main contributors to the net recharge are irrigation of pasture and nearby residential lawns, seepage
from unlined irrigation ditches and perennial recharge from South Boulder Creek. Development of the site will
decrease the overall recharge to ground water by eliminating pasture irrigation and ditch leakage which will lower the
groundwater elevation. The current pattern of recharge will be reduced and the groundwater table will return to more
natural levels. Current basement sump pumping will not be decreased dramatically because other contributors to the
rise in ground water elevation cannot be eliminated by the project.
3. Based on the soil conditions encountered on the site, proposed buildings can be supported on spread footings.
4. There are no natural communities, rare plants, riparian corridors, or critical wildlife habitat as identified by the Boulder
County Comprehensive Plan on the Hogan-Pancost property.
5. The project site contains areas that would become regulatory wetland and wetland buffer areas once the property is
annexed into the city, including 0.465 acres of wetlands areas on the western parcel and 1.622 acres of wetlands on
the eastern parcel. Permanent impacts to wetland areas on the western parcel can be mitigated at a 2:1 ratio by
creating additional wetland areas on the eastern parcel. The wetlands and natural areas on the eastern parcel would
be preserved and enhanced. No development is proposed for the eastern parcel. The 22.17 acre development
would contain 9.404 acres (42.42%) of native habitat including riparian forests, wetlands, and prairies with riparian
trees and shrubs.
6. The Traffic Impact Feasibility Study demonstrates that the existing street network will generally be able to
accommodate the expected Hogan-Pancost traffic. The Kewanee Street connection is expected to continue
operating at an acceptable level of service A in both the am and pm peak hours with the addition of the Hogan-
Pancost anticipated traffic. The study recommends restriping the intersections of South Boulder Road/Manhattan
Drive and South Boulder Road/55th Street to provide dedicated southbound left-turn lanes in order to alleviate some
of the additional delay at these locations. Adding the dedicated southbound left-turn lane to the South Boulder
Road/Manhattan Drive intersection will allow the southbound through- and right-turning movements to operate at a
level of service E in the am peak hour and an acceptable level of service B in the pm peak hour, whereas the
southbound movement is currently operating at a level of service F in both the am and pm peak hours. Adding the
dedicated southbound left-turn lane to the South Boulder Road/55th Street intersection will allow the southbound
right-turning movements to operate at an acceptable level of service C in the am peak and an acceptable level of
service B in the pm peak, whereas the southbound movement is currently operating a level of service D in both the
am and pm peaks.
PUBLIC COMMENT AND PROCESS:
Area neighbors have received periodic updates on the status of the property and detailed project information is routinely
posted on the city's website. A digital copy of the study was forwarded to the neighborhood in June, 2010 when they were
initially submitted to staff for review. A formal notification was also sent to the neighborhood in advance of the proposed
public hearing scheduled for January 6, 2011.
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The Environmental and Engineering Assessment and Feasibility Study has been posted on the city's website at
www.boulderplandevelop.net under "Hot Topics and Current Projects." Property owners within 800-feet of the project
area also received a mailed public notice informing them of the study and this Planning Board meeting and Public
Hearing. The City's website has been updated to include a comment form to allow feedback to be submitted
electronically.
Staff has received electronic comments and e-mails regarding the Environmental and Engineering Assessment and
Feasibility Study (refer to Attachment A). The correspondence received has been in opposition to the any proposed
development based on concerns about increased residential traffic and flooding risks.
ANALYSIS
KEY ISSUE: Has the Environmental and Engineering Assessment and Feasibility Study demonstrated that the
environmental and engineering constraints on the property can be sufficiently mitigated so that the applicant
can move forward with a Concept Plan submittal?
STAFF FINDINGS AND RECOMMENDATIONS:
The City retained CH2MHill, Fox Higgans Transportation Group and Land Stewardship Consulting, Inc., for an
independent review of the study. City staff and the city-contracted consultants generally found that the Environmental
and Engineering Assessment and Feasibility Study demonstrated that the engineering and environmental constraints on
the property could be adequately mitigated and the property could be developed. Staff recommends that the applicant
move forward with Concept Plan.
After an initial review of the reports, a meeting was held with the property owner, the owner's consultants, city staff and
the city-contracted consultants to discuss the reports and any questions that arose during the reviews of the reports.
The owner's consultants revised the reports to address the review questions. Final review reports were received by the
city-contracted consultants (see Attachment B).
As the project progresses and the applicant moves forward with design, the following items should be considered:
• The applicant is correct that the site is not designated as critical wildlife habitat in the Boulder County Comprehensive
Plan. However, a portion of the eastern parcel has a Boulder Valley Comprehensive Plan Natural Ecosystem Overlay
designation. This designation denotes areas that support native plants and animals or possess important ecological,
biological or geological values. In this case, the designation identifies an important buffer between the South Boulder
Creek wet meadow habitat on Open Space and Mountain Parks property and the potential development to the west.
Maintaining this buffer area on the eastern parcel is important for sustaining the biological diversity and viable habitat
for native species in the area, and for protecting the ecological health of the floodplain ecosystem. The purpose of
the Natural Ecosystem Overlay is to guide the city in its decisions and negotiations over conservation easements,
annexations, purchase of development rights, zonings and development review.
• Although the Hogan-Pancost parcel does not support habitat for any plant or animal species of special concern as
identified in the Boulder County Comprehensive Plan, it does support a colony of prairie dogs. Black-tailed prairie
dogs are considered a species of local concern under the Boulder Valley Comprehensive Plan. Preservation of or
mitigation of adverse impacts to prairie dogs and their habitat is one criterion of site plan review under subsection 9-2-
14(h) of the Boulder Revised Code.
• The naturally fluctuating groundwater levels in the area are critical to the protection of the sensitive wet meadow
ecosystems on city-owned property to the east of 55th Street. Permanent dewatering of the Hogan-Pancost site for
basements or other underground development would potentially have a detrimental impact on the adjacent
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ecosystems and the habitat for the Preble's meadow jumping mouse. Basements and underground dewatering
systems should not be constructed on any portion of the Hogan-Pancost parcel.
• The applicant should anticipate dedicating a drainage and flood control easement along the eastern boundary of the
site.
• A final traffic impact study will need to be completed as part of the Site Review.
NEXT STEPS:
1. If the board finds and recommends that the information within the environmental study is adequate and can conclude
that the site is suitable for development, the applicant would then submit a new Concept Plan for review that will ultimately
be brought back to Planning Board for staff and neighborhood review and comment (no approval or denial) on the
fundamental site and building design and land use concepts. Review of more detailed applications (i.e., Annexation and
Initial Zoning, Site Review, and Preliminary Plat) would follow and require Planning Board and City Council review and
approval. Or;
2. If the board finds that additional information and/or studies should be conducted before concluding whether or not site
is suitable to develop, then the applicant would address those specific points requested by the Planning Board and
return to the Planning Board at a later date prior to preparing a new Concept Plan application. The applicant may elect
to move forward in absence of addressing any points raised by Planning Board, but at the risk that the development may
not receive endorsement from the city during the next application review stages.
Approved B
d Driske9, Ex u I hector
Department of Community Planning and Sustainability
ATTACHMENTS:
A. Correspondence Received
B. Review Summaries (from the city's consultant team)
-Exhibit 1: Transportation Impact Feasibility Study Summary
-Exhibit 2: Stormwater, Flood Plain, Groundwater Study Summary
-Exhibit 3: Wetland, Vegetation, Wildlife Habitat Study Summary
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Attachment A
Fox, Debbie
From: Maureen * [moreofrene@gmail.com]
Sent: Sunday, December 19, 2010 6:47 PM
To: Knapp, Katie
Subject: Proposed development of Hogan Pancost area
Hi, Katie Knapp,
My great grandmother's maiden name was Knapp and I have been doing some genealogical research on the
Knapp family. There are several branches of the Knapp family in this Boulder area. Many years ago, one of the
Knapp relatives invited all the 13th and 14th cousins to their home for a reunion. It was great fun.
Now, onto the proposed development of the Hogan Pancoast property. Talk about old names in this area, and
you have to be aware of the many contributions both of those families made to this area. Since the summer of
1969, my family has lived in the old Keewaydin area of Boulder which is close to the proposed development.
We have not personally had any water damage to our home, but I do know there were other homes that were
significantly impacted by the flood of May 1969. It would be good if you could review the Boulder Daily
Camera coverage of that flood. Since May of 1969 there has been significant development in the area. When we
moved here, Manhattan was the street furthest East from our home. The homes built South of Manhattan and
the entrance to East Boulder Rec Center, the apartments built South of us (that are between Illini Way and
South Boulder Road, and all the homes built from Manhattan Drive (by Manhattan School for the Arts) and
extending to
55th Street(or the other entrance to the rec center), were built after the flood of May 1969. I do not know what
studies were made of this area before permission was given to develop those areas. I do have serious
reservations as I understand some of the newer homes that are south of the old Keewaydin area need to have
sump pumps.
I also have long been alarmed that when the apartments on South Boulder Road were built that significantly
increased the amount of concrete and also the run-off from those apartments is slanted to run into the old
Keewaydin neighborhood through a concrete culvert which empties onto Manhattan and then runs down the
street. If a flood in May of 1969 affected this neighborhood to such a degree, imagine how the loss of this land
to absorb water may impact future flooding.
About two years ago, we had one of those quick downpours of rain and I drove around the neighborhood and
took pictures of the water flooding the streets and also filling the basin that is at Foothills Highway and Baseline
Road. The water reached almost to Baseline Road. Hmmm...
Come to think of it, all those apartments on the west side of Manhattan and Foothills Highway were not present
during the flood of 1969.
Another place that some of the water could have been soaked up in 1969. Foothills Highway was called
"Thunderbird" and I believe it was only a two lane road. I know that it stopped at Baseline and beyond that was
empty land.
I remember going to a city council meeting shortly after moving here and I watched a homemade film of the
flood of May, 1969. it was filmed by a
person who lived in the first ranch home facing South Boulder Road south of Manhattan. Hmmm... another
change since 1969 is that there used
to be a farmhouse where the Day's Inn Motel is on Manhattan. The film depicted water gushing through some
of the windows of homes that now
have the apartments in their back yards.
i
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I would like very much to talk with you and perhaps even meet with you and show you the pictures I took of the
toll a fast moving rain storm
took when it moved through a few years ago. Please e-mail me and let me know if that would be possible.
Someone once told us that this area used to be a river bed. Is that true?
Thank you for reading this long e-mail and I look forward to hearing from you.
Maureen McCarthy
z
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Fox, Debbie
From: Maureen * [moreofrene@gmail.com]
Sent: Monday, December 20, 2010 3:34 PM
To: Guiler, Karl; Mahan, Michelle; Matheson, Valerie; Knapp, Katie
Subject: Development of the Hogan Pancost area
Hello to the three of you.
I have already sent a lengthy e-mail to Katie Knapp but thought that I should contact you also with my
concerns. I know that she is the one who will deal with the impacts of flood concerns with this potential
development. I shared with her my concerns and would also encourage the three of you to review the Boulder
Daily Camera coverage of the flood in May of 1969 and how this impacted the original Keewaydin subdivision.
There has been significant development in the areas surrounding the original subdivision since that flood of
May, 1969 which would make the potential for worse flooding significant in the future. There was also a minor
flood in 1974 that impacted this area. A few years ago a "gully washer" hit Boulder. It was short in duration but
intense rainfall. I drove around the development and have copies of the pictures I took if there is any interest in
reviewing these. Water extended out from the basin at Baseline and Foothills Highway to almost both of these
streets. It was significant and would significantly impact traffic flow if it were to happen again.
If this development is allowed to proceed and there is any "building up" of that parcel of land to protect the new
development and obtain the permit to build, excess water will have to be diverted. I am concerned that it will all
flow into the Keewaydin area. So, one fix to allow the development would be a disaster for those of us who live
nearby.
I would think the use of the proposed land for development for open space would be advantageous in two ways
(at least). Open land can absorb rainfall and melted snow much better than concrete and developed areas. Also,
as the gateway into Boulder, it is much more pleasant to see open land than over developed areas. Traffic-wise,
have you ever seen Cherryvale, South Boulder Road, Manhattan, Baseline and Foothills Highway around 8 a.m.
or 5 p.m.? These are already heavily traveled roads especially since the development in Louisville, Lafayette,
Superior and Broomfield. We have lived here since May of 1969 and have seen many changes and lots of
development. Transportation wise, Foothills Highway was not even here. The road west of the development was
Thunderbird and I believe it was only two lanes and ended at Baseline.
So, there is another concern for soaking up any excess water that is no longer in existence. The convergence of
36, 28th Street, Foothills Highway and Table Mesa Drive is already terribly congested and I question the air
quality in this area. Has the Boulder County Health Department been part of any studies around air quality
during high traffic times? Further development seems to be not a good idea on many grounds. I have seen plans
for further transportation development for this area and this would not alleviate the traffic problems or air
quality concerns. It would be good also to review some of the findings on brain development when children
grow up in areas where there are major highways near where they grow up.
Those of us who live in the area have also appreciated through the years the wildlife that occupies this open
space area. It would be
a shame to change the little bit of open area that now exists. One of my greatest fears is that Boulder is evolving
into a city like Santa Fe
where there is overdevelopment and commercialism (really tacky) that leads into "old town" and if you have
ever been there, you know what I mean.
I know that the funds that preserve open space are from residents of Boulder County and I would hope that we
who are residents of the city and county of Boulder would be able to save our area of the county. I must say that
i
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this is a great place to live. I'm wondering if the residents of Broomfield, Weld, Denver, Adams, Arapahoe,
Douglas, Jefferson and other outlying counties that avail themselves of the open space Boulder County has
preserved donate any financial support. Or, do they just drive in to hike, bike, and mountain climb and provide
no financial support?
I understand that membership to Boulder City Recreation Centers is available for a slightly higher rate to non-
residents. Seems like we are providing a lot of services for people who do not live in the City/County of
Boulder and contribute minimally.
Please contact me at (303) 494-1779 if you have any questions or I can be of any further help. Katie, I decided
to include you in this e-mail also after I read it over. Thanks to all of you for your diligence in researching the
implications of this potential development. I know in your deliberations you must respect the rights of the
property owner and developer as well as the homeowners in the neighborhood, but you should also be aware of
where the waters will flow when/if this development is completed. If the developer raises the level of the
ground on his development, the waters will flow downhill to the present homeowners property. There are also
significant implications for flow of traffic.
Thanks for your help.
Maureen McCarthy
2
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Hogan -Pan cost_Property- Date name comment
Return tcfaq ck yyyymmd
d
Hogan-Pancost_Property- 20101209 Doug Benson DO NOT BUILD THE HOGAN-PANCOST PROPERTY!
feedback We need this extra open space, we need LESS traffic
and FEWER people. This will permanently scar the area.
DO NOT APPROVE CONSTRUCTION HERE! Thank
you.
Hogan-Pancost_Property- 20101219 Lisa Weisz What about the safety of the children getting on and off
feedback the school bus? The feasibility study is silent about this.
At the intersection of 55th and Ontario, Eisenhower
Elementary students cross 55th twice a day getting to
and from the bus stop, and one of those times is at 8am
during morning rush hour. Middle school children also
cross this intersection as they are walking or biking to
Manhattan School. During the summer these same
children cross 55th to get to their neighborhood pool.
There is currently a plain crosswalk at the intersection of
55th and Ontario that motorists routinely ignore- This
intersection is already dangerous. What can be done to
make it safer, especially in light of the extra traffic
anticipated in the feasibility study? Although the 55th-
Ontario intersection is the closest intersection to the
proposed development's main entrance, the study
ignored it. I suggest installing a traffic light there, or at a
minimum flashing lights like the ones at CU and a large
raised crosswalk like the ones on 55th just north of
Baseline.
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Attachment B, Exhibit 1
FOX
10
T R A N S P 0 R T A T f C N G R O U P
MEMORANDUM
To: Michelle Mahan
From: Bill Fox
Date: December 15, 2010
Project: Hogan-Pancost Property Development Proposal Review
Subject: Review of Transportation Impact Feasibility Study
At your request, and on behalf of the City of Boulder, I have reviewed the Transportation
Impact Feasibility Study report (May 2010 and Revised November 2010) prepared by
Drexel, Barrell & Co. for the Hogan-Pancost Property. Review comments are
summarized by topic as follows:
General Comments
1. In general, I concur with the traffic study methodology and most of its findings,
but offer the following comments and suggestions that should be addressed in
the final traffic study for this project when completed.
Existing Conditions and Background Traffic
2. The report refers to Kewanee Drive as an east/west "community collector"
roadway and Manhattan Drive as a "local" roadway. I believe these descriptions
would be more accurate if they were reversed, but this would not change any of
the findings of the study.
3. On Figure 2, daily traffic is illustrated on Manhattan Drive and 55t" Street just
north of South Boulder Road. It would be helpful to also illustrate daily traffic
volumes (actual count or estimate from peak hour counts would be acceptable)
just south of Baseline Road on both Manhattan and 55t"
4. Peak hour traffic count dates should be illustrated on Figure 2. It appears that all
peak hour traffic counts used in this study are from 2008 when an earlier version
of this study was prepared. The City may want these counts to be updated for
the final traffic impact study on this project, per the City's traffic study
requirements.
Item 5A Cover Page P.O. Box 1 9768, B❑LJLDER, C❑LORAD❑ 803 ~ItnE Page 14 of 35
PHONE: 303-652-3571 • FAX: 303-772-2329 OR 303-652-6574
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Ms. Michelle Mahan
December 15, 2010
Page 2 of 3
5. Section 3.1 discusses the traffic growth rates used to estimate the background
traffic growth at study area intersections. It appears that the growth rates
referenced are annual rates, but the text does not specifically say so. This
should be clarified in the final traffic study report text.
6. Section 3.2.1 discusses the existing traffic control in the intersection of South
Boulder Road and Manhattan Drive and the existing level of service (LOS). The
study evaluates two options for improving intersection operation. The first is the
restriping of the southbound approach on Manhattan to create a separate left
turn lane. The second is the installation of a traffic signal. The study conducted
a traffic signal warrant analysis at this intersection and concluded that two of the
eight warrants in the MUTCD are currently met.
It is my understanding that the City of Boulder Transportation staff would
consider the restriping of the southbound approach (assuming that no roadway
widening is required), but does not believe that a traffic signal is warranted
currently at this location based on automobile LOS and delay. However, the City
does believe that a traffic signal at this location would be beneficial to RTD riders
who get on/off buses on South Boulder Road at this intersection, particularly
since some of these transit riders who must cross South Boulder Road are
students accessing the Manhattan School. In fact, the City has submitted a grant
application through the Safe Routes to School Program to seek funding for this
traffic signal.
Trip Generation and Distribution
7. The study references the trip generation rates from the 7t" Edition of the ITE Trip
Generation Manual in the text, and the 8t" Edition of the Trip Generation Manual
on Table 2. This inconsistency should be resolved in the final report for this
project. It appears that the most current trip rates have been used in the
analysis.
8. In the initial study the trip generation did not take any reduction for multi-modal
travel that typically occurs in Boulder. At staff's suggestion, the revised study
includes a trip reduction to reflect Boulder specific travel patterns. I believe this
to be more representative.
9. After reviewing the initial report, staff had suggested using area traffic counts to
refine the trip distribution estimates. The initial estimates appeared to
underestimate the traffic that would use Kewanee Drive and Manhattan Drive.
The revised report has included updated trip distribution percentages which I
believe to be much more realistic.
Transportation Impact Analysis
10.1 do not have issue with the intersection LOS analysis presented.
Item 5A Cover Page Agenda Item 5B Page 15 of 35
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Ms. Michelle Mahan
December 15, 2010
Page 3 of 3
Accident Analysis
11. The study reviewed a five year traffic accident history at four major intersections
within the study area. No correctable auto/auto traffic accident patterns were
identified in any of the intersections.
12. It was noted that there were six automobile / bicycle accidents in the Baseline /
55th intersection in the five years studied. I am in the process of procuring and
reviewing the traffic accident reports to help determine if the City should consider
any corrective measures to mitigate bicycle / auto traffic accidents in this
intersection.
13. The study concluded that the additional traffic generated by the project will not
increase the traffic accident frequency at these intersections or result in the need
for any mitigation measures.
Recommendations and Conclusion
14. The study recommends restriping the southbound approach on Manhattan at
South Boulder Road to include a separate left turn lane. It also recommends that
the City consider a traffic signal at this location. As noted above, the City does
not believe that a traffic signal is warranted at this location to accommodate
automobile traffic, but is pursuing funding through the Safe Routes to School
Program to install a traffic signal to accommodate pedestrians crossing South
Boulder Road at this location.
15. The study recommends restriping the southbound approach on 55th at South
Boulder Road to add a separate left turn lane. This treatment was also
recommended in an earlier traffic study completed for the East Boulder
Community Park. I believe that City Transportation staff supports this
recommendation.
16. The study concludes that the transportation network can accommodate the
additional traffic that will be generated by development of the Hogan-Pancost site
with the recommended improvements noted above. I concur that the traffic
generated by this project can be accommodated by the existing transportation
network. Signalization of the South Boulder Road / Manhattan Drive intersection,
and adding restriping to add southbound left turn lanes on Manhattan and 55th
will improve traffic operations at these intersections.
Please let me know if you have any questions.
WC F/
Item 5A Cover Page Agenda Item 5B Page 16 of 35
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Attachment B, Exhibit 2
CH2M HILL
9191 South Jamaica Street
Englewood, Colorado 80112
Tel 303.771.0900
C H 2 RR H I L L Fax 720.286.9250
4W
December 8, 2010
400168.01.02
Ms. Katie Knapp, P.E., CFM
City of Boulder Planning and Development Services
Building Services Center
P.O. Box 791
Boulder, Colorado 80306-0791
Subject: Hogan-Pancost Development/ Annexation Review
-Revised Report Review
Introduction
This letter contains CH2M HILL's review of several reports updated in November 2010 in
response to comments received from CH2M HILL (CH2M HILL, 2010) and during an
October 7, 2010 conference with Boulder Creek Commons, LLC (BCC - the prospective
developer), the developer's consulting engineers and resource consultants, the City of
Boulder, and CH2M HILL. These reports are related to the proposed development of the
Hogan Pancost property, a 22-acre parcel south of the East Boulder Community Park and
Recreation Center. The parcel is broken into 2 pieces with 55t11 street running generally from
south to north through the east third of the parcel. The main parcel west of 55t11 street (West
Parcel) is surrounded on three sides by irrigation ditches with 55t1i street forming the eastern
boundary. The Dry Creek Ditch No. 2 forms the western boundary for the west parcel, The
Bodum Lateral forms the Southern Boundary to the west parcel and the Howard -
Superphostical ditch forms the northern boundary of the west parcel. The parcel east of 55tH
Street is bordered on the North and west by 55th Street and bounded by South Boulder
Creek to the east.
The land has be zoned in the Boulder Valley ConiprehenSiVe Plan (BVCP) as a class IIA area
which is an area appropriate for low density residential development of 2-6 units per an
acre for the parcel west of 55t11 Street (West Parcel) and for the parcel East of 55t1i street (East
Parcel) appropriate for environmental preservation.
The following reports (listed below) were provided to the City of Boulder (and passed along
to CH2M HILL) by the prospective developer, Boulder Creek Commons, LLC in November
2010.
Environmental and Engineering Assessment and Feasibility Study, Executive Summary,
Book 1 of 4. Boulder Creek Commons, LLC. June 2010, Revised November 2010.
Item 5A Cover Page Agenda Item 513 Page 17 of 35
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Environmental and Engineering Assessment and Feasibility Study, Conceptual Storm
Water Management and Floodplain Mitigation Report, Book 2 of 4. Drexel, Barrell
& Co. June 2010, Revised November 2010.
Groundwater Hydrology Monitoring and Wetland Delineation Report. Western
Ecological Resources, Inc. May 2010, Revised November 2010.
Groundwater Evaluation. Telesto Solutions, Incorporated. June 2010, Revised November
2010.
Preliminary Subsurface Investigation. Western Soils, Inc. April 2010, Revised November
2010.
Vegetation and Wildlife Habitat Existing Conditions. Western Ecological Resource, Inc.
May 2010, Revised November 2010.
Wetland Mitigation/Enhancement and Prairie and Riparian Habitat Creations. Western
Ecological Resource, Inc. May 2010, Revised November 2010.
The City of Boulder requested that CH2M HILL review the resubmitted reports to verify
that comments had been addressed and that the reports submitted meet the City of Boulder
Regulations regarding development. These regulations are described in the City of Boulder
Design attd Coltstructiolt Standards, Noveyriber 16, 2000 and in The City of Boulder Revised
Code (BRC) Title 9, Land Use Regulatiotts,1981. These regulations spell out the
requirements and design constraints that must be met to complete development within the
Cities limits and include transportation design, streetscape design, tree protection, general
utilities design, water design, wastewater design, stormwater design, and erosion and
sediment control.
CH2M HILL was asked to provide and impartial third party review of three specific areas
related to the Hogan-Pancost Development Proposal submitted by BBC, Inc. These three
areas are:
1. stormwater design,
2. floodplain mitigation and design;
3. and groundwater issues.
The neighborhood surrounding the proposed property have voiced concern that
development of the property could adversely affect hydrology in the area and cause
increased groundwater and surface water drainage that would impact existing basements
and residences. The City of Boulder also shares these concerns and has asked CH2M HILL
to review the groundwater analysis completed by the developer to address these concerns.
The City of Boulder has specific regulations regarding the stormwater design and floodplain
mitigation and design as laid out in the BRC and Design and Construction standards.
However, there are currently no specific regulations regarding changes in groundwater as
affected by construction and development. To complete the analysis of existing and
proposed improvements and modeling relating to groundwater, CH2M HILL used
currently acceptable engineering standards of practice to review the groundwater analysis
found in the development submittal. In addition, based on concerns from surrounding
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neighborhoods and at request of the City of Boulder, CH2M HILL reviewed the
development submittal for the following issues :
1. negative impacts to the surrounding neighborhood;
2. wetland considerations;
3. drainage systems;
4. construction issues;
5. and the feasibility of basements.
These specific issues outlined above were reviewed in the development re-submittal to
evaluate how comments were addresses regarding issues identified and evaluated in the
original submittal.
Other aspects of the development plan including transportation design, streetscape design,
tree protection, general utilities design, water design, wastewater design, wetlands
identification and mitigation and erosion control are not included in this report. The City of
Boulder has completed internal review or procured the services of additional engineering
firms to complete the review for items not defined in this memorandum. Wetlands issues,
impacts and mitigation were reviewed by an outside consultant. Impacts to wetlands
outlined in this memorandum are specific to issues related to the potential impacts of
fluctuating and changing groundwater conditions based on the proposed development.
This letter summarizes and comments on on-site issues related to wetlands, stormwater
design and drainage, floodplain mitigation and soils; followed by a discussion of off-site
groundwater hydrology issues that could affect the surrounding community.
Development Review Results
A comprehensive review of all submitted documents was completed between August 6,
2010 and August 20, 2010 by CH2M HILL staff. The results of that review are documented
below. In response to comments received from CH2M HILL (CH2M HILL, 2010) and during
an October 7, 2010 conference with Boulder Creek Commons, LLC (BCC - the prospective
developer), the developer's consulting engineers and resource consultants, the City of
Boulder, and CH2M HILL, the developer has resubmitted the reports with the comments
addresses. Below is the review of the resubmitted reports and the verification of comment
incorporation.
Storm Water Design
The following discussion presents the results of reviewing the Hogait-Paitcost
Envirotittietttal and EngineeringAssessinettt aril Feasibility Study Coticeptnal Storm Water
Mattagemettt and Floodplain Mitigation Report, May 2010 and Revised November 2010,
herein referred to simply as Rehortl.
The Report provides a conceptual overview of the proposed storm water management and
mitigation impacts for a proposed development on the Hogan-Pancost Property. CH2M
1 Unless otherwise specified, the Report is binder 2 of 4 of the submittal.
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HILL reviewed the Report for concurrence with the City of Boulder Design and
Construction Standards and Title 9 of the BRC.
Chapter 7 of the City and Boulder Design and Construction Standards (Standards) provides
guidance for storm water design and design criteria for development within the City of
Boulder. Below is a discussion of sections that are considered important to mention or may
not have been fully covered within the Report.
Section 7.01 H specifically details the standards for developing near irrigation ditches and
laterals. The proposed site is bordered on three sides by irrigation ditches. The western edge
of the property is defined by the Dry Creek Ditch No. 2, the southern edge of the property is
bordered by the Bodum Lateral and the north edge of the property is bordered by the
Howard-Superphostical Ditch.
As noted in the initial review by CH2M HILL of the initial development reports, several
issues were noted regarding Section 7.01H of the standards. These included:
- Designated rights-of-way and easements were not specifically included in the report
dated June 2010,
- and written agreements from the Ditch Companies acknowledging and accepting
modifications to their conveyance facilities were not included in the report dated
June 2010.
The property owners have met with the Ditch Companies Board of Directors, which have
reviewed the construction documents and hydraulic calculations regarding improvements
to the specific ditches. During these discussions, verbal agreements have been made with
the ditch companies to complete the improvements. Easements for Dry Creek Ditch No. 2
will be 30' wide and be dedicated to the Ditch Company and the City of Boulder. Easements
for the Bodum lateral have yet to be determined. The geometry of each easement dedication
will be shown during subsequent City Land Use Reviews and the actual dedications will be
provided as part of the City's Technical Document Review application. As discussed at the
October 7, 2010 meeting with the City, at this time the City has indicated that the above
information satisfies the requirements of Section 7.01-H.
Section 7.02 of the standards contains a requirement that the topography datum needs to be
identified. After reviewing the report from June 2010, the following comment was noted. It
is not clear what the topography presented in the Report is based on. To meet the
requirements of the Standards the topography needs to be in the National Geodetic Vertical
Datum (NGVD 29) and clearly documented in the text.
The datum of the topography has been identified and updated in the revised report and is
defined as follows:
- For NGVD 1929 Datum, add 0.4 ft to the elevations presented within the report.
- For NGVD 1988 Datum, add 3.43 ft to the elevations presented within the report.
It should be noted that the report references the NGVD 1988 Datum for the new South
Boulder Creek Flood Study. It is assumed that this was meant to be the North American
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Vertical Datum of 1988 (NAVD 1988 Datum). This typo, NGVD 1988 Datum, should be
fixed to reference NAVD 1988 Datum in the report so that the datum is clear.
In Section 7.05-B of the Standards indicates that a 2-year storm is required to be analyzed for
the hydrologic analysis and hydraulic design stormwater improvements in Single Family
Residential development. Within the original report from June 2010 both the 10-and 100-
year storms are used for detention sizing and sizing of the stormwater facilities. Although
this is a conservative approach to stormwater sizing, an analysis of the 2-year storm needs
to be included to comply with the literal recommendations of Section 7.05-B of the
Standards. A waiver could be obtained to indicate acceptance by the City of the 10-year
design storm.
As discussed at the October 7, 2010 meeting with the City, at this time the City has indicated
that the above information satisfies the requirements of Section 7.05-B and that the minor 2-
year storm will be addressed during the City's Land Use Review and Site Review
Application.
During the initial review of the hydraulic calculations made for open channels, in the initial
report dated June, 2010, it was noted that the hydraulic calculations for Bioswale 1 (Section
1) as found in Appendix D does not include any relevant computations for the 10-year
flowrate since the flow rate is set to 0.00 cfs. The adequacy of this channel cannot be
ascertained until the required calculations are completed as outlined in Section 7.07.
Upon review of the resubmitted report on November 2010, it was clarified that the bioswale
will not convey flow during the 10-year storm and that the reports in Appendix D are
correct.
Section 7.07-D-2-g has requirements for the horizontal curvature of all open channels and
indicates that the horizontal curvature be a minimum of 50 feet or twice the top width of the
proposed channel. It is difficult to determine if the channel radiuses presented on Figure 3d
of the Report fall within a minimum of 50 feet or two times the channel top width. The
adequacy of the channel cannot be ascertained until the required radiuses are detailed as
required in section 7.07-D-2.g of the Standards.
As discussed at the October 7, 2010 meeting with the City, at this time the City has indicated
that the reduced radii in the storm water channels is acceptable and the channel satisfies the
requirements of Section 7.07-D-2. The radius of the channels will be addressed during the
City's Land Use Review and Site Review Application and a variance will be applied for if
necessary.
Floodplain Mitigation
Recently a Flood Hazard Area Delineation was completed on South Boulder Creek. The
revised regulatory floodplain for this area does affect the Hogan Pancost Property so to
develop the property; Title 9 of the BRC will need to be adhered to as well as FEMA
regulatory standards including no-adverse impact to surrounding properties.
Sections 9-3-2 and 9-3-3 and 9-3-6 of Title 9 within the Land Use Code govern floodplains
and floodplain regulations for the City of Boulder. At the conceptual stage, many of the
floodplain rules and regulations do not apply for this submittal. However, the discussion
51 I
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Presented in the Report addresses the flooding and proposed mitigations. After review, it
appears the Report complies with the requirements of the City for a Conceptual Storm
Water Plan. However, Section 9-3-6.b(3) of Title 9 states:
(3) A floodplain analysis by a Colorado registered professional engineer
of the flood profile, elevation, and velocity, using methodology
acceptable to FEMA, including existing and anticipated uses and making
a determination that the proposed construction or development will not
cause a rise in the elevation of the water surface of a one hundred-year
flood;
The Report proposes flood channels and detention within the property to mitigate the
flooding and the effects of flooding on the property. However, an analysis of the 100-year
flood was not completed to determine if the proposed improvements on the Hogan-Pancost
property would cause an adverse impact on surrounding properties upstream or
downstream of the property. Previous studies of the South Boulder Creek Fooodplain have
indicated a complicated interaction between the removal of floodplain storage and impacts
to the surrounding floodplain. An understanding of the flood impacts to surrounding
properties would be required to make this analysis compliant with Title 9 of the BRC.
As discussed at the October 7, 2010 meeting with the City, at this time the City has indicated
that a floodplain analysis using the Regulatory MIKE FLOOD model will not be required. A
conservative analysis of the flows, including flow volume, has been included in the report
that conceptually addresses the storm drainage and floodplain concerns across the site. The
City has indicated, in the October 7, 2010 meeting that floodplain analysis using MIKE
FLOOD may be required in future submittals including the Land Use Review and Site
Review applications.
On-site natural resources, drainage, groundwater and soil issues
As discussed in CH2M HILL's August 2010 review, the groundwater evaluation report was
prepared to address concerns of neighbors that the proposed housing development could
elevate the groundwater table and increase their use of basement sump pumps. Although
the City of Boulder has stormwater and floodplain development rules, there are no explicit
rules related to perturbing groundwater hydrology during development. As such,
CH2M HILL evaluated the groundwater evaluation report against currently acceptable
engineering standards of practice.
One of the principal conclusions from CH2M HILL's review of the June 2010 groundwater
evaluation report was that authors relied heavily on professional judgment to assign flux
rates for recharge, runoff, evapotranspiration, and other hydrologic processes when
estimating water balances in the study area and assigning parameters to their numeric
model. Telesto responded to these comments by adding a separate section to the revised
report - Attachment 1: Calculations and Supporting Documentation for Parameters Used in
the Analysis. This attachment provides rationale for each of the assigned flux rates used in
the ground water evaluation:
• The groundwater withdrawal rate (40 gallons per minute) of resident sump pumps
adjacent to the proposed development.
• Baseline pre-development recharge rates in the study area,
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• Irrigation rates used to account for summer flood irrigation that was conducted on the
property before 2008,
• Groundwater recharge rates from flood irrigation,
• Bioswale evapotranspiration and recharge,
• Landscape irrigation rates and recharge from landscape irrigation
The original report was also modified to include references to the new attachment at each
point in the text where these rates were first discussed.
Telesto also issued a separate response -to-comment letter dated November 8, 2010 (Telesto,
2010b) that reproduced Attachment 1 but also addressed three additional CH2M HILL
comments. Both Attachment 1 and the response-comment letter were further clarified in a
November 30, 2010 follow-up email.
By providing additional rationale on assigned flux rates, Attachment 1 and Telesto's
response-to-comment letter generally resolve CH2M HILL's comments on the groundwater
evaluation report. Specific issues and exceptions are detailed below.
Sump Pump Withdrawals
Basement sump pumping rates were estimated based on anecdotal reports and notes
provided by neighboring landowners. In the attachment, Telesto provides further support
for assigning a combined pumping rate of 40 gallons per minute from resident sump pumps
by providing raw questionnaire response data from the only two respondents that provided
any sort of quantitative information on flow rates from their sump pumps and by describing
how Telesto's assigned rate was derived from the raw data. Note that Telesto identified a
minor error in their write-up (see the November 30, 2010 email): the second quote from the
questionnaires should be attributed to the resident at 250 Cimarron Way. Re-issuing a
corrected Attachment 1 will resolve CH2M HILL's comments on Sump Pump Withdrawal
rates.
Baseline Pre-development Recharge Rates
This section of Attachment 1 presents support for Telesto's assumptions that 10 percent of
annual rainfall percolates to the underlying shallow groundwater aquifer in the study area.
This allocation was based on simplifying assumptions that recharge only takes place during
October, November, and March. No recharge is assumed for the other months because
potential evapotranspiration exceeds precipitation during the summer and the ground is
frozen during December, January, and February. These simplifications evoke the maxim
"All models are wrong. Some models are useful." Recharge to the groundwater table from
precipitation almost certainly takes place outside the October, November, and March
window, but growing season ET and winter frost depth in the study area are significant
constrains on recharge. Telesto's allocations to balance annual precipitation in the study
area are not unreasonable and result in a recharge rate that is estimated at 3.3 percent of
annual precipitation. This budget reveals conservatism in their 90/10 split between recharge
and other pathways used in their groundwater model. Note that Telesto provided
additional clarification in their November 30th email (Attached to letter) that was needed to
reproduce their calculations. Re-issuing a clarified Attachment 1 that explicitly states the
amount of mean precipitation that takes place between December and February will resolve
CH2M HILL's comments on recharge rates from precipitation. There is currently some
71
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discrepancy in this value - the text (page 5) and Table 1 of the report cite 7.4 inches of
precipitation during the winter, but calculations in Section 1.2 of Attachment 1 use 7.7
inches. The report needs to use a consistent value throughout.
Flood Irrigation Rates
No comments.
Recharge Rates for Flood Irrigation
No comments.
Bioswale ET and Recharge Rate
Recharge to groundwater from bioswales in the proposed development was estimated by
performing a winter- and summer-season water balance on water entering these features.
Telesto's accounting is reasonable, but the table in Attachment 1 could be clearer by
including intermediate calculations used to derive the total amount of recharge that takes
place during a season. Telesto should additionally present these fluxes in units of gallons
per minute, the unit that was adopted throughout the text and in tables 2 and 3 of the report
and feet per day as was used throughout Appendix A. The winter and summer bioswale
recharge rates derived in Attachment 1 should match with values used in Table 3 of the
report.
In their supporting documentation, Telesto indicates that the MODFLOW model was
modified to represent the locations of bioswales on the proposed development and that
additional model runs predict a 2.0 gallon per minute drop in sump pump rates between
pre-development and post-development scenarios. This difference is less than the 4.3 gallon
per minute noted in the conclusion of Appendix A (page A-9).
Landscape Irrigation Rates
No comments.
Response to CH2M HILL specific comment #1
See discussion of Telesto's Bioswale ET and Recharge Rate analysis.
Response to CH2M HILL specific comment #2
Flood irrigation represents a reasonable baseline scenario provided the landowner still has
their water right.
Response to CH2M HILL specific comment #3
No comments.
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Summary and Conclusions
In general, Boulder Creek Commons, LLC. has completed the conceptual design and
reported the impacts of the development and has created mitigation plans to mitigate the
impacts of the Hogan-Pancost Development in accordance with the City of Boulder
Development Standards. In addition, the resubmittal of the site development reports has
addressed the majority of comments raised during the initial review of the Reports by
CH2M HILL in August 2010
For the Stormwater and Floodplain mitigation review of the resubmitted reports, one
notable discrepancy required by the City of Boulder Design acrd Coitstnictiorr Standards,
Noz)ernber 16, 2000 or The Cit1/ of Borilder Revised Code (BRC) Title 9, Laird Use
Regulatioirs is noted below:
Storm Water Design
- 7.02-C-2: It appears that a typo has occurred in the report. In the revised Report the
NGVD 1988 Datum is referenced. This should be corrected to reference the North
American Vertical Datum of 1988 (NAVD 1988 Datum)
Floodplain Mitigation
- Section 9-3-6.b(3) of Title 9: The Report proposes flood channels and detention
within the property to mitigate the flooding and the effects of flooding on the
property. However, an analysis of the 100-year flood was not completed to
determine if the proposed improvements on the Hogan-Pancost property would
cause an adverse impact on surrounding properties upstream or downstream of the
property
As discussed at the October 7, 2010 meeting with the City, at this time the City has
indicated that a floodplain analysis using the Regulatory MIKE FLOOD model will
not be required. A conservative analysis of the flows, including flow volume, has
been included in the report that conceptually addresses the storm drainage and
floodplain concerns across the site. The City has indicated, in the October 7, 2010
meeting that floodplain analysis using MIKE FLOOD may be required in future
submittals including the Land Use Review and Site Review applications
On-site natural resources, drainage, groundwater and soil issues
- Sump Pump Withdrawals: Telesto identified a minor error in their write-up. The
second quote from the questionnaires should be attributed to the resident at 250
Cimarron Way. Re-issuing a corrected Attachment 1 will resolve CH2M HILL's
comments on Sump Pump Withdrawal rates.
- Baseline Pre-development Recharge Rates: Telesto provided additional clarification
in their November 30th email (Attached to this letter) to CH2M HILL that was
needed to reproduce their calculations regarding recharge rates. Re-issuing a
clarified Attachment 1 that explicitly states the amount of mean precipitation that
takes place between December and February will resolve CH2M HILL's comments
on recharge rates from precipitation. There is currently some discrepancy in this
Item 5A Cover Page Agenda Item 5B Page 25 of 35
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value - the text (page 5) and Table 1 of the report cite 7.4 inches of precipitation
during the winter, but calculations in Section 1.2 of Attachment 1 use 7.7 inches. The
report needs to use a consistent value throughout.
Bioswale ET and Recharge Rate: T table in Attachment 1 could be made clearer by
including intermediate calculations used to derive the total amount of recharge that
takes place during a season. In addition, the units used for fluxes in the report
should be made consistent by reporting in units of gallons per minute, adopted
throughout the text and in tables 2 and 3 of the report and feet per day as was used
throughout Appendix A. The winter and summer bioswale recharge rates derived in
Attachment 1 should match with values used in Table 3 of the report.
In their supporting documentation, Telesto indicates that the MODFLOW model
was modified to represent the locations of bioswales on the proposed development
and that additional model runs predict a 2.0 gallon per minute drop in sump pump
rates between pre-development and post-development scenarios. This difference is
less than the 4.3 gallon per minute noted in the conclusion of Appendix A (page A-
9).
In general, the reports reviewed in relation to the Boulder Creek Commons, LLC proposed
development of the Hogan/Pancost Property meets the requirements outlined in the City of
Boulder Desigii and Corastrnction Staszdards, N077ernber 16, 2000 and in The Cittl of Boulder
Revised Code (BRC) Title 9, Land Use Regulatioits,198. In addition, a review of On-site
natural resources, drainage, groundwater and soil issues against currently acceptable
engineering standards of practice was completed and found that the modeling and
procedures used to evaluate the On-site natural resources, drainage, groundwater and soil
issues does meet current and acceptable engineering standards of practice and no additional
information is requested at this time.
It is noted that the few discrepancies, and typos noted in the summary and conclusions of
this letter should be fixed before submitting the final report.
We hope that this review of the Hogan-Pancost reports assists the City of Boulder in
evaluating the issues related to the proposed development. Please call or email Alan Turner,
if you have any questions or comments about this information.
Sincerely,
CH2M HILL
L
Alan Turner, P.E., CFM
Project Manager
Water Resources Engineer
Matt Findley, CPSS Rob Healy, RG
Environmental Scientist Geologist
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Email from Telesto November 30, 2010
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Turner, Alan/DEN
From: Account Expired per GGAA (amerrit1) Findley, Matthew/DEN
Sent: Thursday, December 09, 2010 7:09 AM
To: Turner, Alan/DEN
Subject: FW: Boulder Creek Commons: Ground Water Evaluation Response to Comments
Attachments: image001.jpg; Table_1_BioswaleRechargeEstimate.xls
Here ya go.
From: Terry Fairbanks Finailto:tfairbanks@telesto-inc.coml
Sent: Tuesday, November 30, 2010 1:39 PM
To: Findley, Matthew/DEN
Cc: 'Walter Niccoli'; 'Leslie Ewy'
Subject: Boulder Creek Commons: Ground Water Evaluation Response to Comments
Resending to full e-mail address.
Hi Matt,
Here's the info:
1. Table 1 Bioswale Recharge Estimate. See attached Table-l-BioswaleRechargeEstimate.xls-The original file
contains daily Penman Monteith calculations and is 28MB so I have only included the portion that includes the
information in the summary table.
2. "Assuming native ground is populated with pasture grasses, the potential evapotranspiration is 24.3 in/yr." The
24.3 in/yr is the Penman Monteith ET rate. Looking through my notes I see that this should be 23.5 in/yr.
3. 1 do not have information regarding the water right for the property.
4. The anecdotal information on the 15,000 gpd is for the resident at 250 Cimmaron Way.
5. Frost depth: The Colorado State University Colorado Climate Center reported the following for their research
site:
"In most years, the max frost penetration on level, non-shaded ground is only 10-14" (much more in shaded).
The greatest penetration in the past 20 years has been 18" at our site. We have had many mild winters recently,
and we've had some with only a few inches (3-8") penetration. The ground is most likely frozen from just after
Thanksgiving until sometime in early March at our station. This year, the ground remained unfrozen all January
except in the top 2 inches at night and in the morning. This was very unusual."
(http://climate.colostate.edu/questions.php)
6. Regarding the local effect of the bioswale, the model was run with an explicit representation of the bioswale
included at the calculated recharge rate (dark blue area in image below).
i
Item 5A Cover Page Agenda Item 5B Page 28 of 35
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J
F f or'
r
r" ? Wthe
7. On Page 2, Paragraph 4, the winter precipitation of 7.7 inches should be mentioned to make the calculation
clearer. The following table will help:
Winter Precipitation = 7.7 in
Frost Period Runoff = -2.6 in
Soil Storage = -4.4 in
Net Infiltration = 0.7 in
Annual Precipitation = 20.8 in/yr
Net Infiltration / Annual Precipitation = 3.3%
Let me know if you have any other questions.
Terry
Terry Fairbanks
Senior Hydrologist
Telesto Solutions, Inc.
2950 East Harmony Road, Suite 200
Fort Collins, CO 80528
970.484.7704 (ph)
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2
Item 5A Cover Page Agenda Item 5B Page 29 of 35
c
0
0
D
m
m
a
DEVELOPED CONDITION (Bioswale*)
Area
Precipitation (acre) Acre-ft %
Annual 20.8 in 0
Summer 13.1 in 2.52 2.7
Winter 7.7 in 2.52 1.6
Irrigation
Summer (Cattails, Bulrushes, killing frost) 0.0 in 0.00 0.0
Summer (KY Bluegrass) 16.9 in 1.83 2.6
Winter 0.0 in 0 0.0
Runoff (CN=98)
Summer 7.89 in 9.6 6.3
Winter 4.19 in 9.6 3.4
Winter Frost Period
Runoff (CN=69)
Summer 0.30 in 9.6 0.2
Winter 0.03 in 9.6 0.0
Winter Frost Period 2.59 in 9.6 2.1
Evaptranspiration
Summer (Cattails, Bulrushes, killing frost) 24.3 in 0.69 1.4 36% Summer
Summer (KY Bluegrass) 19.3 in 1.83 2.9
Winter 0 in 0.0
Bioswale Recharge
Summer 36.0 in 2.52 7.5 64% Winter
Winter 33.7 in 2.52 7.1 100%
0.0 Summer Check
0.0 Winter Check
* Cover the channel bottom with loamy soils upon which cattails, sedges, and reeds should be established.
Side slopes should be planted with native or irrigated turf grasses.
Agenda Item 5B Page 30 of 35
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Attachment B, Exhibit 3
MEMORANDUM
To: Katie Knapp, City of Boulder Planning and Development Services
From: Alan Carpenter, Land Stewardship Consulting, Inc.
Re: Review of Environmental & Engineering Assessment & Feasibility Study for
Hogan-Pancost Property
Date: November 22, 2010
Introduction
Per your request, I reviewed certain documents provided to the City by the consultants for the
proposed Hogan-Pancost property development project. I reviewed the Executive Summary and
associated figures in Book 1 of the Environmental & Engineering Assessment & Feasibility
Study. I also reviewed the portions of Book 2 of the Environmental & Engineering Assessment
& Feasibility Study relating to wetland delineation, vegetation and wildlife habitat existing
conditions, species of special concern, and wetland mitigation and enhancement. I also visited
the property to a) gain a better understanding of its environmental values, b) check the wetland
delineation, and c) determine if any wetland areas were omitted from the delineation.
On October 7, 2010, 1 attended a meeting at the City office building where the project proponents
and consultants, principally David Johnson, responded to the comments I made in the August 27,
2010 memo. On November 22, 2010,1 reviewed the responses by David Johnson to the
comments in the August 27, 2010 memo as well as to comments made during the October 7, 2010
meeting. This memo reflects slight revisions to my memo dated August 27, 2010.
Wetland Delineation
The hydrology of the subject property has been substantially altered over time. The Dry Creek
Ditch 42 was constructed along the western border of the West parcel and the Howard-Super-
phosticle Ditch bisects the East parcel and runs across a small area of the West parcel. Both of
these ditches convey significant amounts of adjudicated water. The CD Bodam lateral runs along
the southern boundary of the West parcel. Much of the property has been flood-irrigated starting
in the 19th Century.
The consultants established a ground water monitoring program to determine if the wetlands "are
due to a natural high ground water table, a groundwater table elevated by irrigation ditches and
laterals, or due to flood irrigation practices". Flood irrigation was terminated on the West parcel
during 2008 but continued on the East parcel. The consultants installed a number of ground
water monitoring wells from which data were collected in 2008. The consultants also
investigated the vegetation and soils of putative wetlands to determine if they possessed wetland
vegetation and soils. The results of the vegetation and soils investigation and the ground water
monitoring were used to delineate wetlands.
Terminating flood irrigation on the West parcel enabled the consultants to determine if the
putative wetlands exhibited wetland hydrology in the absence of irrigation. Wetland hydrology
was assumed to exist if "The site is inundated (flooded or ponded) or the water table in < 12
inches below the soil surface for > 14 consecutive days during the growing season at a minimum
frequency of 5 years in 10 50% probability)." (National Research Council 1995)
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Item 5A Cover Page Agenda Item 5B Page 31 of 35
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The ground water monitoring indicated that the wetlands on the West parcel are induced by
seepage from Dry Creek Ditch 42 and are not the product of a naturally high ground water table.
Thus, most of the wetlands, most notably Wetlands A, B, and C (per the consultant report), in the
West parcel are not jurisdictional. Areas of wet meadow which I observed during my site visit
and which appeared to be wetland due to the dominance of wetland plant species do not possess
wetland hydrology once irrigation was terminated during 2008, according to the ground water
monitoring data. That notwithstanding, wetlands that are the products of leaky ditches and/or
irrigation are regulated by the City of Boulder under the terns of its Stream, Wetland and Water
Body Protection Ordinance.
The U. S. Army Corps of Engineers concluded that the 0.228-acre linear wetland located along
Dry Creek Ditch 92 is jurisdictional because this ditch flows north to South Boulder Creek. The
Corps also concluded that the 0.227-acre wetland A, the 0.21-acre wetland B, and the 0.28-acre
wetland C are not jurisdictional, because they do not provide flows to the Dry Creek Ditch 92.
The ground water levels in the East parcel are likely influenced by the Howard-Super-phosticle
Ditch which flows all year. Ground water levels in the monitoring wells in the East parcel
exhibited wetland hydrology. However, because flows in this ditch were not terminated during
the ground water monitoring, it was not possible to determine if the wetlands in the East Parcel
are the product of seepage from the ditch or a naturally high water table. Thus, the consultants
assumed that the wetland areas, collectively encompassing 1.622 acres, on the East parcel may
have natural wetland hydrology and are jurisdictional.
Vegetation and Wildlife Habitat
The subject property is characterized by the consultant documents as degraded due to its long
history of intensive agricultural use. The vegetation of the property typically consists of
introduced, alien species, some of which are listed as noxious weeds by the State of Colorado,
and by weedy native species. According to the consultant reports, the vegetation of the property
consists of 10.588 acres of degraded agricultural seeding, 8.355 acres of Colorado noxious and
other weeds, 1.957 acres of man-induced jurisdictional wetlands, 0.465 acres of non jurisdictional
wetlands, and 0.324 acres of plains cottonwoods. Thus, 87% of the subject property is classified
as either degraded agricultural seeding or Colorado noxious and other weeds. The most abundant
noxious weeds on the property are common teasel (Dipsacus frrllonum), Scotch thistle
(Onopordum acanthium), common mullein (Verbascum thapsus), diffuse knapweed (Acosta
diffusa), Canada thistle (Breea ar^vensis), and field bindweed (Convolvulus arvensis).
I observed small areas of wet meadow in the West parcel that are dominated by native wetland
plant species and which are in good condition. As explained elsewhere, these areas were not
classified as wetland by the consultants because they lacked wetland hydrology. In addition,
wetland areas A, B, and C, which were judged to be non jurisdictional, from the standpoint of US
Army Corps of Engineers regulations, are generally dominated by native plant species and are in
fair to good condition.
In. spite of its degraded condition, the property does have some wildlife value, primarily for
generalist species that are common in urban areas. These species include raccoon (Procyon
lotor), striped skunk (Hephitis mephitis), red fox (Vulpes vulpes), and coyote (Canis latrans).
The small area of plains cottonwood forest in the eastern portion of the East parcel is probably the
most significant wildlife habitat on the property, because the canopy of the cottonwoods provides
foraging and nesting habitat for numerous songbird species, e.g., vireos and warblers. In
addition, the Howard-Super-phosticle Ditch and the wet meadows in the West parcel provide
Review of Environmental & Engineering Assessment & Feasibility Study for Hogan- 2
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Item 5A Cover Page Agenda Item 5B Page 32 of 35
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suitable habitat for native small mammal species such as meadow vole (Microtus pennsylvanicus)
and prairie vole (Microtus ochrogaster).
As explained below, the proposed mitigation and enhancements, if successful, could greatly
improve the quality of the vegetation on the property and the amount and quality of the wildlife
habitat.
Species of Special Concern
The consultant reports mentioned a number of species of special concern that are known to occur
in Boulder County. Such species include those that are listed as either threatened or endangered
or as candidates by the federal government or the State of Colorado and species denoted as
"special concern" by the Colorado Division of Wildlife. Also included are significant natural
communities, rare plants areas, significant riparian corridors, and critical wildlife habitats as
shown in the Boulder County Comprehensive Plan.
A number of species were quickly eliminated from active consideration because they do not occur
in the area and/or because the property does not provide suitable habitat for them. The property
could conceivably provide suitable habitat for three of the listed species, namely Preble's
meadow jumping mouse, Ute ladies' tresses orchid, and the Colorado butterfly plant, in the future
if proposed mitigation activities are successful; however, it is very unlikely that these species now
occur on the property. Consultants familiar with the jumping mouse concluded that the property
does not provide suitable habitat for this species, because of the lack of dense riparian vegetation.
It worth noting, however, that the jumping mouse is found on adjacent City of Boulder Open
Space and Mountain Parks (OSMP) land along South Boulder Creek. If the proposed wetland
mitigation and enhancement measures on the East Parcel are successfully implemented, it is
possible that the jumping mouse might colonize the East parcel. Repeated surveys over several
years during the flowering period failed to reveal any Ute ladies' tresses orchids, although this
species occurs on OSMP land about one-fourth mile south of the subject property. The Colorado
butterfly plant is known to occur in Colorado and southeastern Wyoming in plains riparian
habitats on upper portions of stream banks. The only remotely comparable habitat on the
property occurs along the Howard-Super phosticle Ditch; however, the butterfly plant has not
been observed on the property, and it likely does not exist there due to the decades of heavy
agricultural use.
The black-tailed prairie dog (Cynomys ludovicianus) inhabits the property. According the
consultants, the population of prairie dogs is increasing on the property. I observed many prairie
dogs and active burrows during my site visit. If the property is developed for residential use, the
prairie dogs would presumably be relocated or exterminated.
Of the special concern species, the only two that might inhabit the property include the northern
leopard frog (Rana pipiens) and the common garter snake (Thamnophis sirtalis). The property
lacks the standing water habitat favored by the northern leopard frog. However, the common
garter snake "inhabits marshes, ponds, and the edges of streams", according to Hammerson
(1988). The Howard-Super-phosticle Ditch and its strip of riparian vegetation provide suitable
habitat for the common garter snake.
The consultants dismissed all of the areas identified in the Boulder County Comprehensive Plan,
because they do not occur on the property. That is the case. However, the somewhat rare plant,
tulip gentian (Eustoma grandiflora), occurs in wet meadows similar to those that exist on the
property, particularly on the West parcel. Furthermore, the South Boulder Creek wetlands)
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Critical Wildlife Habitat Area lies about '/4 mile northeast of the subject property, although this
species has not been documented from this Area.
In addition, the property appears to abut the South Boulder Creek Natural Area, as shown in the
OPSMP Visitor Master Plan of 2005. The proximity of the subject property to OSMP lands gives
weight to the proposal of the consultants that the East parcel would not be developed and that the
degraded habitat there would be greatly improved via habitat creation and enhancement activities.
Wetland Mitigation and Enhancement
The jurisdictional and non jurisdictional wetlands on the property are typically in fair to poor
condition, reflecting the abundance of introduced alien and weedy native species.
The consultant reports state that 0.228 acres of jurisdictional wetland located along the Dry Creek
Ditch # 2 would be lost due to the proposed development. Because the ditch would be piped
through the property. The Corps of Engineers permit states that this loss of wetland along Dry
Creek Ditch 92 can be mitigated by purchase of 0.261 acres of wetland mitigation credit in the
Middle South Platte River Wetland Mitigation bank. However, the consultant report states that
the mitigation would be accomplished by creating 0.465 acres of wetland on the East parcel. I
did not find any reference to the need to prepare an augmentation plan to compensate for
increased loss of tributary ground water from the created wetlands.
The proposed project would result in the loss of 0.465 aces of non jurisdictional wetland in the
western portion of the West parcel. This loss would be mitigated by restoring 0.227 acres of
wetland (Wetland A per the consultant reports) in the southwestern corner of the West parcel.
The proposed prairie bioswales would include 2.921 acres of shortgtrass prairie, with stringers of
riparian vegetation, as part of the overall proposed mitigation.
Enhancements include controlling noxious weeds and other introduced, alien plant species on
both the West and East parcels. In addition, plains cottonwood and peach-leaf willow trees
would be planted along the lower-elevation areas of the proposed prairie bioswales in the West
parcel, which would function as stormwater conveyance channels. Finally, plains cottonwood
and peach-leaf willow trees would be planted in various areas on the East parcel to create
additional wildlife habitat. The consultant report states that the entire 2.73-acre East parcel would
be restored to native habitats, which would include both wetland and non-wetland areas.
Summary
The wetland delineation, as informed by the ground water monitoring and the field investigation
of vegetation and soils, appears to be reasonable overall. The ground water monitoring data on
the West parcel indicates that presence of the ditches, the lateral, and flood irrigation has
provided the hydrology to support wetlands in portions of the property. I observed a small area
(about 70 feet long and 3 feet wide), along the northern boundary of the West parcel and adjacent
to the southern side of the Howard-Super phosticle Ditch, which appeared to be wetland in that it
was dominated by wetland plant species and had saturated soil, but which was apparently not
mapped as wetland by the consultants. This could be resolved if a new wetland delineation is
performed when the Hogan-Pancost property is annexed to the City. Areas of wet meadow which
I observed during my site visit and which were dominated by wetland vegetation did not meet the
wetland hydrology criteria as set forth in the National Research Council report. The wetland area
Review of Environmental & Engineering Assessment & Feasibility Study for Hogan- 4
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Item 5A Cover Page Agenda Item 5B Page 34 of 35
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along the Dry creek Ditch 92 and the wetland areas in the East parcel were judged to be
jurisdictional.
The property is highly degraded due to its long-term, intensive agricultural use. Development of
the property would be concentrated in areas that have minimal natural habitat or wildlife value.
Some areas of fair to good condition native vegetation (e.g., wet meadow that is not jurisdictional
wetland) would be lost due to development.
The proposed project would likely eliminate one species of special concern, namely the black-
tailed prairie dog, from the property. Presumably, the prairie dogs living on the subject property
would be relocated or exterminated. This would greatly complicate the project if the black-tailed
prairie dog were listed as "threatened" by the federal government. Successful implementation of
the proposed mitigation and enhancements for the project would likely increase the habitat value
of the property for the northern leopard frog, common garter snake, and the tulip gentian, three
species that could inhabit, but which are apparently now absent from, the property.
I believe that conducting the wetland mitigation and enhancements on the subject property would
be preferable to buying credits in a wetland mitigation bank, because the mitigation and
enhancements could greatly increase the quantity and quality of natural habitats on the property.
The property would also have a much greater aesthetic appeal if the proposed mitigation and
enhancements are successful.
The consultants mention that the East parcel would be "preserved" but do not explain exactly
what this means. This could involve conveying a perpetual conservation easement over the East
parcel or perhaps conveying fee title to the East parcel to a qualified organization. Perhaps
another appropriate means of protecting the natural resources of the East Parcel could be
employed.
Attachments
Twenty-two photographs taken on August 19, 2010, and printed four to a page, plus a photolog
with GPS coordinates and brief descriptions of the photo locations.
Please call me at 303.443.8094 or send me an e-mail at alantearpenter(a_>comcast.net if you have
any questions or comments.
Review of Environmental & Engineering Assessment & Feasibility Study for Hogan- 5
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