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HomeMy WebLinkAboutSPRING CREEK FARMS NORTH, FIRST FILING, FINAL PLAT - PDP - 24-00B - REPORTS - DRAINAGE REPORTw �kl �� �� - ;.�, APPENDIX 1 VICINITY MAP 15 APPENDICES 14 B. Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the conveyance of developed on -site runoff to the proposed drainage facilities of the subject site. The combination of the proposed curb and gutter, cross -pans, inlets, and storm pipes will provide for the 2-year and the 100-year developed flows to reach the proposed detention pond at the southeast corner of the site. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. C. Storm water Quality Concept The proposed design has addressed the water quality aspect of storm water runoff. The extended detention basin will provide an opportunity for storm water pollutants to filter out of the storm water runoff before the runoff enters the Foothills Drainage Basin. D. Erosion Control Concept The proposed erosion control concepts adequately provide for the control of wind and rainfall erosion from the Spring Creek Farms development. Through the construction of the proposed erosion control concepts, the City of Fort Collins performance standard shall be met. The proposed erosion control concepts presented in this report and shown on the erosion control plan are in compliance with the City ofFort Collins Erosion Control Criteria. VIII. REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, interim revision January 1997. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. 13 If the disturbed areas will not be built on within one growing season, a permanent seed shall be applied. After seeding, a hay or straw mulch shall be applied over the seed at a minimum rate of 1.5 tons/acre, and the mulch shall be adequately anchored, tacked or crimped into the soil. In the event a portion of the roadway pavement surface and utilities will not be constructed for an extended period of time after overlot grading, a temporary vegetation seed and mulch shall also be applied to the roadway areas as discussed above. All construction activities must also comply with the State of Colorado permitting process for Storm water Discharges Associated with Construction Activity. A Colorado Department of Health NPDES permit will be obtained so that construction grading can continue within this development. C. Performance Standards Spring Creek Farms meets the erosion control performance standards as follows: Per the rainfall performance standard evaluation the PS during construction should be 75.6 and after construction should be 88.9. During Construction the PS is 95.3 and after construction is 97.2, both are well in compliance. The escrow amount required for erosion control is $5,423 based on reseeding the disturbed area. Please note that of the 57.1 acre site, only 5 acres will be disturbed with this project. VII. CONCLUSIONS A. Compliance with Standards 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. 12 B. Specific Details Ponds 5 and 8 will provide a water quality capture volume as follows: Pond WQCV (ac-ft) Water surface elevation 5 .067 4939.70 8 .033 4940.84 Please refer to Appendices calculations. VI. EROSION CONTROL A. General Concept This development lies within the Moderate Rainfall Erodibility Zone and the Moderate Wind Erodibility Zone per the City of Fort Collins zone maps. There should be minimal to no erosion problems after completion of the Spring Creek Farms development. Silt fence will be installed along the north, east and south sides of the site to prevent sediment from leaving the site. Tracking pads will also be placed at entrances/exits to the site. The Erosion Control Plan may be found in Appendix 8. B. Specific Details A silt fence shown on the erosion control exhibit will be installed prior to grading. All disturbed areas not in a roadway or greenbelt area shall have temporary vegetation seed applied within 30 days of initial disturbance. After seeding, a hay or straw mulch shall be applied over the seed at a rate of 1.5 tons/acre minimum, and the mulch shall be adequately anchored, tacked, or crimped into the soil. Those roads that are to be paved as part of the Spring Creek Farms project must have a 1-inch layer of gravel mulch applied at a rate of at least 135 tons/acre immediately after overlot grading is completed. The pavement structure shall be applied within 30 days after the utilities have been installed. 11 The storm drainage fro sub -basin 12 is to account for the future development of the city of Fort Collins police station with sub -basin 5. The storm drainage flows to detention pond 5 DETENTION POND 5 Detention Pond 5 is located at the northwest corner of Katandin Drive and Timberline Road. The discharge rate is 3.7 cfs and has been coordinated with Interwest Engineering, who is the engineer of record for the Timberline Road Improvements. Also, the Timberline Road improvements are constructing a storm sewer from Pond 5 to the North Tributary Storm Sewer at Timberline Road and Drake Road. It is our understanding that the storm sewer will be constructed prior to road construction of this project. DETENTION POND 8 Detention Pond 8 is located at the northwest corner of Nancy Gray Avenue and Timberline Road. The discharge is 1.1 cfs which is the 2 year historic rate. This may be modified when further design is done for that area. It is understood that the 100 year historic rate is being designed for. This outlet structure may me modified at a later date when the design is finalized. It is our understanding that the storm sewer will be constructed prior to road construction of this project. C. Storm Drain Design The storm drains for Spring Creek Farms were designed using UDSewer. V. STORMWATER QUALITY A. General Concept In general detention ponds 5 and 8 will provide for the water quality capture volumes. 10 development. The Storm drainage flows to a 5 foot Type R inlet and then to detention pond 5. SUB -BASIN 5 Sub -basin 5 is the undeveloped area in the center of Katandin Drive, Sagebrush Drive, Nancy Gray Avenue and Timberline Road. The storm drainage flows to detention pond 5. SUB -BASIN 6 and 7 Sub -basin 6 is the south half of Nancy Gray Avenue with a twenty -foot allowance for the adjacent property. The Storm drainage flows to a 5 foot Type R inlet and then to detention pond 8. SUB -BASIN 8 Sub -basin 8 is north ofNancy Gray Avenue and grades from southwest to northeast. In the future all of sub -basin 8 will drain to detention pond 8. Detention pond 8 outlets to a storm drain pipe that is being constructed with the Sidehill Second Filing. SUB -BASIN 9 The storm drainage from sub -basin 9 comes from Timberline road and flows to the north Type R inlet in Katandin Drive and then to detention pond 5. SUB -BASINS 10 The storm drainage from sub -basins 10 flows from Timberline Road to the 5 'Type Inlet in Nancy Gray Avenue, then to detention Pond 8. SUB -BASINS 11 The storm drainage from sub -basing 11 flows north to a low point off -site. It is our understanding that this will be discharged directly into the stormsewer provided by the Timberline Road Project. SUB -BASINS 12 6 conjunction with Interwest (the Timberline Road widening engineer of record) are providing an outlet that is designed for the 100 year historic runoff from the site. In the south the a pipe is being provided that will carry the flows from the northwest corner of Katandin Drive and Timberline Road to the North Tributary Storm Sewer at Drake Rd. and Timberline Rd. Here it will be release into the 42" existing storm drainage system under Drake Road at a maximum rate of 20 cfs. The majority of the developed runoff drains to detention ponds 5 and 8 via storm pipes. The rest of the developed runoff drains to detention pond 2, which is a small temporary detention pond for the runoff from Sagebrush Drive. B. Specific Details The Spring Creek Farms site has been broken down into twelve sub -basins. The attributed runoff from twelve of the basins is routed to the two on -site detention ponds located in the Spring CreekTarms development. SUB -BASIN 1 Sub -basin 1 will remain undeveloped for this site. The storm flow will is from northwest to southeast and drains to an existing storm drain inlet at the northwest corner of East Drake Road and Timberline Road SUB -BASIN 2 Sub -basin 2 is largely undeveloped except for the west half of Sagebrush Drive. The storm drainage flows north to south and discharges to detention pond 2. All of Sub - basin 2 will be allowed to infiltrate in the interim condition. The flows will pass through the existing 9' Utility Easement. Flows for Sub -basin 2 can be found on the Drainage Exhibit provided at the end of this report. SUB -BASIN 3 Sub -basin 3 is largely the south half of Katandin Drive with a twenty -foot allowance for the front yards of the adjacent development. The Storm drainage flows to a 5 foot Type R inlet and then to detention pond 5. SUB -BASIN 4 Sub -basin 4 is mostly the east half of Sagebrush Drive and the north half of Katandin Drive with a twenty -foot allowance for runoff from the front yards of the adjacent 069 C. Hydrologic Criteria The Rational Method was used in determining surface runoff for the project site. The 2-year and 100-year storm event intensities were used in calculating runoff values. The City of Fort Collins intensity duration frequency curves were used to obtain rainfall data for each storm specified. The FAA method was used for sizing detention ponds. MODS WMM was not used to calculate the Pond Volume because of the limited development at this time. The Rational Method used to calculate historic and developed storm water runoff *for all basins. The water quality volumes for both ponds computed using the Water Quality Capture Volume equation from the Urban Storm Drainage Criteria Manual, Volume 3. These calculations and criteria are included in Appendix 4. D. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are also included in the Appendix. E. Variance No variances are being requested for the Spring Creek Farms Project. IV. DRAINAGE FACILITY DESIGN A. General Concept The site is being developed in phases with different portions being developed at different times. The detention for each development will be sized and provided at the time of each development as it occurs. The infrastructure that is being designed at this time is in anticipation of the Fort Collins Police Facility. When the Police Facility is designed it will enlarge the affected detention pond to accommodate its improvements. In the future the different developers will also modify and add to the detention ponds. The detention pond north of Nancy Gray Avenue will be modified when that area is developed. The temporary detention pond that is at the south end of Sagebrush Drive will be relocated when future development will occur. The storm drainage outfalls for the site are located at the north and south end of the site. In the north, JR Engineering(the Sidehill Engineer of Record) in PROJECT DEVELOPMENT PLAN DRAINAGE AND EROSION CONTROL STUDY SPRING CREEK FARMS. FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location Spring Creek Farms is bounded to the east by Timberline Road, to the south by Drake Road, to the west by Union Pacific Railroad and to the south by residential development. The site location can also be described as situated in the southeast quadrant of Section 19, Township 7 North, Range 68 West of the 6ch P.M., of the City of Fort Collins, Larimer County, Colorado, and comprises approximately 55 acres (see vicinity map in Appendix 1). B. Description of Property The property consists of approximately 55 acres of undeveloped agricultural land. The property is zoned as Low and Medium Density Multi -Use Neighborhood Districts (LMN and MMN). Light commercial development will be located along the north side of the property. At this time only a portion of the roads for future development are being constructed for the police station site. The southern portion of the site, approximately 48 acres, generally slopes to the southeast (towards the intersection of Drake Road and Timberline Road) at J approximately 0.4 to 1.0 percent. The northern portion of the site, approximately 7 acres, generally slopes to the northeast at approximately 0.4 to 1.0 percent. II. DRAINAGE BASINS A. Major Basin Description The Spring Creek Farms development lies within the Foothills Basin (See Appendix 1 for location). The Spring Creek Farms site generally flows southeast and drains into the North Tributary Storm Drain, which conveys flows to the Fossil Creek Reservoir Inlet Ditch, which drains directly to Fossil Creek Reservoir. The reservoir ultimately drains into the Cache la Poudre River. Currently, an irrigation ditch runs through the northern portion of the site. This ditch is currently being used by the farmland on the immediate east side of Timberline and by the Cargill Corporation. It is a supply ditch that is supplied by the Aurthur Ditch WRJ APPENDICES VICINITY MAP 1 RATIONAL METHOD HYDROLOGY 2 STREET CAPACITY CALCULATIONS 3 POND RATING CURVES, WQCV 4 AND OUTLET/SPILLWAY STRUCTURES STORM DRAIN SIZING / UDSEWER AND RIPRAP SIZING 5 STORM INLET SIZING / UDInlet EROSION CONTROL CALCULATIONS 31 7 iv TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 5 A. Location 5 B. Description of Property 5 II. DRAINAGE BASINS 5 A. Major Basin Description 5 B. Sub -basin Description 6 III. DRAINAGE DESIGN CRITERIA 6 A. Regulations 6 B. Development Criteria Reference and Constraints 6 C. Hydrologic Criteria 7 D. Hydraulic Criteria 7 E. Variances from Criteria 7 IV. DRAINAGE FACILITY DESIGN 7 A. General Concept 7 B. Specific Details 8 C. Storm Drain Design 10 V. STORMWATER QUALITY 10 A. General Concept 10 B. Specific Details 11 VI. EROSION CONTROL 11 A. General Concept 11 B. Specific Details 12 VII. CONCLUSIONS 12 A. Compliance with Standards 12 B. Drainage Concept 12 C. Storm water Quality Concept 13 D. Erosion Control Concept 13 VIII. REFERENCES 13 iii Stantec Consulting Inc 209 South Meldrum Street Fort Collins CO 80521-2603 Tel: (970) 482-5922 Fax: (970) 482-6368 stantec.com ON Stantm August 3, 2005 Mr. Basil Hamdan City of Fort Collins Water Utilities --Storm water 700 Wood Street Fort Collins, Colorado 80521 RE: Drainage and Erosion Control Study for Spring Creek Farms Dear Basil: We are pleased to submit to you, for your review and approval, this Drainage and Erosion Control Study for Spring Creek Farms. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, Stantec Consulting Ltd. Prepared by: Reviewed by: Jim Allen -Morley, P.E. Design Engineer cc: File 187010140 Drainage and Erosion Control Study for: Spring Creek Farms Stantec Fort Collins, CO August 3, 2005 Stantec Consulting, Inc. 209 S. Meldrum Ft. Collins, CO 80521 Phone: 970-482-5922 Fax: 970-482-6368 Company but is not owned by the Ditch Company. Based on the approval of the farmer and Cargill, the irrigation ditch will be rerouted via a 21" pipe through the site. The irrigation flows will be routed along the north side of Nancy Gray Avenue and released into a manhole on the west side of Timberline Road that is being constructed by the Timberline Road widening project. Stantec has coordinated with JR Engineering and discussed the invert out of the proposed storm drain from the Spring Creek Farms site. An irrigation easement will be provided for the 21 inch diameter pipe which will take the pipe from where the ditch enters the western side of the site and ties in point on the east side of Timberline Road. Currently a second irrigation drain is located near the center of the site. This drain runs underneath the existing railroad and then turns south. This irrigation ditch has been abandoned and no flows from the west enter the Spring Creek Farms site. B. Sub -basin Description The area encompassed by the proposed Spring Creek Farms development has been divided into 12 sub -basins. These sub -basins are shown on the Drainage Exhibit in the back pocket of this report. Runoff for the proposed site is routed to three on -site detention ponds (see Drainage in the back of the report). One pond is permanent to the future police station and one will be replaced or enlarged at a later date one the properties are developed. III. DRAINAGE DESIGN CRITERIA A. Regulations The Urban Storm Drainage Manual (published by the Urban Drainage and Flood control District — Denver, Colorado) and. the City of Fort Collins Storm Drainage Design Criteria have been used to calculate the storm water runoff and design the storm water facilities for the subject site. B. Development Criteria Reference and Constraints The criteria and constraints from the City of Fort Collins will be met. 0