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HomeMy WebLinkAbout3516 S MASON MEDICAL AND RETAIL MARIJUANA STORE - BDR200011 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT April 20, 2021 Dan Mogen, P.E. City of Fort Collins Utilities – Stormwater Engineering 700 Wood Street Fort Collins, CO 80521 RE: 3516 Mason Street BDR – Preliminary Drainage Letter JVA Job No. 3233c Dear Dan: This letter has been prepared to summarize the drainage concept, solutions and changes in impervious area associated with the site improvements for the 3516 Mason Street BDR redevelopment project located at 3516 South Mason Street in the City of Fort Collins. Existing Drainage Patterns The existing site, re-platted as Lot 15 of the South Mesa Subdivision and adjoining tract, is predominantly paved asphalt and consists of the existing Mason Street Plaza building, drive aisles, and parking areas. The existing ground surface is relatively flat, generally sloping either west or east at grades ranging from 0.5% to 4.5%. All stormwater runoff is conveyed via surface flow either to the west into the public right of way or east into the Larimer County No. 2 Canal. See Figure 1: Historic Drainage Map. The site is located in FEMA Flood Zone X, area of minimal hazard, per FEMA Flood Insurance Rate Map number 08069C0987G, effective date 05/02/2012. Proposed Drainage Patterns Proposed drainage patterns are to remain the same as the current. In general, the proposed redevelopment of the site consists of reusing the existing building, reconfiguring the south parking area, removing the northern access to the site, repairing public curb, gutter, and sidewalk, and constructing a courtyard and greenspaces on the west side of the existing building. The site has been divided into three hydrologic basins for analysis. Basin A represents the area of the site draining to the public storm facilities in the right of way. Basin B represents the portion of the site draining to the east and into the Larimer County No. 2 Canal. Basin C represents the small area of roof an landscaping to the north with drains offsite, and eventually into the Larimer County No. 2 Canal. All basins eventually convey stormwater to Fossil Creek. It follows that the proposed improvements will substantially decrease the total impervious area on the site, from 87.6% to 66.4%. See Figure 2: Developed Drainage Map for the drainage basin boundaries and a summary of the existing and proposed impervious areas. Hydrologic and Hydraulic calculations are attached. Per discussions with Wes Lamarque regarding this project, due to the lack of stormwater infrastructure, site constraints, and significant reduction to the impervious area of the site Water Quality and Low Impact Development requirements of the Mile High Flood District will not be required. The proposed development of this site will serve to improve water quality and quantity 3516 Mason Street BRD - Preliminary Drainage Letter April 20, 2021 2 of 2 to natural drainageways by decreasing the frequency, rate, duration, and volume of runoff. The significant reduction in impervious area will facilitate sedimentation and filtration while limiting erosion. Erosion and Sediment Control During construction, temporary erosion and sediment control practices will be used to limit soil erosion and sediment discharge off the site. Please feel free to contact me to discuss any questions you may have. Sincerely, JVA, INCORPORATED By: ________________________________ Erik Nakos, P.E. . Senior Project Manager Associate Enclosures: Figure 1: Historic Drainage Map, Figure 2: Developed Drainage Map, Hydrologic Soil Rating, FEMA Firm Map, Rational Calculations HISTORIC DRAINAGE MAPFIG 1 REVISION DESCRIPTIOND'WNDES'DDATENO.DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC.3516 SOUTH MASONBASIC DEVELOPMENT REVIEWFORT COLLINS, COLORADOSHEET NO. 3233c APR, 2021 ETN NLO NLO JVA, Inc.213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver W W W W W W W W W W DEVELOPED DRAINAGE MAPFIG 2 REVISION DESCRIPTIOND'WNDES'DDATENO.DESIGNED BY: DRAWN BY: CHECKED BY: JOB #: DATE: © JVA, INC.3516 SOUTH MASONBASIC DEVELOPMENT REVIEWFORT COLLINS, COLORADOSHEET NO. 3233c APR, 2021 ETN NLO NLO JVA, Inc.213 Linden Street, Suite 200 www.jvajva.com Fort Collins, CO 80524 970.225.9099 Boulder ● Fort Collins ● Winter Park Glenwood Springs ● Denver Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/20/2021 Page 1 of 444875764487584448759244876004487608448761644876244487576448758444875924487600448760844876164487624493316493324493332493340493348493356493364493372493380493388 493316 493324 493332 493340 493348 493356 493364 493372 493380 493388 40° 32' 21'' N 105° 4' 44'' W40° 32' 21'' N105° 4' 41'' W40° 32' 20'' N 105° 4' 44'' W40° 32' 20'' N 105° 4' 41'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 15 30 60 90 Feet 0 5 10 20 30 Meters Map Scale: 1:344 if printed on A landscape (11" x 8.5") sheet. 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: 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 Survey Area Data: Version 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 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 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/20/2021 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 73 Nunn clay loam, 0 to 1 percent slopes C 0.1 31.4% 89 Renohill clay loam, 0 to 3 percent slopes D 0.3 68.6% Totals for Area of Interest 0.4 100.0% 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. Rating Options Aggregation Method: Dominant Condition Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/20/2021 Page 3 of 4 Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole. A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not. For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods. The aggregation method "Dominant Condition" first groups like attribute values for the components in a map unit. For each group, percent composition is set to the sum of the percent composition of all components participating in that group. These groups now represent "conditions" rather than components. The attribute value associated with the group with the highest cumulative percent composition is returned. If more than one group shares the highest cumulative percent composition, the corresponding "tie-break" rule determines which value should be returned. The "tie-break" rule indicates whether the lower or higher group value should be returned in the case of a percent composition tie. The result returned by this aggregation method represents the dominant condition throughout the map unit only when no tie has occurred. Component Percent Cutoff: None Specified Components whose percent composition is below the cutoff value will not be considered. If no cutoff value is specified, all components in the database will be considered. The data for some contrasting soils of minor extent may not be in the database, and therefore are not considered. Tie-break Rule: Higher The tie-break rule indicates which value should be selected from a set of multiple candidate values, or which value should be selected in the event of a percent composition tie. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 4/20/2021 Page 4 of 4 JVA IncorporatedJob Name: 3516 Mason Street BDR213 Linden Street, Suite 200 Job Number: 3233cFort Collins, CO 80524Date: 4/20/21Ph: (970) 225 9099By: NLO3516 Mason Street BDRHistoric Runoff Coefficient & Time of Concentration CalculationsLocation: Wheat RidgeMinor Design Storm: 2Major Design Storm: 100Soil Type: C/DBasin Design DataI (%) = 100% 90% 90% 40% 25% 25% 2% 2%I (%)tc Comptc FinalBasin NameDesign PointApaved streets (sf)Adrives/conc (sf)Aroof (sf)Agravel (sf)Aplygnd (sf)Aart. turf (sf)Alscape (B soil) (sf)Alscape (C/D soil) (sf)ATotal (sf)ATotal (ac)Imp (%)C2 C5 C10 C100Upper most Length (ft)Slope (%)ti (min)Length (ft)Slope (%)Type of Land SurfaceKVelocity (fps) tt (min)Time of Conc ti + tt = tcTotal Length (ft)tc=(L/180)+10 (min.) Min tcH1 1 3,620633,683 0.08 98.3% 0.81 0.84 0.86 0.8960 2.1%2.9Paved areas & shallow paved swales20 0.0 0.0 2.9 60 10.3 5.0H2 2 6,952 291 3,5811,11311,937 0.27 87.6% 0.72 0.75 0.78 0.84146 4.1%4.8Paved areas & shallow paved swales20 0.0 0.0 4.8 146 10.8 5.0H3 3 8894801,369 0.03 59.1% 0.46 0.52 0.57 0.7345 2.0%5.7Nearly bare ground10 0.0 0.0 5.7 45 10.3 5.7TOTAL SITE 10,572 291 4,470 0 0 0 0 1,656 16,989 0.39 87.6% 0.72 0.75 0.78 0.84Basin NameDesign PointTime of Conc (tc)C2 C5 C10 C100 2 5 10 100ATotal (sf)ATotal (ac)Q2 Q5 Q10 Q100H1 1 5.0 0.81 0.84 0.86 0.89 2.85 0.00 N/A 9.95 3,683 0.08 0.20 0.00 N/A 0.75H2 2 5.0 0.72 0.75 0.78 0.84 2.85 0.00 N/A 9.95 11,937 0.27 0.560.00 N/A 2.30H3 3 5.7 0.46 0.52 0.57 0.73 2.72 0.00 N/A 9.50 1,369 0.03 0.04 0.00 N/A 0.22TOTAL SITE 16,989 0.39 0.79 0.00 0.00 3.26Initial Overland Time (ti)Travel Time (tt) tt=Length/(Velocity x 60)tc Urbanized Check ONRunoff Coeff's Rainfall Intensities (in/hr)Area Flow Rates (cfs)Runoff Coeff's3233c - Rational CalculationsHistoricPage 1 of 1 JVA Incorporated Job Name: 3516 Mason Street BDR 213 Linden Street, Suite 200 Job Number: 3233c Fort Collins, CO 80524 Date: 4/20/21 Ph: (970) 225 9099 By: NLO 3516 Mason Street BDR Composite Runoff Coefficient Calculations Location: Wheat Ridge Minor Design Storm: 2 Major Design Storm: 100 CA 100yr = 0.78i + 0.11 Soil Type: C/D CB 100yr = 0.47i + 0.426 CC/D 100yr = 0.41i + 0.484) Basin Design Data I (%) = 100% 90% 90% 40% 25% 25% 2% 2%I (%) Basin Name Design Point Apaved streets (sf) Adrives/c onc (sf) Aroof (sf) Agravel (sf) Aplygnd (sf) Aart. turf (sf) Alscape (B soil) (sf) Alscape (C/D soil) (sf) ATotal (sf) ATotal (ac) Imp (%)C2 C5 C10 C100 A 1 882 887 158 1,756 3,683 0.08 48.3% 0.37 0.43 0.49 0.68 B 2 4,056 1,294 3,581 487 2,519 11,937 0.27 72.8% 0.58 0.63 0.67 0.78 C 3 889 480 1,369 0.03 59.1% 0.46 0.52 0.57 0.73 Runoff Coeff's 3233c - Rational Calculations Developed C Page 1 of 1 JVA Incorporated Job Name: 3516 Mason Street BDR 213 Linden Street, Suite 200 Job Number: 3233c Fort Collins, CO 80524 Date: 4/20/21 Ph: (970) 225 9099 By: NLO 3516 Mason Street BDR Time of Concentration Calculations Location: Wheat Ridge Minor Design Storm: 2 Major Design Storm: 100 Soil Type: C/D Sub-Basin Data tc Comp tc Final Basin Name Design Point ATotal (ac)C5 Upper most Length (ft) Slope (%) ti (min) Length (ft)Slope (%) Type of Land Surface Cv Velocity (fps) tt (min) Time of Conc ti + tt = tc Total Length (ft) tc=(L/180)+ 10 (min) Min tc A 1 0.08 0.43 60 2.1%7.4 0 0.0% Paved areas & shallow paved swales 20 0.0 0.0 7.4 60 10.3 7.4 B 2 0.27 0.63 146 4.1%6.5 0 0.0% Paved areas & shallow paved swales 20 0.0 0.0 6.5 146 10.8 6.5 C 3 0.03 0.52 45 2.0%5.7 0 0.0% Nearly bare ground 10 0.0 0.0 5.7 45 10.3 5.7 Initial Overland Time (ti)Travel Time (tt) tt=Length/(Velocity x 60) tc Urbanized Check ON 3233c - Rational Calculations Developed Tc Page 1 of 1 JVA IncorporatedJob Name: 3516 Mason Street BDR213 Linden Street, Suite 200Job Number: 3233cFort Collins, CO 80524Date: 4/20/21Ph: (970) 225 9099By: NLO3516 Mason Street BDRDeveloped Storm Runoff CalculationsDesign Storm : 100 YearPoint Hour Rainfall (P1) : 2.23 Basin Name Design Point Area (ac) Runoff Coeff tc (min) C*A (ac) I (in/hr) Q (cfs) Total tc (min) SC*A (ac) I (in/hr) Q (cfs) Inlet Type Q intercepted Q carryover Q bypass Pipe Size (in) or equivalent Pipe Material Slope (%) Pipe Flow (cfs) Max Pipe Capacity (cfs) Length (ft) Velocity (fps) tt (min)Total Time (min) NotesA1 0.08 0.68 7.40 0.06 8.63 0.507.40 0.068.63 0.50B2 0.27 0.78 6.50 0.21 9.06 1.946.50 0.219.06 1.94C3 0.03 0.73 5.70 0.02 9.50 0.225.70 0.029.50 0.22Direct RunoffTotal Runoff InletsPipe Pipe/Swale Travel Time3233c - Rational CalculationsQ100Page 1 of 1 JVA IncorporatedJob Name: 3516 Mason Street BDR213 Linden Street, Suite 200Job Number: 3233cFort Collins, CO 80524Date: 4/20/21Ph: (970) 225 9099By: NLO3516 Mason Street BDRDeveloped Storm Runoff CalculationsDesign Storm : 2 YearPoint Hour Rainfall (P1) : 0.77 Basin Name Design Point Area (ac) Runoff Coeff tc (min) C*A (ac) I (in/hr) Q (cfs) Total tc (min) SC*A (ac) I (in/hr) Q (cfs) Inlet Type Q intercepted Q carryover Q bypass Pipe Size (in) or equivalent Pipe Material Slope (%) Pipe Flow (cfs) Max Pipe Capacity (cfs) Length (ft) Velocity (fps) tt (min)Total Time (min) NotesA1 0.08 0.37 7.40 0.03 2.47 0.087.40 0.032.47 0.08B2 0.27 0.58 6.50 0.16 2.60 0.416.50 0.162.60 0.41C3 0.03 0.46 5.70 0.01 2.72 0.045.70 0.012.72 0.04Direct RunoffTotal Runoff InletsPipe Pipe/Swale Travel Time3233c - Rational CalculationsQ MinorPage 1 of 1