The URL can be used to link to this page

Home My WebLink AboutNIX FARM NATURAL AREAS FACILITY - MAJOR AMENDMENT - MJA160004 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT1218 W. ASH, STE. A, WINDSOR, COLORADO 80550 TEL. 970.674.3300 – FAX 970.674.3303 December 22, 2016 Mr. Wes Lamarque Fort Collins Utilities – Stormwater 700 Wood Street Fort Collins, CO 80522 Re: Nix Farm Natural Areas Facility – Major Amendment 2016 Final Storm Drainage Letter Dear Wes, Please accept the following letter on behalf of the City of Fort Collins department of Natural Areas for the proposed facility improvements demonstrating the site’s ability to comply with the City’s stormwater requirements. INTRODUCTION The Nix Farm Natural Areas Facility – Major Amendment 2016 proposes to construct a new vehicle storage building, expand the existing maintenance yard and provide a total of 14 additional visitor/employee parking stalls at their existing Nix Farm Natural Area Campus. The site is located north of the Burlington Northern Railroad Tracks, west of Timberline Road, south of the Cache La Poudre River, and east of Lemay Avenue. The project is located in a portion of Section 18, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. A vicinity map is attached for reference. The site consists of approximately 27.48 acres, however the proposed improvements will disturb approximately 1.5 acres. The proposed improvements will be completed in one phase of construction. As part of the design efforts, a Master Plan study was conducted. For the purposes of this drainage study, the Master Plan was referenced to review the potential impacts on the existing water quality pond. EXISTING CONDITIONS The project site is located within the Spring Creek Drainage Basin and detention is not required. An existing water quality pond is located southeast of the maintenance yard. The design of the existing water quality pond is described within the “Final Drainage and Erosion Control Report – Nix Farm Natural Areas Facility”, prepared by JR Engineering, dated June 8, 2001. This report was updated with the construction of the Natural Areas office building and is described within the “Final Drainage and Erosion Control Report for Nix Farm Natural Areas Facility – Major Amendment”, prepared by Interwest Consulting Group, dated May 13, 2013. In reference to the most recent 2013 drainage report, the site area draining to the water quality pond is approximately 21% impervious (Basins 102, 103, and 105). Portions of the project are not located within a FEMA mapped 100-yr floodplain though no improvements are proposed within or that would affect the 100-yr floodplain. Nix Farm Natural Areas Facility - Final Storm Drainage Letter December 22, 2016 Page 2 of 4 PROPOSED DEVELOPMENT The project will construct a 5,000 sqft vehicle storage building south of the existing maintenance building and construct an expansion along the west side of the existing maintenance building. The maintenance yard will be expanded to the east and south, and additional parking will be constructed along the north and west drive isles. The project is required to provide water quality capture volume and implement Low Impact Development (LID) techniques for additional water quality enhancement. The previous basin boundaries were referenced and adjusted for the proposed improvements. For the purposes of this report and the adjusted basin boundaries, Basins 102, 103, 105, and 106 were reviewed. The proposed improvements occur within Basins 102, 103, and 105. Basin 106 was reviewed due to the reduction in basin area and is mostly unimproved native grassland. Basin 102 consists of a portion of the existing office building, associated parking and walkways, and half of the western access drive to the maintenance yard. This basin is unchanged with the proposed improvements and is included in the analysis of the water quality pond. Basin 102 is approximately 0.41 acres and 47.1% impervious and runoff is conveyed to the water quality pond via an existing 18” culvert and a proposed swale. Basin 103 consists of north portion of the existing maintenance building, the northern portion of the maintenance yard, and the access drive and parking to the north. The proposed improvements within this basin consist of the expansion of the maintenance yard, improvement of the access drive, and additional parking stalls south of the existing access drive. Basin 103 is approximately 1.13 acres and 67.2% impervious. Runoff from Basin 103 is conveyed to the proposed rain garden than to the water quality pond via a proposed culvert and swale. Basin 105 consists of the south portion of the existing maintenance building, the proposed vehicle storage building, the southern portion of the maintenance yard, half of the western access drive to the maintenance yard, and the proposed parking stalls west of the access drive. Basin 105 is approximately 5.08 acres and 23.4% impervious. Runoff from Basin 105 is conveyed to the water quality pond via overland sheet flow and swales. The total area draining to and treated by the water quality pond is approximately 6.63 acres and is 32.3% impervious. A total of 0.105 acre-ft of water quality capture volume is required. Analyzing the proposed grading, this computes to a water surface elevation of 4927.32 feet. The top of the existing outlet structure is 4928.40 feet which provides a total 0.331 acre-ft of water quality capture volume, exceeding the required volume. The existing orifice plate will need to be replaced with a plate containing one column and 3 rows of 7/8” orifice holes. The attenuated peak 100-yr flow rate from the combined Basins 102, 103, and 105 is estimated to be 22.10 cfs. The existing pond spillway has capacity for this rate with 0.38 feet of freeboard. All calculations and exhibits are attached for reference. MASTER PLAN As part of the Master Plan study we analyzed the proposed improvements to review the impacts to the water quality pond. The Master Plan improvements would require 0.122 acre-ft of water quality volume. It was determined that the existing pond, along with the current proposed grading adjustments, would Nix Farm Natural Areas Facility - Final Storm Drainage Letter December 22, 2016 Page 3 of 4 have capacity without significant grading adjustments. The orifice plate would need to be reconfigured for the appropriate orifice sizes and the spillway would likely need to be adjusted. LOW IMPACT DEVELOPMENT TECHNIQUES In reference to the code requirements for implementation of Low Impact Development (LID) techniques, the use of soft bottom swales and a rain garden are necessary to satisfy these requirements. The soft bottom swales and rain garden promote infiltration while filtering runoff and capturing fine sediment that drains off of the impervious areas. A Standard Operations Procedure will be provided at final design to assist in ensuring that these BMPs will adequately perform over time. Below is a description of the 4 step process for selecting structural BMPs: Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for receiving water protection that focuses on reducing runoff volumes, treating the water quality capture volume (WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process applies to the management of smaller, frequently occurring events. Step 1: Employ Runoff Reduction Practices To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact Development (LID) strategies, including Minimizing Directly Connected Impervious Areas (MDCIA). Runoff throughout the site is mainly conveyed to the water quality pond via overland sheet flow and open swales with soft bottom pans. Culverts are used route runoff under drives and walkways than day light to swales. Allowing runoff to be in contact with site soils, whether overland sheet flow or within swales, slows runoff and promotes infiltration, especially with the incorporation of soft bottom pans in the swales. Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release Once runoff has been minimized as described in Step 1, the remaining runoff shall be treated through the water quality pond designed for a 40-hour drain time. Step 3: Stabilize Drainageways Natural Drainage ways are subject to bed and bank erosion due to increases in frequency, duration, rate and volume of runoff during and following development. Because the site will drain to an existing storm system, bank stabilization is unnecessary with this project. Step 4: Implement Site Specific and Other Source Control BMPs Proactively controlling pollutants at their source by preventing pollution rather than removing contaminants once they have entered the stormwater system or receiving waters is important when protecting storm systems and receiving waters. This can be accomplished through site specific needs such as construction site runoff control, post-construction runoff control and pollution prevention / good housekeeping. It will be the responsibility of the contractor to develop a procedural best management practice for the site. All calculations are attached for reference. Nix Farm Natural Areas Facility - Final Storm Drainage Letter December 22, 2016 Page 4 of 4 EROSION CONTROL Erosion and sedimentation will be controlled on-site by use of silt fences, culvert inlet protection, a gravel construction entrance, and seeding and mulch. The measures are designed to limit the overall sediment yield increase due to construction as required by the City of Fort Collins. During overlot and final grading the soil will be roughened and furrowed perpendicular to the prevailing winds. During the performance of the work required by these specifications or any operations appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor, equipment, materials, and means required. The Contractor shall carry out proper efficient measures wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing naissance to persons. The Contractor will be held liable for any damage resulting from dust originating from his operations under these specifications on right-of-way or elsewhere. It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-way. Wherever construction vehicles access routes or intersect paved public roads, previsions must be made to minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. Stabilized construction entrances are required with base material consisting of 6” coarse aggregate. The contractor will be responsible for clearing mud tracked onto city streets on a daily basis. 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 will require periodic replacement. Maintenance is the responsibility of the contractor. All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall not be considered established until a ground cover is achieved which is demonstrated to be mature enough to control soil erosion to the satisfaction of the City Inspector and to survive severe weather condition. Thank you in advance for your time and if you have any questions or comments please contact me at (970) 347-8917. Sincerely, Jason T. Claeys, P.E., LEED AP Interwest Consulting Group Attachments PROJECT DATUM: NGVD29 UNADJUSTED CITY OF FORT COLLINS BENCHMARK #51-01 WEST SIDE OF TIMBERLINE ROAD AT THE NORTH END OF A BRIDGE OVER THE POUDRE RIVER ON TOP OF THE PARAPET WALL APPROXIMATELY 0.2 MILES SOUTH OF THE SOUTH SIDE OF WEST MULBERRY STREET. ELEV= 4923.75 CITY OF FORT COLLINS BENCHMARK #8-02 ON THE SOUTHEAST CORNER OF THE INTERSECTION OF LEMAY AVENUE AND MULBERRY STREET, IN THE CURB, ON THE SOUTHEAST SIDE OF A TRIANGULAR ISLAND THAT CONTAINS THE TRAFFIC SIGNAL. ELEV= 4936.08 PLEASE NOTE: THIS PLAN SET IS USING NGVD29 UNADJUSTED FOR A VERTICAL DATUM. IF NAVD88 DATUM IS REQUIRED FOR ANY PURPOSE, THE FOLLOWING EQUATIONS SHOULD BE USED: NAVD88 = 4923.75 (NGVD29 UNADJUSTED) + 3.18 NAVD88 = 4936.08 (NGVD29 UNADJUSTED) + 3.19 HORIZONTAL DATUM: COLORADO STATE PLAN COORDINATES NAD 83(2007) DATUM. HORIZONTAL CONTROL BASED VRS. SITE Vicinity Map Nix Farm Natural Area Facility Major Amendment 2016 Hydrologic Soil Group—Larimer County Area, Colorado (Nix Farm Natural Areas Facility - Major Amendment 2016) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/6/2016 Page 1 of 4 4491360 4491400 4491440 4491480 4491520 4491560 4491600 4491360 4491400 4491440 4491480 4491520 4491560 4491600 495900 495940 495980 496020 496060 496100 496140 496180 496220 496260 496300 495900 495940 495980 496020 496060 496100 496140 496180 496220 496260 496300 40° 34' 31'' N 105° 2' 54'' W 40° 34' 31'' N 105° 2' 36'' W 40° 34' 22'' N 105° 2' 54'' W 40° 34' 22'' N 105° 2' 36'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,920 if printed on A landscape (11" x 8.5") sheet. Warning: Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 54 Kim loam, 3 to 5 percent slopes B 0.5 6.5% 95 Satanta loam, 1 to 3 percent slopes B 7.2 93.5% 103 Stoneham loam, 5 to 9 percent slopes B 0.0 0.0% Totals for Area of Interest 7.7 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils 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. Group D. Soils 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. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Larimer County Area, Colorado Nix Farm Natural Areas Facility - Major Amendment 2016 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/6/2016 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Nix Farm Natural Areas Facility - Major Amendment 2016 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/6/2016 Page 4 of 4 Nix Farm Natural Areas Facility DEVELOPED IMPERVIOUS AREA CALCULATION Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016) BASINS: % Impervious Runoff Coefficient C Return Period Frequency Adjustment Factor (Cf ) 100% 0.95 2-year to 10-year 1.00 90% 0.95 100-year 1.25 90% 0.95 40% 0.50 0% 0.25 C2 to C10 C100 102 17,968 0.412 6,092 1,601 1,036 0 9,238 47.1% 0.59 0.74 103 49,301 1.132 25,015 7,129 1,881 0 15,276 67.2% 0.73 0.92 105 221,426 5.083 37,058 16,346 0 0 168,023 23.4% 0.42 0.52 106 38,698 0.888 0 0 0 3,863 34,834 4.0% 0.27 0.34 To WQ Pond (102+103+105) 288,695 6.628 68,165 25,076 2,917 0 192,537 32.3% 0.48 0.60 J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 % Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual Land Use Paved Roof Walks Gravel/Pavers Lawns (Heavy, 2-7% Slope) Sub-basin Designation Atotal (sq feet) Atotal (acres) Weighted % Impervious A COMPOSITE paved Nix Farm Natural Areas Facility DEVELOPED TIME OF CONCENTRATION Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: EQUATIONS: -Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5 -Equation 6-3 CONSTRAINTS: 300 ft - Overland flow shall not exceed for developed condition 500 ft - Overland flow shall not exceed for undeveloped condition Final t c = minimum of t i + t t and urbanized basin check recommended minimum t c = 5 min for urbanized basins BASINS Type of Travel Surface Cv 2 102 47.1% 0.59 0.723 141 0.0100 11.10 155 0.0200 Paved Areas 20 2.83 0.91 12.01 0.0152 12.65 12.01 3 103 67.2% 0.73 0.438 59 0.0240 3.86 343 0.0143 Paved Areas 20 2.39 2.39 6.25 0.0157 9.82 6.25 5 105 23.4% 0.42 1.161 300 0.0042 28.88 657 0.0150 Tilage/Field 5 0.61 17.88 46.77 0.0116 22.90 22.90 5 Combined 32.3% 0.48 6.628 300 0.0042 26.16 657 0.0150 Tilage/Field 5 0.61 17.88 44.04 0.0116 20.64 20.64 SUB-BASIN DATA % Impervious Urban Check tc (min) OVERALL SLOPE (ft/ft) TRAVEL TIME (tt) SLOPE (ft/ft) VELOCITY (ft/s) tt (min) AREA (acres) LENGTH (ft) REMARKS Final tc (min) tc =ti +tt (min) J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 SLOPE (ft/ft) Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016) ti (min) LENGTH Table RO-2 Nix Farm Natural Areas Facility DEVELOPED PEAK RUNOFF Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: Town of Timnth - Design Criteria Manual (2016) Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006) EQUATIONS: I = rainfall intensity (in/hr) Q n = n -yr peak discharge (cfs) P 1 = one-hour point rainfall depth (in) C n = n -yr runoff coefficient t c = time of concentration (min) I n = n -yr rainfall intensity (in/hr) P 1-5yr = 1.14 in A n = Basin drainage area (ac) P 1-10yr = 1.40 in P 1-100yr = 2.86 in BASIN SUMMARY: Runoff Coeff. (C5) C(A) (acres) Intensity (in/hr) Q (ft3/s) Runoff Coeff. (C10) C(A) (acres) Intensity (in/hr) Q (ft3/s) Runoff Coeff. (C100) C(A) (acres) Intensity (in/hr) Q (ft3/s) 2 102 0.412 12.01 0.59 0.24 2.85 0.69 0.59 0.24 3.51 0.85 0.74 0.30 7.16 2.18 3 103 1.132 6.25 0.73 0.83 3.62 3.01 0.73 0.83 4.45 3.69 0.92 1.04 9.09 9.43 5 105 5.083 22.90 0.42 2.13 2.08 4.43 0.42 2.13 2.56 5.44 0.52 2.66 5.22 13.89 5 Combined 6.628 20.64 0.48 3.20 2.20 7.05 0.48 3.20 2.70 8.65 0.60 4.00 5.52 22.10 Design Point Sub-basin Area (acres) tc (min) 5-yr Peak Runoff 100-yr Peak Runoff J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 10-yr Peak Runoff Q n = C n I n A n 0.786651) 1 ( 10 ) 28 . 5 t c P I + = Nix Farm Natural Areas Facility Water Quality Pond and Outlet Sizing Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV): Tributary Area, A 6.628 acres Composite. Imperviousness, I 32.3% WQCV (watershed inches) 0.158 inches 40-Hour Drain Time (Fig SQ-2) Required WQCV 0.105 acre-feet Including 20% for Sedimentation WATER QUALITY OUTLET SIZING (Per USDCM, Volume 3): Design Water Quality Depth, DWQ 1.15 ft Determine K40 K40 = 0.013DWQ 2 + 0.22DWQ - 0.10 0.171 Maximum Area per Row, a a = WQCV / K40 0.615 square inches Number of Rows, nr 3 rows Number of Columns, nc (See Table 6a-1 for Max.) 1 columns Choose Hole Diameter 7/8 inches Use USDCM Volume 3, Figure 5 0.875 inches Total Area per Row, Ao 0.60 square inches Total Outlet Area, Aot 1.80 square inches Does design work? Yes Minimum Steel Plate Thickness 1/4 inch (Not Used) Number of Rows, nr 2 rows Choose Rectangular Hole Width (w/ 2" Height) 0 inches Use USDCM Volume 3, Figure 5 0.000 inches Total Outlet Area, Aot 0.00 square inches Does design work? Yes Minimum Steel Plate Thickness 1/4 inch Urban Storm Drainage Criteria Manual (USDCM) Volume III, Urban Drainage and Flood Control District, June 2001 (Updated November 2010) Circular Perforation Sizing Rectangular Perforation Sizing J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 * * 1 . 2 12 Area WQCV Volume       = 1276-095-00 PondCalcs.xls - WQCV & Outlet Structure Page 1 of 4 Interwest Consulting Group Nix Farm Natural Areas Facility Water Quality Pond and Outlet Sizing Design Engineer: Design Firm: Project Number: Date: J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 WATER QUALITY TRASH RACK SIZING (Per USDCM, Volume 3) Required Open Area, At At =0.5*[77(e -0.124D )]*Aot 62 square inches Min. Distance between Columns, Sc 3 inches Width of Trash Rack and Concrete Opening per Column 3 inches Use USDCM Volume 3, Table 6a-1 Total Width, Wconc 3 inches Height of Trash Rack Screen, Htr 13 13/16 inches Check - Does Not Work Type of Screen S.S. #93 VEE Wire (US Filter) Screen Opening Slot Dimension 0.139" (US Filter) Support Rod Type (See Table 6a-2) Spacing of Support Rod (O.C.) 3/4 inches O.C. Total Screen Thickness (See Table 6a-2) 0.31 inches Carbon Steel Frame Type (See Table 6a-2) (Not Used) Required Open Area, At (including 50% clogging) At =0.5*[77(e -0.124D )]*Aot 0 square inches Width of Trash Rack Opening, Wopening 1 inches Use USDCM Volume 3, Table 6b-1 Width of Concrete Opening, Wconc 12 inches Min Height of Trash Rack Screen, Htr (including 2' 4" below lowest openings) 28.00 inches Type of Screen Kelmp KRP Series Aluminum Bar Gate (or Equal) Screen Opening Slot Dimension 3/16" Bars on 1-3/16" Centers Minimum Bearing Bar Size (See Table 6b-2) Rectangular Perforation Trash Rack Sizing 1 in x 3/16 in #156 VEE 3/8in x 1.0in flat bar Circular Perforation Trash Rack Sizing 1276-095-00 PondCalcs.xls - WQCV & Outlet Structure Page 2 of 4 Interwest Consulting Group Nix Farm Natural Areas Facility Critical Pond Elevations Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016) Stage Storage Volume (pond volume calculated using the prismoidal formula): CONTOUR (FT) AREA (FT2) AREA (ACRE) VOLUME (ACRE-FT) DEPTH (FT) CUMULATIVE VOLUME (ACRE-FT) 4925.65 0 0.000 0.000 0.00 0.000 4926.0 421 0.010 0.001 0.35 0.001 - Orifice Invert = 4926.17 4927.0 4374 0.100 0.047 1.35 0.048 4928.0 10414 0.239 0.176 2.35 0.224 4928.4 12837 0.295 0.107 2.75 0.331 -Top of Existing Outlet Structure 4929.0 16904 0.388 0.204 3.35 0.535 - Spillway 0.105 4927.32 ft J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 Required Water Quality Capture Volume (WQCV) = Acre-Ft Interpolates to an Elev. of ( ) 3 AAAADepth 1 2 1 2 V + + = 1276-095-00 PondCalcs.xls - Pond Stage Storage Page 3 of 4 Interwest Consulting Group Nix Farm Natural Areas Facility Emergency Overflow Spillway Calculations Design Engineer: Design Firm: Project Number: Date: Broad-Crested Weir Equation-Trapezoidal Shape where: Q = Discharge (cfs) C = Weir Coeffecient L = Weir Length (ft) H = Average Weir Head (ft) H:V =Side Slope Calculations Knowns: 4.00 0.62 ft 2.6 4929.00 ft 22.1 cfs 14.91 ft 15 ft 0.38 ft 1.00 ft Topft of Berm Elevation 4930.00 100-yr Pond Inflow Calculated Spillway Use Spillway Length Total Spillway Depth Spillway Freeboard Side Slopes (H:V) Desired Spillway Head Weir Coefficient Spillway Elevation J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 2 5 2 3 H V H QCLH C       = + 1276-095-00 PondCalcs.xls - Spillway Page 4 of 4 Interwest Consulting Group Nix Farm Natural Areas Facility MASTER PLANNED IMPERVIOUS AREA CALCULATION Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016) BASINS: % Impervious Runoff Coefficient C Return Period Frequency Adjustment Factor (Cf ) 100% 0.95 2-year to 10-year 1.00 90% 0.95 100-year 1.25 90% 0.95 40% 0.50 0% 0.25 C2 to C10 C100 102 17,968 0.412 5,006 2,350 1,293 0 9,318 46.1% 0.59 0.73 103 49,301 1.132 25,015 7,129 1,881 0 15,276 67.2% 0.73 0.92 105 221,426 5.083 55,071 21,343 4,846 0 140,167 35.5% 0.51 0.63 106 38,698 0.888 0 0 0 3,863 34,834 4.0% 0.27 0.34 To WQ Pond (102+103+105) 288,695 6.628 85,092 30,823 8,020 0 164,760 41.6% 0.55 0.69 J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 % Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual Paved Roof Walks Land Use Gravel/Pavers Lawns (Heavy, 2-7% Slope) Agravel/pavers (sq feet) Alawn (sq feet) Weighted % Impervious Sub-basin COMPOSITE Designation Atotal (sq feet) Nix Farm Natural Areas Facility Water Quality Pond and Outlet Sizing - Master Plan Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA: REQUIRED WATER QUALITY CAPTURE VOLUME (WQCV): Tributary Area, A 6.628 acres Composite. Imperviousness, I 41.6% WQCV (watershed inches) 0.184 inches 40-Hour Drain Time (Fig SQ-2) Required WQCV 0.122 acre-feet Including 20% for Sedimentation 4371.6558 WATER 10251.QUALITY 604 OUTLET SIZING (Per USDCM, Volume 3): 12783.707 16545.6252 1.25 ft Determine K40 K40 = 0.013DWQ 2 + 0.22DWQ - 0.10 0.195 Maximum Area per Row, a a = WQCV / K40 0.626 square inches Number of Rows, nr 3 rows Number of Columns, nc (See Table 6a-1 for Max.) 1 columns Choose Hole Diameter 7/8 inches Use USDCM Volume 3, Figure 5 0.875 inches Total Area per Row, Ao 0.60 square inches Total Outlet Area, Aot 1.80 square inches Does design work? Yes Minimum Steel Plate Thickness 1/4 inch (Not Used) Number of Rows, nr 2 rows Choose Rectangular Hole Width (w/ 2" Height) 0 inches Use USDCM Volume 3, Figure 5 0.000 inches Total Outlet Area, Aot 0.00 square inches Does design work? Yes Minimum Steel Plate Thickness 1/4 inch J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 Urban Storm Drainage Criteria Manual (USDCM) Volume III, Urban Drainage and Flood Control District, June 2001 (Updated November 2010) Circular Perforation Sizing Rectangular Perforation Sizing * * 1 . 2 12 Area WQCV Volume       = Nix Farm Natural Areas Facility Water Quality Pond and Outlet Sizing - Master Plan Design Engineer: Design Firm: Project Number: Date: J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 WATER QUALITY TRASH RACK SIZING (Per USDCM, Volume 3) Required Open Area, At At =0.5*[77(e -0.124D )]*Aot 62 square inches Min. Distance between Columns, Sc 3 inches Width of Trash Rack and Concrete Opening per Column 3 inches Use USDCM Volume 3, Table 6a-1 Total Width, Wconc 3 inches Height of Trash Rack Screen, Htr 15 inches Check - Does Not Work Type of Screen S.S. #93 VEE Wire (US Filter) Screen Opening Slot Dimension 0.139" (US Filter) Support Rod Type (See Table 6a-2) Spacing of Support Rod (O.C.) 3/4 inches O.C. Total Screen Thickness (See Table 6a-2) 0.31 inches Carbon Steel Frame Type (See Table 6a-2) (Not Used) Required Open Area, At (including 50% clogging) At =0.5*[77(e -0.124D )]*Aot 0 square inches Width of Trash Rack Opening, Wopening 1 inches Use USDCM Volume 3, Table 6b-1 Width of Concrete Opening, Wconc 12 inches Min Height of Trash Rack Screen, Htr (including 2' 4" below lowest openings) 28.00 inches Type of Screen Kelmp KRP Series Aluminum Bar Gate (or Equal) Screen Opening Slot Dimension 3/16" Bars on 1-3/16" Centers Minimum Bearing Bar Size (See Table 6b-2) 3/8in x 1.0in flat bar Circular Perforation Trash Rack Sizing Rectangular Perforation Trash Rack Sizing 1 in x 3/16 in #156 VEE 1276-095-00 PondCalcs - Masterplan.xls - WQCV & Outlet StructurePage 2 of 3 Interwest Consulting Group Nix Farm Natural Areas Facility Critical Pond Elevations - Master Plan Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016) Stage Storage Volume (pond volume calculated using the prismoidal formula): CONTOUR (FT) AREA (FT2) AREA (ACRE) VOLUME (ACRE-FT) DEPTH (FT) CUMULATIVE VOLUME (ACRE-FT) 4925.65 0 0.000 0.000 0.00 0.000 4926.0 421 0.010 0.001 0.35 0.001 - Orifice Invert = 4926.17 4927.0 4374 0.100 0.047 1.35 0.048 4928.0 10414 0.239 0.176 2.35 0.224 4928.4 12837 0.295 0.107 2.75 0.331 -Top of Existing Outlet Structure 4929.0 16904 0.388 0.204 3.35 0.535 - Spillway 0.122 4927.42 ft J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 Required Water Quality Capture Volume (WQCV) = Acre-Ft Interpolates to an Elev. of ( ) 3 AAAADepth 1 2 1 2 V + + = 1276-095-00 PondCalcs - Masterplan.xls - Pond Stage Storage Page 3 of 3 Interwest Consulting Group Nix Farm Natural Areas Facility Low Impact Development Design Engineer: Design Firm: Project Number: Date: DESIGN CRITERIA Low Impact Development Summary Pavement Area Summary 33,331 sqft 0 sqft 0.0% Developed Area Summary 65,169 sqft Total Area required for Treatment (75%): 48,877 sqft 0 sqft 0 sqft 0 sqft 49,301 sqft 49,301 sqft 75.7% City of Fort Collins - Ordinance No. 007, 2016 - Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID techniques, or - Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID techniques when 25% of private driveable surfaces are permeable. J.Claeys Interwest Consulting Group 1276-095-00 December 22, 2016 Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010 Total New Paved Area: Permeable Paver Area: Total Newly Developed Area: Proposed Area of Pavers: Additional Area Treated by Pavers: Total Area Treated by Pavers: Total Area Treated by LID: Percent Site Area Treated by LID: Percent Pavement Area as Permeable Pavers: Area Treated by Rain Garden (Basin 103): Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 67.2 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.672 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.21 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 49,301 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 864.2 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 663 sq ft D) Actual Flat Surface Area AActual = 769 sq ft E) Area at Design Depth (Top Surface Area) ATop = 1292 sq ft F) Rain Garden Total Volume VT= 1,030 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media CoFC Rain Garden Section (12" Growing Media, 6" Pea Gravel, 10" CDOT Class 2) 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = 1.9 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = 864 cu ft iii) Orifice Diameter, 3/8" Minimum DO = 2/3 in Design Procedure Form: Rain Garden (RG) J.Claeys Interwest Consulting Group December 21, 2016 Nix Farm Natural Areas Facility Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO 1276-095-00 UD-BMP_v3.05.xlsm, RG 12/21/2016, 9:41 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) J.Claeys Interwest Consulting Group December 21, 2016 Nix Farm Natural Areas Facility Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO 1276-095-00 UD-BMP_v3.05.xlsm, RG 12/21/2016, 9:41 AM Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 21 2016 East Swale Triangular Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 2.75 Invert Elev (ft) = 4928.13 Slope (%) = 0.50 N-Value = 0.015 Calculations Compute by: Known Q Known Q (cfs) = 9.43 Highlighted Depth (ft) = 0.80 Q (cfs) = 9.430 Area (sqft) = 2.56 Velocity (ft/s) = 3.68 Wetted Perim (ft) = 6.60 Crit Depth, Yc (ft) = 0.81 Top Width (ft) = 6.40 EGL (ft) = 1.01 0 5 10 15 20 25 30 35 Elev (ft) Depth (ft) Section 4927.50 -0.63 4928.00 -0.13 4928.50 0.37 4929.00 0.87 4929.50 1.37 4930.00 1.87 4930.50 2.37 4931.00 2.87 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 21 2016 West Swale Triangular Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 2.75 Invert Elev (ft) = 4930.75 Slope (%) = 1.10 N-Value = 0.015 Calculations Compute by: Known Q Known Q (cfs) = 13.89 Highlighted Depth (ft) = 0.80 Q (cfs) = 13.89 Area (sqft) = 2.56 Velocity (ft/s) = 5.43 Wetted Perim (ft) = 6.60 Crit Depth, Yc (ft) = 0.95 Top Width (ft) = 6.40 EGL (ft) = 1.26 0 5 10 15 20 25 30 35 Elev (ft) Depth (ft) Section 4929.00 -1.75 4930.00 -0.75 4931.00 0.25 4932.00 1.25 4933.00 2.25 4934.00 3.25 Reach (ft) Weir Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 21 2016 <Name> Rectangular Weir Crest = Broad Bottom Length (ft) = 12.00 Total Depth (ft) = 0.50 Calculations Weir Coeff. Cw = 2.60 Compute by: Known Q Known Q (cfs) = 9.43 Highlighted Depth (ft) = 0.45 Q (cfs) = 9.430 Area (sqft) = 5.40 Velocity (ft/s) = 1.75 Top Width (ft) = 12.00 0 2 4 6 8 10 12 14 16 Depth (ft) <Name> Depth (ft) -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft) Weir W.S. Rain Garden Outlet Structure - Weir Calculation 1276-095-00 PondCalcs - Masterplan.xls - WQCV & Outlet StructurePage 1 of 3 Interwest Consulting Group Atotal (acres) Apaved (sq feet) Aroof (sq feet) Awalk (sq feet) (ft) INITIAL/OVERLAND TIME (ti) DESIGN POINT Sub-basin C5 ( ) 0 .33 0 . 395 1 . 1 5 S C L ti − = t c = t i + t t 0 . 5 V = C v S w V L tt 60 = �� = 18 − 15� + � 60 24� + 12 � (sq feet) Aroof (sq feet) Awalk (sq feet) Agravel/pavers (sq feet) Alawn (sq feet) Survey Area Data: Version 10, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado (Nix Farm Natural Areas Facility - Major Amendment 2016) Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/6/2016 Page 2 of 4