HomeMy WebLinkAboutDrainage Report
Stormwater Calculations
Harvest Church – Phase 2
City of Carmel
Hamilton County, Indiana
Prepared:
October 18, 2023
By:
CrossRoad Engineers, PC
115 N. 17th Ave.
Beech Grove, IN 46107
Phone No.: (317) 780-1555
Email: info@crossroadengineers.com
Table of Contents
Section 1: Stormwater Calculations Summary
Pre-Development Conditions ......................................................................... 1
Post-Development Conditions ........................................................................ 1
Exhibits
• Exhibit 1: Location Map ....................................................................... 2
• Exhibit 2: Pre-Development Watershed Map ....................................... 3
• Exhibit 3: Post-Development Watershed Map ..................................... 4
Section 2: Hydrologic Modeling Calculations
Runoff Curve Number Calculations
• Post-Development Conditions .............................................................. 5
• Legacy PUD, Stormwater Development Checklist ............................... 6
• Pre & Post Flood Hydrographs ....................................................... 7-8
• Pre & Post Time of Concentration Worksheets .............................. 9-10
Section 1: Stormwater Calculations Summary
Pre-Development Conditions
The subject site is a portion of an overall ±17.78 acre parcel located on the west side of River
Road approximately 1,300 feet south of the 146th Street & River Road intersection in the City of
Carmel (see Exhibit 1: Location Map). This phase of development shall consist of ±6.84 acres
within the aforementioned overall parcel. In addition, this land is all located within the Legacy
Development. The Legacy development shall provide all necessary storm water detention and
water quality for the Harvest Church property.
The pre-development land use consists of two (2) existing structures, parking lot, and concrete
walks that were developed in the first phase of construction. The area that will be improved
within this phase primarily consists of grass. Existing runoff is mainly conveyed westerly to the
Legacy development, where it eventually flows into the West Fork of the White River (see
Exhibit 2: Pre-Development Watershed Map). The project site lies within Zone X, per
Community Panel 18057 C 0231 G of the Flood Insurance Rate Map of Hamilton County, dated
November 19, 2014. No wetland areas lie within the project limits per the National Wetlands
Inventory Map.
Post-Development Conditions
The improvements include a ±32,000 square foot building expansion, that will connect the two
(2) existing structures and create one larger building. Additionally, a parking lot and concrete
walk areas shall be constructed for the proposed development (see Exhibit 3: Post-Development
Watershed Map). Runoff shall be conveyed via sheet flow to the western side of the property
where it will be collected and routed through a porous asphalt system. The runoff shall then be
discharged into the existing detention/BMP facilities within the Legacy development, where it
shall be treated for water quantity and quality. It is not anticipated to construct any onsite
detention or water quality facilities as the proposed site was master planned within the Legacy
development. The Legacy report identifies the subject site as Basin 700 with an anticipated
curve number of 94. The comparison of the actual developed curve number to the Legacy design
curve number shall be discussed later in this report.
EXHIBIT #1
LOCATION MAP
NORTHPHASE 2 AREA
PHASE 1
AREA
Tract A
N32°37'45"E 270.95'L8L9L10N30°42'26"E 452.03'L1
L2L3
C1S21°48'03"W 191.51'L4
S21°14'47"W 288.92'PHASE 2 BASIN
A=6.84 ac.
CN=76
NORTHEXHIBIT 2:
PRE DEVELOPMENT WATERSHED MAP
N32°37'45"E 270.95'L8L9L10N30°42'26"E 452.03'L1
L2L3
C1S21°48'03"W 191.51'L4
S21°14'47"W 288.92'PHASE 2 BASIN
A=6.84 ac.
CN=89
NORTHEXHIBIT 3:
POST DEVELOPMENT WATERSHED MAP
Section 2: Hydrologic Modeling Calculations
Detention and water quality requirements for the Harvest Bible project have been met with the
implementation of the detention facilities within the Legacy development. In order to ensure the
proposed development does not produce a runoff greater than what was anticipated in the
previously approved Legacy stormwater calculations, it shall be demonstrated that the proposed
curve number is less than or equal to the anticipated curve number.
Runoff Curve Number Calculations
Curve numbers were computed based on the applicable land use and Soil Hydrologic Group B
soils for pre-development conditions. For post-development conditions, Soil Hydrologic Group
C soils were used to compute curve numbers in accordance with the City of Carmel Stormwater
Management Ordinance.
Post-Development Conditions
Table 1
Post-Development Runoff Curve Number Calculations
Phase 2 Watershed
Land Use
Description
Runoff Curve No. For
Hydrologic Group – B
Runoff Curve No. For
Hydrologic Group – C
Average
Runoff Curve
Number
Roof - 98 98
Pavement - 98 98
Grass
(Good Condition) - 74 74
Table 2
Post-Development Weighted Curve Number Calculations
Phase 2 Watershed
Land Use
Description
Land Use Curve
Number Land Use Area Percentage of
Total Area
Weighted Curve
Number
Impervious 98 4.309 ac. 63.00% 61.74
Grass
(Good Condition) 74 2.531 ac. 37.00% 27.38
Total 6.840 ac. 89.12 ≈ 89
Anticipated Legacy Basin 700 Curve Number: 94 – Commercial
Calculated Harvest Bible Phase 1 Curve Number: 89 < 94
The weighted curve number is less than the anticipated curve number; therefore,
detention and water quality capacities provided by the Legacy infrastructure are
adequate.
The following sheets are the Legacy PUD, Stormwater Development Checklist and supporting
hydrograph information, confirming that the proposed improvements are in compliance with the
Legacy detention and water quality design.
HARVEST CHURCH
HARVEST BIBLE CHAPEL OF NORTH INDIANAPOLIS, INC.
14550 RIVER ROAD, CARMEL, IN 46033
CROSSROAD ENGINEERS, P.C.
115 N. 17th AVE., BEECH GROVE, IN 46107
BAS 700 DD10 EAST 94 89 85%63%10 min.13.3 min.
91,514
132,684
41,170
65,872
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023 Tuesday, 10 / 17 / 2023
Hyd. No. 1
PRE PH2 100yr-24hr
Hydrograph type = SCS Runoff Peak discharge = 32.60 cfs
Storm frequency = 100 yrs Time to peak = 722 min
Time interval = 2 min Hyd. volume = 91,514 cuft
Drainage area = 6.840 ac Curve number = 76*
Basin Slope = 0.0 %Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc)= 13.95 min
Total precip.= 6.46 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.592 x 98) + (6.247 x 74)] / 6.840
1
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
5.00 5.00
10.00 10.00
15.00 15.00
20.00 20.00
25.00 25.00
30.00 30.00
35.00 35.00
Q (cfs)
Time (min)
PRE PH2 100yr-24hr
Hyd. No. 1 -- 100 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2023 Tuesday, 10 / 17 / 2023
Hyd. No. 2
POST PH2 100yr-24hr
Hydrograph type = SCS Runoff Peak discharge = 48.61 cfs
Storm frequency = 100 yrs Time to peak = 720 min
Time interval = 2 min Hyd. volume = 132,684 cuft
Drainage area = 6.840 ac Curve number = 89*
Basin Slope = 0.0 %Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc)= 13.28 min
Total precip.= 6.46 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(4.309 x 98) + (2.531 x 74)] / 6.840
2
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Q (cfs)
0.00 0.00
10.00 10.00
20.00 20.00
30.00 30.00
40.00 40.00
50.00 50.00
Q (cfs)
Time (min)
POST PH2 100yr-24hr
Hyd. No. 2 -- 100 Year
Hyd No. 2
Project:Harvest Church
Designer:DJM Date:10/17/2023
Scenario/Structure:Pre TC - Phase 2
Sheet Flow
1.Surface Description grass pvmt grass
2.Manning's Roughness Coeff., (n)0.170 0.011 0.170
3.Flow Length, (L) **total L<= 100 ft 100.00 ft.0.00 ft.0.00 ft.
4.Two-yr 24-hr Rainfall, (P2)2.64 in.2.64 in.2.64 in.
5.Land Slope, (s)0.0186 ft./ft.0.0090 ft./ft.0.0851 ft./ft.
6.Travel Time, (Tt)0.205 hr +0.000 hr +0.000 hr
(Tt = [0.007(nL)^0.8]/[P2^0.5*s^0.4])
Shallow Concentrated Flow
7.Surface Description paved unpaved unpaved
(paved or unpaved)
8.Flow Length, (L)0.00 ft.221.76 ft.0.00 ft.
9.Watercourse Slope, (s)0.0090 ft./ft.0.0186 ft./ft.0.0387 ft./ft.
10.Average Velocity, (V)1.929 ft./s 2.200 ft./s 3.174 ft./s Watershed or
(Vp = 20.3282(s)^0.5)Subarea Tc or Tt =
(Vup = 16.1345(s)^0.5)0.233 hr
or
11.Travel Time, (Tt)0.000 hr +0.028 hr +0.000 hr 13.95 min
(Tt = L/3600V)
Channel Flow
12.Cross Sectional Flow Area, (a)133.48 ft.^2 132.12 ft.^2 174.24 ft.^2
13.Wetted Perimeter, Pw 35.51 ft.30.71 ft.43.74 ft.
14.Hydraulic Radius, (r)3.759 ft.4.302 ft.3.984 ft.
( r = a/Pw)
15.Channel Slope, (s)0.0175 ft./ft.0.0121 ft./ft.0.0084 ft./ft.
16.Manning's Roughness Coeff., (n)0.027 0.027 0.027
17.Velocity, (V)17.727 ft./s 16.136 ft./s 12.769 ft./s
(V = [1.49*r^0.67*s^0.5]/n)
18.Flow Length, (L)0.00 ft.0.00 ft.0.00 ft.
19.Travel Time, (Tt)0.000 hr +0.000 hr +0.000 hr
(Tt = L/3600V)
TIME OF CONCENTRATION or TRAVEL TIME WORKSHEET
Project:Harvest Church
Designer:DJM Date:10/17/2023
Scenario/Structure:Post TC - Phase 2
Sheet Flow
1.Surface Description grass pvmt grass
2.Manning's Roughness Coeff., (n)0.170 0.011 0.170
3.Flow Length, (L) **total L<= 100 ft 70.22 ft.29.78 ft.0.00 ft.
4.Two-yr 24-hr Rainfall, (P2)2.64 in.2.64 in.2.64 in.
5.Land Slope, (s)0.0149 ft./ft.0.0098 ft./ft.0.0851 ft./ft.
6.Travel Time, (Tt)0.168 hr +0.011 hr +0.000 hr
(Tt = [0.007(nL)^0.8]/[P2^0.5*s^0.4])
Shallow Concentrated Flow
7.Surface Description paved unpaved unpaved
(paved or unpaved)
8.Flow Length, (L)302.16 ft.0.00 ft.0.00 ft.
9.Watercourse Slope, (s)0.0098 ft./ft.0.0265 ft./ft.0.0387 ft./ft.
10.Average Velocity, (V)2.012 ft./s 2.627 ft./s 3.174 ft./s Watershed or
(Vp = 20.3282(s)^0.5)Subarea Tc or Tt =
(Vup = 16.1345(s)^0.5)0.221 hr
or
11.Travel Time, (Tt)0.042 hr +0.000 hr +0.000 hr 13.28 min
(Tt = L/3600V)
Channel Flow
12.Cross Sectional Flow Area, (a)0.79 ft.^2 132.12 ft.^2 174.24 ft.^2
13.Wetted Perimeter, Pw 3.14 ft.30.71 ft.43.74 ft.
14.Hydraulic Radius, (r)0.250 ft.4.302 ft.3.984 ft.
( r = a/Pw)
15.Channel Slope, (s)0.0048 ft./ft.0.0121 ft./ft.0.0084 ft./ft.
16.Manning's Roughness Coeff., (n)0.012 0.027 0.027
17.Velocity, (V)3.397 ft./s 16.136 ft./s 12.769 ft./s
(V = [1.49*r^0.67*s^0.5]/n)
18.Flow Length, (L)0.00 ft.0.00 ft.0.00 ft.
19.Travel Time, (Tt)0.000 hr +0.000 hr +0.000 hr
(Tt = L/3600V)
TIME OF CONCENTRATION or TRAVEL TIME WORKSHEET