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HomeMy WebLinkAboutSERIOUS TEXAS BARBECUE AT TIMBERLINE CENTER - MJA/FDP - FDP150017 - REPORTS - DRAINAGE REPORTJuly 15, 2015 Wes Lemarque City of Fort Collins Utilities 700 Wood Street Fort Collins, Colorado 80525 RE: Serious Texas Barbeque Timberline Center, Lot 1 Mr. Lemarque, This letter is to serve as an addendum to the drainage report prepared by North Star Design for the Timberline Center located west of Timberline Road in Fort Collins. This addendum applies to the proposed development location on Lot 1 which is intended to be a Serious Texas Barbeque restaurant. The Lot is located in Sub-basins 18, 19 and 20 which are described below. Sub-basin 18 contains the southwest corner of the Lot and will drain west into the shared entrance (with Big O Tires) into the private drive and then south to a sump inlet. Sub-basin 19 contains the northwest portion of the Lot and that will drain west into the private drive and then north to an existing curb cut and into the detention pond via a metal sidewalk culvert. Sub-basin 20 contains the east half of the lot and the detention pond located east of Lot 1. This has been designed to detain Basins 17 through 20 and release directly to the storm system in Timberline. In general, the site conforms to these basin delineations with small deviations. Basin 20 area is smaller by 2060 square feet, Basin 18 is smaller by 390 square feet and Basin 19 700 Automation Drive, Unit I Windsor, CO 80550 Phone: 970-686-6939 Fax: 970-686-1188 is larger by 2450 square feet. This causes the 100 year flow in Basin 20 to decrease from 7.6 cfs, (from the Big O Tire update) to 7.1 cfs, in Basin 18 to decrease from 6.0 cfs (from the Big O Tire update) to 5.9 cfs (equal to the original flow in Basin 18) and in Basin 19 to increase from 1.1 cfs to 1.6 cfs. The increased flow from Basin 19 will be conveyed in a 2’ curb opening and sidewalk culvert directly into the existing detention pond. This additional flow will not impact any other site and is offset by the decreased flow in Basin 20. Therefore there is no discernable impact to the detention pond and the calculations for the pond were not updated. This site is required to conform to the current LID standards for the City of Fort Collins. This requires that 25% of the proposed pavement be interlocking permeable pavers and that 50% of the site impervious be routed through an LID filtering device. Based on this criteria, this site is required to provide 2455 sf of pavers and have 7302 sf of imperviousness pass through an LID filter. As proposed, the site provides 2448 sf of pavers and routes approximately 7026 sf through an LID filter. See summary table included at the end of this letter update. The building does extend further north than originally planned for in the overall development which will require the owner to vacate a portion of the drainage easement for the detention pond. The 100 year high water elevation for this pond is 4940.30 which is achieved in the remaining drainage easement. The deck located on the east side of the building will be open underneath and the detention pond will be able to exist under the deck space. Therefore this deck will not impact the existing detention volume. The building floor elevation is set at 4943.5 which provides sufficient freeboard for the pond. The finished grade along the east side of the building (detention pond side) will be set at elevations which match the existing grade on site in order to not encroach on the existing volume of the pond. The imperviousness dictated in the Timberline Center drainage report will be met with this development and no additional on-site detention or runoff calculations will be required. Please contact me if you have questions or need additional information. Sincerely, Patricia Kroetch, P.E. North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (NEW IDF CURVE) (100-YEAR) LOCATION: Timberline Center - Revised for Serious Texas BBQ, Lot 1 PROJECT NO: 114-37 COMPUTATIONS BY: PPK DATE: 4/8/2015 100-yr storm, Cf = 1.25 0.234 DIRECT RUNOFF CARRY OVER 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) 18 18 0.61 0.97 5.0 9.95 5.9 5.9 Original Flow=5.9cfs 19 19 0.16 1.00 5.0 9.95 1.6 1.6 Original flow=1.1cfs 20 20 1.11 0.65 5.0 9.95 7.1 7.1 Original flow=7.9cfs Q = C iA Q = peak discharge (cfs) C = runoff coefficient I = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) NOTE: Intensity based on Figure 3-1, 1999 (Regional Analysis) Final Flow.xls Q100 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METHOD PEAK RUNOFF (NEW IDF CURVE) (10-YEAR) LOCATION: Timberline Center - Revised for Serious Texas BBQ, Lot 1 PROJECT NO: 114-37 COMPUTATIONS BY: PPK DATE: 4/8/2015 10-yr storm, Cf = 1.00 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Design Tributary A C Cf tc i Q (10) from Q (10) Q(10)tot Sub-basin (new) Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) 18 18 0.61 0.78 5.0 4.87 2.3 2.3 Original flow=2.3cfs 19 19 0.16 0.86 5.6 4.25 0.6 0.6 Original flow=0.4 cfs 20 20 1.11 0.52 5.0 4.87 2.8 2.8 Original flow=3.1cfs 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) NOTE: Intensity based on Figure 3-1, 1999 (Regional Analysis) Final Flow.xls Q10 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 LOCATION: Timberline Center - Revised for Serious Texas BBQ, Lot 1 PROJECT NO: 114-37 COMPUTATIONS BY: PPK DATE: 4/8/2015 Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria Recommended % Impervious from Urban Storm Drainage Criteria Manual Runoff % coefficient Impervious C Streets, parking lots (asphalt): 0.95 100 Sidewalks (concrete): 0.95 96 Roofs: 0.95 90 Lawns (flat <2%, heavy soil): 0.20 0 SUBBASIN TOTAL TOTAL ROOF PAVED SIDEWALK LANDSCAPE RUNOFF % DESIGNATION AREA AREA AREA AREA AREA AREA COEFF. Impervious REMARKS (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) 18 0.61 26,420 4,590 15,292 525 6,013 0.78 75 19 0.16 7,120 0 5,685 590 845 0.86 88 20 1.11 48,190 14,054 4,880 1,540 27,716 0.52 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 RUNOFF COEFFICIENTS & % IMPERVIOUS Final Flow.xls Cval STORMWATER MANAGEMENT CONTROLS 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 infiltration rate when thoroughly wet and the hazard of water erosion is moderate and the hazard of wind erosion is low. The site is surrounded by lots undergoing development, existing development to the north and existing public and private streets to the east and west. A detention pond exists on the north and east sides of the lot. The construction shall utilize silt fence around the perimeter to control sediment transport from rainfall and from wind. Rock socks will be utilized in the existing detention pond, around existing inlets and in the newly constructed concrete channel to capture sediments that are not fully contained by the silt fence placement. 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 been located on the site map but may be located as construction dictates 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 the erosion control plan for this site for the timing of the construction phases and the sequential installation of all BMP phasing for this site. Refer to the end of this section for the Erosion Control Surety calculations. 2. SWMP contact information Permit holder: Name: Address: Phone Number: Email Address: Appointed agent: Name: Address: Phone Number: Email Address: 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 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. 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 new sidewalk culverts, at existing inlet, refer to site map X Earthen diversion dams Vegetated swales Rock Berm East boundary of site, in existing det pond X Pipe slope drains Geogrid Inlet/outlet protection Culverts Riprap Erosion control mats Inlet protection Vehicle Tracking Control Pad At site entrances, 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. 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 East boundariyof 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 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 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 Erosion Control Plan 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: 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. 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 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 New Impervious Area 14603 sq. ft. Required Minimum Impervious Area to be Treated 7301.5 sq. ft. Impervious Area Treated by Permeable Pavers 7026 sq. ft. Total Impervious Area Treated 7026 sq. ft. New Pavement Area 9822 sq. ft. Required Minimum Area of Porous Pavement 2455.5 sq. ft. Area of Paver Section #1 1355 sq. ft. Run‐on area for Paver Section #1 (up to 3:1 is permited) 3575 sq. ft. Area of Paver Section #2 1093 sq. ft. Run‐on area for Paver Section #2 (up to 3:1 is permited) 3451 sq. ft. Total Porous Pavement Area 2448 sq. ft. Serious Texas Barbeque LID Table Project: Disturbed Acres: 0.55 EROSION CONTROL BMPs Units Estimated Quantity Unit Price Total Price L.F. 585 $3.00 $1,755.00 each 12 $85.00 $1,020.00 each 1 $230.00 $230.00 each 1 $1,500.00 $1,500.00 each 1 $1,200.00 $1,200.00 each 3 $90.00 $270.00 Sub-Total: $5,975.00 1.5 x Sub-Total: $8,962.50 Amount of security: $8,962.50 Total Acres x Price/acre: $660.00 $1,200.00 Sub-Total: $660.00 1.5 x Sub-Total: $990.00 Amount to Re-seed: $990.00 Minimum escrow amount: $3,000.00 Erosion Control Escrow: $8,962.50 Erosion and Sediment Control Escrow/Security Calculation for The City of Fort Collins BMP Amount Silt Fence Concrete Washout Inlet protection Reseeding Amount Rock Berm Miniumum Escrow Amount Serious Texas Barbeque, Lot 1 Timberline Center 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 7/15/2015 4:07 PM N:\347-06 Serious Texas BBQ\drainage\EC Escrow.xls