SW8950303_HISTORICAL FILE_19961210

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW8 C15030'j
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
HISTORICAL FILE
❑ COMPLIANCE EVALUATION INSPECTION
DOC DATE
l°I°i e 1210
YYYYMMDD

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State of North Carolina
Department of Environment, Health, and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr. Division of Water Quality Jonathan B. Howes
Governor Water Quality Section Secretary
December 5, 1996
Mr. Perry Davis, P.E.
Atlantic Coast Design
Post Office Box 203
Wrightsville Beach, North Carolina 28480
Subject:, ADDITIONAL INFORMATION
Stormwater Project No. SW8 950303 Modification
Bald Head Island Sabal Palm Cottages
Brunswick County
Dear Mr. Davis:
The Wilmington Regional Office received previously requested information for the modification to
the Stormwater Management Permit Application for Bald Head Island Sabal Palm Cottages on November
25, 1996. A preliminary review of that information has determined that the application is not complete.
The following information is needed to continue the stormwater review:
1. In your October 14, 1996 calculations, the total impervious area was calculated and used to
determine the required volume. In my additional information request letter of November 15,
1996, I requested that you use the entire drainage area to the pond, including the grassed
areas, to determine the required volume, and indicated that the Schuler Method would be
satisfactory. In your revised calculations, you still use only the impervious area as the
drainage area. This is still not correct. Unless you are able to separate the runoff from the
grassed areas and the runoff from the impervious areas, you must use both impervious and
grassed areas within the drainage area to figure the percent impervious and the volume.
Technically, for the infiltration swale It1, if the impervious area total is .45 acres, and the
drainage area is .45 acres, then your percent impervious is 100%, not 35.7 as you report.
This equates to a drainage area of 1.26 acres. Substituting this into the volume equation yields
a required volume to store of 2,204 cubic feet, not 911 cubic feet. Since the swale provides
2,500 cubic feet of storage, this particular swale is OK, but you must revise the calculations
and provide corrected required volume calculations using the total drainage area to the
swale/ponds.
127 Cardinal Drive Extension, Wilmington, N.C. 28405-3845 • Telephone [phone] • Fax [phone]
An Equal Opportunity Affirmative Action Employer

Mr. Davis
December 5, 1996
Stormwater Project No. SW8 950303 Modification
Please note that this request for additional information is in response to a review of the submitted
information. The requested information should be received by this Office prior to January 6, 1997, or the
application will be returned as incomplete. The return of a project will necessitate resubmittal of all required
items, including the application fee.
If you have any questions concerning this matter please feel free to call me at [phone].
Sincerely,
Ms. Linda Lewis
Environmental EnHineer
KE/arl: S:\WQS\STORMWAT\ADDINFO\950303.DEC
cc: Linda Lewis
Central Files

November 25,1996
Ms. Linda Lewis
NCDEHNR
Atlantic Coast Design, Inc.
Engineers Surveyors Construction
P.O. Box 203
Wrightsville Beach, North Carolina 26480
[phone]
Water Quality Section
127 Cardinal Drive Ext.
Wilmington, NC 28405
Re: 50bal Palm Gottages n E C E 1 V E P
Project No. 5W8 950303 Modification Iu �Sf NOV 2 51996
D E
PROJ #
Dear Ms. Lewis:
The following is a response to your letter dated November 15, 1996 regarding Additional
Information requested for the above referenced project. Attached are two copies of the
revised plan with two copies of additional information to be included with the original design
report. We offer the following comments to the items requested in your letter:
1. The required volume of the ponds has been calculated using the Shuler Method as
suggested in your letter. The design volume of all ponds and swales is greater than
the calculated required volume when compared to the results from the Shuler Method.
Enclosed are two copies of these calculations Signed and sealed.
2.- 5. These items were revised on the plans per your comments. Enclosed are two
copies of the revised plans.
If you have any questions or comments regarding this project please feel free to contact our
office.
Si ely,
Perry avis
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State of North Carolina
Department of Environment, Health, and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr. Division of Water Quality Jonathan B. Howes
Governor Water Quality Section Secretary
November 15, 1996
Mr. Perry G. Davis, Jr., P.E.
Atlantic Coast Design, Inc.
Post Office Box 203
Wrightsville Beach, North Carolina 28480
Subject: ADDITIONAL INFORMATION
Stormwater Project No. SW8 950303 Modification
Sabal Palm Cottages
Brunswick County
Dear Mr. Davis:
The Wilmington Regional Office received a Stormwater Management Permit Application for Sabal
Palm Cottages on October 31, 1996. A preliminary review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater review:
1. The volume that is required to be stored in the infiltration areas must include the entire
drainage area, not just the impervious areas. (See NCAC 2H .1008 (c) (1)) I have enclosed
a copy of the Shuler method the State uses to get a conservative estimate of runoff based on
the percent impervious of the drainage area.
2. Please show the proposed road elevations and proposed contours/drainage patterns for the
finished site.
3. Add a road section detail.
4. Note on the plans that all roof drainage must be directed so as to be picked up by either the
swale or a pond.
5. Add the dimensions of the bottom surface area for each pond..
127 Cardinal Drive Extension, Wilmington, N.C. 28405-3845 • Telephone [phone] • Fax [phone]
An Equal Opportunity Affirmative Action Employer

Mr. Davis
November 15, 1996
Stormwater Project No. SW8 950303 Modification
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to December 15, 1996, or the application will
be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including
the application fee.
If you have any questions concerning this matter please feel free to call me at [phone].
Sincerely,
Ms. Linda Lewis
Environmental Engineer
KE/arl: S:\WQS\STORMWAT\ADDINFO\950303.NOV
cc: Linda Lewis
Central Files
127 Cardinal Drive Extension, Wilmington, N.C. 28405-3845 a Telephone [phone] • Fax [phone]
An Equal Opportunity Affirmative Action Employer

,t
October 24, 1996
Ms. Linda Lewis
Division of Environmental Management
DEHNR - Water Quality Section
127 Cardinal Drive Extension
Wilmington, NC 28405-3845
Dear Linda:
U 1� C---J cmA V (.�3 IIII
OCT 31 1996 �J
Please find enclosed a site plan and subsequent information pertaining to the modified
stormwater plan at Sabal Palm Cottages. Also, enclosed is a check for $385 as required.
Please note that due to the unique vegetation and field conditions there has been some
minor modifications to structure locations and site work. I believe you should have all the
pertinent information required for obtaining approval for this project.
Please contact me at 910-457-7339 with any questions and/or comments.
Sincerely,
Daniel H. Weeks, ASLA
Director of Planning
Enclosures
cc: Ken Kirkman
David Edwards
STORMWATER
(�E C E i V E D
luny OCT 3 11996
PROJ #a W
BALD HEAD ISLAND
Post Office Box 3069 Bald Head Island, North Carolina 28461 (910) 4575000 [phone]

TORMWATEk .
INFILTRATION POND MAINTENANCE
Project Name: Sabal Palm Cottages
Responsible Party Name: Bald Head Island,- Limited
n E C E I VIE D
luny{j OCT 3 11996
PROJ #&,8EgSO,303
MOP -
After every runoff producing rainfall event, or at least monthly, whichever comes first:
1. Inspect the infiltration pond(s) for erosion, trash accumulation, grass coverage, and general
condition of the facility.
2. Repair eroded areas immediately, re -seed as necessary, keep side slopes and bottom
mowed, and remove trash.
3. Check any inlet piping, swales and catch basins. Repair broken piping, reseed swales, and
remove trash.
4. Inspect the bypass/overflow structure for blockage and deterioration. Remove blockage
and repair structure to originally approved design specifications.
5. -Check the depth of the pond(s) every six months. If siltation has occurred to the point that
only 75 % of the original design depth is provided, remove the excess silt to the original
depth. Do not over -excavate, as this may cause the required water table separation to be
reduced, and may affect the ability of the system to perform as designed.
I, Daniel H. Weeks, Director of Planning, agree toberesponsihleforperforming
the maintenance items as listed above for this project. J agree to notify NCDEM of any problems with
the systeeagesin �he�nanect, name of the responsible / i1 ) p party, or address.
Date October 16, 1996
I� allotary Public inthe County'of
State of f,(,a,1A do hereby certify by my
signature below, that __2)i1.c, [w,e. & personally
appeared before me this �h day of �o �o�.� 191E , and acknowledge
the due execution of the foregoing instrument. Witness my seal and signature,
SEAL
My commission expires 1a-12 - 02 od

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SABAL PALM COTTAGES
STORM WATER MANAGEMENT
DESIGN REPORT
PREPARED FOR
BALD HEAD ISLAND, LIMITED
BALD HEAD ISLAND, NORTH CAROLINA
STOR A' ATER OCTOBER 14, 1996
n E C E I V E D PROJECT 96256
II���n�IIJJ{( OCT 3 11996
PROJ k `-M50303
BY
ATLANTIC COAST DESIGN, INC.
P.O. BOX 203
WRIGHTSVILLE BEACH, NC 28480
[phone]

GENEKAL
Bald Head 151and, Limited proposes to construct a 15-unit Single family development with
detached garages on Bald Head 151and, NG. The Site contains approximately 2.27 acres and
drains to Bald Head Creek. Bald Head Creek iS classified aS 5A waters. The proposed project
has an impervious area of approximately 35% and will be considered a high density development.
Infiltration ponds and 5wales will be utilized to treat the runoff from the impervious Surfaces.
This project was previously submitted and approved for a Storm Water Management Plan under
permit #5W8950303. The purpose of this report is to present several modifications to the
approved plan.
PROP05ED MODIFICATIONS
The existing Storm Water Management Plan (5W8950303) was prepared by McKim & Creed
Engineering, PA. , and approved on May 16, 1995. The proposed modifications for this project
con5i5t of refinement of the sub -drainage ba5in5 to more accurately reflect the existing
drainage patterns at the project site. Also, several very old and large trees that will require
removal under the existing approved plan will be retained under the modified plan. In order to
save these trees the location and geometry of the infiltration ponds has been altered. Appendix
A. contains the design calculations for the modifications proposed. The methodology and
design procedure for Sizing the infiltration ponds and 5waleo iS consistent with the design
calculations Submitted previously. The ponds are Sized to Store and release the first 1-1/2" of
runoff from the impervious areas within 5 days. Also, the ponds are sized for "no discharge"
from a 25-year Storm event.
EX15TING CONDITIONS
The proposed project i5 located on Bald Head Island and the Soils at the Site are generally
identified as corolla 5ando. These sands are extremely well drained with infiltration rates of
20-inche5 per hour. The Soil and infiltration rates are well suited for the proposed infiltration
ponds and 5wales. The site has varying Slopes but generally slopes to the east where an existing
lagoon is located. There are no existing drainage channels to the lagoon or across the site. A
Geotechnical Investigation was performed for the previous submittal and will be included and
utilized for the proposed modifications (See Appendix B).

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Bald Head Island
0049-0048.OW
I� SABAL PALMS COTTAGES
APR 0 4 1995 GEOTECHNICAL INVESTIGATION REPORT
BALD HEAD ISLAND
D. E M BRUNSWICK COUNTY, NC
"top #5wSci50303
PROJECT SITE DESCRIPTION:
The proposed project consists of approximately 2.2 acres in the interior of Bald Head
Island. It is located at the end of Sabal Palms culdesac. The tract drains from west to
east with the elevations on the upper end averaging around 11 ft. with small peak high
elevations of 15ft. The perimeter of the east end is adjacent to a lagoon at elevation 4.
The middle of the tract is relatively flat with a steep slope to the south of 20% while the
area to the north slopes at approximately 6%. Along the perimeter towards the lagoon,
the land drops more steeply to the edge of the water.
Bald Head Island proposes to develop the tract with fifteen-1,000 square foot units and
associated drives. In order to meet the North Carolina Department of Environment,
Health and Natural Resources requirements, the storm water will be controlled by
infiltration swales intercepting the runoff prior to leaving the property boundaries.
The purpose of this investigation is to evaluate the soils in regard to their infiltration
capabilities.
SUBSURFACE CONDITIONS:
The soils in this area of Bald Head Island are predominantly corolla fine sands. These
sands are known to have slow run off due to their extremely rapid permeability and high
seepage rate. The corolla sands consist of pale brown fine sands in the upper portion
and lighter brownish gray fine sands toward the lower part. The sand consists of
approximately 3% of clay material. This gives the material a very high permeability rate
of well over 20 inches per hour.
Soil Borings:
5 soil borings were taken at the proposed ponds in order to determine the water table
elevation. These borings indicated that the water table was approximately at elevation
4 across the property. The table below summarizes the findings:
PAGE 1

SOIL BORING DATA
BORING SOIL
1 Fine Sand
2 Fine Sand
3 Fine Sand
w/course shells @ 5' 0 deep
4 Fine Sand
5 Fine Sand
w/dark silt sand @ 3' 9"
SURFACE HIGH WATER
ELEVATION TABLE ELEVAl1ON
6 4
12 <7
9 <5
7 4
7 2.5
At the time the borings were done the area has been in a wet season with indications that
the water table is near its seasonal high elevation. Using an elevation of 4 throughout the
site for the seasonal high water table should provide a conservative basis for design.
SUMMARY:
Based on the geotechnical investigation of the soils. it is expected that using an infiltration
rate of 20 inches per hour and providing a 2 foot separation between the water table at -
elevation 4 and the swales and pond bottoms, should allow the infiltration system to provide
adequate treatment of the soil runoff.
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