HomeMy WebLinkAboutStormwater Technical Letter ReportStormwater Technical Letter Report Weihe Engineers, INC.
4/1/2025
Stormwater Technical Letter Report
Prepared For:
Jacquie’s Catering Exterior
Renovation & Addition
Carmel, IN
Project #W241058
Project Overview:
Adavis LLC is proposing to renovate Jacquie’s Gourmet Catering facilities on a 0.74 +/-
acre parcel located at 4306 W 96th Street, which is part of a commercial complex in the
northwest corner of West 96th Street and US 421(Michigan Street). The renovation will
include the removal of hard impervious surface refurbished with landscaping and
pervious area. A small, 1120 S.F. addition on the northwest corner of the existing 7100
S.F. building will be installed.
The development is on a site at a Latitude of N 39° 55' 35.17" and Longitude W 86° 13'
53.61", falling within Clay Township. The site is generally located in the SE/4 of Section
07, Township 17 North, and Range 3 East, Hamilton County, Carmel, Indiana.
Stormwater Technical Letter Report Weihe Engineers, INC.
4/1/2025
Floodzone:
Based upon a scaled interpretation of the Flood Insurance Map Nos.18057C0225G for
Hamilton County, Indiana, effective date November 19, 2014, the entire subject tract IS
located within Zone X (Areas determined to be outside the 0.2% annual chance
floodplain) as shown below:
Pre-Developed Conditions:
Aerial photography in both clips above illustrates the current land-use of the subject tract
is an existing commercial site. Stormwater runoff from the site surface area drains to
existing storm sewer infrastructure as well as drains to the exiting stormwater pond
located due west, which is the western boundary of the site. The frontage along 96th
Street and the east side of the site is conveyed by the existing storm sewer infrastructure
north into the drainage systems that are part of the US 421. The existing site area is
composed of 0.14-Ac. of pervious surface and 0.63-Ac. impervious surface.
Stormwater Technical Letter Report Weihe Engineers, INC.
4/1/2025
Post-Developed Conditions:
The proposed site will utilize the existing drainage infrastructure and drainage patterns.
The disturbance will be limited to the removal of pavement for the construction of the
proposed 1120 S.F. building addition and the landscaping proposed for the site. The
pervious surface area will be increased to 0.25-Ac. and the impervious surface reduced to
0.52-Ac. The change in impervious area of the site will have an impact on the peak
discharge rates and runoff volume from the site, as shown in the table below:
ANALYSIS OF JACQUIE’S CATERING SITE
COMPUTATIONS BASED ON RATIONAL FORMULA Q = CIA
RUNOFF VOLUME ~ [AREA (ACRES) X RAINFALL/FREQUENCY (IN.) X C] / 12 = AC-FT. FOR 24 HOUR DURATION
RUNOFF RATE~ [AREA (ACRES) X RAINFALL/FREQUENCY (IN.) X C]
RETURN
FREQUENCY
DRAINAGE
AREA NO.
AREA
(ACRES)
RUNOFF
VOLUME
(AC.-FT.)
TIME OF
CONCENTRATION
(MINUTES)
RUNOFF
COEFICIENT
C
INTENSITY (I)
IN/HR.
PEAK
DISCHARGE (Q)
C.F.S.
2 Year Ex Site 0.74 0.123 5 0.75 4.63 2.57
Pro Site 0.74 0.112 5 0.68 4.63 2.33
5 Year Ex Site 0.74 0.151 5 0.75 5.43 3.01
Pro Site 0.74 0.137 5 0.68 5.43 2.73
10 Year Ex Site 0.74 0.177 5 0.75 6.12 3.40
Pro Site 0.74 0.161 5 0.68 6.12 3.08
25 Year Ex Site 0.74 0.218 5 0.75 7.17 3.98
Pro Site 0.74 0.198 5 0.68 7.17 3.61
50 Year Ex Site 0.74 0.255 5 0.75 8.09 4.49
Pro Site 0.74 0.231 5 0.68 8.09 4.07
100 Year Ex Site 0.74 0.299 5 0.75 9.12 5.06
Pro Site 0.74 0.271 5 0.68 9.12 4.59
**Rainfall intensity and depth values were taken from Tables 201-2 & 201-3 of the City
of Carmel Stormwater Technical Manual.
Conclusion:
The propose site improvements will reduce the site runoff with the reduction of 17.5% of
impervious area, which will be a benefit to existing drainage infrastructure of the site.