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Home My WebLink AboutREMINGTON ANNEX - PDP - PDP110017 - REPORTS - DRAINAGE REPORT (3)1501 Academy Ct. Ste. 204 Fort Collins, Colorado 80524 (970) 217-7420 Preliminary Drainage & Erosion Control Study Remington Annex FortCollins Fort Collins, , CO Prepared for: Maxiiimo Development Group LLC 706 S. College Ave #201 Fort Collins, CO 80524 December 19, 2012 Drainage & Erosion Control Report Remington Annex Fort Collins, CO i B11010-DrainageReport-Prelim2.doc TABLE OF CONTENTS PAGE I. GENERAL PROJECT LOCATION AND DESCRIPTION .......................................................... 1 A. Location ................................................................................................................ 1 B. Description of Property ....................................................................................... 1 II. DRAINAGE BASINS AND SUB-BASINS ............................................................................... 1 A. Major Basin Description ...................................................................................... 1 B. Sub-Basin Description .......................................................................................... 2 III. DRAINAGE DESIGN CRITERIA ........................................................................................... 2 A. Regulations .......................................................................................................... 2 B. Hydrological Criteria ............................................................................................ 2 C. Hydraulic Criteria ................................................................................................. 3 D. Variance Request ................................................................................................. 4 IV. DRAINAGE FACILITY DESIGN ............................................................................................ 3 A. General Concept .................................................................................................. 3 B. Specific Details ..................................................................................................... 5 V. CONCLUSIONS .................................................................................................................. 6 A. Compliance with Standards ................................................................................. 6 B. Drainage Concept ................................................................................................ 7 C. Water Quality ....................................................................................................... 7 VI. EROSION AND SEDIMENT CONTROL ............................................................................... 7 VII. REFERENCES .................................................................................................................. 8 APPENDICES APPENDIX A - Runoff Calculations APPENDIX B - Detention Pond Analysis APPENDIX C - Hydraulic Analyses APPENDIX D - References & Previous Studies Drainage & Erosion Control Report Remington Annex Fort Collins, CO 1 B11010-DrainageReport-Prelim2.doc I. General Location and Description A. Location The Remington Annex site is located in the Northwest Quarter of Section 13, Township 7 North, Range 69 West of the 6 th Principal Meridian to the City of Fort Collins, Larimer County, Colorado. The site is located immediately west of Remington Street, north of Plum Street, east of the alley between College Avenue and Remington Street, and south of Laurel Street. There are no known drainages within the project site. The alley behind the site is utilized as a drainage channel for portions of the runoff from both the project site and the adjacent lots. B. Description of Property The Remington Annex site (referred herein as “the site”, “this site) is approximately 0.46 acres in size that will be developed into multi-family housing complex. The following is a summary of the existing conditions: Ground Cover - The site currently contains three buildings and the utilities to serve the residences. The existing ground cover consists mostly of grass. Grades - In general, the majority of the site slopes southeasterly at an approximately 1% slope. Soil Type - According to the NRCS Web Soil Survey, the majority of the site consists of Fort Collins loam, 1 to 3 percent slope (Soil Type B). Utilities – Other than the service lines to each of the existing houses there are no known utilities on the site Detention Ponds and Storm Sewer – There are no detention ponds currently on the site. II. Drainage Basins and Sub-Basins A. Major Basin Description The site is in the Old Town Basin where any increase over the existing imperviousness is required to be detained and released at the 2-year historic rate and to provide water quality for the entire site. Drainage & Erosion Control Report Remington Annex Fort Collins, CO 2 B11010-DrainageReport-Prelim2.doc B. Sub-Basin Description Historically, the runoff from this site flows off the site un-detained into the curb and gutter along Remington Street or the alley between Remington Street and College Avenue. The proposed site will continue to direct the majority of flows towards Remington Street and a small portion of the site will continue to drain towards the alley. This preliminary drainage study includes the calculations from off-site basins OS1A and OS2A, which do not flow into the site. These flows were calculated to assist in determining the alley capacity. III. Drainage Design Criteria A. Regulations The design criteria for this study are directly from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual and the Urban Storm Drainage Criteria Manuals Volumes 2, and 3 (referred to herein as USDCM). B. Hydrological Criteria In accordance with the Fort Collins policy, a minor and major storm for the Fort Collins area is identified as the 2-year and 100-year storms, respectively. A major storm for the Fort Collins area has a recurrence interval of 100 years has a peak intensity of 9.95 in/hr. These storms have been used as a basis for planning and system design. The peak flow rates for design points have been calculated based on the Rational Method as described in the USDCM with storm duration set equal to the time of concentration for each sub-basin. This method was used to analyze the developed runoff from the 2-year (minor) and the 100-year (major) storm events. The Rational Method is widely accepted for drainage design involving small drainage areas (less than 160 acres) and short time of concentrations. The Rational Method is ideal for storm sewer sizing and small detention pond sizing (for tributary areas no larger than 90 to 160 acres). Runoff coefficients were assumed based on impervious area and soil type and are given in Appendices. C. Hydraulic Criteria The developed site will convey runoff to the detention ponds in a safe and effective manner via, swales, concrete pans, and pipes. Detention Areas Drainage & Erosion Control Report Remington Annex Fort Collins, CO 3 B11010-DrainageReport-Prelim2.doc The runoff produced by the site will be conveyed to the proposed detention areas within the development. The detention areas were sized utilizing the Rational Formula-Based Modified FAA Procedure (assuming the required pond volume is maximized at 120 minutes or less) and will have no freeboard. There are two parking lot detention areas (Detention A and Detention B) shown on the west side of the proposed buildings. Detention area A will release through an orifice plate in parking lot curb on the south side of the lot. Detention area B will release through an orifice plate in the parking lot curb on the north side of the lot. These small ponds do not have freeboard, but the spill elevation over the curb is 0.65’ and 0.60’ below the finished floor of the adjacent buildings. Refer to Appendix B for preliminary detention pond calculations. Alley Capacity The alley will be an inverted crown alley that will convey the runoff northerly and southerly. For a 0.5% longitudinal slope and a 2.5% cross slope this cross section has a capacity of approximately 5.5 cfs. Open Channels Most sidewalk chases and curb cuts will be designed for the minor storm with overtopping of the curbs/sidewalks in larger storm events. D. Variance Request This site follows City of Fort Collins guidelines and thus no variances are being requested at this time. IV. Drainage Facility Design A. General Concept The site will ultimately consist of ground covered by pavement, rooftop, and landscape. All referenced tables, charts, formulas, etc. are included in the Appendix. The area, time of concentration, and runoff of each proposed sub-basin is summarized in Appendix A. The project site was divided into several different developed sub-basins as explained further below: Basin A Basin A consists of rooftop, sidewalk, parking lot, and landscaped area on the southwestern portion of the site. Runoff is directed to the parking lot Drainage & Erosion Control Report Remington Annex Fort Collins, CO 4 B11010-DrainageReport-Prelim2.doc detention A, where it will release through an orifice plate on the south side of the parking lot. These flows will run along the south side of the property line and be conveyed to Remington Street through a sidewalk chase and concrete curb channel. Basin B Basin B consists of rooftop, sidewalk, parking lot, and landscaped area on the northwestern portion of the site. Runoff is directed to the parking lot detention B, where it will release through an orifice plate on the north side of the parking lot. These flows will run along the north side of the property line and be conveyed to Remington Street through a sidewalk chase and concrete curb channel. Basin C Basin C consists of rooftop, sidewalk, and landscaped area on the eastern portion of the site. Runoff is directed to the east, which is then conveyed to the curb and gutter in Remington Street via concrete curb channels or sheet flow over the sidewalk. Basin OS1 Basin OS1 consists of pavement and landscaped area on the southwestern portion of the site. Runoff is directed un-detained to the public alley to the west of the site and then flows south towards Plum Street. Basin OS2 Basin OS2 consists of pavement and landscaped area on the northwestern portion of the site. Runoff is directed un-detained to the public alley to the west of the site and then flows north towards Laurel Street. Basin OS1A Basin OS1A consists of mostly rooftop from the building directly to the west of this proposed building. Runoff is directed to the public alley and then flows south towards Plum Street. This offsite basin was included in order to calculate the depth of flow in the alley adjacent to the proposed underground parking garage. These flows combine with Basin OS1 and the sum of the two flows is shown at Design Point OS1. Basin OS2A Basin OS2A consists of mostly rooftop from several buildings directly to the northwest of this proposed building. Runoff is directed to the public alley and then flows north towards Laurel Street. This offsite basin was included in order to calculate the runoff from the 2-year storm event that will pass Drainage & Erosion Control Report Remington Annex Fort Collins, CO 5 B11010-DrainageReport-Prelim2.doc over the sidewalk along Laurel Street. These flows combine with Basin OS2 and the sum of the two flows is shown at Design Point OS2. Existing Basins The existing onsite basins were also calculated to quantify the existing flows that are coming from the site. They were simply broken into flows exiting the site to the northwest (Basin NW), to the southwest (Basin SW), and to the east (E). B. Specific Details The following is a basin summary table: Area Q2 Q100 (sf) (cfs) (cfs) Onsite Basins A 6337 81% 0.58 0.71 0.240 1.028 B 3337 89% 0.69 0.80 0.151 0.607 C 9319 57% 0.34 0.55 0.209 1.171 OS1 689 44% 0.26 0.51 0.012 0.080 OS2 215 2% 0.03 0.36 0.000 0.018 Onsite Total 19897 69% 0.44 0.61 0.612 2.904 Post Detention Q100 = 1.779 Existing Site Totals 19897 44% 0.25 0.50 0.248 1.712 C100 C2 Basin %I Design Point The following is a summary of the alley capacity calculations: Alley Capacity Calcs OS1A 13097 91% 0.73 0.83 0.505 1.999 OS1+OS1A OS1 13786 89% 0.69 0.80 0.504 2.027 OS2A 11731 92% 0.74 0.84 0.458 1.806 OS2+OS2A OS2 11946 90% 0.71 0.81 0.450 1.792 The following is a summary of the detention pond volumes: Pond Req'd Storage Volume (cfs) Total Volume Provided (cfs) Outfall Elevation Spill Elevation Adjacent Building FFE Freeboard Pond A 469 637 4990.90 4991.60 4992.25 0.65 Drainage & Erosion Control Report Remington Annex Fort Collins, CO 6 B11010-DrainageReport-Prelim2.doc The spillway for Ponds A & B will be over top back of curb. The spillway for Pond A will be 0.65’ below the finished floor elevation of the adjacent building. The spillway for Pond B will be 0.6’ below the finished floor elevation of the adjacent building. Water quality for the site is provided by the additional capacity in the parking lot detention and the disconnected impervious areas before it exits to Remington Street. There is also the potential to provide rain gardens on the east side of the building prior to the flows exiting to Remington Street. V. Conclusions A. Compliance with Standards Storm drainage calculations have typically followed the guidelines provided by the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual and/or the Urban Storm Drainage Criteria Manuals Volumes 2, and 3. B. Drainage Concept The drainage system has been designed to convey the runoff to the designated design points and the detention ponds in an effective manner as safe as possible. As proposed, the site has detention pond volumes (2,581 square-feet) in excess of that required (2,470 square-feet). The required volume includes water quality for the entire site and detention storage volume for the additional impervious area of 7,789 square-feet. The post detention 100-year storm runoff is calculated at 1.848 cfs, which is less than the calculated rate of 2.505 cfs for the existing site. C. Water Quality Water quality has been provided through an expanded detention area and disconnected impervious areas. Additional water quality could also be provided with rain gardens on the east side of the building. VI. Erosion and Sediment Control In addition to the permanent low-impact design Best Management Practices (BMP’s), the following temporary and permanent BMP’s will be installed and maintained to control on-site erosion and prevent sediment from traveling off-site during and/or after construction: Drainage & Erosion Control Report Remington Annex Fort Collins, CO 7 B11010-DrainageReport-Prelim2.doc • Silt Fence – a woven synthetic fabric that filters runoff. The silt fence is a temporary barrier that is placed at the base of a disturbed area. • Vehicle Tracking Control – a stabilized stone pad located at points of ingress and egress on a construction site. The stone pad is designed to reduce the amount of mud transported onto public roads by construction traffic. • Straw Wattles – wattles act as a sediment filter in swales around inlets and sidewalk chases. They are a temporary BMP and require proper installation and maintenance to ensure their performance. Additional erosion and sediment control measures will be included as part of the final study. VII. References 1. Geotechnical Investigation Collegio Two South Remington and East Laurel Streets, CTL Thompson, Inc., September 23, 2010. 2. Natural Resources Conservation Service Web Soil Survey at websoilsurvey.nrcs.usda.gov/app 3. Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, Wright Water Engineers, Inc., Denver, Colorado, June 2001. APPENDIX A Runoff Calculations Remington Annex Fort Collins, CO Runoff Summary Area Q2 Q100 (sf) (cfs) (cfs) Onsite Basins A 6337 81% 0.58 0.71 0.240 1.028 B 3337 89% 0.69 0.80 0.151 0.607 C 9319 57% 0.34 0.55 0.209 1.171 OS1 689 44% 0.26 0.51 0.012 0.080 OS2 215 2% 0.03 0.36 0.000 0.018 Onsite Total 19897 69% 0.44 0.61 0.612 2.904 Post Detention Q100 = 1.779 Existing Site Totals 19897 44% 0.25 0.50 0.248 1.712 Alley Capacity Calcs OS1A 13097 91% 0.73 0.83 0.505 1.999 OS1+OS1A OS1 13786 89% 0.69 0.80 0.504 2.027 OS2A 11731 92% 0.74 0.84 0.458 1.806 OS2+OS2A OS2 11946 90% 0.71 0.81 0.450 1.792 C100 C2 Basin %I Design Point Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Summary of Existing and Proposed Site Surfaces Roof (1) Walks(1) Streets(1) Landscape(1 ) %I = 90% %I = 90% %I =100% %I=2% acres sf sf sf sf sf C2 C100 Proposed 0.457 19897 6657 1382 6364 5494 69% 0.44 0.61 Existing 0.457 19897 5576 1899 1738 10682 44% 0.30 0.59 Difference 1081 -517 4626 -5188 Basin Areas Composite Imperviousness (%I) Composite Runoff Total Total Coefficients (2) Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Proposed Site - Runoff Coefficients and % Impervious Roof (1) Walks(1) Streets(1) Landscape(1 ) %I = 90% %I = 90% %I =100% %I=2% acres sf sf sf sf sf C2 C100 Onsite Basins A 0.145 6337 910 274 4050 1103 81% 0.58 0.71 B 0.077 3337 887 158 2020 272 89% 0.69 0.80 C 0.214 9319 4860 950 3509 57% 0.34 0.55 A+B+C 0.436 18993 OS1 0.016 689 0 294 395 44% 0.26 0.51 OS2 0.005 215 0 0 215 2% 0.03 0.36 Onsite Total 0.457 19897 6657 1382 6364 5494 69% 0.44 0.61 Alley Capacity Calcs OS1A 0.301 13097 11199 1892 91% 0.73 0.83 OS1+OS1A OS1 0.316 13786 11199 0 2186 395 89% 0.69 0.80 OS2A 0.269 11731 9433 2296 92% 0.74 0.84 OS2+OS2A OS2 0.274 11946 9433 0 2296 215 90% 0.71 0.81 Notes: (1) Recommended % Imperviousness Values from USDCM Vol 1 - Ch 5 - Table RO-3. Increased Lawns from 0% to 2% Impervious. (2) Runoff C is based on %I, UDFCD Eq RO-7 and correction factors in Table RO-4. (3) Calculated to determine depth of flow in the alley for required height to garage entrance and allowable sheet flow over sidewalk (See note 3) Composite Runoff Basin Coefficients (2) Areas Composite Imperviousness (%I) Total Total Design Pt. Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Proposed Site - Time of Concentration Area Length Slope ti (2) Length Slope Velocity (3) t t (4) Check tc? Total Length tc (5) acres ft % min ft % fps min min u = urban ft min min Onsite Basins A 6,337 walk 0.73 24 2 2.6 110 1 20 2.0 0.9 3.5 u 134 11 5 B 3,337 Roof 0.73 24 10 1.5 72 1 20 2.0 0.6 2.1 u 96 11 5 C 9,319 Roof 0.73 18 10 1.3 55 1 20 2.0 0.5 1.8 u 73 10 5 A+B+C 18,993 5 OS1 689 Street 0.90 10 10 0.5 36 0.5 20 1.4 0.4 1.0 u 46 10 5 OS2 215 Street 0.90 10 10 0.5 32 0.5 20 1.4 0.4 0.9 u 42 10 5 Alley Capacity Calcs OS1A 13,097 Roof 0.73 147 1 8.1 83 0.5 20 1.4 1.0 9.1 u 80 10 9 OS1+OS1A OS1 13,786 9 OS2A 11,731 Roof 0.73 140 1 7.9 93 0.5 20 1.4 1.1 9.0 u 81 10 9 OS2+OS2A OS2 11,946 9 Notes: (1) C5 based initial ground type and Table RO-5 (4) tt =L/(V*60 sec/min) (2) ti = [1.8(1.1-C5 )L 1/2 ]/S 1/3 , S= slope in %, L=length of overland flow (400' max) (5) tc check (for urban or developed areas only) = total length/180 + 10 (3) V=Cv S 0.5 , S=watercourse slope in ft/ft, UDFCD Equation RO-4 (6) min tc = 5 min Final tc (6) tc Check for Urbanized Remington Annex Fort Collins, CO Proposed Site - Rational Method Peak Runoff Final Post Detention Discharge tc (6) I2 I100 Q2 Q100 Q100 sf min in/hr in/hr cfs cfs cfs cfs Onsite Basins A 6,337 5 0.58 0.71 2.85 9.95 0.240 1.028 0.675 0.354 B 3,337 5 0.69 0.80 2.85 9.95 0.151 0.607 0.450 0.157 C 9,319 5 0.34 0.55 2.85 9.95 0.209 1.171 1.171 A+B+C 18,993 0.600 2.806 1.682 OS1 689 5 0.26 0.51 2.85 9.95 0.012 0.080 0.080 OS2 215 5 0.03 0.36 2.85 9.95 0.000 0.018 0.018 Onsite Total 19,897 0.612 2.904 1.779 Alley Capacity Calcs OS1A 13,097 9 0.73 0.83 2.30 8.03 0.505 1.999 OS1+OS1A OS1 13,786 9 0.69 0.80 2.30 8.03 0.504 2.027 OS2A 11,731 9 0.74 0.84 2.30 8.03 0.458 1.806 OS2+OS2A OS2 11,946 9 0.71 0.81 2.30 8.03 0.450 1.792 Design Pt. Reduction from Detention Peak Discharge Area Basin Runoff Coefficients Rainfall Intensity C2 C100 Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Existing Site - Runoff Coefficients and % Impervious Roof (1) Walks(1) Streets(1) Landscape(1) %I = 90% %I = 90% %I =100% %I=2% acres sf sf sf sf sf C2 C100 Existing Onsite Basins (See note 3) NW 0.006 274 197 77 72% 0.48 0.64 SW 0.029 1283 61 1222 7% 0.02 0.39 E 0.421 18340 5576 1901 1480 9383 46% 0.27 0.51 Total 0.457 19897 5576 1901 1738 10682 44% 0.25 0.50 Existing Landscaped (pervious) area = 10682 Proposed Landscaped (pervious) area = 5494 (See "Proposed Runoff Coefficients and Calculations") Difference in pervious areas = 5188 (This is new impervious area that must be detained) Historic Calculation for Release Rate (See note 4) Release Rate 0.119 5188 5188 2% 0.03 0.36 Release Rate 0.119 5188 5188 0 100% 0.89 0.96 Notes: (1) Recommended % Imperviousness Values from USDCM Vol 1 - Ch 5 - Table RO-3. Increased Lawns from 0% to 2% Impervious. (2) Runoff C is based on %I, UDFCD Eq RO-7 and correction factors in Table RO-4. (3) NW = drains to northwest, SW = drains to Southwest, E=drains to the east (4) Calculated to determine the required release rate for the additional impervious area being proposed Composite Runoff Basin Coefficients (2) Areas Composite Imperviousness (%I) Total Total Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff-existing.xlsx Remington Annex Fort Collins, CO Existing Site - Time of Concentration Area Length Slope ti (2) Length Slope Velocity (3) tt (4) Check tc? Total Length tc (5) sf ft % min ft % fps min min u = urban ft min min Existing Onsite Basins NW 274 Street 0.90 13 1 1.3 0.0 1.3 u 13 10 5 SW 1,283 Lawn 0.09 20 1 8.1 0.0 8.1 u 20 10 8 E 18,340 Lawn 0.09 132 1 20.9 0.0 20.9 u 132 11 11 Total 19,897 Lawn 0.09 132 1 20.9 2.0 22.9 u 132 11 11 Historic Calculation for Release Rate Release Rate 5,188 Lawn 0.09 60 1 14.1 0.0 14.1 u 60 10 10 Release Rate 5,188 Street 0.90 60 1 2.8 1.0 3.8 u 60 10 5 Notes: (1) C5 based initial ground type and Table RO-5 (4) tt =L/(V*60 sec/min) (2) ti = [1.8(1.1-C5 )L 1/2 ]/S 1/3 , S= slope in %, L=length of overland flow (400' max) (5) tc check (for urban or developed areas only) = total length/180 + 10 (3) V=Cv S 0.5 , S=watercourse slope in ft/ft, UDFCD Equation RO-4 (6) min tc = 5 min Final tc (6) tc Check for Urbanized Basin Remington Annex Fort Collins, CO Existing Site - Rational Method Peak Runoff Final tc (6) I2 I100 Q2 Q100 sf min in/hr in/hr cfs cfs Existing Onsite Basins NW 274 5 0.48 0.64 2.85 9.95 0.009 0.040 SW 1,283 8 0.02 0.39 2.40 8.38 0.001 0.096 E 18,340 11 0.27 0.51 2.13 7.42 0.240 1.597 Total 19,897 11 0.25 0.50 2.13 7.42 0.248 1.712 Historic Calculation for Release Rate Release Rate 5,188 10 0.03 0.36 2.21 7.72 0.008 0.333 Release Rate 5,188 5 0.89 0.96 2.85 9.95 0.301 1.132 Difference between existing 2 yr and proposed 100 yr for new impervious area (Amount to be detained) = 1.124 Proportion to be detained in Detention Pond A = 0.675 Proportion to be detained in Detention Pond B = 0.450 Peak Discharge Area Basin Runoff Coefficients Rainfall Intensity C2 C100 Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff-existing.xlsx APPENDIX B Detention Pond Analysis Remington Annex Fort Collins, CO Pond Summary Pond Summary Pond Req'd Storage Volume (cfs) Total Volume Provided (cfs) Outfall Elevation Spill Elevation Adjacent Building FFE Freeboard Pond A 469 637 4990.90 4991.60 4992.25 0.65 Pond B 335 528 4991.20 4991.90 4992.50 0.60 Totals 805 1165 Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Detention Pond A 100 year storm into detention facility A Area (sf) Area (acres) Q100 C100*Area %I 6337 0.145 1.028 0.10 81% Release rate out of detention system based on Qout (cfs) cfs/acre Tc (min) 0.354 2.43 5 Rainfall Intensity Inflow Volume Adjustment Factor Average Outflow Rate Outflow Volume Required Storage Volume I Vi=(Qin*T*60) m= 0.5(1 + Tc/T) Qav = m*Qout Vo=Qav*T *60 Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 9.95 1.03 309 1.00 0.35 106 202 10 7.72 0.80 479 0.75 0.27 159 320 15 6.52 0.67 607 0.67 0.24 212 394 20 5.60 0.58 695 0.63 0.22 265 429 25 4.98 0.51 772 0.60 0.21 318 454 30 4.52 0.47 841 0.58 0.21 371 469 35 4.08 0.42 886 0.57 0.20 425 461 40 3.74 0.39 928 0.56 0.20 478 450 45 3.46 0.36 966 0.56 0.20 531 435 50 3.23 0.33 1,002 0.55 0.19 584 418 55 3.03 0.31 1,034 0.55 0.19 637 397 60 2.86 0.30 1,064 0.54 0.19 690 374 70 2.59 0.27 1,124 0.54 0.19 796 328 80 2.39 0.25 1,186 0.53 0.19 902 284 90 2.23 0.23 1,245 0.53 0.19 1,008 236 100 2.08 0.21 1,290 0.53 0.19 1,114 175 110 1.96 0.20 1,337 0.52 0.18 1,221 116 120 1.83 0.19 1,362 0.52 0.18 1,327 35 Max Volume, ft 3 = 469 Delta Volume = (d/3)(A1+A2+(A1*A2)0.5) Elevation d Elevation Area Delta Volume Cumulative Volume ft ft ft 2 ft 3 ft 3 4990.90 0 0 0 4991.00 0.10 114 4 4 4991.20 0.20 593 64 68 4991.40 0.20 1,423 196 264 4991.60 0.20 2,346 373 637 Required Detention Volume Remington Annex Fort Collins, CO Detention Pond A Elev81 - Elev80 (VolRequired-Vol80)+Elev80 Vol81 - Vo80 W.S. Elevation, ft = 4991.60 100-year Depth D, ft = 0.70 Top-of-Berm, ft = 4992.25 Freeboard , ft = 0.65 Orifice Flow Rate, Q (cfs) = CoAo(2gHo)0.5 Area of orifice Ao, ft2 = Q Co = 0.6 Co(2gHo)0.5 Q = Qout of pond, cfs = 0.35 gravitational acceleration g, ft/sec 2 = 32.2 diam, ft = 0.374 Effective head on orifice Ho = D-1/2diam, ft = 0.51 Area of orifice Ao, ft 2 = 0.10 Area of orifice Ao, in 2 = 14.77 diam, in = 4.34 4 3 8 W.S. Elevation, ft = inch diameter opening Orifice Opening Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Remington Annex Fort Collins, CO Detention Pond B 100 year storm into detention facility B Area (sf) Area (acres) Q100 C100*Area %I 3337 0.077 0.607 0.06 89% Release rate out of detention system based on Qout (cfs) cfs/acre Tc (min) 0.157 2.05 5 Rainfall Intensity Inflow Volume Adjustment Factor Average Outflow Rate Outflow Volume Required Storage Volume I Vi=(Qin*T*60) m= 0.5(1 + Tc/T) Qav = m*Qout Vo=Qav*T *60 Vs=Vi-Vo min in/hr cfs ft 3 cfs ft 3 ft 3 5 9.95 0.61 182 1.00 0.16 47 135 10 7.72 0.47 282 0.75 0.12 71 212 15 6.52 0.40 358 0.67 0.10 94 264 20 5.60 0.34 410 0.63 0.10 118 292 25 4.98 0.30 455 0.60 0.09 141 314 30 4.52 0.28 496 0.58 0.09 165 331 35 4.08 0.25 522 0.57 0.09 188 334 40 3.74 0.23 547 0.56 0.09 212 335 45 3.46 0.21 570 0.56 0.09 235 334 50 3.23 0.20 591 0.55 0.09 259 332 55 3.03 0.18 610 0.55 0.09 282 327 60 2.86 0.17 628 0.54 0.08 306 322 70 2.59 0.16 663 0.54 0.08 353 310 80 2.39 0.15 699 0.53 0.08 400 299 90 2.23 0.14 734 0.53 0.08 447 287 100 2.08 0.13 761 0.53 0.08 494 267 110 1.96 0.12 789 0.52 0.08 541 248 120 1.83 0.11 803 0.52 0.08 588 215 Max Volume, ft 3 = 335 Delta Volume = (d/3)(A1+A2+(A1*A2)0.5) Elevation d Elevation Area Delta Volume Cumulative Volume ft ft ft 2 ft 3 ft 3 4991.20 0 0 0 4991.30 0.10 50 2 2 4991.50 0.20 499 47 49 4991.70 0.20 1,213 166 215 4991.90 0.20 1,948 313 528 Required Detention Volume Remington Annex Fort Collins, CO Detention Pond B Elev81 - Elev80 (VolRequired-Vol80)+Elev80 Vol81 - Vo80 W.S. Elevation, ft = 4991.90 100-year Depth D, ft = 0.70 Top-of-Berm, ft = 4991.75 Freeboard , ft = -0.15 Orifice Flow Rate, Q (cfs) = CoAo(2gHo)0.5 Area of orifice Ao, ft2 = Q Co = 0.6 Co(2gHo)0.5 Q = Qout of pond, cfs = 0.16 gravitational acceleration g, ft/sec 2 = 32.2 diam, ft = 0.246 Effective head on orifice Ho = D-1/2diam, ft = 0.58 Area of orifice Ao, ft 2 = 0.04 Area of orifice Ao, in 2 = 6.17 diam, in = 2.80 2 6 8 inch diameter opening W.S. Elevation, ft = Orifice Opening Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx APPENDIX C Hydraulic Analyses Channel Report Hydraflow Express Extension for AutoCAD® Civil 3D® 2012 by Autodesk, Inc. Tuesday, Dec 6 2011 <Name> Triangular Side Slopes (z:1) = 40.00, 40.00 Total Depth (ft) = 0.25 Invert Elev (ft) = 100.00 Slope (%) = 0.50 N-Value = 0.012 Calculations Compute by: Known Depth Known Depth (ft) = 0.25 Highlighted Depth (ft) = 0.25 Q (cfs) = 5.468 Area (sqft) = 2.50 Velocity (ft/s) = 2.19 Wetted Perim (ft) = 20.01 Crit Depth, Yc (ft) = 0.25 Top Width (ft) = 20.00 EGL (ft) = 0.32 0 2 4 6 8 10 12 14 16 18 20 22 24 Elev (ft) Depth (ft) Section 99.75 -0.25 100.00 0.00 100.25 0.25 100.50 0.50 100.75 0.75 101.00 1.00 Reach (ft) COLLEGE AVENUE LAUREL STREET PLUM STREET REMINGTON STREET PROJECT SITE COLORADO STATE UNIVERSITY MATTHEWS STREET PETERSON STREET WHEDBEE STREET MYRTLE STREET PREPARED FOR: DATE SUBMITTED: The engineer preparing these plans will not be responsible for, or liable for, unauthorized changes to or uses of these plans. All changes to the plans must be in writing and must be approved by the preparer of these plans. CAUTION MAXIIIMO DEVELOPMENT GROUP LLC 12/19/2012 REMINGTON ANNEX 7 B11010 PRELIMINARY PLANS NOT FOR CONSTRUCTION Civil Engineering & Consulting 1501 Academy Court, Suite 204 Fort Collins, CO 80524 (970) 217-7420 www.bluesky-engineer.com BLUE SKY E n g i n e e r i n g LEGEND DRAINAGE PLAN DR01 4 EXISTING ITEMS PROPOSED ITEMS SCALE: 1"=400' VICINITY MAP NOTES RUNOFF SUMMARY TABLE POND SUMMARY TABLE Rainfall Duration (T) Qin= ∑C100*Area*I Comments Based only on additional impervious area. Comments Based on 2 yr historic release rate of new impervious Detention Volume and Depth Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Rainfall Duration (T) Qin= ∑C100*Area*I Detention Volume and Depth Comments Based only on additional impervious area. Based on 2 yr historic release rate of new impervious Comments Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (tt) Initial Ground Type C5 (1) Cv ti+tt Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff-existing.xlsx Basin Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (tt) Design Pt. Initial Ground Type C5 (1) Cv ti+tt Calculations by: SME Date: 12/19/2012 C:\Users\Sam\Dropbox\Projects\B11010-RemAnnex\Drainage\Prelim Submittal-2\B11010-Runoff.xlsx Pond B 335 528 4991.20 4991.90 4992.50 0.60 Totals 805 1165