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Home My WebLink AboutDrainage Reports - 06/30/1992PRELIMINARY DRAINAGE REPORT FOR COLLEGE PARK P.U.D. SHIELDS STREET AND STUART STREET FORT COLLINS, COLORADO MAY 28, 1992 (REVISED JUNE 30, 1992) PREPARED FOR: POLARBEK 1900 INTERNATIONAL PARK DRIVE SUITE 50 BIRMINGHAM, ALABAMA 35243 PREPARED BY: PARSONS & ASSOCIATES CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221- 2400 PROJECT NUMBER: 91.11 APT TABLE OF CONTENTS Introduction Area Of Study/Site Description Historic Drainage Design Criteria Proposed Storm Drainage System Proposed Erosion Control Measures Conclusions and Recommendations Design Calculations LIST OF FIGURES Figure 1. Location Map Figure 2. Off -Site Flows Figure 3. Drainage Basin Map Preliminary Drainage Report For College Park P.U.D. Shields Street and Stuart Street Fort Collins, Colorado Introduction This drainage investigation has been prepared in conjunction with a preliminary grading and drainage plan for College Park P.U.D., a proposed multi -family development located on 21.10 acres east of the intersection of Shields Street and Stuart Street. This study has been undertaken to outline the method of conveyance and disposal of storm water for both on -site and off -site conditions which will affect this project. This study was prepared in accordance with the City of Fort Collins "Storm Drainage Design Criteria and Construction Standards" using mapping completed in 1992 by Parsons & Associates and master plans provided by Polarbek, Incorporated. Area of Study The proposed project consists of 180 multi -family units to be constructed on 21 .10 acres located along Shields Street just east of Stuart Street; more specifically identified as a parcel of land in the Northwest Quarter of Section 23, Township 7 North, Range 69 West of the 6th Principal Meridian, State of Colorado, Larimer County, in the City of Fort Collins (see figure 1 ). In recent history this site has been proposed as a multi -family project called Wind Trail Condominiums P.U.D. and as a commercial/multi-family project called The Pulse P.U.D. This parcel is currently vacant with a cover of natural grasses. The site is very flat and currently drains from west to east at a slope of less than 1 %. The site currently sits lower than adjacent streets. The site is bounded on the north by Hobbit Street and the Landmark Apartment Complex. On the east the project is bounded by The Canal Importation Channel. On the east side of this channel are single family residential homes built as part of the Hill Pond 2nd Filing Subdivision. Spring Creek forms the southerly boundary for this site. To the south of the Spring Creek drainage are the Hill Pond Townhomes. The west boundary is formed by Shields Street. West of Shields Street and south of Stuart Street exists Spring Creek Plaza, a small commercial development. North of Stuart Street and west of Shields Street are the Northwood apartments. This project will dedicate parcels for Shields Street right-of-way, Hobbit Street right-of- way, The Canal Importation Channel and Spring Creek. A summary of this follows: -2- PROJECT LOCATION VICINITY MAP N. T. S. East 1 /2 Shields Street & South 1 /2 Hobbit Street Tract "A" Spring Creek Tract "B" Canal Importation Channel Tract "C" Building Site TOTAL PARCEL ACREAGE Historic Drainage 1.62 acres 3.49 acres 1.32 acres 14.67 acres 21.10 acres This project is located in an area with numerous drainage improvements adjacent to the site. These improvements are as follows: SPRING CREEK Spring Creek is a major drainageway through the City of Fort Collins. Existing FEMA maps for Spring Creek show floodway and flood fringe encroaching onto this site. Recent channel improvements have eliminated this situation physically. A LOMR for this site was approved by FEMA on April 20, 1992. Attached is a copy of the new flood limits and the approval letter. -3- It is not anticipated that Spring Creek will have any impact on this project. Project flows will be discharged into the Spring Creek channel without detention. CANAL IMPORTATION CHANNEL The Canal Importation Channel forms the eastern boundary of this project. This channel takes overflow from irrigation channels and tributary areas to the west, and drainage from the Landmark Apartment Project to the north and conveys them around this site. It is not anticipated that The Canal Importation Channel will have any impact on this project. An existing inlet on Hobbit street and channel along the north edge of this site currently discharge into the channel. This drainage will be modified to drain into and through the College Park P.U.D. site. SHIELDS STREET Approximately 8.3 acres of residential area north of this project drain to Shields Street. (See Figure 2) These flows are partially diverted into The Canal Importation Channel. me Remaining flows enter this site at the proposed Stuart Street intersection where they will be diverted through the site and into Spring Creek. Design Criteria The City of Fort Collins "Storm Design Criteria and Construction Standards" was used as the basis for all drainage calculations and storm sewer system design. It is intended that all improvements proposed on this site be consistent with this criteria. The Rational Method was used in all cases to develop runoff quantities for this area. The Rational Method of determining runoff is considered an acceptable method of design in basins less than 200 acres. Proposed Storm Drainage System The intent of the proposed drainage design is to collect runoff into two sedimentation ponds before discharging into Spring Creek. It should be noted that all flows are discharged to the Spring Creek Channel, as follows: -5- Basin A Basin A includes runoff from Shields Street. This 8.3 acre basin includes the east one-half of Shields Street from the Spring Creek Crossing north to Summer Street. Although some water is diverted to the west at the Prospect Road intersection and through inlets at the Canal Importation Channel, we have taken a conservative approach and included runoff from the entire area in the Basin A analysis. These flows are directed to the entrance road at Stuart Street. They continue east along the parking lot where they are collected by inlets and discharged into Spring creek through Storm Sewer Line A. MTW, Basin B includes runoff from Hobbit Street. Flows from the Hobbit Street right- of-way are directed easterly to a cross pan and inlet. This runoff continues in a grass - lined swale to the Canal Importation Channel. This project will eliminate this grass - lined swale and convey runoff to a sedimentation pond in the courtyard between buildings. This water will continue in storm sewer "Line C" to Spring Creek. ME Basin C The easterly one-half of the site, encompassing 7.64 acres, drains to a sedimentation pond located in the courtyard between the easterly buildings. An overflow has been provided at the southwest corner of the basin. Basin "B" flows combine with Basin "C" flows and are conveyed to Spring Creek via Storm Sewer Line „C„ Basin D A small area (0.97 acres) of the southerly portion of the College Park site between the entrance road, parking lot and Spring Creek will sheet flow into Spring Creek. These flows will be from landscaped and recreational areas only. Basin E The westerly one-third of the site (3.47 acres) will drain towards a center court yard area between the westerly buildings. This runoff will include roof, parking lot and landscaped areas as shown. Storm sewer "Line B" will direct this runoff towards Spring Creek. 7- The storm sewers shown as lines "A", "B" and "C" will extend under the bike trail to eliminate the possibility of nuisance water flooding the trail. Basin F The remaining 2.32 acres between Basin C and Basin E is primarily parking lot flows. An inlet on storm sewer "Line B" will direct these flows to Spring Creek. Proposed Erosion Control Measures This project is in an area of moderate wind and high water erosion potential as determined by the City of Fort Collins Erodibility Maps. It is expected that this site and the proposed buildings will be constructed at one time. The tentative construction schedule will be in the summer of 1993 with a late August opening. 1 WIND EROSION Utility and building construction will start immediately once the site is stripped. Due to the time of year and the fact that the existing site is two feet below surrounding improvements, it is expected that wind erosion will be minimal. In addition, building improvements constructed on site early in the construction sequence will act as wind breaks. However, to insure that wind erosion is kept to a minimum it is expected that exposed areas will be mulched and construction areas will be chemically treated or watered to reduce dust caused by traffic. WATER EROSION Because this site is located in an area with a high potential of water erosion and because of its proximity to major drainage improvements, runoff has been routed to sedimentation basins. These basins will provide a method to collect on -site flows and provide erosion mitigation before releasing runoff into the Spring Creek Channel. In addition to mulching the exposed areas of the site the following structural improvements will be provided as follows: In BASIN IMPROVEMENTS A Gravel Inlet Filter B Sediment Trap C Sediment Trap D Silt Fence Around Edge E Sediment Trap F Gravel Inlet Filter -10- 5NIEL05 STQEET i FIGURE III DRAINAGE BASIN MAP U) q0 LL LLI cr Lli Z) F- C9 U LL LL LL O BASIN SUMMARY BASIN AREA (ACRES) Q100 (CFS) DESCRIPTION OFF -SITE A 8.30 47.31 Shields Street B 0.90 7.20 Hobbit Street ON -SITE C 7.64 52.72 Easterly Row of Buildings & Yard D 0.97 3.64 Southern Edge of Site E 3.47 24.98 West Portion of Site F 2.32 17.65 Middle Parking Lot TOTAL 23.6 Tract "A" (Spring Creek) (3.49 Acres) and Tract "B" (Canal Importation Canal) (1.32 Acres) are drainageways and were not included in the development of project runoff quantities. PARSONS & CLIENT j I plot- pQ k 1/1 r JOB NO. 711 f "/I /ram ASSOCIATES PROJECT PII rO Palk CALCULATIONS FOR Past"I r irce { CONSULTING ENGINEERS / R Collin., Colorado &M24 MADEBY J ✓l 'r^�r , /ll,p/ DATE 8 / CHECKED BY DATE SHEET OF_ gvm r1ow1 gr (folio l•(na�` ? C0� fe.( ��CC �lrco ��rr�� 1cC r• � I J J i J Gilefu»�� 1194 f" %fldPf(74 (CAGtII(F>J — FCom rvu(P _ .- --- Zr OOd 7 PIP,( � jar k1l" T lmp = E. 7 /b lG- 7 Ili; i (Sq)Q-3) ; r//.j 1170 fccf /d If ail S c, lJ(� .-- .. r/On FIL(A;r , CT/ OI /Or� ro lmg r(h of rot) <011,ell r % Aw' T (os ' 9.0 l"/bl Q,(f j06 ), (2.0) (a 9) ` nn� � PARSONS & CLIENT ?6 N i' ✓ ,1.! JOB NO. ASSOCIATES PROJECT reIffoa ' �rtFr CALCULATIONS FOR CONSULTING ENGINEERS ) p MADE BY '' F DATE I CHECKED BY DATE SHEET 1 OF Ft. C.M.Q. CaiOod. 13W24 J r,(Ipfit �,; f r 80 f lad Uofln �Fn'//i <oa / S/f? 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I/]) zv. 91 cfj v ' f�r�i i%�G,,, 1 < �i1� aT /r, i C��„� 1r S%lio %oV7 F(ywAr 3 I Cr�� for( &l%76 - f Ivnm-rn,1� Il+r yl,- -- i S� G' r _ Iq .c ��cf f� 37rr�/� 6-oli S=Zn/ G"kx Pt L F7 T ._-4 i � M 11 JS115 f i S d•o / ZY Z R _ y I/ bit( <s/n fl Engineering t JArchitectureItAPR Planning SciencesPurveying1992 Photogrammetry � , l—k 'I GREENHORNE& O'MARA, INC. 3131 SOUTH VAUGHN WAY SUITE228 AURORA, COLORADO 80014 PHONE 303.755-9000 FAX303.755-2765 Parsons Associates DATE 4_2 _ 2 JOB NO. 432 South Link Lane RE: Spring Creek Fort Collins, CO 80524 ATTENTION: Jeff Couch WE ARE SENDING YOU THE FOLLOWING ITEMS ATTACHED: ❑ UNDER SEPARATE COVER: ❑ TRACINGS ❑ PRINTS ❑ COMPUTATIONS ❑ DESCRIPTIONS ❑ SPECIFICATIONS ❑ APPLICATIONS ❑ COPY OF LETTER ❑ VIA: ® MAIL ❑ INSURED ❑ BY HAND ❑ MESSENGER ❑ PICK UP COPIES DATE OR NO. DESCRIPTIONS 1 Copy of letter from the Federal Emergency Management Agency THESE ARE TRANSMITTED AS CHECKED BELOW: ❑ FOR APPROVAL ❑ FOR REVIEW ❑ FOR YOUR USE ❑ AS REQUESTED BY j ❑ AS APPROVED BY ❑ AS SUBMITTED FOR APPROVAL TO ❑ PLEASE RETURN TO US AFTER USING IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE. CC: J. Williac6, P.E. ANNAPOLIS. MD ATLANTA. GA AURORA, CO BALTIMORE, MD CULPEPER, VA DULUTH. GA EXPORT, PA FAIRFAX, VA FREDERICKSBURG, VA GREENBELT, MD LEESBURG, VA MANASSAS, VA MOORESTOWN, NI ORLANDO, FL RALEIGH, NC ROCKVILLE, MO TAMPA, FL WALDORF, MD WEST PALM BEACH, FL Federal Emergency Manage �. Washington, D.C. 20472 CERTIFIED MAIL IN REPLY 1 RETURN RECEIPT REQUESTED 102 The Honorable Susan Kirkpatrick Mayor, City of Fort Collins P.O. Box 580 Fort Collins, Colorado 80522 Dear Mayor Kirkpatrick: JURNE & O'M.ARA, INC. APR 2 2 D92 (DENVER) Community: City of Fort Collins, Colorado FIRM Panel Number: 080102 0003 A FBFM Panel Number: 080102 0003 A Effective Date of This Revision: APR 2 0 1992 This is in response to a letter dated March 17, 1992, from Mr. Robert W. Smith, P.E., Stormwater Utility Manager, City of Fort Collins, regarding the effective Flood Insurance Study (FIS) report, Flood Insurance Rate Map (FIRM), and Flood Boundary and Floodway Map (FBFM) for the City of Fort Collins, Colorado. In response to our letter dated February 11, 1992, Mr. Smith submitted additional data to support his initial request dated December 31, 1991. He had requested that we revise the effective FIRM and FBFM to show the effects of a revised hydraulic analysis along a reach of Spring Creek based on changes in the channel topography, which included the removal of the River Meadows Road crossing. Mr. Smith submitted all data necessary in support of this request with his December 31, 1991, letter and with a letter dated March 17, 1992. We have completed our review of the submitted data with regard to the data used to produce the effective FIRM and FBFM, and have revised the FIRM and FBFM to modify the elevations, floodplain boundary delineations, and floodway boundary delineations of a flood having a 1-percent probability of being equaled or exceeded in any given year (base flood) along Spring Creek from approximately 1,550 feet downstream of the South Shields Street bridge to approximately 1,450 feet upstream of that bridge at the confluence with the canal. As a result of this revision, there is an increase to the base (100- year) flood elevations (BFEs) and a Special Flood Hazard Area (SFHA) extending northward has been added approximately 500 feet downstream of the old River Meadows Road crossing. This land is owned by the City of Fort Collins, as stated by Ms. Susan Duba Hayes, City of Fort Collins Stormwater Utility, during a telephone call on April 7, 1992. The modifications are shown on the enclosed annotated copies of FIRM Panel 080102 0003 A, FBFM Panel 080102 0003 A, Flood Profile Panel 05P, and the Floodway Data Table for Spring Creek. This Letter of Map Revision (LOMR) hereby revises these panels of the effective FIRM and FBFM, both dated July 16, 1979, and the Flood Profile Panel and Floodway Data Table contained in the effective FIS report, dated February 15, 1984. Cross Sections BU-BW have been deleted as a result of the revised hydraulic analysis, which used fewer cross sections. 2 The following table is a partial listing of former and modified BFEs. Existing BFE Modified BFE Location *(feet) *(feet) Approximately 1,550 feet downstream of the South Shields Street bridge *5,004 *5,004 Approximately 50 feet upstream of the South Shields Street bridge *5,015 *5,012 Approximately 900 feet upstream of the South Shields Street bridge *5,019 *5,020 Approximately 1,450 feet upstream of the South Shields Street bridge (at confluence with canal) *5,021 *5,021 *National Geodetic Vertical Datum, rounded to the nearest whole foot. .Because of current funding constraints, we must limit the number of physical map revisions. Consequently, we will not publish a revised FIRM and FBFM for the City of Fort Collins to reflect modifications at this time. However, if in the future, we revise and republish the FIRM and FBFM panels affected by this LOMR, we will incorporate the previously described modifications at that time. The floodway is provided to your community as a tool to regulate floodplain development. Therefore, the floodway modifications described in this letter, while acceptable to the Federal Emergency Management Agency (FEMA), must also be acceptable to your community and adopted by appropriate community action, as specified in Paragraph 60.3(d) of the National Flood Insurance Program (NFIP) regulations. These modifications have been made pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (P.L. 93-234) and are in accordance with the National Flood Insurance Act of 1968, as amended (Title XIII of the Housing and Urban Development Act of 1968, P.L. 90-448), 42 U.S.C. 4001-4128, and 44 CFR, Part 65. Public notification of modifications to the BFEs along Spring Creek will be given in the Coloradoan on or about May 1, 1992 and May 8, 1992. In addition, a Notice of Changes will be published in the Federal Register. As required by the legislation, a community must adopt and enforce floodplain management measures to ensure continued eligibility to participate in the NFIP. Therefore, your community must enforce these regulations using, at a minimum, the BFEs, zone designations, and floodways in the SFHAs shown on the FIRM and FBFM for your community, including the previously described modifications. This response to your request is based on minimum floodplain management criteria established under the NFIP. Your community is responsible for approving all proposed floodplain developments, including this request, and for ensuring that necessary permits required by Federal or State law have been received. With knowledge of local conditions and in the interest of safety, State and community officials may set higher standards for construction, or may limit development in floodplain areas. If the State of 3 Colorado or the City of Fort Collins has adopted more restrictive or comprehensive floodplain management criteria, these criteria take precedence over the minimum NFIP requirements. The basis of this LOMR is a channel -modification project. NFIP regulations, as cited in Section 60.3(b)(7), require that communities assure that the flood -carrying capacity within the altered or relocated portion of any watercourse is maintained. This provision is incorporated into your community's existing floodplain management regulations. Consequently, the ultimate responsibility for maintenance of the channel modification rests with your community. The community number and suffix code listed above will be used for all flood insurance policies and renewals issued for your community on and after the effective date listed above. The modifications described herein are effective as of the date of this letter. However, within 90 days of the second publication in the Coloradoan, your community may request that we reconsider this determination. Any request for reconsideration must be based on scientific or technical data. All interested parties are hereby notified that, until the 90-day period elapses, the determination may be modified. If you have any questions regarding the modifications described herein, please call the Chief, Natural and Technological Hazards Division, FEMA, in Denver, Colorado, at (303) 235-4830, or Mr. Karl Mohr of my staff in Washington, D.C., at (202) 646-2770. Sincerely, William R. Locke Chief, Risk Studies Division Federal Insurance Administration Enclosures cc: Mr. Robert W. Smith, P.E. Stormwater Utility Manager City of Fort Collins . Doug Williams, P.E. Greenhorne 5 O'Mara, Inc. z 00 000. i v ova/ Mt ° W 0 0 0 0 0 0 0,0 0 0 0 0 0 E W H W4 ° w ID ID m m n 0 vi 0 m. 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DEPARTMENT OF HOUSING iNO URBAN DEVELOPMENT EDERAL INSURANCE ADMINISTRATIDN Pr AREA REVISED CIO CI Ce oe APPROXIMATE SCALE 600 0 600 FEET RIVER MEADOWS ROAD NATIONAL FLOOD INSURANCE PROGRAM FLOODWAY FLOOD BOUNDARY AND FLOODWAY MAP CITY OF FORT COLLINS, COLORADO LARIMER COUNTY PANEL 3 OF 5 HIM«O1.RI TO NT[-I J^ DEFLECT LOMR IATED APR 2 0 1992 COMMUNITY -PANEL NUMBER 080102 0003 A EFFECTIVE DATE: IULY 16, 1979 U.S. DEPARTMENT OF HOUSING AND URBANDEVELOPMENT FEDERAL INSURANCE ADMINISTRAT No Text