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Home My WebLink AboutFOSSIL CREEK NURSERY PUD - PRELIMINARY - 40-95 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTs N VICINITY MAP 1 =2000 APPENDIX PAGE 2 VicinityMap............................................................. Excerpts from Fossil Creek Drainage Study ........... 4 BasinHydrology...................................................... 7 WaterQuality.......................................................... 14 Excerpts from Ridgewood Hills Drainage Study...... 20 Tables, Charts, Graphs ........................................... 26 REFERENCES 1. Storm Drainage Design Criteria and Construction Standards, City of Fort Collins, Colorado, May, 1984. 2. Fossil Creek Drainage Basin Master Drainageway Planning Study, Simons, Li & Associates, Inc., August, 1982. 3. Drainage Criteria Manual, Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, March, 1969. 4. Overall/Preliminary First Filing Drainage and Erosion Control Study for Ridgewood Hills P.U.D., RBD, Inc., May 2, 1994 5. Final Drainage and Erosion Control Study for Ridgewood Hills, P.U.D.. First Filing Fort Collins. Colorado, RBD, Inc. March 3, 1995 There is not a large increase in the amounts of impervious area, and those areas that are increased are being provided with a detention pond which will detain the difference between the 2 year historic and 100 year developed storm events. The majority of the site will remain landscaped and grow areas for Nursery stock. Runoff from this area is in a non contributing area to the Fossil Creek Major Drainage Basin, and is contained entirely in Robert Benson Lake. The effects of runoff from this site causes little if any increase in the overall water surface elevation of the Lake. Stormwater Quality Water quality will be an important issue to this owner. Water quality . mechanisms will be incorporated into both of the ponds which are shown in this preliminary plan. Urban Drainage Criteria Manual will be used for design of the Water quality systems for this site. Erosion Control Conceats Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites, at the time of Final Design, the erosion control performance standard will need to be calculated and appropriate measures taken to control rain and wind erosion from the site. I 1 I 1 1 u system. The Urban Drainage criteria manual will be utilized during final design to develop a water quality system. Offsite basins 1, 2, and 3 currently sheet flow towards the low area adjacent to College avenue. As development occurs in these areas, increases in runoff will need to be examined and controlled in relation to the proposed Nursery Site. The master plans shows that these areas now sheet flow to College Avenue. The topography for this areas would tend to show that the majority of these areas is being intercepted by the North Louden Irrigation Ditch, which runs from south to north along the westerly boundary of the Nursery site. Portions of the existing North Louden Irrigation Ditch will need to be piped in culverts to allow access over the Irrigation ditch. Northern Engineering has contacted the Ditch company about this. The ditch company has expressed a concern regarding maintenance of these pipes and culverts. The owner of the Nursery site understands these concerns and has expressed and interest in assuming responsibility of maintenance of those portions of the irrigation ditch located on this property. IV. EROSION CONTROL General Concept Fossil Creek Nursery P.U.D. lies within the Moderate Rainfall Erodibility Zone, and the Moderate Wind Erodibility Zone, per the City of Fort Collins zone maps. At the time of final design, Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites, the erosion control performance standard will need to be calculated, and appropriate measures designed to control rain and wind erosion during and after construction. All construction activities must also comply with the State of Colorado permitting process for Stormwater Discharges associated with construction activities. A Colorado Department of Health NPDES discharge permit will be required before any construction grading can begin. V. CONCLUSIONS Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. Drainage Conceat This development will cause little impacts on the existing drainage in this area. 1 III. DEVELOPED DRAINAGE Developed Conditions Proposed development of the Fossil Creek Nursery will consist of commercial sales buildings and greenhouses, and customer parking. The amount of impervious area will be small, compared to the size of the complex. The existing pond located on the site will be utilized as an irrigation water storage facility. There will also be a pond located directly south of the parking area which will serve as a detention pond as well as a water quality facility. The area around the existing wetlands will also be dredged and enhanced, and this new pond will also function to provide some detention, as well as adding additional water quality capture volume. The existing culvert will be utilized to continue to discharge runoff from the site. Ultimately, runoff will continue to flow to Robert Benson Lake. Although detention is not a requirement of the site, it will provided as the owner does not wish to increase the potential for downstream runoff. A portion of Ridgewood Hills lies within the 125 acres of contributary area that drain to Robert Benson Lake, according to a study entitled "Final Drainage and Erosion Control Study for Ridgewood Hills First Filing". by RBD, Inc. Developed runoff from Ridgewood Hills is conveyed via underground pipe easterly to College Avenue, then southerly across the easterly side of the Nursery site, and via open channel to the existing 24" culvert under College Avenue. Per City criteria, since this is not a named drainageway, the developer of Ridgewood Hills would have been required to obtain all downstream easements to Robert Benson Lake. Therefore, it is assumed that all offsite easements necessary for Drainage purposes have been obtained. Design Criteria and References Drainage criteria outlined in both the Cily of Fort Collins Storm Drainage Design Manual, and Storm Drainage Criteria Manual by the Urban Drainage and Flood Control District have been used for this Preliminary Drainage Study. The Fossil Creek Drainage Basin Master Drainageway Planning Stud[, by Simons, Li & Associates has also been used as a reference for this study. Hydrologic Criteria The Rational method was used to estimate peak runoff from the proposed site. The 100 year storm event was used to estimate the size of the proposed I Preliminary Drainage Report for Fossil Creek Nursery I. GENERAL LOCATION AND SITE DESCRIPTION The proposed Fossil Creek Nursery site is approximately 14.6 acres located in the southern part of Fort Collins, adjacent to and west of College Ave. and approximately 1/2 mile south of Trilby Road. The site is bordered on the north by Carolyn's Cuisine, on the west by the North Louden Irrigation Ditch, and the Del Webb O.D.P., and on the south by the Del Webb O.D.P. More particularly the site can be described as a part of Section 14, Township 6 North, Range 68 West of the 6th P.M., City of Fort Collins, Larimer County, Colorado. Presently, the site has an existing residence and a few small outbuildings and barns. These existing buildings will be incorporated into the new Nursery complex. The vast majority of the site is farmland and native grasses. A small pond is located in the northerly section of the site. There is a small wetlands area, approximately 0.3 acres located in the southeasterly section of the site adjacent to College Ave. and the existing 24" culvert draining the site. There are no major drainageways located on this site. Plans for the site include greenhouses, a sales office, caretakers residence, customer parking, landscape storage yards, and grow areas. II. HISTORIC DRAINAGE The site is located within the Fossil Creek Major Drainage Basin, as defined by the City of Fort Collins Stormwater Utility, and is included as a part of a study entitled "Fossil Creek Drainage Basin Master Drainagewavnin this y", by Simons & Li, dated August 1982. Portion of that study, applicable have been included in the appendix of this report. This site is part of approximately 125 acres that have been identified as a Non Contributing Area to Fossil Creek. Drainage from this 125 acres is conveyed under College Avenue via an existing 24" culvert to Robert Benson Lake. According to the Fossil Creek study, area within the Fossil Creek Master Drainage Basin are not required to provide on -site detention. 1 II August 21, 1995 I Mr. Glen Schleuter City of Fort Collins Stormwater Utility 235 Mathews Fort Collins, Colorado 80522 ' RE: Fossil Creek Nursery P.U.D. Fort Collins, Colorado Project Number: 9539.00 Dear Glen: Northern Engineering is pleased to submit this Preliminary Drainage Report for Fossil Creek Nursery P.U.D. for your review. It represents a study of existing and proposed stormwater characteristics of the project site. This report was prepared in compliance with technical criteria set forth in the, ' City of Fort Collins, Storm Drainage Design Criteria and Construction Standards manual. If you should have any questions or comments as you review this report, please feel free to contact me at your convenience. Sincerely, NORTHERN ENGINEERING SERVICES, INC. 01IIREGIST��iii •s0000 No N GG•FPF�Gi Roger A. Curtiss, P.E. = o� 2 �j 73 n 62 a //�ojFSSION ��/lllllllll111\ Preliminary Drainage Report for Fossil Creek Nursery P.U.D. City of Fort Collins, Colorado August 21, 1995 Prepared For: Jack Fetig Fossil Creek Nursery Fort Collins, CO Prepared By: Northern Engineering Services, Inc. 420 South Howes, Suite 202 Fort Collins, Colorado 80521 (970)221-4158 Fax (970)221-4159 Project Number: 9539.00