The URL can be used to link to this page

Home My WebLink AboutRIVERSIDE SELF-STORAGE - PDP/FDP - FDP140026 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT FOR FIRST REPLAT OF PROSPECT RIVERSIDE SUBDIVISION (RIVERSIDE STORAGE) FINAL DRAINAGE AND EROSION CONTROL REPORT FOR FIRST REPLAT OF PROSPECT RIVERSIDE SUBDIVISION (RIVERSIDE STORAGE) Prepared for: Wickham Gustafson Architects 1449 Riverside Avenue Fort Collins, CO 80524 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 October 10, 2014 Job Number 264-02 ii October 10, 2014 Glen Schlueter City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Report for First Replat of Prospect Riverside Subdivision (Riverside Storage) Dear Glen, I am pleased to submit for your review and approval, this Final Drainage and Erosion Control Report for First Replat of Prospect Riverside Subdivision. I certify that this report for the drainage design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Patricia Kroetch, P.E. 700 Automation Drive, Unit I Windsor, CO 80550 Phone: 970-686-6939 Fax: 970-686-1188 iii TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................... iii 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location ...................................................................................................................1 1.2 Description of Property ............................................................................................1 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description ..........................................................................................1 2.2 Sub-Basin Description .............................................................................................1 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations ..............................................................................................................2 3.2 Development Criteria Reference and Constraints ...................................................2 3.3 Hydrologic Criteria ..................................................................................................2 3.4 Hydraulic Criteria ....................................................................................................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept ......................................................................................................3 4.2 Specific Flow Routing .............................................................................................3 4.3 Drainage Summary ..................................................................................................4 5. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis .....................................................................................................4 5.2 SWMP Contact Information ...................................................................................5 5.3 Identification and location of all potential pollution sources ..................................6 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention ...........6 5.5 BMP Implementation ...............................................................................................8 6. CONCLUSIONS 6.1 Compliance with Standards ..................................................................................11 6.2 Drainage Concept ..................................................................................................11 7. REFERENCES ..................................................................................................................12 APPENDICES A Vicinity Map B Hydrologic Computations C Detention Pond Sizing Calculations D BMP Schedule and Cost Estimate E Figures and Tables 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location This site is located on the east side of Riverside Drive north of East Prospect Road in the Southeast Quarter of Section 18, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the Vicinity Map in Appendix A of this report. This project is bounded on the north by existing storage units, on the east by existing Union Pacific Railroad tracks, on the west by Riverside Drive, and on the south by existing Rivendell School. 1.2 Description of Property The entire project consists of approximately 2.2 acres. The site is currently developed, with areas of existing asphalt and gravel. Existing slope is to the northeast with slopes ranging from approximately 1.5% to 3%. The site currently drains into an existing swale located at the northeast corner of the site. Proposed development on-site will include one office building, five self-storage buildings, and associated drives, parking, and walks. Existing drainage patterns will not be significantly altered with this development. 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description The proposed development lies within the Spring Creek Drainage Basin. Both stormwater detention and extended water quality detention are required in this basin. The City requirement for stormwater detention in the Spring Creek basin is a single-stage detention with a 100-year release rate equal to the existing 2-year runoff. 2.2 Sub-basin Description Runoff from this site currently flows to an existing swale located in the northeast corner of the site. From there, the runoff is conveyed in a proposed pipe and the existing swale to the north along the rear of the adjacent properties to an existing pipe under the railroad 2 tracks. The existing swale across the adjacent properties was determined to be a historic conveyance for this site. With the proposed drainage concept for this site, the detained runoff will continue to be released into the existing swale via a short outfall pipe. 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications except where variances are requested as noted in Section 4.2 of this report. Where applicable, the criteria established in the “Urban Storm Drainage Criteria Manual” (UDFCD), 2001, developed by the Denver Regional Council of Governments, has been used. 3.2 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City of Fort Collins Stormwater Department. Both stormwater runoff detention and extended water quality detention are required for this site and are being provided by the proposed on-site detention pond. The release rate from the site will be equal to the existing 2-year runoff. 3.3 Hydrologic Criteria Runoff computations were prepared for the 2-year minor and 100-year major storm frequencies utilizing the rational method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub-basins. Detention volume was calculated using the runoff rate for the 2-year rainfall event with existing site conditions, which includes existing sections of asphalt paving and gravel. The FAA method for detention pond sizing was utilized to determine the required volume. Water quality volume was calculated using the method recommended in the “Urban Storm Drainage Criteria Manual”. Refer to the detention calculations included in Appendix C of this report. 3 3.4 Hydraulic Criteria Hydraulic elements have been designed per City of Fort Collins standards to adequately convey the 100-year storm runoff from this site to the proposed detention pond. An existing drainage swale will convey the detained runoff from the site to the downstream railroad crossing. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The runoff from this site will flow into the parking lot and drive aisles which will be constructed using conventional materials (asphalt or concrete) and porous pavers. The runoff from the site will either flow on the surface or enter a perforated pipe via the porous pavers. In a situation where the porous pavements are clogged, the runoff will flow on the surface and enter the detention pond on the east side of the site. On-site runoff will also be conveyed to the detention pond via flows in LID swales along the north and south property boundaries. The detained runoff will discharge into the existing swale located at the northeast corner of the site. From there, runoff will be conveyed in the existing swale downstream to an existing railroad crossing. This existing swale may need to be cleaned out (with permission of the downstream property owner) to ensure adequate conveyance and removal of any obstructions. 4.2 Specific Flow Routing With this design, the site is modeled as a single basin (Basin 1). This basin includes all of the proposed improvements on site including the office building, parking for the office building, the five storage buildings, the drives between the storage buildings, the sidewalks and all of the water quality enhancement features. The runoff from the site will follow the historic runoff path and will flow from the west (Riverside Avenue) to the east and into the detention area. Drainage design for this site has been designed to convey on-site runoff to the proposed detention pond and incorporate the required water quality enhancement features. On-site runoff will be conveyed to the detention pond via surface flow in the drive aisles, in the LID swales and subsurface in the perforated pipes. The detention pond will release the detained runoff from the site at the existing (historic) 2-year runoff rate of 2 cfs. The 4 developed 2-year runoff rate for this Basin is 3.8 cfs and the developed 100-year runoff rate is 18.9 cfs. One variance is requested for this project. A variance is being requested to reduce the minimum freeboard for the detention pond from 1.0’ to 0.7’. This will not impact the structure on site or on the adjacent site. 4.3 Drainage Summary This site has been designed to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications except where variances are requested as noted in Section 4.2 of this report. The proposed drainage design for this site has been designed to convey on-site runoff to the detention pond while minimizing future maintenance. All drainage facilities proposed with this project, including the detention pond and outlet structure are private and will be owned and maintained by the property owner or Owner’s Association. 5. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis The soils on this site are classified by the USGS Soil Survey as Kim Loam with a small area of Santana Loam and are classified in the hydrologic group B. The soils are described as having a slow runoff rate and the hazard of water erosion is slight and the hazard of wind erosion is moderate. The site is surrounded by developed sites including streets and paved areas. The construction shall utilize silt fence around the perimeter to control sediment transport from rainfall and from wind. The silt fence that is located in the proposed pavement areas will be removed prior to placing new pavement. Rock socks will be utilized in the existing curb and the newly constructed swales to capture sediments that are not fully contained by the silt fence placement. The locations of the rock socks will be in the areas of concentrated flow such as in the existing curb, at the new swales and on the existing concrete sidewalks as needed. 5 The site will also utilize a vehicle tracking control pad to minimize sediment from being tracked onto adjacent pavements. Sediment that is tracked will be removed and placed within the site or permanently disposed of offsite. A concrete washout will be used on site during the concrete placement. All hardened concrete will be disposed of offsite. These BMP’s have not been located on the site map due to the fact that the site is very small and these BMP’s will need to be placed by the contractor in locations that are most beneficial and will minimize disruption of adjacent traffic. Permanent erosion control consists of covering the soils with a building, concrete walks, concrete drives and sod. No soil will be left exposed to erosion after the construction is complete. Refer to the landscape plan for areas of and instructions for placement of sod and soil amendments required prior to placement of sod. Refer to Appendix D for the timing of the construction phases and the sequential installation of all BMP phasing for this site. Refer to the Appendix E for the Erosion Control Surety calculations. 5.2 SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: 6 5.3 Identification and location of all potential pollution sources Potential Pollutant Source Activity Potential Pollutant Generated Applicable to this project Disturbed Areas Sediment X Soil stockpiles Sediment X Travel to adjacent public streets Tracked sediment X Contaminated soils Sediment, chemicals Loading and unloading chemicals Chemicals Unloading of building materials Trash, debris X Outdoor storage of chemicals Chemicals On site equipment maintenance Oil, grease On site equipment fueling Diesel, gasoline X Dust generating activities Particulates, sediment X Use of fertilizer, pesticides, herbicides Fertilizer, pesticides Use of detergents, solvents, oils Detergents, solvents, oil X Waste dumpsters, waste piles Chemicals, trash, debris X Concrete washout Concrete, sediment, wash water X On site equipment washing Detergents, oil On site asphalt batch plant Asphaltic cement, sediment On site concrete batch plant Cement, sediment Portable toilets Domestic sewage X 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention Structural Practices for Erosion and Sediment Control Structural practices for the site will consist mainly of silt fence and rock sock filters and are described in detail in the following paragraphs. These BMP's are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP's are in place and/or removed at the appropriate time in the construction sequence. All temporary and permanent erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. Silt fence and rock sock filters shall be in place prior to commencement of construction activities. During clearing and grubbing necessary for silt fence installation, all cleared material shall be placed on the uphill side so that if erosion occurs from the cleared material, the sediment will be trapped and not transported downstream. Rock socks shall be implemented in the existing curb line as shown on the Drainage & Erosion Control Plan. 7 All BMP's shall be installed per the details shown on the construction plan set. Temporary & Permanent Structural BMP’s: Structural BMP Approximate location on site Applicable to this Project Silt Fence Site perimeter, refer to site map X Straw bale dams Rock Socks At existing sidewalk culverts, in existing gutters, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond East boundary of site, in proposed det pond X Pipe slope drains Geogrid Inlet/outlet protection In the detention Pond X Culverts Riprap Erosion control mats Inlet protection Vehicle Tracking Control Pad At site entrance, refer to site map X Concrete Washout To be located by Contractor, near site entry X Non-Structural Practices for Erosion and Sediment Control: Soils exposed during the earthwork phase and landscape prep phase shall be kept in a roughened condition by ripping or disking along land contours until mulch, vegetation, or other permanent erosion control is installed. No large amount of soils (in excess of 15 yards) will be allowed to be stock piled on site. Overburden from the utility pipe trenching will be piled adjacent to trenches upstream of sediment controls and will be replaced in the trenches within 72 hours. Excess excavated materials from the demolition and grading phases of the project that cannot be reused on site will be exported as it is excavated. This includes any asphalt pavement from the existing site that is to be removed. A vehicle tracking pad will be installed at a location most beneficial to the site construction as determined by the contractor. Vehicles will not be permitted in the excavated area if soil is muddy. Gravel sub base will be placed and compacted in the areas indicated for pavement following excavation. In the current pre construction state the site enables tracking of silt onto the adjacent streets during wet conditions. During construction activities the street will be monitored for foreign debris tracked out of the site and mechanical sweeping and clean up will be performed as needed. 8 No area shall remain exposed by land disturbing activity for more than thirty (30) days before required temporary or permanent erosion control (e.g. seed/mulch, landscaping, etc.) is installed. Temporary & Permanent non-structural BMP’s: Non-Structural BMP Approximate location on site Applicable to this Project Surface roughening Entire site X Soil stockpile height limit (less than 10’) Perimeter vegetative buffer West and north boundaries of site X Minimization of site disturbance Mulch Seed & mulch stockpiles after 30 days Stockpile toe protection (silt fence, wattles or ditch) Preservation & protection of existing vegetation & trees West and north boundaries of site X Good site housekeeping (routine cleanup of trash & constr debris) Entire Site X Sweeping & scraping of hardscape areas On and off site pavements X Heavy equip staged on site, properly maintained & inspected daily (no onsite maintenance) Staging area X 5.5 BMP Implementation 1) Phased BMP Implementation BMP’s are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP’s are in place and/or removed at the appropriate time in the construction sequence. A construction sequence schedule has been included on the Drainage & Erosion Control Plan and included in the construction plans for this site. All BMP’s shall be inspected and repaired or replaced as required to satisfy the conditions of the Stormwater Discharge Permit. All BMP’s must be maintained and repaired as needed to assure continued performance of their intended function. Refer to Appendix D for the BMP schedule and estimated costs. 2) Materials Handling and Spill Prevention: 9 Materials Handling & Spill Prevention BMP Approximate location on site Applicable to this Project Portable toilets, anchored & located away from drainages Contractor to determine X Fuel storage located in bulk tanks with secondary containment & spill kit Mobile fueling performed at least 200 feet away from drainages & fully attended Contractor to determine X Fertilizers, form oil, solvents, cleaners, detergent stored in 55 gal or smaller containers, kept in storage units Contractor to determine X Dumpsters containing used chemicals containers & liquid wastes kept covered Contractor to determine X Equipment cleaning (on site) uses no detergents & flows to onsite retention basin In case of a release of fuel or other chemicals, absorbent booms or earthen berms will be immediately constructed to contain the spill & prevent runoff to adjacent surface waters Location of spill X MSDS sheets for onsite chemicals will be kept at the construction trailer to facilitate spill response & cleanup Contractor to determine X 3) Dedicated Asphalt or Concrete Batch Plant: Not proposed with this development 4) Vehicle Tracking Pad: Vehicle tracking control pad shall be installed wherever construction vehicle access routes intersect paved public roads. Vehicle tracking control pads shall be installed to minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved surface. Any mud tracked to public roads shall be removed on a daily basis and after any significant storm that causes sediment to be transported. It is unlawful to track sediment/mud onto public streets and may be enforced by the City of Fort Collins, by the State of Colorado or by the EPA. 10 5) Waste Management and Disposal: Portable toilets will be anchored & periodically maintained by waste management company. Dumpsters on site will be covered & periodically emptied by waste management company. Concrete waste will be allowed to harden and then will be removed from site. No washing activities will occur on site. Location of the concrete washout is shown on the site map. The washout will be sufficiently deep to accommodate all anticipated concrete truck wash water. Waste concrete will be allowed to harden and be removed from site periodically as the washout reaches 50% of its capacity. Truck wash water will not be allowed to reach the curb & gutter or any other water course. 6) Groundwater and Stormwater Dewatering: No groundwater was encountered during soils exploration therefore ground water is not anticipated to be an issue. If groundwater is encountered a groundwater discharge permit shall be obtained and a detailed report shall be completed describing the location and the route of where pumped groundwater will be conveyed and the measures taken to prevent the transport of any pollutants to downstream waters. 7) Inspection & Maintenance: It is required that routine site inspections are performed to effectively address maintenance and repair of Best Management Practices (BMP's). The site inspections are to performed by the contractor or an inspector designated by the administrator at a minimum of once every fourteen (14) calendar days on active construction sites and after any significant storm event (an event causing runoff). As part of the site inspections the inspector is required to keep documentation of all inspections and BMP maintenance, including an updated Site Map indicating new BMP's or the removal of BMP's since the previous inspection. Any maintenance, repair, or necessary installation of BMP's that are noted during the inspection must be completed within seven (7) calendar days from the date of the inspection 6. CONCLUSIONS 6.1 Compliance with Standards 11 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”, the “City of Fort Collins Storm Drainage Design Criteria Manual”, and the “Urban Storm Drainage Criteria Manual” except where variances are requested as noted in Section 4.2 of this report. 6.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provide for the collection and conveyance of on-site runoff to the detention area. Conveyance elements exist to adequately convey detained runoff downstream. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 12 7. REFERENCES 1. City of Fort Collins, “Storm Drainage Criteria Manual”, (SDCM), dated March, 1986. 2. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria Manual”, Volumes 1 and 2, dated March, 1969, and Volume 3 dated September, 1992. A APPENDIX A VICINITY MAP B APPENDIX B HYDROLOGIC COMPUTATIONS North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RUNOFF COEFFICIENTS & % IMPERVIOUS LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-03 COMPUTATIONS BY: ppk DATE: 10/16/2014 Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria Recommended % Impervious from Urban Storm Drainage Criteria Manual % Runoff Impervious coefficient C Streets, parking lots (asphalt): 100% 0.95 Sidewalks: 96% 0.95 Gravel: 40% 0.50 Roofs: 90% 0.95 Lawns (flat <2%, heavy soil): 0% 0.20 SUBBASIN TOTAL TOTAL ROOF PAVED SIDEWALK GRAVEL LANDSCAPE % RUNOFF DESIGNATION AREA AREA AREA AREA AREA AREA AREA Impervious COEFF. (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) Existing 2.18 95,094 0 17,700 0 19,530 57,864 30% 0.46 Proposed 2.18 95,094 31,743 38,365 1,763 0 23,223 72% 0.77 Equations - Calculated C coefficients & % Impervious are area weighted C =  (Ci Ai) / At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At = total area over which C is applicable; the sum of all Ai's Flow.xls Cval North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-03 COMPUTATIONS BY: ppk DATE: 10/16/2014 2-yr storm Cf = 1.00 FINAL REMARKS tc DESIGN SUBBASIN(s) Area C Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 POINT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) 1 Existing 2.18 0.46 225 2.8 12.2 225 1.6 0.030 1.4 2.77 15.0 450 12.5 12.5 1 Proposed 2.18 0.77 66 1.0 4.9 406 0.6 0.016 1.6 4.35 9.2 472 12.6 9.2 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 minutes TIME (ti) TRAVEL TIME / GUTTER OR CHANNEL FLOW (tt) tc CHECK (URBANIZED BASIN) STANDARD FORM SF-2 TIME OF CONCENTRATION - 2 YEAR SUB-BASIN DATA INITIAL /OVERLAND Flow.xls TOC-2 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-03 COMPUTATIONS BY: ppk DATE: 10/16/2014 100-yr storm Cf = 1.25 FINAL REMARKS tc DESIGN SUBBASIN(s) Area C C*Cf Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 POINT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) 1 Existing 2.18 0.46 0.58 225 2.8 10.0 225 1.6 0.030 1.4 2.77 12.8 450 12.5 12.5 1 Proposed 2.18 0.77 0.96 66 1.0 2.1 406 0.6 0.016 1.6 4.35 6.4 472 12.6 6.4 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L 0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 minutes TIME OF CONCENTRATION - 100 YR STANDARD FORM SF-2 SUB-BASIN DATA TIME (ti) INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW (tt) tc CHECK (URBANIZED BASIN) Flow.xls TOC-100 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (2-YEAR) LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-03 COMPUTATIONS BY: ppk DATE: ######## 2-yr storm, Cf = 1.00 TOTAL REMARKS Design Tributary A C*Cf tc i Q (2) from Q (2) Q(2)tot Sub-basin (new) Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) 1 Existing 2.18 0.46 12.5 2.02 2.0 2.0 Allowable pond release 1 Proposed 2.18 0.77 9.2 2.28 3.8 3.8 Q = Cf C iA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) DIRECT RUNOFF CARRY OVER Flow.xls Q2 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (100-YEAR) LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-03 COMPUTATIONS BY: ppk DATE: ######## 100-yr storm, Cf = 1.25 TOTAL REMARKS Des. Area A C*Cf tc i Q (100) from Q (100) Q(100)tot (new) Design Point Design. (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) 1 Existing 2.18 0.58 12.5 7.03 8.9 8.9 1 Proposed 2.18 0.96 6.4 9.04 18.9 18.9 Q = C iA Q = peak discharge (cfs) C = runoff coefficient I = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) DIRECT RUNOFF CARRY OVER Flow.xls Q100 C APPENDIX C DETENTION POND SIZING CALCULATIONS Detention Pond Outlet Sizing (100 yr event) LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-02 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: ######## Submerged Orifice Outlet: release rate is described by the orifice equation, Qo = CoAo sqrt( 2g(h-Eo)) where Qo = orifice outflow (cfs) Co = orifice discharge coefficient g = gravitational acceleration = 32.2 ft/s Ao = effective area of the orifice (ft2) Eo = greater of geometric center elevation of the orifice or d/s HGL (ft) h = water surface elevation (ft) Qo = 2.0 cfs outlet pipe dia = D = 12.0 in Invert elev. = 4934.30 ft Eo = 4934.63 ft h = 4936.10 ft - 100 yr WSEL Co = 0.62 solve for effective area of orifice using the orifice equation Ao = 0.331 ft2 = 47.7 in2 orifice dia. = d = 7.79 in Check orifice discharge coefficient using Figure 5-21 (Hydraulic Engineering ) d / D = 0.65 kinematic viscosity, u = 1.22E-05 ft2/s Reynolds no. = Red = 4Q/(pdu) = 3.21E+05 Co = (K in figure) = 0.62 check Use d = 7.80 in A o = 0.332 ft 2 = 47.78 in 2 Q max = 2.0 cfs Project: Basin ID: Design Information (Input): Design Information (Input): Catchment Drainage Imperviousness Ia = 72.00 percent Catchment Drainage Imperviousness I a = 72.00 percent Catchment Drainage Area A = 2.180 acres Catchment Drainage Area A = 2.180 acres Predevelopment NRCS Soil Group Type = C A, B, C, or D Predevelopment NRCS Soil Group Type = C A, B, C, or D Return Period for Detention Control T = 10 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100) Time of Concentration of Watershed Tc = 9 minutes Time of Concentration of Watershed Tc = 9 minutes Allowable Unit Release Rate q = 0.92 cfs/acre Allowable Unit Release Rate q = 0.92 cfs/acre One-hour Precipitation P1 = 1.61 inches One-hour Precipitation P 1 = 2.61 inches Design Rainfall IDF Formula i = C1* P1 /(C2+Tc )^C3 Design Rainfall IDF Formula i = C1 * P1/(C2 +Tc)^C3 Coefficient One C1 = 28.50 Coefficient One C 1 = 28.50 Coefficient Two C2 = 10 Coefficient Two C 2 =10 Coefficient Three C3 = 0.789 Coefficient Three C 3 = 0.789 Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated): Runoff Coefficient C = 0.59 Runoff Coefficient C = 0.69 Inflow Peak Runoff Qp-in = 5.73 cfs Inflow Peak Runoff Qp-in = 10.87 cfs Allowable Peak Outflow Rate Qp-out = 2.01 cfs Allowable Peak Outflow Rate Qp-out = 2.01 cfs Mod. FAA Minor Storage Volume = 3,507 cubic feet Mod. FAA Major Storage Volume = 10,059 cubic feet Mod. FAA Minor Storage Volume = 0.081 acre-ft Mod. FAA Major Storage Volume = 0.231 acre-ft 5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes) Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume minutes inches / hr acre-feet "m" cfs acre-feet acre-feet minutes inches / hr acre-feet "m" cfs acre-feet acre-feet (input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output) 5 5.42 0.048 1.00 2.01 0.014 0.034 5 8.78 0.091 1.00 2.01 0.014 0.077 10 4.32 0.076 0.96 1.93 0.027 0.050 10 7.00 0.145 0.96 1.93 0.027 0.118 15 3.62 0.096 0.81 1.62 0.033 0.063 15 5.87 0.182 0.81 1.62 0.033 0.149 20 3.13 0.111 0.73 1.46 0.040 0.071 20 5.08 0.211 0.73 1.46 0.040 0.170 25 2.78 0.123 0.68 1.37 0.047 0.076 25 4.50 0.233 0.68 1.37 0.047 0.186 30 2.50 0.133 0.65 1.31 0.054 0.079 30 4.05 0.252 0.65 1.31 0.054 0.198 35 2.28 0.141 0.63 1.27 0.061 0.080 35 3.69 0.268 0.63 1.27 0.061 0.207 40 2.09 0.148 0.62 1.23 0.068 0.081 40 3.40 0.281 0.62 1.23 0.068 0.214 45 1.94 0.155 0.60 1.21 0.075 0.080 45 3.15 0.294 0.60 1.21 0.075 0.219 50 1.81 0.161 0.59 1.19 0.082 0.079 50 2.94 0.305 0.59 1.19 0.082 0.223 55 1.70 0.166 0.58 1.17 0.089 0.077 55 2.76 0.315 0.58 1.17 0.089 0.226 60 1.61 0.171 0.58 1.16 0.096 0.075 60 2.60 0.324 0.58 1.16 0.096 0.228 65 1.52 0.175 0.57 1.14 0.102 0.073 65 2.47 0.332 0.57 1.14 0.102 0.230 70 1.45 0.179 0.57 1.13 0.109 0.070 70 2.34 0.340 0.57 1.13 0.109 0.231 75 1.38 0.183 0.56 1.13 0.116 0.067 75 2.23 0.347 0.56 1.13 0.116 0.231 80 1.32 0.187 0.56 1.12 0.123 0.064 80 2.14 0.354 0.56 1.12 0.123 0.231 85 1.26 0.190 0.55 1.11 0.130 0.060 85 2.05 0.360 0.55 1.11 0.130 0.230 90 1.21 0.193 0.55 1.11 0.137 0.056 90 1.97 0.367 0.55 1.11 0.137 0.229 95 1.17 0.196 0.55 1.10 0.144 0.052 95 1.89 0.372 0.55 1.10 0.144 0.228 100 1.12 0.199 0.55 1.10 0.151 0.048 100 1.82 0.378 0.55 1.10 0.151 0.227 105 1.09 0.202 0.54 1.09 0.158 0.044 105 1.76 0.383 0.54 1.09 0.158 0.225 110 1.05 0.205 0.54 1.09 0.165 0.040 110 1.70 0.388 0.54 1.09 0.165 0.223 115 1.02 0.207 0.54 1.08 0.172 0.036 115 1.65 0.393 0.54 1.08 0.172 0.221 120 0.99 0.210 0.54 1.08 0.178 0.031 120 1.60 0.397 0.54 1.08 0.178 0.219 125 0.96 0.212 0.54 1.08 0.185 0.027 125 1.55 0.402 0.54 1.08 0.185 0.216 130 0.93 0.214 0.54 1.07 0.192 0.022 130 1.51 0.406 0.54 1.07 0.192 0.214 Project: Basin ID: UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.34, Released November 2013 DETENTION VOLUME BY THE MODIFIED FAA METHOD Riverside storage 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0 50 100 150 200 250 300 350 Volume (acre-feet) Duration (Minutes) Inflow and Outflow Volumes vs. Rainfall Duration Minor Storm Inflow Volume Minor Storm Outflow Volume Minor Storm Storage Volume Major Storm Inflow Volume Major Storm Outflow Volume Major Storm Storage Volume UD-Detention_v2.34.xls, Modified FAA 10/16/2014, 2:19 PM Project: Basin ID: WQCV Design Volume (Input): Catchment Imperviousness, Ia = 72.0 percent Catchment Area, A = 2.18 acres Diameter of holes, D = 0.562 inches Depth at WQCV outlet above lowest perforation, H = 1 feet Number of holes per row, N = 1 Vertical distance between rows, h = 4.00 inches OR Number of rows, NL = 3.00 Orifice discharge coefficient, Co = 0.62 Height of slot, H = inches Slope of Basin Trickle Channel, S = 0.005 ft / ft Width of slot, W = inches Time to Drain the Pond = 40 hours Watershed Design Information (Input): 1.1 Percent Soil Type A = % Percent Soil Type B = 0 % Percent Soil Type C/D = 100 % Outlet Design Information (Output): Water Quality Capture Volume, WQCV = 0.346 watershed inches Water Quality Capture Volume (WQCV) = 0.063 acre-feet 0.00 Design Volume (WQCV / 12 * Area * 1.2) Vol = 0.075 acre-feet Outlet area per row, Ao = 0.25 square inches Total opening area at each row based on user-input above, Ao = 0.25 square inches Total opening area at each row based on user-input above, Ao = 0.002 square feet 3 Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8 Row 9 Row 10 Row 11 Row 12 Row 13 Row 14 Row 15 Row 16 Row 17 Row 18 Row 19 Row 20 Row 21 Row 22 Row 23 Row 23  34.04 34.37 34.71 Flow 34.05 0.0009 0.0000 0.0000 0.00 34.15 0.0028 0.0000 0.0000 0.00 34.25 0.0039 0.0000 0.0000 0.00 34.35 0.0048 0.0000 0.0000 0.00 34.45 0.0055 0.0024 0.0000 0.01 34.55 0.0061 0.0036 0.0000 0.01 34.65 0.0067 0.0045 0.0000 0.01 34.75 0.0072 0.0053 0.0017 0.01 34.85 0.0077 0.0059 0.0032 0.02 34.95 0.0082 0.0065 0.0042 0.02 35.05 0.0086 0.0071 0.0050 0.02 35.15 0.0090 0.0076 0.0057 0.02 35.25 0.0094 0.0080 0.0063 0.02 35.35 0.0098 0.0085 0.0069 0.03 35.45 0.0102 0.0089 0.0074 0.03 35.55 0.0105 0.0093 0.0079 0.03 35.65 0.0109 0.0097 0.0083 0.03 35.75 0.0112 0.0101 0.0088 0.03 35.85 0.0115 0.0104 0.0092 0.03 35.95 0.0119 0.0108 0.0096 0.03 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A STAGE - STORAGE TABLE (100-YEAR) LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-02 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/1/2008 100 yr Detention Volume Required = 0.231 Water Quality Volume Required = 0.075 Total Volume Required= 0.306 Surface Incremental Total Stage Area Storage Storage (ft) (ft2) (ac-ft) (ac-ft) 4934.30 0 4935.0 7,850 0.042 0.04 WQCV 4935.17 8,801 0.032 0.075 4936.0 13,442 0.242 0.284 100 WSEL 4936.10 15,105 0.033 0.316 4937.0 30,070 0.487 0.770 Emergency Overflow Spillway Sizing LOCATION: First Replat of Prospect Riverside Subdivision PROJECT NO: 264-02 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 5/24/2005 Equation for flow over a broad crested weir Q = CLH3/2 where C = weir coefficient = 2.8 H = overflow height L = length of the weir The pond has a spill elevation 0 ft above the maximum water surface elevation in the pond Spillways will be designed with 0.25 ft flow depth, thus H = 0.25 ft Size the spillway assuming that the pond outlet is completely clogged. Q (100) = 18.9 cfs Spill elev = 4936.35 ft 100 yr WSEL = 4936.10 ft Top of berm elev.= 4937.00 Weir length required: L = 54 ft Use L = 55 ft v = 1.20 ft/s D APPENDIX D BMP SCHEDULE & COST ESTIMATE Project: Disturbed Acres: 2.18 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 1300 $3.00 $3,900.00 each 15 $85.00 $1,275.00 each 1 $1,500.00 $1,500.00 each 1 $1,200.00 $1,200.00 each 1 $65.00 $65.00 Sub-Total: $7,940.00 1.5 x Sub-Total: $11,910.00 Amount of security: $11,910.00 Total Acres x Price/acre: $2,616.00 $1,200.00 Sub-Total: $2,616.00 1.5 x Sub-Total: $3,924.00 Amount to Re-seed: $3,924.00 Minimum escrow amount: $3,000.00 Erosion Control Escrow: $11,910.00 Example Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence Concrete Washout Rock Berm Reseeding Amount Miniumum Escrow Amount Riverside Storage Unit Price of Seeding per acre: “The amount of the security must be based on one and one-half times the estimate of the cost to install the approved measures, or one and one-half times the cost to re-vegetate the disturbed land to dry land grasses based upon unit cost determined by the City's Annual Revegetation and Stabilization Bid, whichever is greater. In no instance, will the amount of security be less than one thousand five hundred dollars ($1,500) for residential development or three thousand dollars ($3,000) for commercial development” Rock Sock Vehicle Tracking Control Pad (add all other BMPs for the site in this list) Final Escrow Amount 10/16/2014 2:10 PM \\Nstar\projects\264-03 Riverside Storage\drainage\Example Escrow.xls #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A Override Area Row 1 Override Area Row 2 Override Area Row 3 Override Area Row 4 Override Area Row 5 Override Area Row 6 Override Area Row 7 Override Area Row 8 Override Area Row 9 Override Area Row 10 Override Area Row 11 Override Area Row 12 Override Area Row 13 Override Area Row 14 Override Area Row 15 Override Area Row 16 Override Area Row 17 Override Area Row 18 Override Area Row 19 Override Area Row 20 Override Area Row 21 Override Area Row 22 Override Area Row 23 Override Area Row 24 Central Elevations of Rows of Holes in feet Collection Capacity for Each Row of Holes in cfs STAGE-DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET Riverside Storage 1 UD-Detention_v2.34.xls, WQCV 10/16/2014, 2:20 PM 135 0.90 0.216 0.53 1.07 0.199 0.017 135 1.47 0.410 0.53 1.07 0.199 0.211 140 0.88 0.218 0.53 1.07 0.206 0.012 140 1.43 0.414 0.53 1.07 0.206 0.208 145 0.86 0.220 0.53 1.07 0.213 0.007 145 1.39 0.418 0.53 1.07 0.213 0.205 150 0.84 0.222 0.53 1.06 0.220 0.002 150 1.36 0.422 0.53 1.06 0.220 0.202 155 0.82 0.224 0.53 1.06 0.227 -0.003 155 1.32 0.425 0.53 1.06 0.227 0.198 160 0.80 0.226 0.53 1.06 0.234 -0.008 160 1.29 0.429 0.53 1.06 0.234 0.195 165 0.78 0.228 0.53 1.06 0.241 -0.013 165 1.26 0.432 0.53 1.06 0.241 0.191 170 0.76 0.230 0.53 1.06 0.248 -0.018 170 1.24 0.435 0.53 1.06 0.248 0.188 175 0.75 0.231 0.53 1.06 0.254 -0.023 175 1.21 0.439 0.53 1.06 0.254 0.184 180 0.73 0.233 0.53 1.05 0.261 -0.028 180 1.18 0.442 0.53 1.05 0.261 0.180 185 0.72 0.235 0.52 1.05 0.268 -0.034 185 1.16 0.445 0.52 1.05 0.268 0.177 190 0.70 0.236 0.52 1.05 0.275 -0.039 190 1.14 0.448 0.52 1.05 0.275 0.173 195 0.69 0.238 0.52 1.05 0.282 -0.044 195 1.12 0.451 0.52 1.05 0.282 0.169 200 0.68 0.239 0.52 1.05 0.289 -0.050 200 1.09 0.454 0.52 1.05 0.289 0.165 205 0.66 0.241 0.52 1.05 0.296 -0.055 205 1.07 0.456 0.52 1.05 0.296 0.160 210 0.65 0.242 0.52 1.05 0.303 -0.061 210 1.06 0.459 0.52 1.05 0.303 0.156 215 0.64 0.244 0.52 1.05 0.310 -0.066 215 1.04 0.462 0.52 1.05 0.310 0.152 220 0.63 0.245 0.52 1.04 0.317 -0.072 220 1.02 0.464 0.52 1.04 0.317 0.148 225 0.62 0.246 0.52 1.04 0.323 -0.077 225 1.00 0.467 0.52 1.04 0.323 0.143 230 0.61 0.248 0.52 1.04 0.330 -0.083 230 0.99 0.469 0.52 1.04 0.330 0.139 235 0.60 0.249 0.52 1.04 0.337 -0.088 235 0.97 0.472 0.52 1.04 0.337 0.135 240 0.59 0.250 0.52 1.04 0.344 -0.094 240 0.95 0.474 0.52 1.04 0.344 0.130 245 0.58 0.251 0.52 1.04 0.351 -0.100 245 0.94 0.477 0.52 1.04 0.351 0.126 250 0.57 0.253 0.52 1.04 0.358 -0.105 250 0.92 0.479 0.52 1.04 0.358 0.121 255 0.56 0.254 0.52 1.04 0.365 -0.111 255 0.91 0.481 0.52 1.04 0.365 0.116 260 0.55 0.255 0.52 1.04 0.372 -0.117 260 0.90 0.484 0.52 1.04 0.372 0.112 265 0.55 0.256 0.52 1.04 0.379 -0.122 265 0.88 0.486 0.52 1.04 0.379 0.107 270 0.54 0.257 0.52 1.04 0.386 -0.128 270 0.87 0.488 0.52 1.04 0.386 0.102 275 0.53 0.259 0.52 1.04 0.393 -0.134 275 0.86 0.490 0.52 1.04 0.393 0.098 280 0.52 0.260 0.52 1.04 0.399 -0.140 280 0.85 0.492 0.52 1.04 0.399 0.093 285 0.52 0.261 0.52 1.04 0.406 -0.146 285 0.84 0.494 0.52 1.04 0.406 0.088 290 0.51 0.262 0.52 1.03 0.413 -0.151 290 0.83 0.496 0.52 1.03 0.413 0.083 295 0.50 0.263 0.52 1.03 0.420 -0.157 295 0.82 0.498 0.52 1.03 0.420 0.078 300 0.50 0.264 0.52 1.03 0.427 -0.163 300 0.81 0.500 0.52 1.03 0.427 0.073 305 0.49 0.265 0.52 1.03 0.434 -0.169 305 0.79 0.502 0.52 1.03 0.434 0.068 Mod. FAA Minor Storage Volume (cubic ft.) = 3,507 Mod. FAA Major Storage Volume (cubic ft.) = 10,059 Mod. FAA Minor Storage Volume (acre-ft.) = 0.0805 Mod. FAA Major Storage Volume (acre-ft.) = 0.2309 Determination of MAJOR Detention Volume Using Modified FAA Method (For catchments less than 160 acres only. For larger catchments, use hydrograph routing method) (NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended) UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.34, Released November 2013 Determination of MINOR Detention Volume Using Modified FAA Method DETENTION VOLUME BY THE MODIFIED FAA METHOD Riverside storage 1 UD-Detention_v2.34.xls, Modified FAA 10/16/2014, 2:19 PM