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HomeMy WebLinkAboutAWEIDA - PDP - PDP180008 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTi 4101 South Taft Hill Road FORT COLLINS PRELIMINARY DRAINAGE REPORT Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 Prepared for: Aweida Properties, Inc August 22, 2018 Project Number 385-01 ii August 22, 2018 Wes Lemarque City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Preliminary Drainage Report for 4101 South Taft Hill Road Dear Wes, I am pleased to submit for your review and approval, this Preliminary Drainage Report for a multi-use building at 4101 South Taft Hill Road in Fort Collins. 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 .............................................................................................2 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations ..............................................................................................................2 3.2 Four Step Process to Minimize Adverse Impacts of Urbanization ..........................2 3.3 Development Criteria Reference and Constraints ...................................................3 3.4 Hydrologic Criteria ..................................................................................................4 3.5 Hydraulic Criteria ....................................................................................................4 4. DRAINAGE FACILITY DESIGN 4.1 General Concept ......................................................................................................4 4.2 Specific Flow Routing .............................................................................................4 4.3 Drainage Summary ..................................................................................................5 5. CONCLUSIONS 5.1 Compliance with Standards ....................................................................................6 5.2 Drainage Concept ....................................................................................................6 6. REFERENCES ....................................................................................................................7 APPENDICES A Vicinity Map B Hydrologic Computations C Detention System Sizing Calculations E BMP Schedule and Cost Estimate F Erosion & Sediment Control Report 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location This site is located on the southwest corner of the intersection of West County Road 38E and South Taft Hill Road in the Southeast Quarter of Section 33, 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 and east by existing arterial rights of ways and on the west and south by existing residences. 1.2 Description of Property The entire project consists of approximately 0.35 acres. This site was previously unplatted and was used for a single residence with a gravel driveway. There are some older trees on site that will be removed and volunteer grasses and weeds cover the site. All of the surrounding area is large lot residential county development and are not part of a subdivision. There are no major drainageways, facilities or easements within or adjacent to the site. Proposed development on-site will include a single multi use building, a private drive with access to both CR 38E and Taft Hill Road, a parking area and sidewalks. Existing drainage patterns will be altered to route flow to a proposed underground detention system in the west portion of the site under the drive which will release into the existing storm system near the northeast corner of the site. Irrigation of the site will be through a drip system connected to the potable water system. 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description The proposed development lies within the Mail Creek Drainage Basin. The basin generally drains from west to east to the confluence of Mail Creek and Fossil Creek, and ultimately to Fossil Creek Reservoir. Three irrigation canals intercept stormwater to transport it out of the basin, but runoff spills into the basin when their capacity is exceeded. There are no irrigation facilities within this Basin which will influence or be 2 influenced by the local drainage design. This site is not within a FEMA defined floodway or floodplain. No previous drainage studies have been completed for this site. Stormwater detention and water quality enhancement are required for this site. 2.2 Sub-basin Description Runoff from this site currently flows to the existing streets on the north and east. Currently, there are small roadside ditches and driveway culverts that collect the water from this site. Both adjacent properties direct their runoff to the adjacent street and no runoff from those sites will impact this site. With the proposed drainage concept for this site, the runoff from the site will flow to an underground detention system located under the access drive on the west side of the building. This detention facility will release the runoff at a composite historic rate into the existing storm system to the north of the site. Curb & gutter will be added to the adjacent streets therefore street runoff will no longer impact this site. 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. 3.2 Four Step Process to Minimize Adverse Impacts of Urbanization Because this site is small, the ability to disconnect impervious areas is difficult. The site does not benefit from disconnecting the impervious areas therefore this has not been accomplished on this site. Step 1. Employ Runoff Reduction Practices – reduction of runoff peaks, volumes, and pollutant loads as the site is developed by implementing Low-Impact Development (LID) strategies including:  Increase time of concentration by routing flows along the drive aisles and increasing the length of the flow path.  Routing runoff from the proposed site into the underground detention/water 3 quality to promote infiltration and biological uptake.  Routing flows through filter material in the underground detention to increase time of concentration, promote infiltration and provide initial water quality. Step 2. Implement BMPs That Provide a Water Quality Capture Volume with Slow Release - The efforts outlined in Step 1 will facilitate the reduction of runoff. Runoff will be routed through the rain gardens and then to an underground detention storage facility that will provide attenuation prior to release into the public storm system to reduce the amount of runoff generated from the site through infiltration, and also treat the runoff prior to releasing it from the site. Step 3. Stabilize Streams - There are no major drainageways in or near this site therefore Step 3 it not directly applicable this project. However, this project will pay stormwater development fees and monthly stormwater utility fees which contribute to the City’s ongoing efforts to attain stream stability where and as needed. Step 4. Implement Site Specific and Other Source Control BMPs - This step applies to covering storage/handling areas and spill containment and control. Vehicle maintenance and washing during construction will be completed off site to prevent potential spills of vehicle fluids. Any handling of chemicals will be completed inside the building and will be handled per the applicable MSDS (material safety data sheet). Spills will be contained immediately and cleaned up using appropriate absorption materials. 3.3 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the Mail Creek Drainage Basin and the City of Fort Collins Stormwater Department. There are no previous drainage studies for this or the adjacent sites. This site is highly constrained due to the small size of the site and the requirement for dedication of additional right of way for the adjacent arterial streets. Stormwater runoff detention is required for this site with on-site detention. The release rate from the site will be at the calculated composite release rate of 0.60 cfs. 3.4 Hydrologic Criteria 4 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 predetermined composite release rate of 0.60 cfs. The FAA method for detention sizing was utilized to determine the required volume. Refer to the detention calculations included in Appendix C of this report. 3.5 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 underground detention area. A proposed 12” storm pipe will convey the detained runoff from the site to an existing manhole located on the northwest corner of Taft Hill Road and CR 38E. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The runoff from this site will surface flow to two on site low points on the entry drives. The runoff will then enter the underground detention and infiltrate into the subgrade in the water quality chambers. The flow will be attenuated and the detained runoff will discharge into the proposed inlet and storm pipe located in the northeast corner of the site on CR 38E. 4.2 Specific Flow Routing With this design, the site has been considered as a single basin which described in the following paragraph. Basin 1 contains the entire site including the building, parking lot, sidewalks, entrance drives and underground detention. The runoff from this basin will flow north to one low point in the entrance drive from CR 38E and will flow east to another low point in the access drive from Taft Hill Road. Flow from both low points will flow to the underground detention via storm pipes. From here, the attenuated flow will release into the existing storm system at a rate of 0.60 cfs. 5 The underground detention chamber system will release the detained runoff from the site at the rate of 0.60 cfs. This rate was calculated by determining the area of the site that is historically impervious and using the 2 year historic runoff then determining the area of the site that is historically pervious and using the 100 year historic runoff. The total of these 2 historic values was used as the allowable release rate from the detention storage. This totals an allowable release rate of 0.60 cfs. A drainage easement will be dedicated on the plat to encompass the detention storage system. Pipes are also shown on the plan to convey runoff from the west and the south to the existing storm system at the northwest corner of the intersection of Taft Hill Road and CR 38E. These pipes will fall within the right of ways and will not require separate drainage easements. 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 LID (Low Impact Development) volume in the chambers in addition to the detention volume. Refer to the end of Appendix E for a table indicating the sizing of the required volume for LID treatment. All drainage facilities proposed with this project, including the underground detention chambers, drain basins, inlets and storm pipe are private and will be owned and maintained by the property owner. The pipes and the storm manholes in the right of way will be owned and maintained by the City of Fort Collins. 6 5. CONCLUSIONS 5.1 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”. 5.2 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 underground detention system. Conveyance elements exist in County Road 36E 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. 7 6. 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. APPENDIX A VICINITY MAP B APPENDIX B HYDROLOGIC COMPUTATIONS North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: 4101 South Taft Hill Road PROJECT NO: 385-01 COMPUTATIONS BY: ppk DATE: 6/12/2018 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 0.34 14956 2660 5645 1787 0 4,864 65% 0.71 Total to pond 0.34 14,956 2,660 5,645 1,787 0 4,864 65% 0.71 Historic landscape 0.23 9,927 9,927 0% 0.20 Historic hardscape 0.12 5,029 1,370 1,572 690 1,397 0 80% 0.82 Historic Site 0.34 14,956 1,370 1,572 690 1,397 9,927 27% 0.41 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: 4101 South Taft Hill Road PROJECT NO: 385-01 COMPUTATIONS BY: ppk DATE: 6/12/2018 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 0.34 0.71 19 2.0 2.5 115 0.1 0.016 0.5 3.89 6.3 134 10.7 6.3 Historic landscape 0.23 0.20 158.5 2.2 15.7 0 1.0 0.020 1.6 0.00 15.7 158.5 10.9 10.9 Historic hardscape 0.12 0.82 158.5 2.2 4.8 0 1.0 0.020 1.6 0.00 4.8 158.5 10.9 5.0 Historic Site 0.34 0.41 158.5 2.2 12.0 0 1.0 0.020 1.6 0.00 12.0 158.5 10.9 10.9 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: 4101 South Taft Hill Road PROJECT NO: 385-01 COMPUTATIONS BY: ppk DATE: 6/12/2018 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 0.34 0.71 0.88 19 2.0 1.4 115 0.1 0.016 0.5 3.89 5.2 134 10.7 5.2 Historic landscape 0.23 0.20 0.25 158.5 2.2 14.8 0 1.0 0.020 1.6 0.00 14.8 158.5 10.9 10.9 Historic hardscape 0.12 0.82 1.00 158.5 2.2 1.7 0 1.0 0.020 1.6 0.00 1.7 158.5 10.9 5.0 Historic Site 0.34 0.41 0.51 158.5 2.2 10.2 0 1.0 0.020 1.6 0.00 10.2 158.5 10.9 10.2 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: 4101 South Taft Hill Road PROJECT NO: 385-01 COMPUTATIONS BY: ppk DATE: 6/12/2018 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 0.34 0.71 6.3 2.64 0.6 0.6 Historic landscape 0.23 0.20 10.9 2.14 0.1 0.10 Historic hardscape 0.12 0.82 5.0 2.14 0.2 0.20 Allowable release rate Historic Site 0.34 0.41 10.9 2.14 0.3 0.30 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: 4101 South Taft Hill Road PROJECT NO: 385-01 COMPUTATIONS BY: ppk DATE: 6/12/2018 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 0.34 0.88 5.2 9.81 3.0 3.0 Historic landscape 0.23 0.25 10.9 7.63 0.43 0.4 Allowable release rate Historic hardscape 0.12 1.00 5.0 7.63 0.88 0.9 Historic Site 0.34 0.51 10.2 7.63 1.34 1.3 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 SIZING CALCULATIONS MINIMUM DETENTION VOLUME REQUIRED FAA METHOD (100-YEAR) LOCATION: 4101 South Taft Ave PROJECT NO: 385-01 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/22/2018 Equations: A trib. To pond = 0.34 acre QD = CiA C100 = 0.88 Vi = T*CiA = T*QD Developed C*A = 0.3 acre Vo =K*QPO*T QPO = 0.60 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 3.0 893 180 713 0.016 10 7.72 2.3 1386 360 1026 0.024 20 5.60 1.7 2011 720 1291 0.030 30 4.52 1.4 2434 1080 1354 0.031 40 3.74 1.1 2686 1440 1246 0.029 50 3.23 1.0 2899 1800 1099 0.025 60 2.86 0.9 3081 2160 921 0.021 70 2.62 0.8 3292 2520 772 0.018 80 2.38 0.7 3418 2880 538 0.012 90 2.22 0.7 3587 3240 347 0.008 100 2.05 0.6 3680 3600 80 0.002 110 1.93 0.6 3811 3960 -149 -0.003 120 1.80 0.5 3878 4320 -442 -0.010 130 1.60 0.5 3734 4680 -946 -0.022 140 1.40 0.4 3519 5040 -1521 -0.035 150 1.20 0.4 3231 5400 -2169 -0.050 160 1.15 0.3 3303 5760 -2457 -0.056 170 1.10 0.3 3357 6120 -2763 -0.063 180 1.05 0.3 3393 6480 -3087 -0.071 Required Storage Volume: 1354 ft3 <-- To column 9 0.031 acre-ft Number of Chambers req'd = 1354 cf / 45.9 cf = 29.51 = 30 Chambers  To column 10 WATER QUALITY POND SIZE LOCATION: 4101 South Taft Ave PROJECT NO: 385-01 COMPUTATIONS BY: PPK SUBMITTED BY: North Star Design, Inc. DATE: 8/22/2018 From Urban Storm Drainage Criterial Manual Use: 12-hour drain time a=0.80 Required Storage Water Quality Capture Volume = WQCV = [required storage] * [Area] 12 Trib. % Imperv. Req. Storage WQCV WQCV WQ Flow area from Fig. EDB-2 (To column 1) (To column 2) (ac) (in. of runoff) (ac-ft) (cu-ft) (cfs) POND 0.34 69 0.271 0.008 334 0.33 For all Flow to the Underground Storage Flow (WQ)= C*i/2*A= 0.71 * 2.64/2 * 0.35 = 0.33 cfs All Chambers are SC-740 Release rate = 0.0236 cfs Chamber volume = 45.9 cf Chamber volume with aggregate = 74.9 cf Minimum No. Chambers req'd = 401 cf / 74.9 cf = 4.46 = 5 Chambers Total release rate = 5 * 0.0236 = 0.12 cfs a * [0.91 (i 3) - 1.19 (i 2) + 0.78(i)] 12345678910 11 12 13 1415 Req'd Flow Chamber Chamber Chamber Ch. Volume Min # of Total Req'd Volume Min # of # of Chambers Storage Provided Storage Provided # of Isolator Depth to WQ Volume WQ Type Release Volume w/ Aggregate Chambers Release Rate FAA Method Chambers Req'd in Req'd Chambers in Chambers & Agg Chambers achieve (cf) (cfs) (cfs) (cf) (cf) incl. aggregate (cfs) (cf) chamb. only (Greater of Column 7 (cf) (cf) Provided Req'd (Column 1/ (Column 4* (Column 9/ or Column 10) (Column 5 * Column 11) (Column 6 * Column 11) Volume Column 6) Column 7) Column 5) (in) 334 0.33 SC-740 0.0236 45.9 74.9 5 0.12 1354 30 30 1377 2247 10 12.6  StormTec Chamber Summary Table Information provided by StormTec E APPENDIX E BMP SCHEDULE & COST ESTIMATE Project: Disturbed Acres: 0.35 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 426 $3.00 $1,278.00 each 5 $85.00 $425.00 each $180.00 $0.00 each 1 $255.00 $255.00 each 1 $1,500.00 $1,500.00 each 1 $1,200.00 $1,200.00 Sub-Total: $4,658.00 1.5 x Sub-Total: $6,987.00 Amount of security: $6,987.00 Total Acres x Price/acre: $420.00 $1,200.00 Sub-Total: $420.00 1.5 x Sub-Total: $630.00 Amount to Re-seed: $630.00 Minimum escrow amount: $3,000.00 Erosion Control Escrow: $6,987.00 Miniumum Escrow Amount 4101 South Taft Hill Road 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 Final Escrow Amount Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence Concrete Washout Reseeding Amount Rock Berm Inlet Protection 6/12/2018 2:22 PM N:\385-01 South Taft site\drainage\FC Escrow.xls F APPENDIX F EROSION & SEDIMENT CONTROL REPORT G EROSION & SEDIMENT CONTROLS 1. Written Analysis An Erosion and Sediment Control Plan is included herewith. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 - Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. Grading and Erosion Control Notes can be found on Sheet 2 of the Utility Plans. In addition to this report and the plan sheets, the Contractor shall be aware of and adhere to the applicable requirements outlined all Development Agreements pertaining to this property. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division - Stormwater Program, before commencing any earth disturbing activities. The Contractor shall also develop a comprehensive Storm Water Management Plan (SWMP) conforming to applicable requirements including descriptions of the ongoing activities, inspections and maintenance of construction BMPs. H • The site is approximately .35 acres all of which will undergo earthmoving operations. The existing site has existing ground cover (volunteer grasses and weeds) on approximate 45% - 50% of the site as the site has been historically used for storage of materials and vehicles for adjacent properties. Runoff from this site currently discharges to Conifer Street on the south side of the site. With the proposed development, this site will also be sloped to drain to the southeast. The runoff will then enter the proposed detention pond and be released to the existing storm system in Conifer Street as the historic flow path dictates. The soils on this site are classified by the USGS Soil Survey as Caruso Clay Loam (3%) which is classified in the hydrologic group D and Nunn Clay Loam (97%) which is classified in the hydrologic group C. The D soils are described as having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. The rainfall erodibility is deemed to be moderate and the wind erodibility is deemed to be moderate to high. The C soils are described as having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. The rainfall erodibility is deemed to be moderate and the wind erodibility is deemed to be moderate to high. The site is surrounded by developed sites including streets, buildings 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 proposed bio 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 concrete sidewalk chase and on the concrete pans. 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 I 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 pavement, recycled asphalt pavement 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 for the timing of the construction phases and the sequential installation of all BMP phasing for this site. Refer to the Appendix for the Erosion Control Surety calculations. J 2. SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: K 3. Identification and location of all potential pollution sources Potential Pollutant Source Activity Potential Pollutant Generated Applicable to this project Control Measure Disturbed Areas Sediment X Silt Fence, Rock Socks Soil stockpiles Sediment X Silt Fence, Rock Socks Travel to adjacent public streets Tracked sediment X Tracking Pad, street sweeping Contaminated soils Sediment, chemicals Possible Remove contaminated soils from site ** Loading and unloading chemicals Chemicals Unloading of building materials Trash, debris, track out X Trash dumpsters, Waste Management Firm ** Outdoor storage of chemicals Chemicals On site equipment maintenance Oil, grease On site equipment fueling Diesel, gasoline X Containment berm ** Dust generating activities Particulates, sediment X Water truck Use of fertilizer, pesticides, herbicides Fertilizer, pesticides Use of detergents, solvents, oils Detergents, solvents, oil X If spilled, remove contaminated soils from site ** Waste Chemicals, trash, debris X Waste Management Firm Concrete wash Concrete, sediment, wash water X Remove hardened concrete, dispose of offsite ** 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 Waste Management Firm ** Refer to Section 5 for additional Materials Handling & Spill Prevention BMP 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. L 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. 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. All BMP's shall be installed per the details shown on the construction plan set. Temporary & Permanent Structural BMP’s: Refer to table in Section 3 for purpose of Structural BMP noted below Structural BMP Approximate location on site Applicable to this Project Silt Fence Site perimeter, refer to site map X Rock Socks At existing sidewalk culverts, in existing gutters, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond Pipe slope drains Geogrid Inlet/outlet protection Culverts Refer to site map X 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 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 M 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. 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. 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: Refer to table in Section 3 for purpose of Non Structural BMP noted below 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 east boundary of site X Minimization of site disturbance Mulch Seed & mulch stockpiles after 30 days Preservation & protection of existing vegetation & trees east 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 N 5. Material Handling & Spill Prevention Refer to table in Section 3 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 B) Dedicated Asphalt or Concrete Batch Plant: Not proposed with this development C) 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. D) 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 O management company. Concrete waste will be allowed to harden and then will be removed from site. No vehicle or equipment 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. E) 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. 6. BMP Implementation A) 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 E for the BMP schedule and estimated costs. B) 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 P 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. 7. Soil Amendments, Permanent Seeding & Mulching A) Soil Amendments Soil in the Rain Gardens shall be amended per the City of Fort Collins Bioretention Sand Media Specifications found at: http://www.fcgov.com/utilities/img/site_specific/uploads/Bioretention_Sand_Media_Specs.pdf Soil treatment in the detention area will be to spread imported or stockpiled topsoil to a minimum depth of four inches over areas to be planted. B) Permanent Seeding The following seed mix shall be applied at the rates indicated in the bioswale and in the water quality pond. Other landscaped areas on site shall be treated per the landscape plan. Mulch shall be applied after seeding as the notes indicate below. Drill seed specified mix in two passes, each at right angles to each other. Drill half of the seed in each pass. If areas are too wet or steep to drill seed, broadcast seed in two Q opposite directions. Restore fine grade after seeding, and cover seed to depth of 1/4 inch by raking or dragging. Firm seeded areas with a roller weighing maximum of 100 lbs. per foot of width. Ground cover shall be considered established when 70% of the seed has been germinated. At the point that the seed is considered established, the temporary erosion control measures may be removed. C) Mulching All planted areas should be mulched preferably immediately following planting, but in no case later than 14 days from planting. Mulch conserves water and reduces erosion. The most common type of mulch used is hay or grass that is crimped into the soil to hold it. However, crimping may not be practical on slopes steeper than 3:1. The following guidelines should be followed with mulching: • Only weed-free and seed-free straw mulch should be used (grass hay often contains weedy exotic species). Mulch should be applied at 2 tons/acre and adequately secured by crimping, tackifier, netting, or blankets. • Crimping is appropriate on slopes of 3:1 or flatter and must be done so as to tuck mulch fibers into the soil 3 to 4 inches deep. • Tackifier or netting and blankets anchored with staples should be used on slopes steeper than 3:1. • Hydraulic mulching may also be used on steep slopes or where access is limited. Wood cellulose fibers mixed with water at 2,000 to 2,500 pounds/acre and organic tackifier at 100 pounds per acre should be applied with a hydraulic mulcher.