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Home My WebLink AboutMINI-MART AT ELIZABETH & SHIELDS PUD - PRELIMINARY/FINAL - 50-94 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTCONCLUSIONS AND RECOMMENDATIONS After review of historic and proposed drainage information and existing drainage information, the following conclusions can be made. 1) Runoff from the site will collect to a common outfall point. The minor flows will be conveyed in gutter pans, shallow drain pans or street flow across impervious surfaces. 2) Proposed development will actually decrease (slightly) the storm flows from the initial (10 year) storm. 3) The intersection of Shields and Elizabeth will continue to flood, the proposed convenience store will offer more complete protection from the maximum surface that is planned for the intersection. -6- I% II II II II ,A-V,!T& 01 PROJECT: MINI MART F.UD. SEQUENCE FOR 19 94 ONLY TABLE 1 . CONSTRUCTION SEQUENCE COMPLETED BY: R VU STANDARD FORM C DATE: 9109194 Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. YEAR MONTH 1994 NOV. DEC 1994 ✓AN FEB. MAR OVERLOT GRADING WIND EROSION CONTROL Soil Roughing Perimeter Barrier Additional Barriers Vegetative Methods Soil Sealant Other RAINFALL EROSION CONTROL STRUCTURAL: Sediment Trap/ Basin Inlet Filters Straw Barriers Silt Fence Barriers Sand Bags Bare Soil Preparation NOTE: Contour Furrows EXISTING PAVING AT NORTH Terracing Asphalt/ Concrete Paving PARKING LOT WILL REMAIN Other LINTK ENTIRE SITE IS READ Y FOR PA VEMENT VEGETATIVE: Permanent Seed Planting Mulching/ Sealant Temporary Seed Planting Sod Installation Nettings/ Mats/ Blankets Other TABLE 2 EROSION CONTROL METHODS EROSION CONTROL C—FACTOR P—FACTOR COMMENTS METHOD VALUE VALUE SILT FENCE 1.00 0.50 SOUTH & WEST PROP LINES CONC./ASPHALT PAVEMENT 0.01 1.00 ALL ROADWAYS INLET PROTECTION 1.00 0.80 OUTLET TO SHIELDS I ` '\ C MEROSION CONTROL NThis project is located within an area of moderate wind erosion and moderate rainfall erosion according to the City of Fort Collins wind and rainfall erodibility maps. NWIND EROSION Wind erosion protection will be provided by existing buildings on the northern and western perimeter of the project. Asphalt paving of the parking area and seeding and mulching (or landscaping) of all disturbed areas will provide final stabilization upon completion of this project. WATER EROSION Net effectiveness calculations included in Appendix B of this report show that methods proposed for this development will be adequate at minimizing the erosion potential of rainfall events. As stated above, final stabilization will occur with completion of paving and landscaping features. All erosion control calculations and cost estimates are included in Appendix B of this report. -5- 5,lS7iNG CCAMERCIAl BUILD!NG 7 PROPOSED BUILDING ADDITION "S L .ram LL STORE AND AND Y'1,� (2 STORY) EL ho'I\�,01 ��:O�DI FIGURE 3 Ch m V) DEVELOPED SITE The composite "C" for the developed (proposed) site was calculated as 0.88, with approximately 2100 sq. ft. of landscape and 21,300 sq. ft. of impervious surface, please refer to Figure 3. This represents a net decrease in impervious area and should have no adverse effect on storm drainage patterns or maximum surface elevations during any frequency storm event. Drainage patterns will be adjusted to accommodate two spill locations to Shields. A four foot pan will transfer flows along the northern boundary of the project at Cambridge Place and a small 2 foot sidewalk chase will collect and convey flows to Shields just north of the new pump islands. During the 100 year storm water will continue to overtop the curb and sidewalk areas but the building will be protected from high water. -4- oil IEXISTING CMIMERCIAL DU!LDING I PARKING AREA ASPHALT DRIVE GRAVEL AREA a w EbSTING BUILDING z. Z U' WALK =, PARKING AREA u o / l\ � ASPHALT DRIVE �2 SIDEWALK WEST ELIZABETH STREET UAREA EWE- 0 I EXISTING SITE FIGURE 2 G N n HYDROLOGIC ANALYSIS The Rational Method has been used to calculate the stormwater runoff for the 10-year and 100-year return period events for the Historic and proposed improvements to the Minimart site. ' The historic (existing) 10-year and 100-year events were developed to compare existing (historic) conditions to the fully developed (proposed) conditions. The composite "C" coefficients for the historic show a C=0.91, or approximately 1600 sq. ft. of landscaped area on the existing site with approximately 21,800 sq. ft. of impervious surface, please refer to Figure 2. The stormdrainage study "Evaluation of Existing Drainage Conditions for Shields Street", Lidstone & Anderson, 1993 was used to evaluate flooding conditions at the intersection of Shields and Elizabeth. According to this study the 10 year and 100 year storms will overtop the existing curb lines and cause shallow flooding at the intersection. The 100 year surface 23.2 ft. (per report) was Iused to protect the finished floor of the proposed convenience store and reduce the area of ponding for the proposed improvements. -3- � 11 J SITE DESCRIPTION The site is located in the Southeast Quarter of Section 15, Township 7 North, Range 69 West of the Sixth Principal Meridian, Larimer County, State of Colorado. The project area (approximately .54 acres) consists of two parcels; the Minimart parcel and the parking area to the north. The project is bounded on the north by an access drive to Cambridge Place, on the east by Shields street right of way, on the west by additional shops and on the south by West Elizabeth. The site currently drains to a curb inlet on the north flowline of West Elizabeth. Existing vegetation on the site consists of scattered shrubs and is surrounded by pavement walks or building envelopes. The historic and proposed development for the tract is commercial as outlined above. The entire project will be developed in one phase with all improvements proposed for construction. -2- 1 1 L WL �vm �r7'rPt T.7 VICINITY MAP 1" = 1000' VICINITY MAP FIGURE 1 FINAL DRAINAGE AND EROSION CONTROL REPORT FOR MINIMART AT SHIELDS AND ELIZABETH INTRODUCTION The purpose of this study is to provide drainage and erosion control information for the development of a .54 acre commercial site which will include a gas station and convenience store on South Shields Street at West Elizabeth. All design specifications are prepared in accordance with the City of Fort Collins Drainage Design and Construction Standards. This site has historically been used as a convenience store/gas station. Changes to turn lanes and Shields Street improvements by the City of Fort Collins has necessitated the relocation of the convenience store and improvements to the parking lot on the north end of the project. -1- TABLE OF CONTENTS Introduction Site Description Hydrologic Analysis Erosion Control Wind Erosion Water Erosion Conclusions and Recommendations Figure 1 Figure 2 Figure 3 Appendix A Appendix B Table 1 Table 2 Exhibit 1 Vicinity Map Existing Site Developed Site Drainage Calculations Erosion Calculations Construction Sequence Erosion Control Methods Drainage and Erosion Control Plan 1 2 314 5 5 5 6 Back Pocket FINAL DRAINAGE & EROSION CONTROL REPORT FOR MINIMART AT SHIELDS AND ELIZABETH SEPTEMBER 12, 1994 PREPARED FOR MR. TERRY OLDFIELD MINIMART, INC. P.O. BOX 3259 CASPER, WY. 82602 PREPARED BY: PARSONS AND ASSOCIATES, INC. CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 94.08MNI r 4'i