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Home My WebLink AboutPROSPECT INDUSTRIAL PARK, LOT 19 - PDP - 28-98E - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTF C /) D E. ROSP C RD. -n SITE ok O o w Off J W co a E. DRAKE RD. VICINITY MAP SCALE: 1 " = 1000' APPENDIX A VICINITY MAP A 1 7. REFERENCES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March, ' 1986. ' 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September 1999. 0 fence and by using the detention and water quality pond and a sediment trap during construction. The erosion control escrow amount is $. 1 5.2 Specific Details To limit the amount of silt leaving the site several erosion control measures shall be implemented during construction. Wattles will be used where appropriate, and the boundaries of the property shall have silt fence installed. A vehicle tracking pads shall be installed at the proposed drive connection to Midpoint Drive to control the mud being ' tracked onto the existing pavement. During overlot grading, disturbed areas are to be kept in a roughened condition and watered to reduce wind erosion. The detention and water quality pond will, be used as a sediment trap during construction. 6. CONCLUSIONS 6.1 Compliance with Standards I All computations that have been completed within this report are in compliance with the City of Fort Collins Erosion Control Reference Manual for Construction Sites and the Storm Drainage Design Criteria Manual. 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for stormwater quantity and quality treatment of proposed impervious areas. Conveyance elements have been designed to pass required flows and to minimize future maintenance. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 5 spillway from the pond have been designed to convey the 100-year flows from this off site area. Basin 1 includes the majority of the roof which will drain to the swale on the west side of the Lot. The roof will sheet flow to the west and then the channel carries runoff to the south. Basin 1 and Basin OS both flow to the proposed 12" culvert pipe and into the detention and water quality pond. Basin 2 includes the majority of the site including all of the parking, the proposed detention pond, a portion of the building and the small area to the north that could be used for future expansion of the building or the parking. The basin sheet flows to the north and east to a perimeter trickle pan. The pan is in the bottom of a large but shallow water quality and detention pond. The area inundated by the pond includes most of the site. Basin 3 includes the front face of the detention pond and the portion of the driveway that drains directly to Midpoint Drive. This area does not reach the detention pond. The off site area that drains to the pond offsets this deficiency. 4.3 Drainage Summary Drainage facilities located outside of the right of way (including the detention and water quality pond, proposed storm drain system and the pond outlet) will be maintained by the owners of the property. 5. EROSION CONTROL 5.1 General Concept This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins Zone Maps. The potential exists for silt movement from the site and into the existing drainage areas on the west and north sides of the site. Potential also exists for tracking of mud onto existing streets which could then wash into existing storm systems. The required performance standard for the site is 75.6%. During construction and after final paving and building construction, this figure has been exceeded with the use of silt 4 City of Fort Collins Drainage Criteria and are included in Appendix C of this report. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The majority of the proposed development will be routed via sheet and gutter flow to the proposed detention and water quality pond around the perimeter of the site. The pond releases to a sidewalk culvert into Midpoint Drive. The pond has 0.9' of depth for water quality and an additional 0.9' of depth for detention. The pond has a pan at 0.4% at the bottom and will back up into the parking and yard areas (all of which are going to be concrete). The pond will accept the flows from Lot 20 (0.32 acres) and will free release the basin adjacent to Midpoint Drive (Basin 3). The pond was calculated using all of Lot 19 (including Basin 3). This was done in order to determine the ideal pond size for the lot (if all of the lot could drain to a pond).. Since the off site area draining into the pond is larger than what is lost, the pond meets and exceeds the City's requirement. For a given storm, downstream facilities will be less impacted with the proposed development and detention pond than with existing conditions. The only variance needed on this project is related to freeboard. The pond spillway elevation is 1.0' lower than the finished floor of the building and the spillway is only 0.4' deep. When the spillway is flowing, there will not be 12" of elevation between the water and the building. This is mostly due to the very flat nature of this site. The building is protected adequately from large storms as proposed. 4.2 Specific Flow Routing A summary of the drainage patterns within each basin is provided in the following paragraphs. Basin OS includes the portion of Lot 20 that drains into the site from the northwest. From a field visit and aerial photography, it appears that the southeast half of the building roof drains into the site as well as a portion of the land to the north of the building. Because of existing trees on Lot 20, it does not appear that it is possible to route this lot to Midpoint Drive rather than into Lot 19. The proposed culvert pipe, as well as the r �, 3 of this site. 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage Design Criteria Manual' specifications. Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual" (UDFCD), developed by the Denver Regional Council of Governments, has been used. 3.2 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City Stonnwater Department. Water quality facilities are required for the new construction proposed on the site. The Poudre River Basin requires that new development detain the 100-year event to the 2-year historic rate. 3.3 Hydrologic Criteria Runoff computations were prepared for the 2-year and 10-year minor and 100-year major storm frequency utilizing the rational method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub - basins. Standard Form 9 (SF-9) provides a summary of the design flows for all Sub - basins and Design Points associated with this site. Water quality volume was calculated using the method recommended in the "Urban Storm Drainage Criteria Manual'. Detention volume was determined using the "Rational" or "FAA" method. All pond calculations are in Appendix D of this report. 3.4 Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the 2 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location Holsinger Drywall is located in southeast Fort Collins. The project is located on Lot 19, Prospect Industrial Park Subdivision. It is located Section 20, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in Appendix A. The project is located on the north side of Midpoint Drive approximately'/2 mile east of Timberline Road and 1100 feet northwest of Midpoint Drive's intersection with Sharp Point Drive. The Liberty Common School Track and Field Facility is behind the property, the City of Fort Collins' indoor shooting range is adjacent to the northwest (Lot 20) and Lot 18 on the southwest side is vacant. 1.2 Description of Property The entire project consists of approximately 0.85 acres of land, all of which will undergo grading and other construction activity. The project will consist of an office -warehouse building, associated parking and drives, and area for fixture expansion. The land currently slopes to the southeast (to Lot 18 and Midpoint Drive) at approximately 1%. The land is vacant with dryland vegetation over approximately 70% of the site. There is off site flow from the west (Lot 20) that presently drains through the property. There are no mapped floodplains on the property. 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description The proposed development lies within the Poudre River Master Drainage Basin. 2.2 Sub -basin Description This site drains south to Midpoint Drive. Midpoint drains south to the intersection with Sharp Point Drive. At the intersection, there is a small storm sewer system which drains to the ponds adjacent to the river; any flows above the storm sewer's capacity top over the road to the ponds. The existing drainage paths will be maintained with the development 1 TABLE OF CONTENTS TABLE OF CONTENTS .............. "' 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location ............ :...................................................................................................... 1 1.2 Description of Property ............................................................................................1 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description..........................................................................................1 2.2 Sub -Basin Description.............................................................................................I 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations..............................................................................................................2 3.2 Development Criteria Reference and Constraints....................................................2 3.3 Hydrologic Criteria..................................................................................................3 3.4 Hydraulic Criteria....................................................................................................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept.......................................................................................................4 4.2 Specific Flow Routing.............................................................................................4 4.3 Drainage Summary ...................................................................................................5 5. EROSION CONTROL 5.1 General Concept......................................................................................................5 5.2 Specific Details........................................................................................................5 6. CONCLUSIONS 6.1 Compliance with Standards....................................................................................6 6.2 Drainage Concept.....................................................................................................6 7. REFERENCES....................................................................................................................7 APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic Calculations D Detention and Water Quality Pond Sizing E Erosion Control Calculations (with FCP submittal) F Figures and Tables iii INTERWEST W CONSULTING G R O U P December 19, 2006 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Drainage and Erosion Control Report for Holsinger Drywall Dear Basil, I am pleased to submit for your review and approval, this Drainage and Erosion Control Report for Holsinger Drywall. I certify that this report for the drainage design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Michael Oberlander, P.E., L.S.I. ii 1218 W: ASH, STE, C • WINDSOR, COLORADO 80550 r[ t. 970. 67 A. 3300 • Fix. 970. 67d. 3303 DRAINAGE AND EROSION CONTROL REPORT HOLSINGER DRYWALL (Lot 19, Prospect Industrial Park) Prepared for: Holsinger Drywall 1312 Blue Spruce Drive #6 Fort Collins, CO 80524 Prepared by: Interwest Consulting Group 1218 West Ash, Suite C Windsor, Colorado 80550 (970) 674-3300 December 19, 2006 Job Number 1053-038-00