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Drainage Report 12-17-21
115N 17th AVE, BEECH GROVE, IN 46107 // 317.780.1555 // CROSSROADENGINEERS.COM Stormwater & Water Quality Calculations Carmel Police Headquarters Building Addition 3 Civic Square Carmel, Indiana 46032 Drainage Submittal: December 17, 2021 Prepared By: CrossRoad Engineers, PC 115 N 17th Avenue Beech Grove, IN 46107 Phone No.: (317) 780-1555 Fax No.: (317) 780-6525 Email: info@crossroadengineers.com Table of Contents Section 1: Stormwater Calculations Summary ❑ Introduction.................................................................................................... 1 ❑ Pre-Development Conditions ........................................................................ 1 ❑ .... Post-Development Conditions ................................................................... 1-2 ❑ Storm System Design ..................................................................................... 2 ❑ Exhibit 1: Vicinity and Location Map ............................................................ 3 Section 2: Runoff Summary ................................................................. 4-8 ❑ .... Existing Conditions ........................................................................................ 4 ❑ Proposed Conditions ................................................................................... 5-6 ❑ Exhibit 2: Pre-Development Watershed Map............................................... 7 ❑ Exhibit 3: Post-Development Watershed Map ............................................. 8 Section 3: Stormwater Detention Calculations .............................. 9-13 ❑ Detention Volume Calculations ............................................................... 9-10 ❑ Exhibit 4: Underground Detention Details ................................................ 11 ❑ Weir Report ................................................................................................... 12 ❑ Exhibit 5: Emergency Overflow Weir Report ............................................. 13 Section 4: Pipe Sizing Calculations ................................................. 14-21 ❑ Pipe Sizing Summary .................................................................................... 14 ❑ Table 201-1: Runoff Coefficients ................................................................. 15 ❑ Table 201-2: Rainfall Intensities ............................................................. 16-17 ❑ Pipe Sizing Calculations Table ..................................................................... 18 ❑ Hydraflow Outputs.................................................................................. 19-20 ❑ Exhibit 6: Inlet Basin Map ............................................................................ 21 Section 5: Storm Inlet Calculations ................................................ 22-27 ❑ Storm Inlet C ............................................................................................ 22-23 ❑ Local Flood Routing Calculations ........................................................... 23-24 ❑ Flood Routing Hydrograph Reports ....................................................... 25-27 Section 6: Water Quality Calculations ........................................... 28-36 ❑ Water Quality Calculations ......................................................................... 28 ❑ Storm and Sanitary WQ Calculations Report ........................................ 29-32 ❑ City of Indianapolis SQU Selection Guide .................................................. 33 ❑ WQ Curve Number Selection Chart ............................................................ 34 ❑ Exhibit 7: Water Quality Basin Map ............................................................ 35 ❑ Exhibit 8: Water Quality Unit Details ......................................................... 36 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 1: Stormwater Calculations Summary Introduction This submittal of stormwater drainage calculations and construction plans are for the review and approval of the site design for the proposed Carmel Police Department Building Expansion. The site is located 3 Civic Square in Carmel, IN. Refer to Exhibit 1 for the Location Map and Vicinity Map. Pre-Development Conditions The existing project site consists of the existing Police Department Building lot, ±1.369 acres, and the existing Huntington Bank lot, 0.411 acres, located along the west side of Rangeline Rd between Gradle Drive and Red Truck Road. Existing storm infrastructure routes runoff from both sites and Gradle Drive to a 30 inch trunkline that outlets just west of the fire department into the existing ditch to the east of the Monon Trail known as the JW Hawkins arm of the WR Fertig regula ted drain. See Exhibit 2 for the pre-developed watershed maps. The subject properties are located within Flood Zone X (areas to be determined to be outside the 500-year floodplain) per Community Panel Number 18057C0209G of the Flood Insurance Rate Map of Hamilton County, Indiana and the City of Carmel (map dated November 19, 2014). There are no wetland areas present according to the National Wetlands Inventory Map. Post-Development Conditions This project includes the construction of a ±18,000 sq. ft. 3-story addition to the Carmel Police Department Headquarters on adjacent lot to the east that is currently occupied by a Huntington Bank Branch. Infrastructure including asphalt drives and parking areas, storm sewers, sanitary sewer laterals, domestic and fire suppression water services and other required utilities will be constructed with the development. Privately maintained and operated underground detention systems will also be constructed with this project. All stormwater shall be collected via an existing and proposed storm sewer network and routed to the existing storm sewer system which outlets into the JW Hawkins arm of the WR Fertig regulated drain ditch ±325 ft. to the west of the Station. Per discussions with the City of Carmel, the site will provide detention as necessary to allow for a “no net increase” in runoff from the existing conditions of the Police Station and Huntington Bank site. In order to do so, an underground detention 1 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs system will be designed and constructed as shown in the enclosed calculations and plans. Per discussions with the City, a stormwater quality unit will be provided by an inline Cascade hydrodynamic separator as manufactured by Contech that will treat the runoff of the expansion area only. Stormwater System Design As discussed above, the detention system was designed under a “no net increase” policy as follows: Overall Site Allowable Release Rates: Redeveloped 10-yr ≤ Existing 10-yr Redeveloped 100-yr ≤ Existing 100-yr The proposed storm sewer network was designed to accommodate a 10-year storm event and does not overburden the existing storm sewer network. The Rational Method was used to perform the storm sewer pipe network calculations. Structures and Grates were designed and placed so the depth of ponding above the grate does not exceed the top of curb or adjacent building finished floor. 2 Development ConsultantsTransportation &NORTHLOCATION MAP VICINITY MAP PROJECT LOCATION CARMEL PROJECT LOCATION VETERANS WAYCIVIC SQUARE GRADLE DRIVE S RANGELINE ROADNAPPANEE DRIVE GRADLE DRIVE MONON GREEN BOULEVARD UNNAMED FIRE RD EXHIBIT 1: LOCATION AND VICINITY MAPS 3 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 2: Runoff Summary All runoff and detention calculations were completed per the City of Carmel Stormwater Technical Standards (STSM) Manual for development sites less than or equal to 5 acres in size, with a contributing drainage area less than or equal to 50 acres and no depressional storage. The Rational Method was utilized to calculate the runoff for direct discharge areas. The Modified Rational Method was utilized to calculate the peak detention volume. EXISTING CONDITIONS: ATOT = 1.691 Ac. CAVG = 0.668 AGRASS = 0.496 Ac. C = 0.20 AROOF = 0.303 Ac. C = 0.90 APAVEMENT = 0.892 Ac. C = 0.85 TC = 5.0 min. (assumed) • I10 = 6.12 in/hr Q10 = (0.668)(6.12)(1.691) =6.92 cfs • I100 = 9.12 in/hr Q100 = (0.668)(9.12)(1.691) =10.31 cfs See Exhibit 2 for existing watershed map. PROPOSED CONDITIONS: The following represents the proposed conditions by separating the detained and undetained watersheds of the developed site as shown in Exhibit 3 to determine the allowable release rates of the proposed underground detention facility. 4 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Undetained Watershed: ATOT = 0.991 Ac. CAVG = 0.718 AGRASS = 0.216 Ac. C = 0.20 AROOF = 0.188 Ac. C = 0.90 APAVEMENT = 0.587 Ac. C = 0.85 TC = 5.0 min. (assumed) • I10 = 6.12 in/hr Q10 = (0.718)(6.12)(0.991) =4.35 cfs • I100 = 9.12 in/hr Q100 = (0.718)(9.12)(0.991) =6.49 cfs Detained Watershed: ATOT = 0.700 Ac. CAVG = 0.828 AGRASS = 0.061 Ac. C = 0.20 AROOF = 0.489 Ac. C = 0.90 APAVEMENT = 0.150 Ac. C = 0.85 TC = 5.0 min. (assumed) • I10 = 6.12 in/hr Q10 = (0.828)(6.12)(0.700) =3.55 cfs • I100 = 9.12 in/hr Q100 = (0.828)(9.12)(0.700) =5.29 cfs To accomplish a “no net increase” in overall runoff from the site, the combined undetained and detained runoff cannot exceed the predeveloped site runoff. 5 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Design Storm Total Developed Runoff - Predeveloped Runoff = Required Storage Rate 10-YR 4.35 cfs + 3.55 cfs - 6.92 cfs = 0.98 cfs 100-YR 6.49 cfs + 5.29 cfs - 10.31 cfs = 1.47 cfs Design Storm Detained Runoff Rate - Storage Rate = Allowable Detention Release Rate 10-YR 3.55 cfs - 0.98 cfs = 2.57 cfs 100-YR 5.29 cfs - 1.47 cfs = 3.82 cfs 6 GRADLE DRIVEVETERANS WAYCIVIC SQUARERED TRUCK ROAD S RANGELINE ROADEXHIBIT 2: PRE-DEVELOPED WATERSHED MAP Development ConsultantsTransportation &NORTH7 GRADLE DRIVEVETERANS WAYCIVIC SQUARERED TRUCK ROAD S RANGELINE ROADEXHIBIT 3: POST-DEVELOPED WATERSHED MAP Development ConsultantsTransportation &NORTH8 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 3: Stormwater Detention Calculations As indicated in Section 1, the underground detention system for this project will be designed such that the rates will not exceed the following: Overall Site Allowable Release Rates: Redeveloped 10-yr ≤ Existing 10-yr Redeveloped 100-yr ≤ Existing 100-yr Detained Basin Detention Allowable Release Rates: Q10 = 2.57 cfs Q100 = 3.82 cfs Detention Volume Calculations: The detention volume required was calculated utilizing the Rational Method b per Section 302.04 of the City of Carmel STSM. Allowable Detention Release Rate Qu (cfs) Detained Area Inflow Qd (cfs) Storage Rate S(td) (cfs) Required Storage Volume SR (ac-ft) Required Storage Volume SR (cft) Post-Dev 10- YR Storm 2.57 3.55 0.98 0.007 298 Post-Dev 100- YR Storm 3.82 5.29 1.47 0.010 444 Detention Size: 22’x20’x4.95’ of No. 8 Stone at 40% porosity Bottom of Detention Elevation: 831.50’ Peak 10-yr Redevelopment Discharge Rate = 2.57 cfs ≤ 2.57 cfs (allowable) Peak Water Surface Elev. = 833.19 < 834.02 (top of weir plate) +2’ < 836.05 (FFE) Peak 100-yr Redevelopment Discharge Rate = 3.82 cfs ≤ 3.82 cfs (allowable) Peak Water Surface Elev. = 834.02 ≤ 834.02 (top of weir plate) +2’ < 836.05 (FFE) 10-Yr Orifice calculations: Depth of Water in Detention: 298 cft = 22’x20’xdepth Depth=1.69’ 𝑄𝑂𝑟𝑖𝑐𝑖𝑐𝑐=𝐶𝑐(1 4 𝜋𝐶2 )√2𝑔ℎ 9 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs QOrifice=2.57 cfs Cd=0.6 g= 32.2 𝑐𝑟 𝑟𝑐𝑐2 h=1.69’-0.792 2 = 1.305’ D = 0.792’ = 9.25” 100-Yr Weir & Orifice calculations: Depth of Water in Detention: 444 cft = 22’x20’xdepth Depth=2.52’ 𝑄𝑂𝑟𝑖𝑐𝑖𝑐𝑐=𝐶𝑐(1 4 𝜋𝐶2 )√2𝑔ℎ QOrifice=3.26 cfs Cd=0.6 g= 32.2 𝑐𝑟 𝑟𝑐𝑐2 h= 2.52’-0.792 2 = 2.11 ft D = 0.792’ = 9.25” Qweir = 3.82 cfs – 3.26 cfs = 0.56 cfs See Hydraflow Express Results within this section for sizing of weir cutout at top of restrictor plate. Emergency Spillway In addition to controlling release rates, the outlet structure and weir plate will also function as the emergency spillway for the underground detention system. The sharp crested weir emergency spillway was designed to convey 1.25 times the peak runoff 100-year storm event inflow to the detention system. See Exhibit 5 Hydraflow Express Results in this section for results of the resulting depth of the water over the spillway. Top of Weir Plate Elev. = 834.02 Min. Freeboard = 1 ft. 1.25xQ100= 1.25 x 5.29 cfs = 6.61 cfs Height of Water over Weir: 0.63’ (from Exhibit 5) Min. Bottom of Precast Manhole Cap = 834.02 + 0.63’ (H) + 1.00’ (freeboard) = 835.65 < 836.05 (FFE) Min. Casting Rim Elev. = 835.68 + 0.67’ (cap) + 0.33’ (casting) = 836.65 < 838.04 (proposed rim elev.) 10 EXHIBIT 4: UNDERGROUND DETENTION DETAILS Development ConsultantsTransportation & DETENTION FACILITY OUTLET STRUCTURE STR. NO. 13 SHARP CRESTED WEIR DETAIL SECTION A-A SECTION B-B 11 Weir Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Oct 29 2021 Restrictor Plate - 100-Year Weir Calculation Rectangular Weir Crest = Sharp Bottom Length (ft) = 0.50 Total Depth (ft) = 0.50 Calculations Weir Coeff. Cw = 3.33 Compute by: Known Q Known Q (cfs) = 0.56 Highlighted Depth (ft) = 0.48 Q (cfs) = 0.560 Area (sqft) = 0.24 Velocity (ft/s) = 2.32 Top Width (ft) = 0.50 0 .1 .2 .3 .4 .5 .6 .7 Depth (ft) Depth (ft)Restrictor Plate - 100-Year Weir Calculation -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft)Weir W.S.12 Friday, Oct 29 2021Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Restrictor Plate - Emergency Overflow Weir Calculation Rectangular Weir = SharpCrest = 4.00Bottom Length (ft) = 2.00Total Depth (ft) Calculations = 3.33Weir Coeff. Cw Known QCompute by: = 6.61Known Q (cfs) Highlighted = 0.63Depth (ft) = 6.610Q (cfs) = 2.51Area (sqft) = 2.64Velocity (ft/s) = 4.00Top Width (ft) 0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 Depth (ft)Depth (ft)Restrictor Plate - Emergency Overflow Weir Calculation -1.00-1.00 0.000.00 1.001.00 2.002.00 3.003.00 Length (ft)Weir W.S. Exhibit 5 - Emergency Overflow Weir Report 13 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 4: Pipe Sizing Calculations Pipe Sizing Summary The Rational Method was used to size the onsite storm sewer to convey the peak runoff from the 10-year storm. As discussed in Section 1, runoff leaving the site will be conveyed to existing on-site storm sewers. The enclosed calculations verify that the proposed storm sewer meets the design requirements of the City of Carmel Stormwater Technical Standards Manual. The rainfall data table, 10-year storm event pipe sizing calculations, and Inlet Basin Map Exhibits 6 are included within this section. Since the overall runoff from the site remains the same as the pre-developed conditions, there will be no adverse effects on the existing storm pipe. 14 TABLE 201-1: Runoff Coefficients © for Use in the Rational Method TYPE OF SURFACE RUNOFF COEFFICIENT © Non-Urban Areas Bare earth 0.55 Steep grassed areas (slope 2:1) 0.60 Turf meadows 0.25 Forested areas 0.20 Cultivated fields 0.30 Urban Areas All watertight roof surfaces 0.90 Pavement 0.85 Gravel 0.85 Impervious soils (heavy) 0.55 Impervious soils (with turf) 0.45 Slightly pervious soil 0.25 Slightly pervious soil (with turf) 0.20 Moderately pervious soil 0.15 Moderately pervious soil (with turf) 0.10 Business, Commercial & Industrial 0.85 Apartments & Townhouses 0.70 Schools & Churches 0.55 Single Family Lots < 10,000 SF 0.45 Lots < 12,000 SF 0.45 Lots < 17,000 SF 0.40 Lots > ½ acre 0.35 Park, Cemetery or Unimproved Area 0.30 200-5 15 200-6 TABLE 201-2: Rainfall Intensities for Various Return Periods and Storm Durations Rainfall Intensity (Inches/Hour) Return Period (Years) Duration 2 5 10 25 50 100 5 Min. 4.63 5.43 6.12 7.17 8.09 9.12 10 Min. 3.95 4.63 5.22 6.12 6.90 7.78 15 Min. 3.44 4.03 4.55 5.33 6.01 6.77 20 Min. 3.04 3.56 4.02 4.71 5.31 5.99 30 Min. 2.46 2.88 3.25 3.81 4.29 4.84 40 Min. 2.05 2.41 2.71 3.18 3.59 4.05 50 Min. 1.76 2.06 2.33 2.73 3.07 3.47 1 Hr. 1.54 1.80 2.03 2.38 2.68 3.03 1.5 Hrs. 1.07 1.23 1.42 1.63 1.91 2.24 2 Hrs. 0.83 0.95 1.11 1.37 1.60 1.87 3 Hrs. 0.59 0.72 0.84 1.04 1.22 1.42 4 Hrs. 0.47 0.58 0.68 0.84 0.99 1.15 5 Hrs. 0.40 0.49 0.58 0.71 0.83 0.97 6 Hrs. 0.35 0.43 0.50 0.62 0.72 0.85 7 Hrs. 0.31 0.38 0.44 0.55 0.64 0.75 8 Hrs. 0.28 0.34 0.40 0.49 0.57 0.67 9 Hrs. 0.25 0.31 0.36 0.45 0.52 0.61 10 Hrs. 0.23 0.28 0.33 0.41 0.48 0.56 12 Hrs. 0.20 0.24 0.29 0.35 0.41 0.48 14 Hrs. 0.17 0.22 0.25 0.31 0.36 0.42 16 Hrs. 0.16 0.19 0.23 0.28 0.32 0.38 18 Hrs. 0.14 0.17 0.20 0.25 0.29 0.34 20 Hrs. 0.13 0.16 0.19 0.23 0.27 0.31 24 Hrs. 0.11 0.14 0.16 0.20 0.23 0.27 Source: Purdue,A.M., et. al., "Statistical Characteristics of Short Time Incremental Rainfall", Aug., 1992. (Values in this table are based on IDF equation and coefficients provided for Indianapolis, IN.) TABLE 201-3: Rainfall Depths for Various Return Periods 16 Rainfall Depth (Inches) Return Period (Years) Duration 2 5 10 25 50 100 24 Hrs. 2.66 3.27 3.83 4.72 5.52 6.46 Source: Purdue,A.M., et. al., "Statistical Characteristics of Short Time Incremental Rainfall", Aug., 1992.(Values in this table are based on IDF equation and coefficients provided for Indianapolis, IN.) TABLE 201-4: NRCS Type 2 Rainfall Distribution Ordinates (for use when not already built in the computer program ) Cumulative Percent Cumulative Percent of Storm Depth Cumulative Percent Cumulative Percent of Storm Depth of Storm Time of Storm Time 0 0 52 73 4 1 53 75 10 2.5 54 77 15 4 55 78 20 6 56 80 25 8 57 81 30 10 58 82 33 12 60 83.5 35 13 63 86 38 15 65 87 40 16.5 67 88 42 19 70 89.5 43 20 72 91 44 21 75 92 45 22 77 93 46 23 80 94 47 26 83 95 48 30 85 96 48.5 34 87 97 48.7 37 90 98 49 50 95 99 50 64 100 100 51 71 200-7 17 Carmel Police Headquarters Building Expansion Pipe Sizing Calculations Downstream Structure Length (ft) Pipe Diameter (in) Pipe Material Invert Slope (%) Mannings Number n Catchment Area (ac) Roof Runoff Coefficient C Roof Catchment Area (ac) Grass Runoff Coefficient C Grass Catchment Area (ac) Pavement Runoff Coefficient C Pavement Total Area A (ac) Composite Coefficient C Tc (min) Rainfall Intensity (i) in/hr Q=CiA (cfs) Total Area A (ac) Runoff Coefficient C Time in Upstream Pipe (min) Total Time of Concentration Tc (min) Intensity I (in/hr) Total Pipe Flow (cfs) Pipe Capacity Qmax (cfs) Full Pipe Velocity (ft/s) % of Full Flow Capacity Str. 1 Str. 2 (Ex. Pipe)22 12 HDPE 0.50 0.012 0.000 0.900 0.017 0.20 0.072 0.85 0.089 0.73 5.00 6.12 0.40 0.089 0.726 N/A 5.00 6.12 0.40 2.72 3.47 14.51% Str. 3 Str. 5 55 12 RCP 0.31 0.013 0.000 0.900 0.000 0.20 0.047 0.85 0.047 0.85 5.00 6.12 0.24 0.047 0.850 N/A 5.00 6.12 0.24 1.98 2.52 12.35% Str. 4 Str. 5 6 6 HDPE 37.00 0.012 0.000 0.900 0.021 0.20 0.055 0.85 0.076 0.67 5.00 6.12 0.31 0.076 0.670 N/A 5.00 6.12 0.31 3.68 0.00 8.47% Str. 5 Str. 6 130 12 RCP 0.31 0.013 0.000 0.000 0.000 0.00 0.000 0.00 0.000 0.00 0.00 0.00 0.00 0.123 0.739 0.36 5.36 6.05 0.55 1.98 2.52 27.80% Str. 6 Str. 8 34 15 HDPE 0.30 0.012 0.489 0.900 0.000 0.20 0.000 0.85 0.489 0.90 5.00 6.12 2.69 0.652 0.859 0.86 6.22 5.90 3.30 3.83 3.12 86.27% Str. 7 Str. 6 4 6 HDPE 33.00 0.012 0.000 0.900 0.008 0.20 0.032 0.85 0.040 0.72 5.00 6.12 0.18 0.040 0.720 N/A 5.00 6.12 0.18 3.48 5.07% Str. 8 Str. 9 49 15 HDPE 0.30 0.012 0.652 0.859 0.18 6.40 5.87 3.28 3.83 3.12 85.79% Str. 9 Detention 8 15 HDPE 0.00 0.012 Str. 10 Str. 9 21 12 HDPE 1.00 0.012 0.000 0.900 0.039 0.20 0.011 0.85 0.050 0.34 5.00 6.12 0.10 0.050 0.343 N/A 5.00 6.12 0.10 3.85 4.90 2.72% Str. 11 (Detention Outlet)Ex. Structure 50 12 HDPE 0.75 0.012 2.57* 3.34 4.25 77.03% Structure Pipe Data Pipe AnalysisContributing Watershed DataInlet Watershed Data 18 19 20 GRADLE DRIVEVETERANS WAYCIVIC SQUARERED TRUCK ROAD S RANGELINE ROADEXHIBIT 6: INLET BASIN MAP Development ConsultantsTransportation &NORTH21 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 5: Storm Inlet Calculations Storm inlets were placed throughout the site to ensure that there will be adequate capacity to pass the design 10-year flow with 50% of the sag inlet clogged with the maximum depth of water not exceeding 6 inches. Inlet Casting Information Type Width (ft) Length (ft) P (ft) A (sq. ft.) 3287-10V 1.14 2.71 5.50 2.10 R-4353 2.0 (dia.) 6.70 1.80 R-4996-A 0.67 12.00 25.33 2.40 R-4215-C 2.83 2.83 11.30 3.30 To simulate a 50% clogged condition, the perimeters and open areas of the castings were reduced to half of the above stated values. For depths less than 0.3 feet, the inlet grate acts as a weir and the maximum capacity of the grate, assuming ponding depths equal to the maximum allowable, can be calculated as follows: Q = 3.3P(h)1.5 Where: P = perimeter of the grate; h = head above the casting; Q = Capacity For depths greater than 0.4 feet, the inlet grate acts as an orifice and the maximum capacity of the grate, assuming ponding depths equal to the maximum allowable, can be calculated as follows: Q = 0.6A√2gh Where: A = open area of the grate, h = head above the casting; Q = Capacity The following table indicates the maximum inlet capacity assuming ponding depths up to the maximum allowable. Please refer Inlet Basin Map for additional information. 22 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Structure Casting Type 10-yr Inlet Watershed Flow (cfs) 50% Wetted Perimeter (ft.) 50% Open Area (sq. ft.) 10-yr Ponding (Weir Eq) (ft) Str. 1 3287-10V 0.40 2.75 1.05 0.13 Str. 3 R-4215-C 0.24 5.65 1.65 0.06 Str. 4 R-4996-A 0.31 12.67 1.20 0.04 Str. 7 R-4996-A 0.18 12.67 1.20 0.03 Str. 10 R-4353 0.10 3.35 0.90 0.05 Bottom of stone section: 834.75’ + 105 𝑐𝑟.𝑐𝑟. 233 𝑐𝑟.𝑐𝑟 x 1 ft = 835.20’ < 836.05’ (Entrance Elevation) Structure 4: Due to existing roadway constraints, there is no scenario where 100-YR runoff to Str 4 in plugged condition will have an emergency overflow route that would not be below the 836.01; however, there is a very low chance that Str. 4 would ever be fully clogged, given that there is little to no vegetation near Str. 4 that would be of concern to cause clogging. In the unlikely event that Str. 4 were to be clogged, the 100-YR runoff volume would overtop east of the trench drain at an elevation of 836.01 near the eastern man door, east of garage. The 100-YR volume would be able Local Flooding Calculations Per the Carmel Stormwater Technical Standards Manual 303, the Lowest Adjacent Grade for commercial buildings shall be one (1) foot above the above a noted overflow path/ponding within the lot. This is attainable for all proposed inlets except Structures 3, 4 and 10. Calculations in this section verify that there will be no adverse effects to the proposed and existing building. Structure 3: The resulting runoff for Inlet Basin 3 from a 100-Year storm event was calculated utilizing Hydraflow Hydrograph Extension software. Per the results included in this section, the total runoff equates to 105 cu. ft. Provided that the gravel section in the basin is comprised of 582 sq. ft. of a 12 inch section No 8 Stone with 40% void space, the following calculation shows that the water level in the stone section will not exceed the entrance elevation of 836.05: 582 sq. ft. x 1 ft x 40%= 233 cu. ft of storage 23 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs to be contained within the mechanical yard gravel basin in addition to the Str. 3 volume mentioned above. 843.75’ x 105 𝑐𝑟.𝑐𝑟.(𝑆𝑟𝑟.3)+ 139 𝑐𝑟.𝑐𝑟(𝑆𝑟𝑟 4) 233 𝑐𝑟.𝑐𝑟 x 1 ft = 835.79’ < 836.05’ (Entrance Elevation) Structure 10: The resulting runoff for Inlet Basin 10 from a 100-year storm event was calculated utilizing Hydraflow Hydrograph Extension software. Per the results included in this section, the total runoff equates to 47 cubic feet. Based on the stage storage table below, the runoff will result in a 100-year stage elevation of 840.61’ which is below the top of wall elevation of 842.00’. The staged runoff is contained within the grass area surrounding the inlet and does not stage against the proposed building foundation and retaining wall surrounding the artificial turf area. Str No 10 Stage Storage Table Contour Elevation Contour Area (sft) Depth (ft) Incremental Volume Avg. End (cft) Cumulative Volume Avg. End 839.50 3.02 N/A N/A 0 840.00 21.92 0.5 4.99 4.99 841.00 116.56 1 69.24 74.23 842.00 238.54 1 177.55 251.78 24 Hydrograph Report Tuesday, 11 / 2 / 2021Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 Hyd. No. 1 Str. No 3 = 0.349 cfsPeak dischargeHydrograph type = 5 minTime to peakStorm frequency = 105 cuftHyd. volumeTime interval = 0.85Runoff coeff.Drainage area = 5.00 minTc by UserIntensity = 1/1Asc/Rec limb factIDF Curve 0 1 2 3 4 5 6 7 8 9 10 Q (cfs) 0.000.00 0.050.05 0.100.10 0.150.15 0.200.20 0.250.25 0.300.30 0.350.35 0.400.40 0.450.45 0.500.50 Q (cfs) Time (min) Str. No 3 Hyd. No. 1 -- 100 Year Hyd No. 1 = Rational = 100 yrs = 1 min = 0.047 ac = 9.120 in/hr = SampleFHA.idf 25 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2022 Monday, 12 / 20 / 2021 Hyd. No. 3 Str. No 4 Hydrograph type = Rational Peak discharge = 0.464 cfs Storm frequency = 100 yrs Time to peak = 5 min Time interval = 1 min Hyd. volume = 139 cuft Drainage area = 0.076 ac Runoff coeff. = 0.67 Intensity = 9.120 in/hr Tc by User = 5.00 min IDF Curve = Carmel.IDF Asc/Rec limb fact = 1/1 0 1 2 3 4 5 6 7 8 9 10 Q (cfs) 0.00 0.00 0.05 0.05 0.10 0.10 0.15 0.15 0.20 0.20 0.25 0.25 0.30 0.30 0.35 0.35 0.40 0.40 0.45 0.45 0.50 0.50 Q (cfs) Time (min) Str. No 4 Hyd. No. 3 -- 100 Year Hyd No. 3 26 Hydrograph Report Tuesday, 11 / 2 / 2021Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2021 = 0.155 cfsPeak discharge= RationalHydrograph type = 5 minTime to peak= 100 yrsStorm frequency = 47 cuftHyd. volume= 1 minTime interval = 0.34Runoff coeff.= 0.050 acDrainage area = 5.00 minTc by User= 9.120 in/hrIntensity = 1/1Asc/Rec limb fact= SampleFHA.idfIDF Curve 0 1 2 3 4 5 6 7 8 9 10 Q (cfs) 0.000.00 0.050.05 0.100.10 0.150.15 0.200.20 0.250.25 0.300.30 0.350.35 0.400.40 0.450.45 0.500.50 Q (cfs) Time (min) Str. No 12 Hyd. No. 2 -- 100 Year Hyd No. 2 Hyd. No. 2 Str. No 10 27 December 17, 2021 // Carmel Police Headquarters Building Addition Calcs Section 6: Water Quality Calculations Water Quality requirements for the project will be met utilizing an inline Contech Cascade Separator. The proposed mechanical units provide sufficient removal of sediment and floatables prior to runoff entering the existing on-site storm system. In accordance with the City of Carmel Stormwater Manual, the treatment rate has been determined using the SCS Type II distribution for 1 inch of rainfall in 24-hours utilizing Storm and Sanitary Analysis (SSA) software. Water Quality Treatment Rate Watershed Structure No. Watershed Area (ac.) Water Quality Curve Number Required Treatment Rate (cfs) 10- Year Flow (cfs) Propos ed Water Quality Unit Max Treatment Rate (cfs) Max 10- Year On- Line Flow Rate (cfs) WQ-1 Str No. 8 0.80 98 1.23 3.20 Inline CS-4 1.80 4.03 Per the above table, the proposed Contech unit meets the treatment rate for the respective watersheds. In accordance with standard design procedures, the Contech Cascade Separator will be installed in an in-line configuration with an internal bypass. Please refer to the following documents included within this section of the report: post development storm results for the 1 inch – 24hr storm event, WQ CN Selection Chart, City of Indianapolis Stormwater Quality Unit sizing chart, Exhibit 7: WQ Treatment Watershed Map and Exhibit 8: Contech Details. 28 Project Description WQ.SPF Project Options CFS Elevation SCS TR-55 User-Defined Hydrodynamic YES NO Analysis Options Sep 30, 2021 00:00:00 Oct 01, 2021 00:00:00 Sep 30, 2021 00:00:00 0 days 0 01:00:00 days hh:mm:ss 0 00:05:00 days hh:mm:ss 0 00:05:00 days hh:mm:ss 30 seconds Number of Elements Qty 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 Outlets .......................................................................... Pollutants .............................................................................. Land Uses ............................................................................ Links...................................................................................... Channels ...................................................................... Pipes ............................................................................ Pumps .......................................................................... Orifices ......................................................................... Weirs ............................................................................ Nodes.................................................................................... Junctions ...................................................................... Outfalls ......................................................................... Flow Diversions ........................................................... Inlets ............................................................................ Storage Nodes ............................................................. Runoff (Dry Weather) Time Step .......................................... Runoff (Wet Weather) Time Step ........................................ Reporting Time Step ............................................................ Routing Time Step ................................................................ Rain Gages ........................................................................... Subbasins.............................................................................. Enable Overflow Ponding at Nodes ...................................... Skip Steady State Analysis Time Periods ............................ Start Analysis On .................................................................. End Analysis On ................................................................... Start Reporting On ................................................................ Antecedent Dry Days ............................................................ File Name ............................................................................. Flow Units ............................................................................. Elevation Type ...................................................................... Hydrology Method ................................................................. Time of Concentration (TOC) Method .................................. Link Routing Method ............................................................. 29 Subbasin Summary SN Subbasin Area Peak Rate Weighted Total Total Total Peak Time of ID Factor Curve Rainfall Runoff Runoff Runoff Concentration Number Volume (ac) (in) (in) (ac-in) (cfs) (days hh:mm:ss) 1 WQ-1 0.80 484.00 98.00 1.00 0.79 0.63 0.96 0 00:05:00 30 Subbasin Hydrology Subbasin : WQ-1 Input Data Area (ac) ..................................................... 0.80 Peak Rate Factor ........................................ 484.00 Weighted Curve Number ............................ 98.00 Rain Gage ID ............................................... Composite Curve Number Area Soil Curve Soil/Surface Description (acres) Group Number - 0.80 - 98.00 Composite Area & Weighted CN 0.80 98.00 Subbasin Runoff Results Total Rainfall (in) ......................................... 1.00 Total Runoff (in) .......................................... 0.79 Peak Runoff (cfs) ........................................ 0.96 Weighted Curve Number ............................ 98.00 Time of Concentration (days hh:mm:ss) ..... 0 00:05:00 31 Subbasin : WQ-1 32 City of Indianapolis Stormwater Quality Unit (SQU) Selection Guide Pg. 2 02/11/2020 Version 17.0 Manufactured SQU SQU System Model Max Treatment Flow (cfs) Max 10-yr On-Line Flow Rate (cfs) Cleanout Depth (Inches) 4-ft 1.12 2.95 9 6-ft 2.52 6.63 12 8-ft 4.49 11.81 15 10-ft 7.00 18.40 18 Hydro International Downstream Defender1 12 ft 10.08 26.51 21 3-ft 0.85 1.84 9 4-ft 1.5 3.24 9 5-ft 2.35 5.08 9 6-ft 3.38 7.30 9 7-ft 4.60 9.94 9 Hydro International First Defense High Capacity1 8-ft 6.00 12.96 9 HS-3 0.50 1.00 6 HS-4 0.88 1.76 6 HS-5 1.37 2.74 6 HS-6 1.98 3.96 6 HS-7 2.69 5.38 6 HS-8 3.52 7.04 6 HS-9 4.45 8.9 6 HS-10 5.49 10.98 6 HS-11 6.65 13.3 6 HydroStorm by Hydroworks, LLC1 HS-12 7.91 15.82 6 XC-2 0.57 1.16 6 XC-3 1.13 2.30 6 XC-4 1.86 3.79 6 XC-5 2.78 5.66 6 XC-6 3.88 7.90 6 XC-7 5.17 10.52 6 XC-8 6.64 13.51 6 XC-9 8.29 16.87 6 XC-10 10.13 20.62 6 XC-11 12.15 24.73 6 XC-12 14.35 29.20 6 AquaShield Aqua-Swirl Xcelerator1 XC-13 15.53 31.60 6 CS-4 1.80 4.03 9 CS-5 2.81 6.29 9 CS-6 4.05 9.07 9 CS-8 7.20 16.1 9 CS-10 11.3 25.3 9 Contech Cascade Separator CS-12 16.2 36.3 9 33 06/28/07 Exhibit 701-1: Curve Number Calculation for Water Quality Storm Event Water Quality Curve Number7072747678808284868890929496981000 102030405060708090100Percent ImperviousnessWater Quality Curve Number (CNwq)34 GRADLE DRIVEVETERANS WAYCIVIC SQUARERED TRUCK ROAD S RANGELINE ROADEXHIBIT 7: WATER QUALITY BASIN MAP Development ConsultantsTransportation &NORTH35 EXHIBIT 8: WATER QUALITY UNIT DETAILS (4'-0" [1219])SOLIDS STORAGE SUMP INLET PIPE (MULTIPLE INLET PIPES MAY BE ACCOMMODATED) OUTLET PIPE VARIESB 2'-3" [686]PLAN VIEW B-B NOT TO SCALE ELEVATION A-A NOT TO SCALE FIBERGLASS INTERNAL COMPONENTS FLOW CONTRACTOR TO GROUT TO FINISHED GRADE GRADE RINGS/RISERS A A 48" [1219] I.D. MANHOLE STRUCTURE TOP SLAB ACCESS (SEE FRAME AND COVER DETAIL)FLOW TOP OF CENTER CHAMBER (EXTENSIONS AVAILABLE AS REQUIRED) PERMANENT POOL ELEVATION FRAME AND COVER (DIAMETER VARIES) NOT TO SCALE www.ContechES.com ® www.contechES.com CASCADE SEPARATOR DESIGN NOTES THE STANDARD #### CONFIGURATION IS SHOWN. ALTERNATE CONFIGURATIONS ARE AVAILABLE AND ARE LISTED BELOW. SOME CONFIGURATIONS MAY BE COMBINED TO SUIT SITE REQUIREMENTS. CONFIGURATION DESCRIPTION GRATED INLET ONLY (NO INLET PIPE) GRATED INLET WITH INLET PIPE OR PIPES CURB INLET ONLY (NO INLET PIPE) CURB INLET WITH INLET PIPE OR PIPES GENERAL NOTES 1.CONTECH TO PROVIDE ALL MATERIALS UNLESS NOTED OTHERWISE. 2.FOR SITE SPECIFIC DRAWINGS WITH DETAILED STRUCTURE DIMENSIONS AND WEIGHT, PLEASE CONTACT YOUR CONTECH ENGINEERED SOLUTIONS LLC REPRESENTATIVE. www.ContechES.com 3.CASCADE SEPARATOR WATER QUALITY STRUCTURE SHALL BE IN ACCORDANCE WITH ALL DESIGN DATA AND INFORMATION CONTAINED IN THIS DRAWING. CONTRACTOR TO CONFIRM STRUCTURE MEETS REQUIREMENTS OF PROJECT. 4.CASCADE SEPARATOR STRUCTURE SHALL MEET AASHTO HS20 LOAD RATING, ASSUMING EARTH COVER OF 0' - 2' [610], AND GROUNDWATER ELEVATION AT, OR BELOW, THE OUTLET PIPE INVERT ELEVATION. ENGINEER OF RECORD TO CONFIRM ACTUAL GROUNDWATER ELEVATION. CASTINGS SHALL MEET AASHTO M306 AND BE CAST WITH THE CONTECH LOGO. 5.CASCADE SEPARATOR STRUCTURE SHALL BE PRECAST CONCRETE CONFORMING TO ASTM C478 AND AASHTO LOAD FACTOR DESIGN METHOD. 6.ALTERNATE UNITS ARE SHOWN IN MILLIMETERS [mm ]. INSTALLATION NOTES A.ANY SUB-BASE, BACKFILL DEPTH, AND/OR ANTI-FLOTATION PROVISIONS ARE SITE-SPECIFIC DESIGN CONSIDERATIONS AND SHALL BE SPECIFIED BY ENGINEER OF RECORD. B.CONTRACTOR TO PROVIDE EQUIPMENT WITH SUFFICIENT LIFTING AND REACH CAPACITY TO LIFT AND SET THE CASCADE SEPARATOR MANHOLE STRUCTURE. C.CONTRACTOR TO INSTALL JOINT SEALANT BETWEEN ALL STRUCTURE SECTIONS AND ASSEMBLE STRUCTURE. D.CONTRACTOR TO PROVIDE, INSTALL, AND GROUT INLET AND OUTLET PIPE(S). MATCH PIPE INVERTS WITH ELEVATIONS SHOWN. ALL PIPE CENTERLINES TO MATCH PIPE OPENING CENTERLINES. E.CONTRACTOR TO TAKE APPROPRIATE MEASURES TO ASSURE UNIT IS WATER TIGHT, HOLDING WATER TO FLOWLINE INVERT MINIMUM. IT IS SUGGESTED THAT ALL JOINTS BELOW PIPE INVERTS ARE GROUTED. SITE SPECIFIC DATA REQUIREMENTS STRUCTURE ID WATER QUALITY FLOW RATE (cfs [L/s]) PEAK FLOW RATE (cfs [L/s]) RETURN PERIOD OF PEAK FLOW (yrs) RIM ELEVATION PIPE DATA:INVERT MATERIAL DIAMETER INLET PIPE 1 INLET PIPE 2 OUTLET PIPE NOTES / SPECIAL REQUIREMENTS: CS-4 CASCADE SEPARATOR STANDARD DETAIL 36