20050732 Ver 09_Stormwater Info_20100121

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EcoEngineering
A division of The John R. McAdams Company, Inc.
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LETTER OF TRANSMITTAL
To: Ms. Annette Lucas Date: January 20, 2010
North Carolina Division of Water Quality
2321 Crabtree Boulevard, Suite 250
Raleigh, North Carolina 27604
[phone]
Re: Briar Chapel - Phase 5 South
I am sending you the following item(s):
COPIES DATE NO. DESCRIPTION
1 SWMP Approval Clarification Letter r, r-, ,?. ,_,
DENR-
These are transmitted as checked below:
? As requested ? For your use
® For approval ?
® For review and comment ?
Remarks: Annette - Attached is a hard copy of the request for clarification letter associated with the
_existing Stormwater Management Plan Approval (DWQ Project # 05-0732v9) for Phase 5 South of
the Briar Chapel development in Chatham County NC. If acceptable please issue an updated SWMP
approval letter. Please call if you have any questions. Thanks. %
Copy to:
** FEDERAL EXPRESS **
Job No.: NEW-09007
Signed:
J(rAm f p. Finch, PE
FOR INTERNAL USE ONLY
® Copy Letter of Transmittal Only to File
? Copy Entire Document to File
20110
BRANCH
2905 Meridian Parkway, Durham, North Carolina 27713
PO Box 14005, RTP, North Carolina 27709
EcolEngineering
A division of The John R. McAdams Company, Inc.
January 20, 2010
Ms. Annette Lucas
NC Division of Water Quality
2321 Crabtree Boulevard, Suite 250
Raleigh, North Carolina 27604
U&3@R0Y[Ab
JAN 2 ? 2Cio
VOE LWSA AND OORR? WATER SPANCN
Re: Briar Chapel Community Phase 5 South - Chatham County, NC
NEW-09007
Stormwater Management Plan Approval Language Clarification
DWQ Project # 05-0732v9
Dear Ms. Lucas:
On behalf of Newland Communities and Chatham County, we are requesting
clarification of specific language in the DWQ approved Stormwater
Management Plan (see DWQ project number referenced above) for Phase 5
South of the Briar Chapel Community that was approved as part of the 401
Water Quality Certification. The project is located off US Highway 15-501,
north of Andrews Store Road and south of Mann's Chapel Road in Chatham.
County, North Carolina.
APPROVED DESIGN
To address the 401 Water Quality Certification stormwater requirements for
Phase 5 South of Briar Chapel, final stormwater management plans and
calculations for 1 wet pond with a preformed scour hole/level spreader outlet
that provided sheet flow of the 1" runoff volume into the existing vegetated
stream buffer (which serves as the vegetated filter strip) was originally
submitted to and approved by NCDWQ in June 2008.
In December 2008, rather than construct the entire approximately 22-acre
Phase 5 South all at one time, the owner decided to divide the construction
into two parts: Phase 5 South `A' and Phase 5 South `B'. Phase 5 South `A' is
the initial stage of construction involving approximately 9.8-acres and will
consist of 28 single-family residential lots, along with the associated utility
and roadway infrastructure. Phase 5 South `B' is the second stage of
development that will involve the construction of the remaining portions of
the overall Phase 5 South. As a result of the staged construction, a temporary
wet pond BMP was submitted to and approved by the DWQ in December
2008. This temporary wet pond BMP will be constructed to serve as water
quality treatment for Phase 5 South `A' during the interim period until the wet
Research Triangle Park, NC and approved in June 2008 is constructed sometime in the future as art of
Post Office Box 14005 p p
Research Triangle Park, Phase 5 South `B'. Once construction of Phase 5 South `B' including the
North Carolina 27709 previously permitted wet pond is complete, the temporary stormwater best
2905 Meridian Parkway management practice serving Phase 5 South `A' will be removed.
Durham, North Carolina 27713
800-733-5646
919-287-4262
919-361-2269 Fax
www.ecoengr.com Design Services Focused On Client Success
EcoEngineering
A division of The John R. McAdams Company, Inc.
Ms. Annette Lucas
NC Division of Water Quality
January 20, 2010
Page 2
CLARIFICATION OF APPROVAL LANGUAGE
As is typically the case during land development projects, the permitted wet
pond for Phase 5 South will be constructed during the initial site clearing and
grading operations and will be utilized as a sediment and erosion control
facility during the construction of the upstream development. During this
period, this facility will not contain all the features of a typical wet pond BMP
such as the fully vegetated aquatic shelf, meaning it will not be constructed as
per the DWQ approved plans during this interim period. However, upon
completion of construction and stabilization of the upstream drainage area, all
sediment deposited during construction will be removed, the eroded areas
repaired, vegetated shelf installed, and all other aspects of the DWQ approved
design will be constructed before operation as a permanent stormwater BMP
begins.
In contrast to the above understanding, the existing Stormwater Management
Plan Approval for Phase 5 South specifically states "when the entire Phase 5
South site is constructed, then the stormwater management plan that was
approved by the DWQ on June 13, 2008 must be in place prior to occupation
of any of the homes in the "B " portion of this site". This language would
require the wet pond BMP be fully converted to its permanent condition as
approved by the DWQ during the erosion control stage of the project, which
would not be an ideal situation due to the sensitivity of the permanent wet
pond BMP to the sediment load from the upstream drainage area. As a result
of this conflict, it is proposed that this language in the existing stormwater
management plan approval be replaced with the following:
"It is understood by the DWQ that the approved wet pond BMP for Phase S
South will be utilized as a sediment and erosion control device during
construction of this phase of the project. Furthermore, so long as there is an
active land disturbance permit utilizing this facility as a sediment and
erosion control device, occupation of the homes may occur so long as the
stormwater management plan that was approved by the DWQ on June 13,
2008 is in place upon expiration of the land disturbance permit and close
out of the sediment and erosion control stage of the project"
Clarification of this language is greatly appreciated. If you should have any
questions or require additional information, please do not hesitate to contact
me at [phone].
Sincerely,
EcoEngineering
A division of The John R. McAdams Company, Inc.
Ms. Annette Lucas
NC Division of Water Quality
January 20, 2010
Page 3
THE JOHN R McADAMS COMPANY, INC.
Jeremy Finch, PE
Project Manager
EcoEngineering