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Home My WebLink AboutRIGDEN FARM, 11TH FILING, BROOKLYN PARK ROW HOUSES - PDP - 56-98AD - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTi i i i i i i ,i m m i i i m i iW"m in ja v,nsr zZT 3 NospitaJ �] M a ro .I S r CXT e � n [t - E Harsetooth Rd W a rran Park CvJliRdaJc gighorn Rd Rd .:'nrrrn Caurss �owir G� _. Carib au Dr i VICINITY MAP N.T.S. r. cm N NInnah Ln Chinook Ln APPENDIX A VICINITY MAP r I 2. 3. City of Fort Collins, "Storm Drainage Design Criteria and Construction Standards" (SDDCCS), May 1984. "Final Drainage and Erosion Control Report for Rigden Farm Filing One" by JR Engineering dated September 7, 1999. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated June 2001, and Volume 3, dated September 1992. 3.3 Tracking Mud on City Streets It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights -of - way unless so approved by the Director of Engineering in writing. Wherever construction vehicles access routes or intersect paved public roads, provisions must be made to minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved surface. Stabilized construction entrances are required per the detail shown on the detail sheet, with base material consisting of 6" coarse aggregate. The contractor will be responsible for clearing mud tracked onto city streets on a daily basis. 3.4 Maintenance All temporary and permanent erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. Straw bale dikes or silt fences will require periodic replacement. Maintenance is the responsibility of the developer. 3.5 Permanent Stabilization A vegetative cover shall be established within one and one-half years on disturbed areas and soil stockpiles not otherwise permanently stabilized. Vegetation shall not be considered established until a ground cover is achieved which is demonstrated to be mature enough to control soil erosion to the satisfaction of the City Inspector and to survive severe weather conditions. Drainage and Erosion Control Report Rigden Faun 13'h Filing — Brooklyn Park Row Houses Page 5 April 6, 2005 where to is the time of concentration in minutes, ti is the initial or overland flow time in minutes, and tt is the conveyance travel time in minutes. The initial or overland flow time is calculated with the SDDCCS Manual equation: ti = (1.87(l.1 - CCf)L0.5xs)0.33 (3) where L is the length of overland flow in feet (limited to a maximum of 500 feet), S is the average slope of the basin in percent, and C and Cf are as defined previously. All hydrologic calculations associated with the sub -basins shown on the attached drainage plan are included in Appendix B of this report. 3. EROSION CONTROL 3.1 Erosion and Sediment Control Measures Erosion and sedimentation will be controlled on -site by use of silt fences, as well as seeding and mulch. The measures are designed to limit the overall sediment yield increase due to construction as required by the City of Fort Collins. During overlot and final grading the soil will be roughened and furrowed perpendicular to the prevailing winds. Erosion control effectiveness, rainfall performance calculations and a construction schedule are provided in Appendix C. 3.2 Dust Abatement During the performance of the work required by these specifications or any operations appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor, equipment, materials, and means required. The Contractor shall carry out proper efficient measures wherever necessary to reduce dust nuisance. Efficient measures shall be taken to prevent dust nuisance that has originated from the contractor's operations from damaging crops, orchards, cultivated fields, and dwellings, or causing nuisance to persons. The Contractor will be held liable for any damage resulting from dust originating from his operations under these specifications on right-of-way or elsewhere. Drainage and Erosion Control Report Rigden Farm 13ih Filing - Brooklyn Park Row Houses Page 4 April 6, 2005 (UDFCD) dated 1984, developed by the Denver Regional Council of Governments have been utilized. The rainfall criteria used was the April 1999 amended criteria. 1.5 Master Drainage Basin Rigden Farm 13t' Filing is located within the Foothills Master Drainage Basin. 2. LOCAL DEVELOPED DRAINAGE DESIGN 2.1 Method The Rational Method was used to determine the 2-year and 100-year flows for the drainage areas indicated in this drainage report. Drainage facilities were designed to convey the 100- year peak flows. The hydrologic calculations are found in Appendix B of this report. 2.2 Hydrologic Analysis of the Proposed Drainage Conditions The Rational Method was used to determine the 2-year and 100-year peak runoff values for each sub -basin. Runoff coefficients were assigned using Table 3-2 ofthe SDDCCS Manual. The Rational Method is given by: Q = CfCIA (1) where Q is the maximum rate of runoff in cfs, A is the total area of the basin in acres, Cf is the storm frequency adjustment factor, C is the runoff coefficient, and I is the rainfall intensity in inches per hour for a storm duration equal to the time of concentration: The frequency adjustment factor, Cf, is 1.0 for the initial 2-year storm and 1.25 for the major 100- year storm. The runoff coefficient is dependent on land use or surface characteristics. The rainfall intensity is selected from Rainfall Intensity Duration Curves for the City of Fort Collins (Figure 3.1 of SDDCCS). In order to utilize the Rainfall Intensity Duration Curves, the time of concentration is required. The following equation is used to determine the time of concentration to = ti + tt (2) Drainage and Erosion Control Report Rigden Farm 13" Filing — Brooklyn Park Row Houses Page 3 April 6, 2005 a Proposed Basins OS 1, OS2, OS3 and OS4 (which is Basin 108C from the Rigden Filing One Report) release flows directly onto Iowa and Custer Drive ultimately discharging into an existing triple combination inlet, just west of the intersection of Custer Drive and Kansas Drive. Calculations provided in the back of this report show that Basins OS 1, OS2, OS3 and OS4 have a combined 2-year developed flow of 1.60 cfs and a 100-year developed flow of 7.60 cfs. The combined flows for these proposed basins are less than that of Basin 108C, as mentioned in the approved Rigden Filing One Report by JR Engineering, and decrease flows by approximately 0.8 cfs in the 2-year event and 4.52 cfs in the 100-year event. Proposed on -site Basins 1 through 8 will discharge directly into the existing 43"x68" Horizontal Elliptical Reinforced Concrete Pipe (HERCP) at various locations. This pipe flows south along the easterly property line and eventually discharges into Water Quality Pond 2, designed with the Rigden Filing One Report by JR Engineering. Calculations provided in the back of this report show a combined 2-year developed flow of 3.40 cfs and a 100-year developed flow of approximately 14.0 cfs. This is an increase from the flows mentioned in the Rigden Filing One Report by JR Engineering for Basin 108G. It is an increase of approximately 1.8 cfs in the 2-year event and approximately 7.0 cfs in the 100- year event. In conclusion, the proposed development is adding approximately 1.0 cfs in the 2-year event and 2.50 cfs in the 100-year event to the existing storm sewer system along the eastern property line. The capacity of this existing 43"x68" HERCP storm pipe is approximately 136.40 cfs. The calculated flow as designed and approved with the Rigden Filing One Drainage Report by JR Engineering is approximately 93.5 cfs, which gives the existing pipe an excess capacity of 42.9 cfs. Due to the minimal increase in flows, as mentioned above, and the excess capacity in the existing storm sewer, it appears the existing storm pipe has the capacity to handle the additional flows of 1.0 cfs in the 2-year event and 2.50 cfs in the 100- year event. 1.4 Design Criteria This report was prepared to meet or exceed the submittal requirements established in the City of Fort Collins' "Storm Drainage Design Criteria and Construction Standards" (SDDCCS), dated May 1984 and revised in January 1997 and that of the Final Drainage and Erosion Control Report for Rigden Farm Filing One by JR Engineering dated September 7, 1999. Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual" Drainage and Erosion Control Report Rigden Farm 13" Filing — Brooklyn Park Row Houses Page 2 April 6, 2005 II1. INTRODUCTION 1.1 Project Description Brooklyn Park Row Houses is aproposed single-family condominium project located in the Rigden Farm Subdivision, in the northwest quarter of Section 29, Township 7 North, Range 68 West, of the 6`h Principal Meridian in the City of Fort Collins, Larimer County, Colorado. A vicinity map is provided in Appendix A. 1.2 Existing Site Characteristics The existing site is bordered on the south by Timberline Church, on the west by Iowa Drive, the east by Rigden Farm 12`h Filing and on the north by Custer Drive. 1.3 Proposed Site Characteristics This report defines the proposed drainage and erosion control plan for Rigden Farm 13`h Filing - Brooklyn Park Row Houses. The plan includes consideration of all on -site and off - site runoff and the design of all drainage facilities required with this development. The Final Drainage and Erosion Control Report for Rigden Farm Filing One by JR Engineering dated September 7, 1999 was referenced and adhered to during the design of this project. The proposed development completely falls within basins 108C and 108G as mentioned in the Rigden Farm Filing One Drainage and Erosion Control Report. The calculations done by JR Engineering for these two basins have been provided in Appendix D of this report. The 2-year developed flow for Basin 108C is 2.43 cfs and 12.12 cfs for the 100-year developed flow. Basin 108G has a 2-year developed flow of 1.59 cfs and 6.92 cfs for the 100-year developed flow. Therefore, the combined flows from these two basins are approximately 4.70 cfs for the 2-year event and 19.04 cfs for the 100-year event per the calculations completed by JR Engineering. 41 - A Drainage Exhibit has been provided in the back pocket of this report depicting the different drainage basins associated with the proposed development. On this exhibit you will find a total of (8) eight on -site basins and (4) four off -site basins, which discharge directly onto Iowa and Custer Drive.. The four off -site basins directly correlate with Basin 108C of the Rigden Filing One Report by JR Engineering. The eight on -site basins correlate with Basin 108G of the Rigden Filing One Report. Drainage and Erosion Control Report Page 1 Rigden Farm 13'' Filing — Brooklyn Park Row Houses April 6, 2005 M TABLE OF CONTENTS PAGE 1. INTRODUCTION..................................................................................................................1 1.1 Project Description..........................................................................................................1 1.2 Existing Site Characteristics...........................................................................................1 1.3 Proposed Site Characteristics..........................................................................................1 1.4 Design Criteria................................................................................................................2 1.5 Master Drainage Basin....................................................................................................3 2. LOCAL DEVELOPED DRAINAGE DESIGN...................................................................3 2.1 Method............................................................................................................................3 2.2 Hydrologic Analysis .of the Proposed Drainage Conditions............................................3 3. EROSION CONTROL...........................................................................................................4 3.1 Erosion and Sediment Control Measures........................................................................4 3.2 Dust Abatement...............................................................................................................4 3.3 Tracking Mud on City Streets.........................................................................................5 3.4 Maintenance.........................................................................:..........................................5 3.5 Permanent Stabilization................................................................................:.................5 4. REFERENCES........................................................................................................................6 Appendix A: Vicinity Map Appendix B: Hydrologic Calculations Appendix C: Erosion Control Calculations Appendix D: Calculations by Others INTERWEST M CONSULTING GROUP April 6, 2005 Mr. Basil Hamdan City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, CO 80521 RE: Drainage and Erosion Control Report — Rigden Farm 13`h Filing — Brooklyn Park Row Houses Dear Basil: We are pleased to submit to you for your review and approval this Drainage and Erosion Control Report for Rigden Farm 13`h Filing — Brooklyn Park Row Houses. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria and the approved Rigden Farm Filing One Drainage and Erosion Control Report by JR Engineering dated September 7, 1999. We greatly appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. �David Holloway Project Engineer -M