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Home My WebLink AboutRAW URTH DESIGNS - PDP - PDP150007 - REPORTS - DRAINAGE REPORTFINAL DRAINAGE AND EROSION CONTROL REPORT FOR RAW URTH DESIGNS (LOT 20, BLOCK 3, EVERGREEN REPLAT 1) FINAL DRAINAGE AND EROSION CONTROL REPORT FOR RAW URTH DESIGNS (LOT 20, BLOCK 3, EVERGREEN REPLAT 1) Prepared for: Raw Urth Designs P.O. Box 369 Bellvue, CO 80537 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 August 6, 2015 Job Number 264-10 ii August 6, 2015 Dan Mogen City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Report for Raw Urth Designs Dear Dan, I am pleased to submit for your review and approval, this Final Drainage and Erosion Control Report for Raw Urth Designs (Lot 20, Block 3, Evergreen Replat 1). 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 ..................................................................................................5 5. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis .....................................................................................................6 5.2 SWMP Contact Information ...................................................................................7 5.3 Identification and location of all potential pollution sources ..................................8 5.4 Best Management Practices (BMP’s) for Stormwater Pollution Prevention ...........8 5.5 BMP Implementation .............................................................................................10 6. CONCLUSIONS 6.1 Compliance with Standards ..................................................................................13 6.2 Drainage Concept ..................................................................................................13 7. REFERENCES ..................................................................................................................14 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 north side of Conifer Street, west of Red Cedar Circle and east of the existing alley in the Northwest Quarter of Section 1, Township 7 North, Range 69 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 an existing building, on the east by existing Red Cedar Circle, on the west by a paved alley, and on the south by existing Conifer Street. 1.2 Description of Property The entire project consists of approximately 0.9 acres. The site is currently undeveloped, with areas of existing volunteer weeds and grasses. The existing site is flat with existing slope to the southeast at approximately 0.5% to 1%. The site currently drains into the adjacent streets and alley. Proposed development on-site will include one building, a private drive along the north side of the building, a parking lot and sidewalks. Existing drainage patterns will be altered to direct flow to a proposed detention pond in the southeast corner of the site which will release into the existing storm system in this location. 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description The proposed development lies within the Dry Creek Drainage Basin. Stormwater detention is required for this basin but water quality extended detention is not required because it is provided in the North East College Corridor Outfall (NECCO) detention pond. The City requirement for stormwater detention in the Dry Creek basin is a single- stage detention with a 100-year release rate equal to the existing 2-year runoff (0.2 cfs per acre). 2 2.2 Sub-basin Description Runoff from this site currently flows to the existing streets and alley. From there, the runoff enters an existing inlet near the intersection of Red Cedar and Conifer. With the proposed drainage concept for this site, the runoff from the site will flow to a proposed detention pond and be released at the 2 year historic runoff rate into the storm system near the intersection of Red Cedar and Conifer. 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 Dry Creek Drainage Basin and the City of Fort Collins Stormwater Department. Both stormwater runoff detention and water quality extended detention are required for this site with on-site detention and offsite water quality. The release rate from the site will be equal to the existing 2-year runoff (0.2 cfs per acre). 3.3 Hydrologic Criteria Runoff computations were prepared for the 10-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 predetermined release rate of 0.2 cfs per acre. The FAA method for detention pond sizing was utilized to determine the required volume. 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. A proposed 12” storm pipe will convey the detained runoff from the site to the existing manhole at the southeast corner of the site. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The runoff from this site will flow into the drive aisle and parking lot which will be constructed using conventional materials (asphalt or concrete) and permeable interlocking pavers. The runoff from the site will either flow on the surface or enter a storm pipe via the permeable interlocking pavers or inlet. In a situation where the permeable interlocking pavements are clogged, the runoff will flow on the surface and enter the detention pond through a metal sidewalk culvert. On-site runoff will also be conveyed to the detention pond via flows in LID swales along the north property boundary to an area inlet and storm pipe. The detained runoff will discharge into the existing storm pipe located at the southeast corner of the site. 4.2 Specific Flow Routing With this design, the site has been broken into 3 basins which correspond with the LID feature that the basin flows to. The basin are described in the following paragraphs. Basin 1 is located in the northmost portion of the site and contains a majority of the private drive and LID feature #1 which is an LID swale without an underdrain. The runoff from the paved area will flow to the swale and will be collected in an area inlet. The storm pipe then conveys the flows to the south into the detention pond. Basin 2 is located in the eastmost portion of the site and contains a portion of the paved private drive and the parking lot which is surfaced with porous pavers. The runoff from this basin flows to a low point in the private drive then south into the parking lot porous pavers. The flow, if it exceeds the capacity of the pavers, will flow into the detention pond via a metal sidewalk culvert. 4 Basin 3 is located in the southwest portion of the site and contains the building and the detention pond (landscape area). The roof of the storage building is sloped to drain to the south and the bottom of the detention area is sloped to drain east. This basin accepts runoff from Basins 1 and 2. The detained runoff will enter the existing storm system via a new storm pipe with an orifice to restrict flows to the 2 year historic rate (0.2cfs per acre). Basin OS is the site area that drains to the street undetained. A majority of the area that is draining to the street is a narrow landscape strip located between the detention pond wall and the sidewalk. The impervious area is a portion of the drive entry (approximately 300 square feet) that drains to Red Cedar. The amount of runoff is quantified as 0.0 cfs in the minor storm and 0.1cfs in the 100 year storm event. Drainage design for this site has been designed to convey on-site runoff to the proposed detention pond and incorporate the required LID enhancement features. On-site runoff will be conveyed to the detention pond via surface flow in the drive aisles, in the LID swale 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 0.2 cfs per acre. The developed 2-year runoff rate for this site is 1.3 cfs and the developed 100-year runoff rate is 6.2 cfs. 4.3 Drainage Summary This site has been designed to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications. The proposed drainage design for this site has been designed to convey on-site runoff to the detention pond while minimizing future maintenance. The site incorporates a LID (Low Impact Development) treatment areas including an LID swale without underdrain along the north property line, and permeable interlocking pavers in the parking lot. Refer to the end of Appendix D for a table indicating the size of the LID treatment area and the area of the site that drains to that LID treatment area. All drainage facilities proposed with this project, including the detention pond, LID features, porous pavers and outlet structure are private and will be owned and maintained by the property owner. 5 5. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis The soils on this site are classified by the USGS Soil Survey as Nunn Clay Loam and are classified in the hydrologic group C. The soils are described as having a slow runoff rate and the hazard of water erosion is moderate 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 as needed. 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. 6 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 D 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: 7 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. 8 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 sidewalk culverts, in swales, at new inlet, in existing gutters, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond 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. 9 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 North boundary 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 North boundary 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. 10 2) Materials Handling and Spill Prevention: 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. 11 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 suitably deep to accommodate all anticipated concrete truck wash water. Waste concrete will be allowed to harden & be removed from site periodically as the washout reaches 50% of 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 be 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 12 6. CONCLUSIONS 6.1 Compliance with Standards 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. 13 7. REFERENCES 1. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria Manual”, 2001 Edition Volume 1 updated June 2001, January 2004 and April 2008; Volume 2 updated June 2001 and April 2008; and Volume 3 updated November and December 2010. 2. The Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual, adopted by the City Council of the City of Fort Collins, as referenced in Section 26-500 (c) of the Code of the City of Fort Collins. 3. ORDINANCE NO. 152, 2012 of the Council of the City of Fort Collins amending Chapter 26 of the Code of the City of Fort Collins and the Fort Collins Stormwater Criterial Manual to incorporate provisions implementing Low Impact Development (LID) Principles. A APPENDIX A VICINITY MAP B APPENDIX B HYDROLOGIC COMPUTATIONS North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Raw Urth Designs PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 8/12/2015 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) 1 0.19 8474 0 6368 0 0 2,106 75% 0.76 2 0.15 6427 0 5,354 360 0 713 89% 0.87 3 0.51 22236 12415 0 904 0 8,917 54% 0.65 ALL 0.89 38,584 12,415 12,010 1,264 0 12,895 63% 0.70 OS 0.03 1,178 0 300 0 0 878 25% 0.39 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: Raw Urth Designs PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 8/12/2015 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 1 0.19 0.76 35 1.5 3.1 204 0.5 0.030 0.8 4.49 7.6 239 11.3 7.6 1 2 0.15 0.87 24 1.5 1.8 146 0.6 0.016 1.6 1.56 3.4 170 10.9 5.0 1 3 0.51 0.65 67 1.0 6.6 283 0.6 0.030 0.8 5.68 12.3 350 11.9 11.9 1 ALL 0.89 0.70 67 1.0 5.9 283 0.6 0.030 0.8 5.68 11.6 350 11.9 11.6 1 OS 0.03 0.39 13 3.5 3.0 0 0.6 0.030 0.8 0.00 3.0 13 10.1 5.0 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: Raw Urth Designs PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 8/12/2015 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 1 0.19 0.76 0.95 35 1.5 1.4 204 0.5 0.030 0.8 4.49 5.8 239 11.3 5.8 1 2 0.15 0.87 1.00 24 1.5 0.8 146 0.6 0.016 1.6 1.56 2.3 170 10.9 5.0 1 3 0.51 0.65 0.81 67 1.0 4.2 283 0.6 0.030 0.8 5.68 9.9 350 11.9 9.9 1 ALL 0.89 0.70 0.87 67 1.0 3.3 283 0.6 0.030 0.8 5.68 9.0 350 11.9 9.0 1 OS 0.03 0.39 0.49 13 3.5 2.6 0 0.6 0.030 0.8 0.00 2.6 13 10.1 5.0 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: Raw Urth Designs PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 8/12/2015 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 1 0.19 0.76 7.6 2.45 0.4 0.4 To area inlet 1 2 0.15 0.87 5.0 2.85 0.4 0.4 to sidewalk culvert 1 3 0.51 0.65 11.9 2.05 0.7 0.7 To Det Pond 1 ALL 0.89 0.70 11.6 2.08 1.3 1.3 To Det Pond 1 OS 0.03 0.39 5.0 2.85 0.0 0.0 To Streets 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: Raw Urth Designs PROJECT NO: 177-06 COMPUTATIONS BY: ppk DATE: 8/12/2015 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 1 0.19 0.95 5.8 9.41 1.7 1.7 To area inlet 1 2 0.15 1.00 5.0 9.95 1.5 1.5 to sidewalk culvert 1 3 0.51 0.81 9.9 7.74 3.2 3.2 To Det Pond 1 ALL 0.89 0.87 9.0 7.96 6.2 6.2 To Det Pond 1 OS 0.03 0.49 5.0 9.95 0.1 0.1 To Streets 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 Grass Type Limiting Manning's n A0.06 B0.04 C 0.033 D0.03 E 0.024 Analysis of Trapezoidal Grass-Lined Channel Using SCS Method NRCS Vegetal Retardance (A, B, C, D, or E) A, B, C, D or E Manning's n (Leave cell D16 blank to manually enter an n value) n = 0.030 Channel Invert Slope SO = 0.0055 ft/ft Bottom Width B = 0.00 ft Left Side Slope Z1 = 6.00 ft/ft Right Side Slope Z2 = 4.00 ft/ft Check one of the following soil types: Soil Type: Max. Velocity (VMAX) Max Froude No. (FMAX) Sandy 5.0 fps 0.50 Non-Sandy 7.0 fps 0.80 Minor Storm Major Storm Max. Allowable Top Width of Channel for Minor & Major Storm TMAX = 10.00 10.00 feet Max. Allowable Water Depth in Channel for Minor & Major Storm dMAX = 6.00 6.00 feet Allowable Channel Capacity Based On Channel Geometry Minor Storm Major Storm MINOR STORM Allowable Capacity is based on Top Width Criterion Qallow = 11.45 11.45 cfs MAJOR STORM Allowable Capacity is based on Top Width Criterion dallow = 1.00 1.00 ft Water Depth in Channel Based On Design Peak Flow Design Peak Flow Qo = 0.40 1.70 cfs Water Depth d = 0.28 0.49 feet AREA INLET IN A TRAPEZOIDAL GRASS-LINED CHANNEL Raw Urth Inlet 1 Minor storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Major storm max. allowable capacity GOOD - greater than flow given on sheet 'Q-Peak' Choose One: Sandy Non-Sandy INlet 1.xlsm, Area Inlet 8/12/2015, 1:17 PM AREA INLET IN A TRAPEZOIDAL GRASS-LINED CHANNEL Raw Urth Inlet 1 Inlet Design Information (Input) Type of Inlet Inlet Type = Angle of Inclined Grate (must be <= 30 degrees) θ = 0.00 degrees Width of Grate W = 1.35 feet Length of Grate L = 2.00 feet Open Area Ratio ARATIO = 0.42 Height of Inclined Grate HB = 0.00 feet Clogging Factor Cf = 0.50 Grate Discharge Coefficient Cd = N/A Orifice Coefficient Co = 0.64 Weir Coefficient Cw = 2.05 MINOR MAJOR Water Depth at Inlet (for depressed inlets, 1 foot is added for depression) d = 0.28 0.49 Total Inlet Interception Capacity (assumes clogged condition) Qa = 1.18 2.04 cfs Inlet Capacity IS GOOD for Minor and Major Storms (> Q PEAK) Bypassed Flow, Qb = 0.00 0.00 cfs Capture Percentage = Qa/Qo = C% 100 100 % Warning 02: Depth (d) exceeds USDCM Volume I recommendation. User-Defined INlet 1.xlsm, Area Inlet 8/12/2015, 1:17 PM C APPENDIX C DETENTION POND SIZING CALCULATIONS MINIMUM DETENTION VOLUME REQUIRED FAA METHOD (100-YEAR) LOCATION: Raw Urth Designs PROJECT NO: 177-09 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/12/2015 Equations: A trib. To pond = 0.89 acre QD = CiA C100 = 0.87 Vi = T*CiA = T*QD Developed C*A = 0.8 acre Vo =K*QPO*T QPO = 0.18 cfs S = Vi - Vo K = 1 (from fig 2.1) Rainfall intensity from City of Fort Collins IDF Curve Storm Rainfall QD Vol. In Vol. Out Storage Storage Duration, T Intensity, i (cfs) Vi Vo SS (min) (in/hr) (ft3) (ft3) (ft3) (ac-ft) 5 9.95 7.7 2311 55 2256 0.052 10 7.72 6.0 3587 110 3476 0.080 20 5.60 4.3 5203 221 4982 0.114 30 4.52 3.5 6300 331 5969 0.137 40 3.74 2.9 6950 442 6509 0.149 50 3.23 2.5 7503 552 6951 0.160 60 2.86 2.2 7972 662 7310 0.168 70 2.62 2.0 8520 773 7748 0.178 80 2.38 1.8 8846 883 7962 0.183 90 2.22 1.7 9282 994 8289 0.190 100 2.05 1.6 9524 1104 8420 0.193 110 1.93 1.5 9863 1214 8649 0.199 120 1.80 1.4 10035 1325 8710 0.200 130 1.60 1.2 9663 1435 8228 0.189 140 1.40 1.1 9106 1546 7560 0.174 150 1.20 0.9 8362 1656 6706 0.154 160 1.15 0.9 8548 1766 6782 0.156 170 1.10 0.9 8688 1877 6811 0.156 180 1.05 0.8 8781 1987 6793 0.156 Required Storage Volume: 8710 ft3 0.200 acre-ft STAGE - STORAGE TABLE (100-YEAR) LOCATION: Raw Urth Designs PROJECT NO: 177-09 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/1/2008 100 yr Detention Volume Required = 0.200 Water Quality Volume Required = 0.000 Total Volume Required= 0.200 Surface Incremental Total Stage Area Storage Storage (ft) (ft2) (ac-ft) (ac-ft) 4768.80 0 4769.0 761 0.001 0.001 4770.0 1,695 0.027 0.029 4771.0 4,321 0.067 0.095 100 yr WSEL 4771.80 7,253 0.104 0.200 4772.0 8,009 0.139 0.235 4772.3 9,337 0.060 0.294 Detention Pond Outlet Sizing (100 yr event) LOCATION: Raw Urth Designs PROJECT NO: 177-09 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/12/2015 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 = 0.18 cfs outlet pipe dia = D = 12.0 in Invert elev. = 4768.80 ft Eo = 4768.88 ft h = 4771.8 ft - 100 yr WSEL Co = 0.62 solve for effective area of orifice using the orifice equation Ao = 0.021 ft2 = 3.1 in2 orifice dia. = d = 1.97 in Check orifice discharge coefficient using Figure 5-21 (Hydraulic Engineering ) d / D = 0.16 kinematic viscosity, u = 1.22E-05 ft2/s Reynolds no. = Red = 4Q/(pdu) = 1.14E+05 Co = (K in figure) = 0.62 check Use d = 1.95 in A o = 0.021 ft 2 = 2.99 in 2 Q max = 0.18 cfs Emergency Overflow Spillway Sizing LOCATION: Raw Urth Designs PROJECT NO: 177-09 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) = 6.2 cfs Spill elev = 4971.80 ft 100 yr WSEL = 4971.8 ft Top of berm elev.= 4972.30 Weir length required: L = 18 ft Use L = 20 ft v = 0.89 ft/s D APPENDIX D BMP SCHEDULE & COST ESTIMATE New Impervious Area 25689 sq. ft. Required Minimum Impervious Area to be Treated (50%) 12845 sq. ft. Impervious Area Treated by LID Treatment Method #1 (LID swale with underdrain) 6368 sq. ft. Impervious Area Treated by Porous Pavement 5714 sq. ft. Total Impervious Area Treated (47%) 12082 sq. ft. New Pavement Area 12010 sq. ft. Required Minimum Area of Porous Pavement (25%) 3003 sq. ft. Area of Paver Section A 3047 sq. ft. Run‐on area for Paver Section A 2667 sq. ft. Total Porous Pavement Area (25%) 3047 sq. ft. Raw Urth LID Table Project: Disturbed Acres: 0.90 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 730 $3.00 $2,190.00 each 15 $85.00 $1,275.00 each 1 $1,500.00 $1,500.00 each 1 $1,200.00 $1,200.00 Sub-Total: $6,165.00 1.5 x Sub-Total: $9,247.50 Amount of security: $9,247.50 Total Acres x Price/acre: $1,080.00 $1,200.00 Sub-Total: $1,080.00 1.5 x Sub-Total: $1,620.00 Amount to Re-seed: $1,620.00 Minimum escrow amount: $3,000.00 Erosion Control Escrow: $9,247.50 Miniumum Escrow Amount Raw Urth Designs 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 Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence Concrete Washout Reseeding Amount 5/12/2015 3:13 PM N:\177-09 Raw Urth\drainage\Example Escrow.xls E APPENDIX E FIGURES AND TABLES 33 (11) Section 4.0 is amended to read as follows: 4.0 Intensity-Duration-Frequency Curves for Rational Method: The one-hour rainfall Intensity-Duration-Frequency tables for use the Rational Method of runoff analysis are provided in Table RA-7 and in Table RA-8. Table RA-7 -- City of Fort Collins Rainfall Intensity-Duration-Frequency Table for Use with the Rational Method (5 minutes to 30 minutes) 2-Year 10-Year 100-Year Duration (min) Intensity (in/hr) Intensity (in/hr) Intensity (in/hr) 5 2.85 4.87 9.95 6 2.67 4.56 9.31 7 2.52 4.31 8.8 8 2.4 4.1 8.38 9 2.3 3.93 8.03 10 2.21 3.78 7.72 11 2.13 3.63 7.42 12 2.05 3.5 7.16 13 1.98 3.39 6.92 14 1.92 3.29 6.71 15 1.87 3.19 6.52 16 1.81 3.08 6.3 17 1.75 2.99 6.1 18 1.7 2.9 5.92 19 1.65 2.82 5.75 20 1.61 2.74 5.6 21 1.56 2.67 5.46 22 1.53 2.61 5.32 23 1.49 2.55 5.2 24 1.46 2.49 5.09 25 1.43 2.44 4.98 26 1.4 2.39 4.87 27 1.37 2.34 4.78 28 1.34 2.29 4.69 29 1.32 2.25 4.6 30 1.3 2.21 4.52 34 Table RA-8 -- City of Fort Collins Rainfall Intensity-Duration-Frequency Table for Use with the Rational Method (31 minutes to 60 minutes) 2-Year 10-Year 100-Year Duration (min) Intensity (in/hr) Intensity (in/hr) Intensity (in/hr) 31 1.27 2.16 4.42 32 1.24 2.12 4.33 33 1.22 2.08 4.24 34 1.19 2.04 4.16 35 1.17 2.0 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.87 39 1.09 1.86 3.8 40 1.07 1.83 3.74 41 1.05 1.8 3.68 42 1.04 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1.56 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.1 54 0.88 1.5 3.07 55 0.87 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.84 1.43 2.92 59 0.83 1.42 2.89 60 0.82 1.4 2.86 36 RAINFALL INTENSITY-DURATION-FREQUENCY CURVE 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 STORM DURATION (minutes) RAINFALL INTENSITY (inches/hour) 2-Year Storm 10-Year Storm 100-Year Storm Figure RA-16 City of Fort Collins Rainfall Intensity-Duration-Frequency Curves (13) Section 5.0 is deleted in its entirety. (14) Section 6.0 is deleted in its entirety. (15) Section 7.0 is deleted in its entirety. (16) Section 7.1 is deleted in its entirety. (17) Section 7.2 is deleted in its entirety. (18) Section 7.3 is deleted in its entirety. (19) Section 8.0 is deleted in its entirety. (20) Table RA-1 is deleted in its entirety. 40 Table RO-10 Rational Method Minor Storm Runoff Coefficients for Zoning Classifications Description of Area or Zoning Coefficient R-F 0.3 U-E 0.3 L-M-In 0.55 R-L, N-C-L 0.6 M-M-N, N-C-M 0.65 N-C-B 0.7 Business: C-C-N, C-C-R, C-N, N-C, C-S 0.95 R-D-R, C-C, C-L 0.95 D, C 0.95 H-C 0.95 C-S 0.95 Industrial: E 0.85 I 0.95 Undeveloped: R-C, T 0.2 P-O-L 0.25 For guidance regarding zoning districts and classifications of such districts please refer to Article Four of the City Land Use Code, as amended. 41 Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Character of Surface Runoff Coefficient Streets, Parking Lots, Drives: Asphalt 0.95 Concrete 0.95 Gravel 0.5 Roofs 0.95 Recycled Asphalt 0.8 Lawns, Sandy Soil: Flat <2% 0.1 Average 2 to 7% 0.15 Steep >7% 0.2 Lawns, Heavy Soil: Flat <2% 0.2 Average 2 to 7% 0.25 Steep >7% 0.35 (4) A new Section 2.9 is added, to read as follows: 2.9 Composite Runoff Coefficient Drainage sub-basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: ( ) t n i i i A C A C ∑ = = 1 * (RO-8) Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (Ai) Ai = Area of Surface with Runoff Coefficient of Ci, acres or feet2 n = Number of different surfaces to be considered At = Total Area over which C is applicable, acres or feet2 (5) A new Section 2.10 is added, to read as follows: 42 2.10 Runoff Coefficient Adjustment for Infrequent Storms The runoff coefficients provided in tables RO-10 and RO-11 are appropriate for use with the 2-year storm event. For storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapo-transpiration and other losses that have a proportionally smaller effect on storm runoff. This adjustment is applied to the composite runoff coefficient. These frequency adjustment factors are found in Table RO-12. Table RO-12 Rational Method Runoff Coefficients for Composite Analysis Storm Return Period (years) Frequency Factor Cf 2 to 10 11 to 25 26 to 50 51 to 100 1.00 1.10 1.20 1.25 Note: The product of C times Cf cannot exceed the value of 1, in the cases where it does a value of 1 must be used (6) Section 3.1 is deleted in its entirety. (7) Section 3.2 is deleted in its entirety. (8) Section 3.3 is deleted in its entirety. (9) A new Section 4.3 is added, to read as follows: 4.3 Computer Modeling Practices (a) For circumstances requiring computer modeling, the design storm hydrographs must be determined using the Stormwater Management Model (SWMM). Basin and conveyance element parameters must be computed based on the physical characteristics of the site. (b) Refer to the SWMM Users’ Manual for appropriate modeling methodology, practices and development. The Users’ Manual can be found on the Environmental Protection Agency (EPA) website (http://www.epa.gov/ednnrmrl/models/swmm/index.htm). (c) It is the responsibility of the design engineer to verify that all of the models used in the design meet all current City criteria and regulations. 4.3.1 Surface Storage, Resistance Factors, and Infiltration Table RO-13 provides values for surface storage for pervious and impervious surfaces and the infiltration rates to be used with SWMM. Table RO-13 also lists the appropriate infiltration decay rate, zero detention depth and resistance factors, or Manning’s “n” values, for pervious and impervious surfaces to be used for SWMM modeling in the city of Fort Collins.