HomeMy WebLinkAboutPEAK VIEW SUBDIVISION - PDP - 26-00 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTI
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1 PRELIMINARY DRAINAGE REPORT
CALCULATIONS
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' Design Criteria
' The design methodology used during the analysis portion (hydrology and hydraulics) of the
proposed design is outlined in the City of Fort Collins Storm Water Management Manual. The
water quality BMP design procedures and rip rap design procedures used are outlined in the City
' of Fort Collins Manual or the UDFCD manual.
Variance
' No variance is requested with this Preliminary Drainage Report. However, we are currently
evaluating the possibility of regrading the Stormwater Department's detention facility in the park.
If that option appears feasible, it may be presented at the time of final submittal. Therefore, we
are reserving the right to present that option at the time of final submittal.
' Conclusions and Recommendations
' 1) The proposed final drainage design will use the existing drainage patterns, to the extent
possible.
2) The site in not in a federally identified jurisdictional floodplain.
3) One detention pond, north of the PV&L Canal, will be used to reduce flow and modify
water quality.
4) Hydrology and hydraulic design procedures and construction details, presented in this
report and proposed for construction are outlined in the Larimer County Storm Water
Management Manual.
5) Construction phase and post -construction phase erosion control calculations will be
presented as part of the final design.
' 6) A variance may be requested to store the detention volume in the city's facility in the
park.
' References
' I) City of Fort Collins Storm Water Management Manual
2) UDFCD, "Urban Storm Drainage Criteria Manual, Volumes I, II and III"
3) USDA, Larimer County, Colorado Soils Survey
' 4) American Concrete Pipe Association, Design Manual
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' the block wall is to maximize volume of the limited detention pond site. The U.S. Corps of
Engineers has conducted much research on using this construction technique for channel and
' detention construction and finds the technique acceptable. Furthermore, Arapahoe County has
accepted this construction method for detention ponds. There are numerous vertical -walled
detention ponds in the vicinity of Park Meadows Mall.
Type "R" catch basins are used for the streets and 24 inch by 24 inch grated catch basins are used
for turf areas.
Steady-state flow calculations are provided to estimate pipe sizes. A UDSEWER model will be
provided in the Final Drainage Report.
' Erosion Control
' Considered erosion control practices are considered in two parts: during construction and post -
construction (permanent).
' Both during construction and post -construction BMPs are shown on the drainage plan provided
as part of this report.
' Construction phase BMPs include:
'0 Silt Fence
• Strawbale dikes
• Temporary seeding and mulching
'0 Vehicle Traction Control
• Pavement scheduling
• gravel filters
' Proposed post -construction phase BMPs are:
'0 Water quality capture volume in detention pond (w/ water quality outlet)
• Permanent seeding
'0 Pavement
• Designed grass swales
' During individual lot construction, it will be the specific owners responsibility to manage erosion
control.
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Existing Conditions
' The Pleasant Valley and Lake Canal crosses the site in the southern 1/3 of the site. The proposed
project will impact the canal owner (please see, "Developed Site Conditions", below).
' The northern 2/3's (+/-_ of the site is considered as having flat to moderate slopes, tending north
to south. The slope of the land in this portion of the site in up to 3-percent. The land south of the
Canal is more steeply sloped with grades to 12-percent.
Off -site tributary flow enters the site in the north portion of the site from flow in the east -bound
lane of West Elizabeth Street. Adjacent to the site, and crossing the site is the Pleasant Valley
' and Lake Canal (PV&L). The maximum decreed flow in the and the figure used for design is 40
cfs. The PV&L also has tributary surcharge flood flows entering the canal upstream of the site.
' The City of Fort Collins, Canal Importation Basin masterplan describes the flow as being
immediately upstream of the site.
Developed Conditions
The proposed street network shown on the drainage plan shows two access points onto West
' Elizabeth Street and two connections to Pleasant Valley Road in the southern part of the site.
Generally, design discharge will be carried on the surface until gutter capacity is reached and
' then an appropriately sized underground pipe collection system will direct the flow to the
detention pond (for the northern portion of the site). More specifically, the multi -family portion
of the site will be over -detained in the proposed detention facility and released at the two year
' historic discharge. The area south of the canal will be release undetained.
Realignment of the Pleasant Valley and Lake Canal will be part of the planned improvements.
To alleviate the canal bank over topping, an emergency overflow structure and sluice gate will be
constructed. These facilities will discharge to the Clearview Channel drainage system. A water
' surface profile will be presented in the final drainage report. For purposes of the Preliminary
Drainage Report, a "snapshot" cross-section of the canal cross-section is provided.
' As stated above, the proposed drainage system will outfall to the Clearview Channel. Off -site
improvements are planned to covey the allowable release and the emergency spill to be conveyed
to the ponds on park property. These improvements include the construction of a shallow, broad
swale and the reconstruction of a portion of the existing bike/pedestriantrail. These
improvements will be shown at the time of final design because mapping was not available
during the preliminary design phase.
The proposed detention pond will have a concrete masonry unit (CMU) face to approximate a
vertical wall. The blocks will probably be Keystone interlocking blocks. The purposed on using
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Preliminary Drainage Report
' Peak View
August 16, 2000
Introduction
The report describes how the City of Fort Collins, Colorado Drainage Criteria is applied to the
' drainage system design and to document the analysis of the drainage system presented.
Purpose and Scope
The report outlines the historic and developed flows, and supports the drainage portion of the
' proposed design by providing detailed design analysis and calculations. Furthermore, the report
addresses stormwater quality Best Management Practices (BMPs) for the construction period and
as part of the permanent design features. However, at this preliminary level detailed calculations
' analyzing the BMP's shown on the exhibit are not provided. These calculations will be provided
in the Final Drainage Report.
' The narrative portions of the report are written to be approachable by a more general audience
and describes the proposed drainage features. Appended to the report are several collections of
documents that are the technical materials supporting the design and are provided for Larimer
' County's and the irrigation companies' detailed review. It is anticipated that the Pleasant Valley
and Lake Canal Irrigation Company will review the report with a view to the potential impacts
and proposed design features that impact their facilities.
' The scope of the report and supporting documentation are limited to the Preliminary Design
Documents for on -site features of the proposed project and tributary hydrology impacting the size
' of the proposed site features.
Site Description
The proposed Peak View Subdivision is South of West Elizabeth Street, in west Fort Collins.
' The site is 9.22 acres (+/-). The proposed subdivision will consist of single-family
condominiums and single-family detached lots. The site is not located within a designated
federal jurisdiction floodplain.
' Currently, access to the site is along West Elizabeth Street, which runs along the north property
boundary. Immediately east of the site is The Siena PUD. Adjacent to the southern boundary is
' Clearview Park. The on -site drainage outfall location, the Clearview Channel runs through this
park. The property West of the site is Lory Ann Estates PUD.
TABLE OF CONTENTS
1)
Introduction............................................................1
2)
Purpose and Scope........................................................1
3)
Site Location...........................................................1
4)
Site Description.........................................................I
► Existing Conditions................................................I
► Developed Conditions..............................................2
5)
Erosion Control.........................................................3
6)
Design Criteria..........................................................
2
7)
Variance...............................................................4
8)
Conclusions and Recommendations .........................................
4
AppendixA .......................................................... Hydrology
Appendix B.......................................................... Hydraulics
Drainage and Erosion Control Plan ..................................... In Map Pocket
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August 16, 2000
Mr. Basil Harridan
City of Fort Collins, Utilities Department
700 West Street
Fort Collins, CO 80521
RE: Peak View - Preliminary Drainage Report
Dear Basil:
Engineering Design and Research Corporation (EDRC) in collaboration with Loonan and
Associates, Inc. is pleased to present the attached Preliminary Drainage Report for your review.
The drainage report identifies on -site and tributary off -site historic and developed flow.
Additionally, the report supports the design for conveying the developed flow through the site to
the receiving waters, the Clearview channel system south of the site.
Also included as part of the design is the construction of the permanent Best Management
Practices (BMPs) for modifying the water quality of storm water run-off. The methods outlined
in the City of Fort Collins, Storm Drainage Design Manual are used and their analysis methods
will be presented in the Final Design, technical appendix of the report.
Our team looks forward to working with you to finalize the design and complete a successful
project from the City's standpoint. Thus, I urge you to call with questions and comments as they
arise, so we may discuss solutions and thus expedite your review process. I may be reached at
the telephone number at the bottom of the page.
Sincerely,
EDRC
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Craig C. oudeshell, P.E.
President
attachment
' CCH/jab
303-627-7162 • Fax — 303-727-6635
5616 South Gibraltar Way • Suite H • P.O. Box 110 • Aurora, Colorado 80015
Preliminary Drainage Report
for
Peak View Subdivision
August 16, 2000
' �.'oonan and of.6.6ocia&6, Qnc.
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