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Home My WebLink AboutRAMS PARK - PDP/FDP - 12-00 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFuel Drainage Report Fairview Lake PUD March 28, 2000 Northern Engineering Services, Inc. APPENDIX Section A - Historic/Developed Hydrology PAGE Historic Site Drainage Exhibit..............................................................Al Historic Site 2, and 100-Year Calculations..........................................A2-A5 Developed Site 100-Year Calculations.................................................A6-A7 Section B - Water Quality Water Quality Pond Volume and Outlet Design Documentation. .......... Bl-B6 Water Quality Pond 2 Design. ............................................................... B7-B8 Section C - Detention Pond 2 Calculations...............................................................................C1-C8 Pond 3 Calculations...............................................................................C9-C16 Combined Hydrograph for Ponds 2 and 3 Outlflow and Basin 1...........C17 Pond 1 Calculations..............................................................................C18-C22 Section D - Kentucky Fried Chicken Restaurant Detention Ponds West Pond Calculations..................................................................•......Dl-D4 East Pond Calculations..........................................................................C5-D8 Section E - Erosion Control Calculations Section F - Approved Drainage Report for Kentucky Fried Chicken Restaurant Site Page 5 Final Draimlge Report Fairview Lake PLO March 28, 2000 Northern En®nceaing Services, Inc. REFERENCES 1) Storm DLairgge Design Criteria and Construction Standards City of Fort Collins Stormwater Utility, Fort Collins, Colorado, May 1984. Page 4 Final Dram Report Northem Engineering Services, Inc. Fairview Lake PUD March 28, 2000 The required water quality measures for this site will be implemented at Ponds 1 and 2. Pond 2 has been designed to include 1302 cubic feet of extended detention with a 40-hour holding time. Pond 1 has been designed with a sand and grease trap at its outlet. 4.6 Kentucky Fried Chicken Restaurant Detention Ponds 1 As a result of the proposed development, the size of the west detention pond of the neighboring Kentucky Fried Chicken restaurant will be decreased. Upon analysis of this pond, it was determined that there will be a lack in pond volume in the 100-year storm. It is proposed to remedy this lack of volume in the west pond by changing the release rates of both the east and west ponds. It is proposed to replace the existing orifice of the east pond with a 2.5-inch orifice, which, in a 100-year storm, would release a maximum of .18 cfs. For the west pond, it is proposed to replace the existing orifice with a 5.5-inch orifice. Ina 100-year storm this new orifice would release a maximum of .63 cfs. Installation of the new orifice plates on the east and west ponds was analyzed using the Modified Puts method. With the installation of the new orifice plates, the total release rate for the Kentucky Fried Chicken site would be.63cfs + .18 cfs = .81 cfs. This is greater than the current release of .65 cfs, however it is still less than the maximum allowable release rate for the site of ' .95 cfs as described in the approved drainage report for Kentucky Fried Chicken. A copy of the approved drainage report and detailed calculations are found in the appendix of this report. V. EROSION CONTROL Erosion control will consist of the following measures. Gravel inlet filters will be placed at the one curb cut draining to Pond 1, at the two curb cuts draining to Pond 2, and at the upstream end of the outlet of Pond 3. A gravel sediment trap will be placed at the upstream end of the outlets for Pond 1 and Pond 2. All landscaped areas will receive hay mulch and temporary seeding until permanent growth is established. Poge 3 Final Drainage Report Northern Engineering Services, Inc. Fairview Lake PUD March 28, 2000 is described in section 4.6 of this report. 4.2 Design Criteria and References Drainage criteria outlined in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards has been referenced in the preparation of this study. 1 4.3 Hydrologic Criteria Due to the relatively small basin size, the rational method has been used to estimate peak stormwater runoff from the project site. Hydrologic calculations along with other supporting material, are contained in the appendix to this report. The 100-year design storm was used to evaluate the proposed drainage system. Rainfall intensity data for the Rational Method has been taken from City of Fort Collins new rainfall criteria published April 12, 1999. 4.4 Hydraulic Criteria The City of Fort Collins Storm Drainage Design Criteria and Construction Standards has been referenced for all hydraulic calculations. In addition, the computer models, "Watershed Modeling" , and "Surface Modeling" by Eagle Point software have been utilized to calculate detention pond stage vs. storage curves, orifice rating curves, and required pond volumes. 4.5 Draigne Concept Developed stormwater will be conveyed to Ponds 1,2 and 3 where flows will be detained and released at controlled rates. Basins 03 and 2 drain to Pond 2, where 100-year developed flows are detained and released at a maximum of .06 cfs. The release from Pond 2 is directed to Pond 1. Basins 3 and 4 drain to Pond 3, where 100-year developed flows are detained and released at a maximum of .06 cfs. The release from Pond 3 is also directed to Pond 1. Pond 1 receives the release from Pond 2 and Pond 3, and also receives drainage from Basin 1. In a 100-year storm the combination of these flows are detained in pond 1 and released at a maximum of .85 cfs to West Elizabeth Street. Thus, the maximum 100-year release from the developed site will be less than historic 2-year release rate of 1.0 cfs. The Modified Puls reservoir routing method has been used to size Ponds 1,2, and 3. Pond 2 and Pond 3 are modeled as having the hydrograph from a single, lumped basin flowing into the pond, and an orifice rating curve to represent flow out of the pond. Pond 1 was modeled as having the two outflow hydrographs from Ponds 2 and 3, and the hydrograph from Basin 1 flowing into the pond, and an orifice rating curve to represent flow out of the pond. Please see the appendix for these calculations. Basins 5 and 03 concentrate at design point 5 and will contribute 0.7 cfs to the existing offsite swale to the north of the site in the 100-year storm. Historically, Basin HI drained to this swale and contributed 0.2 cfs in the 100-year storm Basin H4 also drained to this Swale and contributed 1.0 cfs. Thus, the swale should have adequate capacity for the proposed flow of 0.7 cfs. Page 2 I Final Drainage Report for Rams Park Apartments Fort Collins, Colorado March 28, 2000 I. INTRODUCTION 1.1 Objective The purpose of this report is to provide documentation pertaining to the final drainage system design and analysis for the proposed Rams Park Apartments. Storm drainage design critera set forth in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards has been followed in the design of proposed storm facilities. II SITE LOCATION AND DESCRIPTION 2.1 Site Location The site is located in the northeast quarter of Section 16, Township 7 North, Range 69, west of the 6te Principle Meridian, City of Fort Collins, Colorado, County of Larimer, State of ' Colorado. The site is bounded by West Elizabeth Street on the south, Kentucky Fried Chicken on the east, an apartment complex on the north, and a residential neighborhood on the west (see vicinity map). ' 2.2 Site Description The site is approximately 3.1 acres, gently sloping from the east and west inward. Two homes exist on the site. Both homes are located near the south property boundary, close to West Elizabeth Street. M. HISTORIC DRAINAGE 3.1 Historic Drainage Patterns The site historically drains from the east and west to a retention area in the northeast portion of the property. It is assumed that in both the minor (2-year) and major (100-year) storms �. this retention area fills and then drains to the north into a swale that flows west into the adjacent apartment complex. The historic two year flow to design point H4 (See Historic Drainage ' Exhibit) is 1.0 cfs. This is considered to be the allowable detention release rate for the proposed site. The two homes on the existing site appear to have their roof and driveway drainage ' directed to West Elizabeth Street. A fairly Small offsite basin at the northwest comer of the site appears to contribute runoff to the site at the northwest property comer. This runoff is routed across the site and into the retention area. VI. DEVELOPED DRAINAGE 4.1 Developed Conditions 1 Development of the site will consist of the construction of 4 apartment complexes and - improvement of West Elizabeth Street. The neighboring Kentucky Fried Chicken restaurant has a portion of its west detention pond within the bounds of the proposed site. The size of this detention pond will be decreased as a result of the proposed development. Analysis of this pond I VICINITY MAP 1V 1"=1500' NORTHERN March 28, 2000 Mr. Basil Hamdan City of Fort Collins Stormwater Utility 700 Wood St. Fort Collins, Colorado 80521 RE: Rams Park Apartments Fort Collins, Colorado Project No. 2000.00 Dear Steve: Northern Engineering is pleased to submit this Final Drainage Report for Rams Park Apartments for your review. This report complies with technical criteria set forth in the City of Fort Collins Storm Drainage Desien Criteria and Construction Standards. If you should have any questions or comments as you review this report please feel free to contact me at your earliest convenience. Sincerely, NORTHERN ENGINEERING SERVICES, INC. n Aaron Cvar Reviewed by; 30325 Mary B. 420 SOUTH HOWES, SUITE 202, FORT COLLINS, COLORADO 80521, (970) 221-4158, FAX (970) 221-4159 Final Drainage Report for Rams Park Apartments Fort Collins, Colorado March 28, 2000 Prepared For: Bellisimo Construction, Inc. 7307 Streamside Drive Fort Collins, Colorado 80525 Prepared By: Northern Engineering Services, Inc 420 S. Howes, Suite 202 Fort Collins, Colorado 80521 Phone: (970)221-4158 Project Number: 2000.00