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Home My WebLink AboutBEST BUY PUD FINAL - 29 92A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTr � . '� Phase III (Basin C) drain towards this site. Also, runoff from South College Avenue (Basin B) adjacent to this site (0.33 acres) will be routed into the proposed detention pond (see Figure 3). An orifice plate will meter flows from the detention pond into a storm sewer which will be extended from the Market Place storm sewer system. Approximately 23,010 cubic feet of detention will be required for this site. This volume can be provided in the parking lot with .2 feet of freeboard available. Calculations for the detention pond are attached. A pipe will collect roof drainage at the southeast corner of the building and convey it to the storm sewer in front of the orifice plate. See Drainage and Grading Plan. Erosion Control This project is located within areas of moderate wind and water erosion potential as identified by the City of Fort Collins. Wind_ Erosion Due to the small size of the site, the protection provided to the site by existing buildings and the proposed summer construction schedule, no wind erosion problems hT`>" Ts 0 l < I 1 If [Flml�,Pc u III II I I � II e�Dc I RIGHT OF WAY I AR» —_—_-- _— — KWG FOUNTAINHEAD P.U.D. PHASE 3_ RETNj ESTAURI,I AII N T ZONED NO ; A II S / I OFSlPAED VEME T I Fj II SLOG 0 1 \ 8 DECEL LANE INL13 ET I DETENTION POND R B - - IS 15 `• I I wroscAPE A �� AREA INLET —AREAG AV PROJECT I.D. I I ' 2.84Ac FILTER 15 �� o 15' SIDEWALK k UTIL o ' EASEMENT I I 15'I 1s Li pan SIGN � v �— — AREA INLET TO BE REMOVED I I i Z Z / R LLI wPROPOSED I II \ B J SIDEWALK ' ." I V GRAVEL 11 0 t RAMP 20 FILTER 15" t = RIGHT —Of —WAY I / I I / GONG 1 I I 1 i i PAD 1 1 I1 13 \\\ ` RETAINING WALL ` \ I -1) 11 I I AI \ lO' � SCREENING ASkRD. �, I:Ihrrn�uur�10 LOADING DOCK \ I � \ I r n Im�l v � qal I \ I 2 ,0 1 1 \ 1511 I'1li`IIII,� Alll�Aplp 1�l albl"I IIGI q NpNpl l - _ I'1 pi'j IICURB LET IIllrF? L IJ IJ ►J \ 1 ��-JJ c= J i \ 8 13 —RETAINING / \ R_ - \ SCREENING 4 REO-O. �� r -TENTI IIO�NI, POND /,s \O�A� Irl. R DING A \LGR AREA INLET 34 Ac FILTER 15 �`-- 151' AREA INLET p2 TRAVEL —� -ILTER 15" ------------� V \a ,3 1 IJM JI OWN] u 1 PPTE TIAL\ \ \ 1 I \ \ \\ 7 I � \\11��TTEERR� 1 - UNmEYEL� 1I((M11ED HR I \\ I \ 1 \ I ` � I \ \ POSSIHI C SIDE WALK GIMINI:GIIQN TO MARKET y� \ PI.ACT `\iT� 4Qh CHAR-MGR FIGURE Il BASIN SUMMARY 1 1 1 1 1 11 1 I I , I I 1 I I , I I / / PROF are expected and no provisions have been made for wind erosion control. Water Erosion The detention pond will also be used as a sedimentation pond to mitigate erosion caused by stormwater runoff. Conclusions and Recommendations It is recommended that a detention pond be provided to mitigate erosion and storm water runoff from the proposed Best Buy P.U.D. The detention pond will provide 23,010 cubic feet of detention in the parking lot. Off -site flows from College Avenue adjacent to the site and from a small area of Fountainhead Phase III are routed through the detetnion pond. Metered flows from the detention pond will be conveyed through the storm sewer system provided by the Market Place P.U.D. and discharged into the Larimer #2 Canal. IN LE FINAL DRAINAGE & EROSION CONTROL REPORT FOR BEST BUY P.U.D. MAY 28, 1992 PREPARED FOR MR. GEORGE HOLTER PREPARED BY ' PARSONS & ASSOCIATES CONSULTING ENGINEERS 432 LINK LANE PLAZA ■ FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 92.10 BUY II II TABLE OF CONTENTS Introduction Site Description Historic Drainage Master Drainage Drainage Criteria Drainage Under Developed Conditions Erosion Control Conclusions and Recommendations Calculations Grading and Drainage Plan Figure 1 Vicinity Map Figure 2 Outlet Imrovements Figure 3 Drainage Schematic W Introduction FINAL DRAINAGE & EROSION CONTROL REPORT FOR BEST BUY P.U.D. FORT COLLINS, COLORADO This drainage report has been prepared along with final engineering drawings to provide design information for the development of a Best Buy retail store along the east side of South College Avenue between the Fountain P.U.D. Phase 3 and the Market Place P.U.D. This report was prepared in conformance with the City of Fort Collins "Storm Drainage Design I Criteria and Construction Standards". Site Description IThe proposed Best Buy P.U.D. is located in the west one-half of Section 36, Township 7 North, Range 69 West of the 6" Principal Meridian, City of Fort Collins, Larimer County, IColorado (see figure 1). The northern portion of the site is also part of Lot 18'of the Observatory Heights Subdivision. The property is a 2.845 acre site which sits between the IFountainhead and Market Place commercial centers. Currently the parcel contains one single -1- PROJECT SITE VICINITY MAP N.T.S. family residence with some smaller farm buildings and is screened from the commercial Icenters and South College Avenue by mature trees and other landscaping. IThis project will include the construction of a 28,520 square foot retail building with ' 137 parking spaces. South College Avenue forms the western boundary and Fountainhead P.U.D. Phase 3 forms the northern boundary. A water line and access will tie to this project ' from the north. The adjacent parcel to the east is currently vacant, but is zoned HB and is j planned for a commercial building. The southern boundary of this project is adjacent to the Market Place P.U.D. (Phar Mor Site). Water, sewer, storm drainage and roadway improvements were installed as part of the Market Place P.U.D. to provide service to this site. Historic Drainage Construction of the adjacent commercial developments has affected the drainage from this site. Prior to the construction of these centers, water ran from northwest to southeast towards the Larimer #2 Canal. The majority of the drainage from the north was eliminated when the Fountainhead Project was constructed. Fountainhead sits approximately two (2) feet higher and diverts water away from this site. A natural ridge along the eastern boundary -2- El keeps water from the undeveloped eastern property away from this site. South College Avenue drains from north to south in this area and flows are kept in the curb where they are eventually diverted to the Market Place detention ponds by two curb openings. Detailed topography was completed by field survey which verifies the direction of off -site flows. Refer to the Final Grading Plan for additional detailed information. The Market Place drainage system provides detention for the Market Place Development and an outfall line to the Larimer #2 Canal. As part of the Market Place development, an outfall line was extended into the Best Buy P.U.D. property to drain the low area that was created. Sheet 15 of 16 of the Final Drainage Report for the Market Place (dated 1-2-90) shows that the outflow pipes were sized to convey this historic flow. Runoff on the Best Buy P.U.D. parcel currently runs from the edges of the site to an inlet where it is conveyed to the Larimer #2 Canal. Sheet 4 of 8 of the Market Place construction plans shows these improvements (see Figure 2). Master Drainage The property is located within the Heart Special Improvement District. Runoff from areas within this district is limited to 0.87 cfs per acre of developed area before being -3- As 1 UTURE DE�Vr L-OptAGT= T-C��ADE TO btZAlt i TO pSAS," SI pE DiTL'1 I.ES. 1-�-- AREA \NLE-T A2A- ____p2Attt TO CAT+=N �C-3P Orr faRATC��1.00 \NV. ZT.ZO .T— ZO� 32 STD. VERT c.4 C, (TYP) 31'25 �... 5 3 -�\\20 J—t N OUTFALL G E U (TYP.) , � v / 4 In / 20 �► ub U- -- J 90' co If1 30 20 20 31 ARE \h4\_ET A•Z N9 � �� /- "'I 'CC7 OF CaRA"CE 2�i.Sq.•L \o .Yt1v. \N (.N) Z�.8014, �I5"J__. � 25 � 20 $ nw- discharged into the Larimer #2 Canal. The Final Drainage Report for the Market Place identifies this site as a separate basin and includes historical flows of 2.83 cfs from this site in the design of its storm sewer improvements. The Market Place Drainage provides for four parking lot detention ponds. These ponds overflow to the south via a driveway to Troutman Parkway when they eventually discharge into the Larimer #2 Canal. The Best Buy detention pond is designed to spill into these ponds. Drainage Criteria The Rational Formula was used to develop flows for this project. The Rational Formula is an excellent predictor of runoff in basins less then 200 acres. Drainage Under Developed Conditions The grading plan for the Best Buy P.U.D. site shows drainage flowing to a detention pond in the main parking lot west of the proposed building. This grading matches the existing terrain closely and conforms to the Market Place Drainage Plan. 0.33 Acres of Fountainhead -4-