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Home My WebLink AboutBEST BUY PUD PRELIMINARY - 29 92 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT0 PRELIMINARY DRAINAGE & EROSIONiCONTROL REPORT FOR BEST BUY P.U.D. 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 .* PARSONS & :Nr GfUfo, l B ter JOB NO. ~ F W ( ASSOCIATES. PROJECT P u D, CALCULATIONS FOR PlAf 11 all CONSULTING ENGINEERS q MADE BY— 1W( DATE _ � /� CHECKEDBY 0� DATE S � _ � SHEET I OF ' Ft. Collins,Colorado 80524. •_ 1 ., _....� i`__. _• r �.__.r i T--. t �.. i ,__...may - 1 r i_ QP51 _Qu_y �C1,{411164 _ ; E _ , II I E 7 ore f CY]cfsfAs�e. Cs.._.' �. j I-- = ysy T � �^ 1I00 v TiAe 1�{c�s 1y , _Orscbu�. Volume) . , ' o(aan yl/c1_aW( _(ifs I) ! _I2 D . zd 63 37V Zo S;IS JY,4s'. L17,',SYa 30 121M Ya 3,50 i I 1 , ` 1 6o 40 6o Z Go 17 `ro, 2G `YD 17171Z I I I - ' peie4 04 1/A�uMe '...Qe u�. �C44 y �f • : I I E ��3 147 ]Of 3s��ln.} (1 0)0s;VO) 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 PRELIMINARY DRAINAGE & EROSION CONTROL REPORT FOR BEST BUY P.U.D. FORT COLLINS, COLORADO Introduction This drainage report has been prepared along with preliminary 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 Criteria and Construction Standards". -1- Site Description The 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, Colorado (see figure 1). The northern portion of the site is also part of Lot 18 of the Observatory Heights Subdivision. The property is a 2.8454 acre site which sits between the Fountainhead and Market Place commercial centers. Currently the parcel contains one single family residence with some smaller farm buildings and is screened from the commercial centers and South College Avenue by mature trees and other landscaping. This project will include the construction of a 18,048 square foot retail building with 157 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 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 -2- I PROJECT SITE VICINITY MAP N. T. S. 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. 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 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. 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. 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. -3- I 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 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 from this site in the design of its storm sewer improvements. 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. 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 18,100 cubic feet of detention will be required for -4- this`site Thiswolume,can-be�provided irrthe parking lot with .3 feet of freeboard available. Calculations for the detention pond are attached. 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 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. 0 M 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 18,100 cubic feet of detention in the parking lot. 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. -7-