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Home My WebLink AboutSTETSON CREEK PUD, 3RD & 4TH FILINGS - PRELIMINARY - 16-89I - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPreliminary Drainage Report for Stetson Creek Third and Fourth Filing P.U.D. City of Fort Collins, Colorado January 22, 1996 Prepared For. Geneva Corporation 344 East Foothills Parkway, Suite 12 Fort Collins, Colorado 80525 Prepared By: Northern Engineering Services, Inc. 420 South Howes, Suite 202 Fort Collins, Colorado 80521 (970)221-4158 Fax (970)221-4159 Project Number: 9601.00 Northern Engineering Services, Inc. January 22, 1996 City of Fort Collins Stormwater Utility 235 Mathews Fort Collins, Colorado 80522 RE: Stetson Creek Third and Fourth Filing P.U.D. Fort Collins, Colorado Project Number: 9601.00 Dear Staff: Northern Engineering is pleased to submit this Preliminary Drainage Report for Stetson Creek Third and Fourth Filing P.U.D. for your review. This report was prepared in compliance with technical criteria set forth in the City of Fort Collins Storm Draina a Desi n 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 Mary B. Woh ACES, INC. 420 S. Howes, Suitc 202 • Fort Collins, Colorado 80521 • (970) 221-4158 • Fax (970) 221-4159 J `;ED�C\�RAN1N.e�efR ;GGR-EkRT_DW v Preliminary Drainage Report for Stetson Creek Third and Fourth Filing P.U.D. I. INTRODUCTION 1.1 Ob*ective To provide a preliminary drainage scheme for the proposed Stetson Creek Third and Fourth Filing planned unit developments based on master drainageway planning and overall/ preliminary drainage concepts developed by others. Specific objectives as part of this study are: 1. To adopt the drainage concepts contained in the Overall/Preliminary Drainage and Erosion Control Study for Stetson Creek P.U.D., (Reference 1), 2. To consider the drainage schemes of all adjacent developments (References' 2 & 3), 3. To acknowledge SWMM modeling conducted by RBD, Inc. for the Stetson Creek and Timber Creek developments, 4. To consider any possible adverse effects downstream of the development due to developed stormwater, 1.2 Mapping and Surveying A field survey of the site was conducted by Landstar Surveying, Inc. Loveland, Colorado in December, 1995. Based on this field survey information, topographic mapping was computer generated by Landstar Surveying with a contour interval of one (1) foot. 1.3 Site Reconnaissance A site visit was conducted on Wednesday January 10, 1996 by the project engineer. Based on the topographic mapping, existing drainage basins and land use were confirmed as well as existing structures. The location and dimensions of existing culverts and storm inlets were verified as well as their condition and flow direction. Stetson Creek Third and Fourth Filing P.U.D. Page 2 Preliminary Drainage Report II. SITE LOCATION AND DESCRIPTION 2.1 Site Location The project is located in the West Half of Section 5, Township 6 North, Range 68 West of the 6th Principal Meridian in Fort Collins, Colorado. The project is bounded by Timberline Road to the west and Harmony Road on the north. (See Vicinity Map). Adjacent developments include Timber Creek P.U.D. to the north and Stetson Creek P.U.D. First Filing to the west. 2.2 Site Description The Stetson Creek Third and Fourth Filing P.U.D.'s include a total of 38.711 acres and have historically been furrowed agricultural land. The site has been previously overlot graded as part of both Timber Creek P.U.D. and Stetson Creek First Filing P.U.D. construction and is currently covered with temporary vegetation. The McClellands Basin Drainageway is located south of the site and flows from west to east. 2.3 Irrigation Ditches and Reservoirs The Dixon Canyon irrigation lateral currently parallels the site (off -site) adjacent the east propertyline of the Third Filing, flowing from to north to south. This lateral will not require relocation or modification as part of the development of the Third and Fourth Filings. Detention Pond #373 , constructed as part of Timber Creek P.U.D., is located in the southeast corner of the site and detains stormwater from portions of Stetson Creek First Filing P.U.D., all of Timber Creek P.U.D. and the proposed Stetson Creek Third and Fourth Filings. This pond will not require modification as part of the development of the Third or Fourth Filings. III. HISTORIC DRAINAGE BASIN 3.1 Mai r Basin Description The site is located in the McClellands Drainage Basin and is included in the report entitled McClellands Basin Master Drainage Plan, by Greenhorne & O'Mara, Inc., June 20, 1986. SWMM modeling for this basin has been updated by RBD, Inc. Engineering Consultants as part of the Stetson Creek First Filing P.U.D. and incorporates both the Timber Creek and Stetson Creek developments. The Stetson Creek Third and Fourth Filings are included in the modeling as part of Subcatchment 314 (See Appendix). Modifications to the SWMM model will not be necessary in connection with this submittal. Stetson Creek Third and Fourth Filing P.U.D. Page 3 Preliminary Drainage Report 3.2 Historic Drainage Patterns The site has historically drained from northwest to southeast at a very gradual slope of approximately 1%. IV. DEVELOPED DRAINAGE BASIN 4.1 Developed Conditions The proposed development of the Third and Fourth Filings include: • new local and collector streets, • new water services and sanitary sewer, • and culvert crossings, 4.2 Design Criteria and References Drainage criteria outlined in both the City of Fort Collins Storm Drainage Design Criteria Manual (SDDCM) and Storm Drainage Criteria Manual by the Urban Drainage and Flood Control District have been referenced for this Final Drainage Study. 4.3 Hydrologic Criteria The Rational Method has been used to estimate peak stormwater runoff from the developed site. The initial 2-year and major 100-year design storms have been used in the evaluation of the proposed drainage system. Rainfall intensity data for the Rational Method has been taken from Figure 3-1 of SDDCM. Culvert 228 has been sized for a future 10-year storm, including off -site flows, with no overtopping of Rock Creek Drive and for a 100-year storm with less than 0.5' of water over the crown. Culvert 706 has been sized for the 100-yr storm with a maximum depth of 0.50' over the crown in Stetson Creek Drive. 4.4 Hydraulic Criteria The City of Fort Collins Storm Drainage Design Criteria has been referenced for all hydraulic calculations. In addition, the following computer programs have been utilized: • The computer program "HY8" by the U.S. Department of Transportation, Federal Highway Administration has been used to size all culvert crossing, • The computer program "UDINLET" has been used to analyze sidewalk culvert capacities, • The computer program "Flowmaster" has been used to analyze the capacity of proposed swales, aa Stetson Creek Third and Fourth Filing P.U.D. Page 4 Preliminary Drainage Report 4.5 Drainage Concept Developed stormwater from Stetson Creek Third and Fourth Filings will be conveyed overland to Detention Pond #373 via curb and gutter and grasslined swales. Pond #373 was designed and constructed as part of Timber Creek First Filing P.U.D. and was intended to detain stormwater runoff from the Stetson Creek Third and Fourth Filings. An existing swale (#167) was also constructed which leads from Timber Creek to Pond #373 and will not be altered as part of the Third Filing improvements. Off -site stormwater entering from the north (Timber Creek P.U.D.) and west (Stetson Creek First Filing P.U.D.) from adjacent developments is also conveyed to Pond #373 via existing streets, swales and storm sewer. The existing storm sewer line in Stetson Creek Drive from Stetson Creek First Filing will not be extended. Culvert 706 has been sized to include the 100-yr discharge of 34.17 cfs from the existing storm sewer. V. EROSION CONTROL 5.1 Erosion Control Plan Permanent riprap will be provided at the outlet of all sidewalk culverts and at the outlet of Culvert 706. Grass -lined swales shall be seeded immediately upon completion with the permanent seed mix specified on the Grading Plan. Temporary sediment control consisting of straw bale dikes will be used in swales until permanent vegetation is established. Gravel filters will be required at all curb inlets. VI. CONCLUSIONS 6.1 Compliance with Standards All drainage analyses have been performed according to the City of Fort Collins Storm Drainage Design Criteria Manual (SDDCM) and the Urban Drainage and Flood Control District's Drainage Criteria Manual. Stetson Creek Third and Fourth Filing P.U.D. Preliminary Drainage Report Page 5 REFERENCES 1. Overall/Preliminary Drainage and Erosion Control Study for Stetson Creek P.U.D., Fort Collins, Colorado, RBD, Inc. Engineering Consultants, December, 1993. 2. Final Drainage and Erosion Control Study for Stetson Creek P.U.D. First Filing, Fort Collins, Colorado, RBD, Inc. Engineering Consultants, August 29, 1994. 3. Final Drainage and Erosion Control Study for Timber Creek P.U.D. First Filing, Fort Collins, Colorado, RBD, Inc. Engineering Consultants, April 7, 1994. 4. McClellands Basin Master Drainage Plan, Greenhorne & O'Mara, Inc., June 20, 1986. 5. Storm Drainage Design Criteria and Construction Standards, City of Fort Collins, Colorado, May, 1984. 6. Drainage Criteria Maunal, Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, March, 1969.