HomeMy WebLinkAboutCUNNINGHAM - DURRANCE ENGINEERS INC. PAPERWORKCUNNINGHAM & DURRANCE
Consulting Engineers, Inc.
400 Executive Center Drive, Suite 108
West Palm Beach, Fl. 33401
Telephone (561) 689-5455 Fax (561) 640-7815
E-mail CDCONENG@AOL.COM
Drainage Statement For SCANNED
National Navy UDT-Seal Museum BY
St. Lucie County, Florida St. Lucie County
The Addition to the National Navy UDT-Seal Museum located at 3300 North Highway
AIA, Fort Pierce, Florida is a 8,503 Square Foot building. Parking is provided by use of
the existing Pepper Park parking, which is shared between the museum and beach goers.
The National Navy UDT-Seal lease a 3.220 acre portion of the park from Saint Lucie
County for the museum. The total impervious area for the proposed addition to the
museum, plus the existing buildings and walkways is only 0.537 acres. Since the total site
area is less than 10 acres and the impervious area is less than 10 acres, combined with the
fact that no work is in wetlands or is located east of the coastal construction control line,
the project qualifies for a no notice permit from the South Florida Water Management
District, which means application is not required.
According to the FEMA Flood Insurance Rate Map No. 120285-018 1 -G, a portion of the
proposed building is outside of a flood hazard area, and the remainder is zone AO (Depth
l'), the existing maximum existing ground is elevation 7.0 under the proposed building,
therefore the minimum Finish Floor Elevation for the proposed addition was set at
elevation 8.0 Feet NAVD (9.49 Feet NGVD). The elevation of the adjacent roadway,
State Road A-1-A, is elevation 6.9 feet NAVD. The elevation of the adjacent onsite
building, which will be joined to the proposed building is elevation 7.48 Feet NAVD. In
accordance with Section 7.04.0l.C.2.b.2 of the Land Development Code, the calculated
100 year zero discharge elevation for the lease parcel is elevation 7.1 Feet NAVD. Since
the calculated flood elevation and flood elevation based on the FEMA Flood Insurance
Rate Map meet the requirements, and since the elevation of the adjacent structure, which
is being connected to the proposed addition is at elevation 7.48 Feet NAVD, the fact that
the Proposed Finish Floor Elevation of 8.0 Feet NAVD, is less than 18 inches above the
State Road A-1-A elevation 6.9 feet NAVD, this can be discounted and approved by the
Growth Management Director, in accordance with Section 7.04.0l.C.3 of the Land
Development Code, which states "When topographical conditions are such that
compliance with this subsection would be impracticable or cause grade level conditions
detrimental to adjacent or nearby property, the Growth Management Director shall grant
relief from the provisions of this subsection, consistent with Flood Protection
regulations. "
The soils at the site are classified as Palm Beach Fine Sand according to the Soil Survey
of Saint Lucie County. This excessively drained, nearly level or gently sloping soil is on
dune like ridges that are generally parallel to the coast. Typically Palm Beach sand does
not have a water table within 80 inches annually. Available water capacity is very low,
and permeability is very rapid. The soils test conducted by Allterra Engineering and
Testing confirmed the above. The depth to the water table was in excess of 6 feet, and the
permeability rate of 1.4 to 1.5 x 10-4 is very rapid. Based on criteria from the South
CUNNINGHAM & DURRANCE
Consulting Engineers, Inc.
400 Executive Center Drive, Suite 108
West Palm Beach, Fl. 33401
Telephone (561) 689-5455 Fax (561) 640-7815
E-mail CDCONENG@AOL.COM
Florida -Water Management District Permit Information Manual Volume IV, Figure`E-1,
the Coastal soils with a depth to water table of 4 feet or greater will store 10.9 inches of
water and taking into account the impervious area; will result in the storage of 9.3 inches
of runoff, or the rainfall from a 10 year - 3 day rainfall event. This combined with the
rapid permeability rate of the soil will allow the water to permeate into the soil rapidly,
thus negating the requirement for a positive legal outfall. According to the Saint Lucie
Land Development Code, Section 11.20.09.2.e Identification of legal positive outfall, if
applicable. Since the onsite soil has available capacity to store the rainfall from the
design 10 year - 3 day storm event, based on the percent impervious for the site, the
applicable positive legal outfall for the site is soil storage, which will rapidly permeate
into the underlying soils and will help maintain the fresh water aquifer on the Island.
As shown in the drainage plan a 17,500 square feet retention area will be provided. This
area is greater than 2 times the additional impervious area of 8,503 square feet for the
addition, thus meeting the requirements of the Saint Lucie Land Development Code, -
Section 7.07.09.A.2, which requires. If an existing development has a total impervious
area of more than four thousand (4, 000) square feet on the effective date of this Code or
subsequently expands and/or alters its impervious area to exceed a total of four
thousand (4, 000) or more square feet, additions or alterations to the development shall
require compliance with the provisions of this Code at a ratio of two (2) square feet of
managed treatment area for every one (1) square foot of new or altered impervious
surface. Adequate storage for the runoff for a 3 year - 24 hour storm is provided with a
bottom elevation of 6.0 to elevation 6.4 feet NAVD, for the existing onsite walkways,
and a 25 year - 3 day storm is retained below elevation 6.8 feet NAVD, which is the
perimeter berm elevation for the lease site.
Prepared By:
Cunningham Durrance Consulting Engineers, Inc.
EB No. 4502
400 Executive Center Drive, Suite 108
West Palm Beach, Fl. 33401
December 13, 2010
Stuart H. Cunningham, PE No. 30896
10-032 (10-032 Drainage Statement)
Navy
Seal Museum St Lucie County, FI.'
STAGE/STORAGE COMPUTATION
NAME
RETENTION
SITE
BUILDING
TOTAL
GRADING
AREA
(ACRE)
(ACRE)
(ACRE)
(ACRE)
AREA
0.402
3.060
0.305
3.767
START EL.
6.00
6.00
7.50
END EL.
6.00
7.40
FEET
STORAGE
STORAGE
STORAGE
STORAGE
NGVD
AC -FT
AC -FT
AC -FT
AC -FT
6.00
0.00
0.00
0.00
0:00
6.50
0.20
0.27
0.47
0.47
7.00
0.40
1.09
1.49
1.49
7.50
0.60
2.46
3.06
3.06
8.00
0.80
3.98
4.78
4.78
8.50
1.00
5.51
6.51
6.51
9.00
1.21
7.04
8.24
8.24
9.50
1.41
8.57
9.97
9.97
10.00
1.61
10.10
11.71
11.71
10.50
1.81
11.63
13.44
13.44
Prepared by Cunningham & Durrance Consulting Engineers, Inc. 12/13/2010 Page 1
WATER MANAGEMENT CALCULATIONS
FOR
— Navy Seal Museum - St Lucie County, FI.
I.
GIVEN:
A.
ACREAGES
1.
TOTAL AREA (AC.)
3.767
2.
IMPERVIOUS
a.
Building (Ac.)
0.305
b.
Paved Areas (Ac.)
0.242
3.
LAKE
0.000
4.
RETENTION AREA
0.402
5.a.
PERVIOUS (OPEN SPACE)
2.818
b.
PERVIOUS
0.000
TOTAL PERVIOUS
3.220
6.
Commercial / Industrial(AC.)
0.000
B.
MINIMUM ELEVATION
1.
Walks
6.40
2.
FINISHED FLOOR ELEVATION
7.50
3.
Gravel Drive
6.90
C.
LAND USE
Recreational
D.
WATER LEVEL ELEVATION
1.
WET SEASON GWT EL.
1.5
2.
DRY SEASON GWT EL.
1.0
3.
RETENTION AREA EL.
6.00
4.
CONTROL WATER EL. (NGVD)
5.0
E.
3 YEAR 24 HOUR RAINFALL (IN.)
4.5
F.
5 YEAR 24 HOUR RAINFALL (IN.)
5.0
G.
10 YEAR 72 HOUR RAINFALL (IN.)
9.0
H.
25 YEAR 72 HOUR RAINFALL (IN.)
10.0
I.
100 YEAR 72 HOUR RAINFALL (IN.)
12.0
J.
ALLOWABLE DISCHARGE (CFS) cis crs/sn)
0.21
C-51 Basin (Area 23)
Prepared by Cunningham & Durrance Consulting Engineers, Inc. 12/13/2010 Page 1
WATER MANAGEMENT CALCULATIONS
FOR
Navy Seal Museum - St Lucie County, FI.
II.
COMPUTATIONS
A.
QUALITY
1.
FIRST 1" RUNOFF (AC. FT.)
0.31
2.
2.5" X % IMPERVIOUS (AC. FT.)
a.
Site Area for Water Quality
3.46
b.
Impervious Area
0.24
C.
Water Quality % Impervious
0.07
d.
2.5' X % Impervious (In.)
0.17
e.
Volume Detention Reqd. (Ac. Ft.)
0.05
3.
DRY DETENTION VOLUME REQUIRED
FIRST 0.5" RUNOFF (AC. FT.)
0.00
4.
Total Retention Volume Required (75% Dry Detention)
0.23
B.
STAGE/STORAGE
C.
Detention CREST EL. (N.G.V.D.)
6.25
Prepared by Cunningham & Durrance Consulting Engineers, Inc. 12113/2010 Page 2
WATER MANAGEMENT CALCULATIONS
FOR
Navy Seal Museum - St Lucie County, FI.
E.
DETERMINE SOIL STORAGE
1.
IMPERVIOUS AREA (ACRE)
0.55
2.
PERVIOUS AREA (ACRE)
3.22
3.
COMPUTE DEPTH TO WATER TABLE
a.
Avg. finish site elevation (NGVD)
6.7
b.
Wet season avg. GWf EL. (NGVD)
1.5
C.
Avg. depth to water table (Ft.)
5.2
4.
AVAILABLE SOIL MOISTURE STORAGE
FROM FIGURE E-1 (IN.) (Coastal)
10.90
5.
COMPOSITE SOIL STORAGE (IN.)
9.3
F.
DETERMINE MAXIMUM DESIGN 25 YEAR STORM EL.
1.
TOTAL 3 Day RAINFALL (P) (IN.)
10.0
2.
TOTAL RUNOFF (INCHES)
3.8
3.
TOTAL RUNOFF VOLUME (AC. -FT.)
1.2
4.
ZERO DISCHARGE STAGE (FT. NGVD)
6.8
F.
DETERMINE MAXIMUM DESIGN 3 YEAR STORM EL.
1.
TOTAL 24 Hour RAINFALL (P) (IN.)
4.5
2.
TOTAL RUNOFF (INCHES)
0.6
3.
TOTAL RUNOFF VOLUME (AC. -FT.)
0.19
4.
ZERO DISCHARGE STAGE (FT. NGVD)
6.6
Prepared by Cunningham & Durrance Consulting Engineers, Inc. 12/13/2010 Page 3
H.
1.
2.
3.
4.
WATER MANAGEMENT CALCULATIONS
FOR
Navy Sea[ Museum - St Lucie County, FI. —
CHECK MINIMUM FINISH FLOOR EL
TOTAL 3-DAY RAINFALL (P) (IN.) 12.0
TOTAL RUNOFF (INCHES) 5.3
TOTAL RUNOFF VOLUME (AC. -FT.) 1,66
ZERO DISCHARGE STAGE (FT. NGVD) 7.1
Prepared by Cunningham & Durrance Consulting Engineers, Inc. 12/13/2010 Page 4