DRAINAGE CALCULATIONS
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June 2007
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Kohls
Boynton Beach
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Drainage Calculations
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Prepared for:
South Florida Water Management District
3301 Gun Club Road
West Palm Beach, FL 33466
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Prepared by:
Kimley-Horn and Associates, Inc.
601 21 st Street, Suite 400
Vero Beach, FL 32960
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ilIiJfr/1
Pe r J. Van Rens, P.E.
Date: June 11, 2007
Florida Registration .No. 55553
Corp Registration #: CA 00000696
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1IIII"'1-_InI. Kimley-Horn
-.J r, and Associates, Inc.
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I. SITE LOCATION: TARGET SHOPPING CENTER BOYNTON
BEACH
The site is located at 1901 North Congress Avenue on the Southwest corner of
Congress Avenue and Gateway Boulevard. It consists of an existing Target
store, planned for a conversion to a Kohl's, on 8.84 acres, with a Carrabas and
CVS on the remaining portion of the 12.72 acres site.
II. MODIFICATION SUMMARY
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The Target is permitted as part of the Congress Lakes P.UD. (Permit #50-
01116-8). This surface water management permit was modified August 9,
1990. The permit modification includes Carriage Homes 36.11 acre, off site
mobile home park 37.04 acre, and the Target Shopping Center 13.18 acre.
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This report will address the improvements being made to the existing Target
future Kohls building which is part ofthe Target Shopping Center.
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III. POST-DEVELOPMENT SITE DATA
Below are the permitted and proposed area breakdowns for the Target
Shopping Center.
Previously Permitted (#50-01116-S) Kohls Modifications (Proposed)
Parameter Area (ac) Parameter Area (ac)
Buildings 3.51 Buildings 3.25
Pervious Area 0.80 Pervious Area 1.61
Impervious Area 8.87 Impervious Area 7.86
Total 13.18 Total 12.72
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IV. WATER QUALITY
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We have evaluated the water quality requirement for the proposed
modifications and compared them to the water quality provided for the Target
site based on the permitted site data. There is less water quality required in the
post-development than was originally permitted. Therefore, no water quality
improvements are proposed. See below for the calculations..
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The permitted water quality was 2.5" x % impervious.
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2.5" x % impervious is as follows:
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a) 13.18 - (roof)
b) 9.67 - green area
c) % impervious
d) 2.5 * % impervious
e) 2.293" * 9.67 ac
13.18 - (3.51)
9.67- 0.80
(8.87/9.67)* 1 00
2.5 * .917
22.173 ac-in
= 9.67 ac
= 8.87 ac
= 91.7 %
= 2.293 in
= 1.85 ac-ft
The proposed water quality is 2.5" x % impervious.
2.5" x % impervious is as follows:
a) 12.72 - (roof)
b) 9.47 - green area
c) % impervious
d) 2.5 * % impervious
e) 2.075" * 9.47 ac
12.72 - (3.25)
9.47- 1.61
(7.86/9.47)*100
2.5 * .830
19.650 ac-in
= 9.47 ac
= 7.86 ac
= 83.0 %
= 2.075 in
= 1.64 ac-ft
From the calculations 1.64 ac-ft < 1.85 ac-ft, therefore this site meets permitted
requirements for water quality.
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V. PERMITTED DESIGN PARAMETERS
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3 year 1 day = 6.50 in rainfall
25 year 1 day = 12.0 in rainfall
100 year 3 day = 21.74 in rainfall
Control Water Elevation = 8.5 ft NGVD (6.97 NA VD)
FFE =13.77 ft NGVD (12.24 NA VD)
Lowest Inlet =11.51 ft NGVD (9.98 NA VD)
25 year Berm EI =12.81 ft NGVD (11.28 NA VD)
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VI.
ALLOWABLE DISCHARGE
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We are not adding any additional area to the original permit and not modifying
any of the discharge structures. Therefore, no increase in discharge is
proposed.
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VII. CONCLUSIONS
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There is no additional water quality treatment, no change in the stage/storage
assumptions, and no additional discharge relative to the Congress Lakes P.UD.
Permit #50-01116-S. Therefore, no modifications to the stormwater system are
proposed other than some minor piping/inlet relocations.
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