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Home My WebLink AboutHORSETOOTH EAST BUSINESS PARK PUD, FILING TWO - PRELIMINARY - 43-94A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTVIC/1V/7TY MAP Ho S r, oo� st �a PLATTER/VER POWER In i�a AUTHORITY MMJ£TaorH R040 COL. L. I t4ogf CCCF COL)RS E _JUvUUD APPENDIX REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1991. 2. Storm Drainage Report of Horsetooth Business Park, First Filing, by Stewart & Associates, Inc., 5 April 1991. 3. Final Storm Drainage and Erosion Control Report for Horsetooth East Business Park Minor Subdivision, by Stewart & Associates, Inc., 22 August 1994. I I 5 I ME VI. STORM WATER QUALITY A. General Concept The water quality of storm water runoff must be addressed on all final design utility plans. The Horsetooth East Business Park development is anticipating construction beginning in 1995. Therefore, final design for this project will determine applicable Best Management Practices for the treatment of storm water runoff. EROSION CONTROL A. General Concept During final design for this site, appropriate measures will be designed to control erosion from the site. The first of these measures to limit erosion is to properly reseed all disturbed areas which will not be paved. All construction activities must comply with the State of Colorado permitting process for Stormwater Discharges Associated with Construction Activity. A Colorado Department of Health NPDES Permit will be required before any construction grading can begin. CONCLUSIONS A. 1.1 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. Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the transmission of developed on -site runoff to the proposed on -site detention ponds and existing downstream detention facilities. The combination of onsite street capacities in the curb and gutter and the onsite storm drain system will provide for the 10-year and the 100-year developed flows to reach the proposed detention ponds. If, at the time of construction for some unforeseen reason, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 4 IV. DRAINAGE FACILITY DESIGN A. General Concept The on -site runoff produced by the proposed Horsetooth East Business Park development will flow to one of three proposed on -site detention ponds or to sub - basin area inlets. The outflow from these area inlets and proposed detention ponds is then routed south and east via the existing storm drain system underneath Big Horn Drive. Additional storm drain laterals will be installed as necessary to connect proposed area inlets to the existing storm drain system. The proposed drainage, erosion control, and grading plans are included in the back pocket of this report. B. Specific Details The Horsetooth East Business Park development has been broken down into 15 sub -basins. Runoff from sub -basins 1 through 10 will be conveyed south towards the site detention ponds by surface flows, with a minimal amount of nuisance flows being intercepted by area inlets tied into the existing storm drain system. Runoff from sub -basins 11 through 13 will flow into detention ponds within these basins before being routed to the south by the existing storm drain system. The existing storni drainage system for the site will be used. When the storm drain system is surcharged, flows will back-up into the detention ponds. An equalizing pipe will be installed between the two southern ponds. To restrict outflow from the storm drain system, all flows will be routed through the detention pond in the southwest corner of the site. The outlet from this pond has been sized to restrict outflow to 1.6 cfs. Outflow from the site is eventually transported via the existing storm drain system to the downstream Collindale Regional Detention Pond. According to the Stewart & Associates 1991 Storm Drainage Report of Horsetooth Business Park First Filing, the 18-inch RCP entering the site from the west was to be plugged at the manhole in Automation Way. Thus no off -site flows are incurred on this site. Basins 14 and 15 have been previously designed by Stewart & Associates in their 1991 Storm Drainage Report of Horsetooth East Business Park First Filing. These basins will neither contribute flows to or accept flows from the internal site basins 1 through 13. The downstream culvert and storm improvements have the available capacity for the Horsetooth East Business Park development. 3 buildings and street improvements. These sub -basins are shown on the Preliminary Grading and Drainage Plan in the back pocket of this report. III. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Development Criteria Reference and Constraints In accordance with the 1991 Horsetooth Business Park Storm Drainage Report by Stewart & Associates, runoff from this site is limited to the 2-year undeveloped flow condition. According to Stewart & Associates, the 2-year runoff is 0.17 cfs/acre, for a total allowable runoff of 1.61 cfs from the site. Runoff is transported from the site via an existing 15-inch storm drain. Additional runoff is detained on -site and released at the 2-year undeveloped flow rate. The streets and associated drainage systems surrounding the site --including Timberline Road, Horsetooth Road, Automation Way, and Big Horn Drive --are existing. Storm drainage for these areas was previously designed by Stewart & Associates in their 1991 report. As currently proposed, this site will neither accept flows from or contribute flows to the surrounding street sub -basins. I C. Hydrological Criteria The Rational Method for determining surface runoff was used for the project site. The 10-year and 100-year storm event criteria, obtained by the City of Fort Collins, were used in calculating runoff values. These calculations and criteria are included in the Appendix of this report. I 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. Variances from Criteria No variances are being sought for the proposed project site. 2 I PRELIMINARY DRAINAGE STUDY FOR THE HORSETOOTH EAST BUSINESS PARK DEVELOPMENT, FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Horsetooth East Business Park development is bounded by Automation Way on the west, Horsetooth Road on the north, Timberline Road to the east, and Big Horn Drive on the south. The site location can also be described as situated in Section 31, Township 7 North, Range 68 West of the 6th P.M., City of Fort Collins, Larimer County, Colorado. The site location can be seen on page 2 of the Appendix. g B. Description of Property The Horsetooth East Business Park development contains approximately 12.5 acres, more or less. Of this, approximately 3.0 acres of the property have already been developed as the surrounding streets; the remaining property is generally undeveloped at the present. The property is being proposed for commercial development w&mthe City of Fort Collins Zoning District and will be developed consistent with other Horsetooth Business Park filings. Native and pasture grasses presently cover the property. The topography of the site generally slopes from northwest to southeast at approximately 1.5 percent. II. DRAINAGE BASINS A. Major Basin Description The proposed development lies within the Foothills Drainage Basin. Runoff from the project area is routed by gutters and culverts to an existing storm drain system which exits the site along the south property line. B. Sub -basin Description The Horsetooth East Business Park development has been divided into 13 internal sub -basins. These 13 basins will be developed consisting of proposed commercial I I TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION 1 A. Location 1 B. Description of Property 1 II. DRAINAGE BASINS 1 A. Major Basin Description 1 B. Sub -basin Description 1 III. DRAINAGE DESIGN CRITERIA 2 A. Regulations 2 B. Development Criteria Reference and Constraints 2 C. Hydrological Criteria 2 D. Hydraulic Criteria 2 E. Variances from Criteria 2 IV. DRAINAGE FACILITY DESIGN 3 A. General Concept 3 B. Specific Details 3 V. STORM WATER QUALITY 4 A. General Concept 4 VI. EROSION CONTROL 4 A. General Concept 4 VII. CONCLUSIONS 4 A. Compliance with Standards 4 B. Drainage Concept 4 REFERENCES 5 APPENDIX VICINITY MAP 2 HYDROLOGY 3 DETENTION 8 DESIGN OF INLETS, STORM DRAIN, AND SWALES 16 CHARTS, FIGURES AND TABLES 23 i INC. iEngineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 303Y482.5922 FAX: 303/482-6368 iNovember 21, 1994 Mr. Glen Schlueter City of Fort Collins Utility Services Stormwater 235 Mathews Street iFort Collins, Colorado 80522 RE: Preliminary Drainage Study for Horsetooth East Business Park Development II Dear Glen: i We are pleased to submit to you, for your review and approval, this Preliminary Drainage Study for the Horsetooth East Business Park development. All computations within this report have i 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, RBD Inc. Engineering Consultants Prepared by: Reviewed by: :�&' -�7 (no+ �cJa�lu6��J iDavid K. Thaemert, E.I.T. Kevin W. Gingery, P.E. Water Resources Engineer Water Resources Project Manager cc: I I 1 IDenver 3031458-5526 I i i PRELIMINARY DRAINAGE STUDY FOR THE HORSETOOTH EAST BUSINESS PARK DEVELOPMENT, FORT COLLINS, COLORADO November 21, 1994 Prepared for: W.W. Reynolds Companies 4875 Pearl East Circle, Suite 300 Boulder, CO 80301 Prepared by: RBD, Inc. Engineering Consultants 209 South Meldrum Fort Collins, Colorado 80521 (303) 482-5922 RBD Job No. 088-013 I "LIMINARY DRAINAGE STUDY :)R THE HORSETOOTH EAST 3INESS PARK DEVELOPMENT, SORT COLLINS, COLORADO