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HomeMy WebLinkAboutDrainage Reports - 01/29/2016NA This Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in Its entirety. When a hard copy is absolutely necessary, we recommend double -sided printing. November 11, 2015 City of Fort Collins Approved Plans Approved by: Date: I/"/�t(+7 FINAL DRAINAGE REPORT FOR Stead Fort Collins, Colorado Prepared for: Shane Roberts 255 South Taft Hill Road Fort Collins, Colorado 80521 Prepared by: NORTHERN ENGINEERING 301 North Howes Street, Suite 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 Fax: 970.221.4159 www. northemen®neering.com Project Number: 1130-001 NorthernEnaineerina.com // 970.221.4158 1 1 NORTHERN ENGINEERING November 11, 2015 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Final Drainage Report for STEAD Dear Staff: Northern Engineering is. pleased to submit this Final Drainage Report for your review. This report accompanies the Project Development Plan submittal for the proposed Stead project. This report has been prepared in accordance to Fort Collins Stormwater'Criteria Manual (FCSCM), and serves to document the stormwater impacts associated with the proposed project. We understand )hat review by the City is to assure general compliance with standardized criteria contained in they FCSCM. If you should have any questions as you review this report, please feel free to contact us. Sincerely, /1DO <<C NORTHERN ENGINEERING SERVICES, INC. Wit'igF'!-s •,c4 Danny Weber Nicholaw� LEED Project Engineer Project Ma AP 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 I 970.221.4158 I www.northernengineering.com ' ■V INGIRTHERN ENGINEERING Stead 1 1 J TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION...................................................................4 A. Location.............................................................................................................................................4 B. Description of Property.....................................................................................................................4 C. Floodplain..........................................................................................................................................6 II. DRAINAGE BASINS AND SUB-BASINS....................................................................... 7 A. Major Basin Description....................................................................................................................7 B. Sub -Basin Description.......................................................................................................................7 III. DRAINAGE DESIGN CRITERIA................................................................................... 8 A. Regulations........................................................................................................................................8 B. Four Step Process..............................................................................................................................8 C. Development Criteria Reference and Constraints............................................................................8 D. Hydrological Criteria.........................................................................................................................8 E. Hydraulic Criteria..............................................................................................................................8 F. Modifications of Criteria...................................................................................................................8 IV. DRAINAGE FACILITY DESIGN.................................................................................... 9 A. General Concept...............................................................................................................................9 B. Specific Details..................................................................................................................................9 V. CONCLUSIONS........................................................................................................9 A. Compliance with Standards..............................................................................................................9 B. Drainage Concept............................................................................................................................10 REFERENCES.................................................................................................................. 10 APPENDICES: ' APPENDIX A - Hydrologic Computations APPENDIX B - Hydraulic Computations 1 1 LIST OF FIGURES: Figure 1 — Aerial Photograph................................................................................................ 5 Figure 2 — Proposed Site Plan............................................................................................... 6 Figure 3 — Existing Floodplains............................................................................................. 7 MAP POCKET: H1 - Historic Drainage Exhibit DR1 - Developed Drainage Exhibit 1 Final Drainage Report ■V INORTHERN ENGINEERING 1. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map 2. The project site is located in Section 9, Township 7 North, Range 69 West of the 6" Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. 3. The project site is located north of the intersection of South Taft Hill Road and West Mulberry Street, and is a flag lot extending to South Taft Hill Road. 4. The project site lies within the Canal Importation Drainage Basin. 5. This is an infill, flag -shaped lot, surrounded entirely by existing development. 6. The project site received no offsite flows from the surrounding areas. B. Description of Property 1. The development area is roughly 0.68 net acres. Final Drainage Report 1 'NORTHERN ENGINEERING Stead i 1 1 1 1 1 1 1 Figure 1 — Aerial Photograph 1 2. The subject property is currently undeveloped, with the majority of the site covered with native grasses while the leg portion of the flag lot is mostly covered with gravel. 1 Existing ground slopes are mild to moderate (i.e., ±1 - 4%) through the interior of the property. General topography slopes from northwest to southeast. 1 3. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey website: http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx, 1 the site consists of Nunn Clay Loam, which falls into Hydrologic Soil Group C. 4. The proposed project site plan is composed of the development of a single-family 1 residential unit, garage, and barn. 1 1 1 ' Final Drainage Report NORTHERN ENGINEERING Stead Figure 2— Proposed Site Plan NORTH 5. There is a private irrigation ditch in the northwest corner of the site that will not be disturbed by this development. 6. The proposed land use is a single-family residential unit in the Low Density Mixed -Use Neighborhood District (L-M-N). C. Flood plain 7. The project site is not encroached by either a Fort Collins Flood Plain Map of a FEMA Flood Plain Map (Map #08069C0978G). Final Drainage Report NORTHERN I ENGINEERING Stead i -- I Project Site J Figure 3 —Area Floodplain Mapping J e NORTH II. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description 1. The project site lies within the Canal Importation Drainage Basin. Current City of Fort Collins Stormwater Regulations do not require on -site detention or water quality measures for single-family developments and are not proposed. B. Sub -Basin Description 1. The subject property historically drains overland from northwest to southeast. Runoff from the majority of the site has historically collected at a point near the southeast corner of the site where it drains onto the adjacent property, then into the South Taft Hill Road Right -Of -Way, and ultimately onto West Mulberry Street. 2. A summary of the historic runoff rates for each basin is tabularized on the Historic Drainage Exhibit in the Map Pocket at the end of this report. Final Drainage Report NORTHERN ENGINEERING Stead ' III. DRAINAGE DESIGN CRITERIA A. Regulations There are no optional provisions outside of the FCSCM proposed with the proposed ' project. B. Four Step Process ' The Four Step Process will not be employed as no water quality measures are required for single-family developments. The permanent site will be either landscaped, roofed, or hardscaped and, therefore, provides as the water quality measures. No portion of the ' developed site shall be non -vegetated. C. Development Criteria Reference and Constraints ' The subject property is surrounded by currently developed properties. Thus, several constraints have been identified during the course of this analysis that will impact the proposed drainage system including: ' m Existing elevations along the property lines will generally be maintained. m As previously mentioned, overall drainage patterns of the existing site will be maintained. Elevations of existing downstream facilities that the subject property will release to will be maintained. ' D. Hydrological Criteria 1. The City of Fort Collins Rainfall Intensity -Duration -Frequency Curves, as depicted in ' Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations associated with the proposed development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. 2. The Rational Method has been employed to compute stormwater runoff utilizing ' coefficients contained in Tables RA-7 and RA-8 of the FCSCM. Please see Appendix A. 3. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. ' E. Hydraulic Criteria 1. As previously noted, the subject property maintains historic drainage patterns. 2. All drainage facilities proposed with the project are designed in accordance with ' criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual. Please see Appendix B. 3. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. ' F. Modifications of Criteria 1. The proposed development is not requesting any modifications to criteria at this time. Final Drainage Report ' ■V (NORTHERN ENGINEERING Stead tIV. DRAINAGE FACILITY DESIGN ' A. General Concept 1. The main objectives of the project drainage design are to maintain existing drainage ' patterns, and to ensure no adverse impacts to any adjacent properties. 2. Drainage patterns anticipated for drainage basins shown in the Drainage Exhibit are described below. ' Basin W ' Basins W is largely unmodified with the exception of a proposed barn in the western half of the site. This basin will follow similar historic patterns sheet draining to the southeast corner of the site. Due to minor re -grading around the proposed single- family structure, Basin W has a smaller watershed area than Historic Basin W. This results in a release rate from proposed Basin W less than Historic Basin W, so no downstream impacts are expected. ' Basin E Basin E has enlarged as compared to Historic Basin E to encompass the proposed garage and single-family structure. This basin is graded such that runoff will collect in a concrete pan surrounding the development and route flows east down the drive -way to the Taft Hill Rd Right -of -Way through a sidewalk chase. Although the release rate has increased in comparison to the Historic Basin E, no on -site detention or water ' quality measures are required per the City of Fort Collins Stormwater Regulations. The increased runoff from this basin are considered negligible and no downstream impacts are expected. ' B. Specific Details t J 1. Summaries of the runoff rates for both the Historic basins and Developed basins are included on the Drainage Exhibits in the Map Pocket at the end of this report. 2. Proper maintenance of the drainage facilities designed with the proposed development is a critical component of their ongoing performance and effectiveness. V. CONCLUSIONS A. Compliance with Standards 1. The drainage design proposed with the proposed project complies with the City of Fort Collins' Stormwater Criteria Manual. 2. The drainage design proposed with this project complies with requirements for the Canal Importation Drainage Basin. 3. The drainage plan and stormwater management measures proposed with the proposed development are compliant with all applicable State and Federal regulations governing stormwater discharge. Final Drainage Report NORTHERN ENGINEERING Stead B. Drainage Concept 1. The drainage design proposed with this project will effectively limit any potential damage associated with its stormwater runoff. 2. The drainage concept for the proposed development is consistent with requirements for the Canal Importation Drainage Basin. REFERENCES 1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 2. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 4. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, Revised April 2008 Final Drainage Report ' APPENDIX A HYDROLOGIC COMPUTATIONS j F �.'^ia,JS. .l " . _ • • {e ss. c't .FL A. 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Section A -A ' User -defined Highlighted 'Invert Elev (ft) = 5075.76 Slope (%) = 0.50 Depth (ft) Q (cfs) N-Value = 0.024 Area (sqft) 'Velocity Calculations (ft/s) Wetted Perim (ft) Compute by: Known Q Crit Depth, Yc (ft) ' Known Q (cfs) = 2.03 Top Width (ft) EGL (ft) (Sta, El, n)-(Sta, El, n)... ' ( 0,00, 5076.05)-(9.50, 5175,10, 0.025)-(10.00, 5075,76, 0.013)-(10.50, 1071,80, 0.013)-(15.00, 5076,01, 0,025) ' Elev (ft) Section W--- -- Wednesday, Nov 11 2015 = 0.28 = 2.030 = 1.87 = 1.09 = 14.44 = 0.23 = 14.43 = 0.30 �U / /.UU 1 1076.50 1 1076.00 1075.50 1075.00 -2 0 2 4 6 8 10 12 14 16 18 1 Sta (ft) Depth (ft) I 1.24 0.74 Kl]PZ.! -0.26 -0.76 Channel Report ' Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Section B-B Swale ' User -defined Highlighted 'Invert Elev (ft) Slope (%) = 5074.86 = 0.50 Depth (ft) Q (cfs) N-Value = 0.024 Area (sqft) 'Velocity Calculations (ft/s) Wetted Perim (ft) Compute by: Known Q Crit Depth, Yc (ft) ' Known Q (cfs) = 2.03 Top Width (ft) EGL (ft) (Sta, El, n)-(Sta, El, n)... ' ( 0,00, 5075.34)-(17.50, 5074,90, 0.025)-(18,00, 5074.86, 0.013)-(18,50, 5074,90, 0.013)-(20,00, 5075,17, 0,025) ' Elev (ft) Section Wednesday, Nov 11 2015 = 0.30 = 2.030 = 1.81 = 1.12 = 12.81 = 0.24 = 12.78 = 0.32 �U/b.UU 1075.50 1075.00 1074.50 1074.00 -2 0 2 4 6 8 10 12 14 16 18 20 22 1 Sta (ft) Depth (ft) 1.14 0.64 0.14 -0.36 o] . Channel Report ' Hydraflow Express Extension for Autodesk® AutoCAD® Civil 313® by Autodesk, Inc. Sidewalk Chase ' Rectangular 'Bottom Width (ft) Total Depth (ft) = 1.00 = 0.50 'Invert Elev (ft) Slope (%) = 5074.00 = 2.00 N-Value = 0.013 ' Calculations Compute by: ' Known Q (cfs) ' Elev (ft) ff075.00 0 .25 Known Q = 2.03 Section Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s) Wetted Perim (ft) Crit Depth, Yc (ft) Top Width (ft) EGL (ft) 5 .75 1 Reach (ft) 1.25 Wednesday, Nov 11 2015 = 0.36 = 2.030 = 0.36 = 5.64 = 1.72 = 0.50 = 1.00 = 0.85 1.5 Depth (ft) I 1.00 0.75 0.50 0.25 MM -0.25 MAP POCKET H1 - HISTORIC DRAINAGE EXHIBIT DR1 - DEVELOPED DRAINAGE EXHIBIT NorthernEnaineerino.com 11 970.221.4158 I I I I F]9ING Raxl WMM TI zTT[ IGYTTc NWT oE51a11 eAvx MFA a aG ciao E�1 TR =13 b ® NORTH a w w FD PRx M III ) TUN. wx LEGEND PROI S,aY SiMER PRavosm Ix�T ■ EPaPOSEO N FMISTHG CONTOUR PRSO4o PROPOSED NHB A GOTTEN ' PRCI BOUNDARY DESG1 POINT Q ROW ARROW 'wW ORAINM£ BI LQU- NG WY Tye U9 DPNXACE BASH BCVNOAPY IIIIIIIIP FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION DaFKAOON CENTEM OF AR.AD • Ian.Hw.rnbelay. 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