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Home My WebLink AboutAMIGOS AT SHIELDS FINAL PUD - 47 90B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE & EROSION CONTROL REPORT FOR AMIGOS AT SHIELDS P.U.D. JANUARY 29, 1993 PARSONS & ASSOCIATES , CONSULTING ENGINEERS EROSION CONTROL This project is located within areas of moderate wind and rainfall erosion potential as identified by the City of Fort Collins wind and rainfall erodibility maps. Wind Erosion 0 Due to the small size of the site (less than one acre), no wind erosion protection measures need to be taken. The site is also protected by trees and buildings around the perimeter. Water Erosion Net effectiveness calculations attached show that no erosion control measures need to be taken. However, it is suggested that silt fences be placed around the perimeter of the site immediately after demolition and striping to control erosion prior to paving of the parking lot. The detention area will act as a sedimentation pond (trap) to mitigate erosion and sediment transport downstream. The landscaped and grassed areas will also act as buffers to control erosion caused by stormwater runoff. All erosion control calculations n-Appendix_B_of_this_report. CONCLUSIONS AND RECOMMENDATIONS The replacement of the existing Texaco service station with an Amigos restaurant will have minimal impact on the drainage in this area. The site is divided into two subbasins, west (A2) and east (132), with minimal off -site flows contributed from the south by subbasins Al and 61. The location and grade of the existing structure will insure that changes to the quantity of runoff are minimal. The 1400 square feet of landscaped/grassed area in subbasin B2 will actually reduce the amount of runoff to Shields Street. The amount of runoff will increase in subbasin A2, however, the small parking lot detention area with the metered 8" ADS outlet will insure that the flow released to the west is maintained at the historic rate. -7- FINAL DRAINAGE & EROSION CONTROL REPORT FOR AMIGOS AT SHIELDS P.U.D. JANUARY 29, 1993 PREPARED FOR: AMIGOS GROWTH MANAGEMENT CORPORATION 2546 SOUTH 48TH STREET P.O. BOX 6189 LINCOLN, NEBRASKA 68506 PREPARED BY: PARSONS & ASSOCIATES CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 92.17 AMI TABLE OF CONTENTS Introduction 1 Site Description 1 Historic Drainage 4 Master Drainage 4 Drainage Under Developed Conditions 5 Erosion Control 6 Conclusions and Recommendations 6 Drainage and Erosion Control Back Pocket Figure 1 Vicinity Map Figure 2 Drainage Schematic Appendix A Drainage Calculations Appendix B Erosion Control Calculations FINAL DRAINAGE & EROSION CONTROL REPORT FOR AMIGOS AT SHIELDS P.U.D. FORT COLLINS, COLORADO INTRODUCTION This drainage report has been prepared along with final engineering drawings to provide design information for the development of an Amigos Restaurant P.U.D. along the west side of South Shields Street between University Avenue and West Elizabeth Street. This report was prepared to provide information for on and off -site drainage. All design specifications are prepared in accordance with the City of Fort Collins "Storm Drainage Design Criteria and Construction Standards". SITE DESCRIPTION The proposed site for the Amigos restaurant at Shields P.U.D. is located at 1015 South Shields Street on a 230' by 132' lot approximately 0.7 acres. The Campus West Texaco Service Station is located -on -the -existing -site.. —The -site -is -located -in -the -Southeast -Quarter of Section 15, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, Larimer county, Colorado (See Figure 1). -1- M A 0 O FIGURE / This site is zoned Limited Business (B-L) and is in an area of intense activity. The area is totally impervious except for a small dirt area at the rear (western edge) of the lot, 41' by 132'. Based on field verified topography, there is a drainage boundary that runs north and south, and splits the site into two basins (See Figure 2). The western one-half of the lot with an approximate area o 0.29 acres (subbasin A2) drains to the northwest into a parking lot. The eastern one-half of the lot with an approximate area of 0.39 acres (subbasin B2) drains to the east and northeast, into the existing Shield Street curb and gutter. The property to the south is undeveloped and is composed of roughly 70% grass/lawns and 30% gravel/dirt. The drainage boundary that divides the existing Texaco service station lot continues to the south to divide this undeveloped property. The western one-half of this area drains into subbasin A2 and is labeled subbasin Al with an approximate area of 0.16 acres on Figure 2. The eastern one-half of this area is labeled subbasin B1 with an approximate area of 0.15 acres that drains to subbasin B2. Flow direction arrows and drainage .basin boundaries, and areas are shown on Figure 2. The property to the west of the Amigos site is topographically lower and is used as a parking lot. The corner of Shields Street forms the eastern basin boundary and is used as an arterial roadway with an existing curb and mpus West shops which are topographically lower than the existing site and drain into the Shields Street curb and gutter. This project will include the construction of a 2332 square foot restaurant with 33 parking spaces and a drive -up lane. Small grassed areas as well as an outdoor patio will be included with the proposed site. Trees and bushes will shield the edges of the site. Proposed water and sanitary sewer lines will tie to this project from the south. -3- EDGE OF PAVEMENT j I I I 1 1 1 1 I I 1 1 I 1 ./5 I I 1 I I i I 1 1 1 1 I so a3(11 IPA 7 HI DINT 2 qtL,J^2 XL-1 F-L i r— AREA INLET SEE DETAIL SHEET ORIFICE PLATE SEE DETAIL SHEET PAN SEE DETAIL >f 8 0 0 .23.30 Im co z ti �px I ryy. IV .�h So. SHIELDS LEGEND NORTH 132.01T CONTOUR INTERVELaim . FLOW DIRECTION SCALE: 1" A2 BASIN LABEL ®DRAINAGE AREA S/ TE TOP 0 & DRA /NA GE MAP SCALE: 1" = 30' FIGURE 2 HISTORIC DRAINAGE As described in the previous section, a drainage ridge runs north/south through the site to divide the flows running off this area. The existing Texaco service station is located near the middle of the lot with the roof being the highest spot. The western one-half of the site, subbasins A 1 and A2, drainage across the church parking lot in a northwesterly direction and eventually drains into an existing 24" storm sewer. The eastern one-half of the site (front lot), basins 61 and B2, drains into the Shields Street curb and gutter which flows to the north and into the existing curb inlets. Detailed topography was completed by field survey which verifies the direction of off -site flows. Refer to the Final Grading Plan for additional information. This historic runoff from each of the four subbasins was determined from the Rational Method. The Rational Formula is widely accepted predictor of runoff from basins less than 200 acres. The runoff from subbasins Al and A2 for the 2, 10 and 100 year frequency events are approximately 0.6, 1.0 and 2.0 cfs, respectively (See Calculation Sheets) There are no storm sewers on the existing site. MASTER DRAINAUh This site is located within the Spring Creek drainage basin. Local outflow initially moves toward the north, major storm sewers capture surface flows and redirect the flow in a subsurface storm sewer system to the southeast and into Spring Creek which in turn flows to the Poudre River. -4- DRAINAGE UNDER DEVELOPED CONDITIONS The existing flow patterns will be maintained at the proposed site. The grading plan for this site will create a ridge as shown on Figure 2 to split the flow to the east and west. This grading matches the existing terrain closely. The off -site area (Subbasins Al and B1) to the south will continue to flow onto the proposed site. Subbasins B1 and B2 will continue to flow into Shields Street curb and gutter with relatively no change in historic quantity. Subbasin B2 will include approximately 1400 square feet of landscaped area which will reduce the amount of runoff onto Shields Street. The historic discharge from this area is not being increased, therefore, no detention or drainage improvements are proposed. The combined runoff from subbasins Al and A2 will increase due to an increase in paved area over the existing gravel. The runoff under fully -developed conditions for the 2, 10 and 100-year frequency events are 0.7, 1.2, and 2.5 cfs, respectively. A 8" ADS pipe will be installed in the northwest corner of the lot. An orifice plate with a 6.385 inch diameter will meter flows to the historic 2-year discharge. In order to accomplish this release, parking lot detention storage will be provided to capture the 100-year discharge. The detention volume is calculated to be approximately 1605 cubit feet and the proposed area is shown on Figure 2. The calculations for the detention storage are available in Appendix A. The detention volume is wedge-shaped with a maximum depth of 6 inches (0.5 feet) at the outlet. See the drainage and grading plan. A 15 foot easement has been proposed and is currently being reviewed by the Archdiocese of Denver. The easement is 130 feet long and ends at an area inlet historically used to drain this and surrounding areas. -5-