20110476 Ver 1_More Info Received_20110711

July 11, 2011
Mr. Andrew Williams
Regulatory Project Manager
U.S. Army Corps of Engineers
Wilmington District, Raleigh Field Office
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina. 27587
C, LP
The University of North Carolina at Chapel Hill
Department of Environment, Health & Safety
1120 Estes Drive Ext., CB# 1650
Chapel Hill, North Carolina 27599-1650
Reference: Response to June 9, 2011 Notice of Incomplete Application
SAW-2011-01068.
Duct Bank Utility Line Project
The University of North Carolina at Chapel Hill
Orange County
North Carolina
Dear Mr. Williams:
The following responses and attached documentation are provided to address the remarks
contained in your June 9, 2011 Notice of Incomplete Application pertaining to the Nationwide
Permit #12 Application for the Duct Bank Utility Line Project. Each United States Army Corp of
Engineers' (USACE) remark is provided in italics and The University of North Carolina at
Chapel Hill's (UNC-CH or University) response follows:
Remarks
Based on a review of your application, you propose impacts to I jurisdictional perennial
stream channels. In order to minimize degradation of water quality, flow within these
channels should be diverted around the work (fill) area during construction. Please provide
additional details regarding your proposed method of stream diversion. If you plan to use
temporary coffer dams, please be aware that coffer dams are considered as temporary fill
and update/adjust your application and plans accordingly. Please include a restoration plan
for any temporary fills.
During construction activities that will impact Crow Branch Creek, a pump-around
will be used to divert water around the work area. UNC-CH anticipates using sand
bags to create a temporary dam upstream of the work area. A properly sized pump
and associated hose will transport the volume of flow in the creek from above the
sand bag dam to an area downstream of the in-stream work, allowing the work to be
conducted in relatively dry conditions. Upon completion of work in the stream, the
sand bag dam will be removed. A pump-around detail with explanatory text has been
included as an attachment to this response letter.
2. The Wilmington District Regional Condition 4.3.1 for NWP#12 states that pipeline/utility line
construction through jurisdictional waters and wetlands will be accomplished utilizing
directional drilling/boring methods to the maximum extent practicable. Please consider this
technique and either adjust your plans to utilize directional boring or provide a brief
discussion regarding the reasons this technique cannot be used for this project.
While it is possible to directionally bore under the stream at the stream crossing, it would be
both extremely difficult and cost prohibitive to do so. It is important to maintain slope on the
duct bank between vaults, and to do so would require launch and receiving pits approximately
25 feet deep. Based on a surface evaluation of the site, it is reasonable to assume that
bedrock would be encountered during any boring operation, further increasing the cost and
difficulty. After considering the design requirements, site constraints and the unknowns,
UNC-CH and its design engineers for the project determined that an open trench excavation
with the use of a pump-around is the best solution for crossing the creek and wetlands.
3. Your current plans indicated that you will impact 0.137 acre of forested/scrub shrub type
wetlands. Please indicate, both verbally and with updated drawings, the total amount of
wetlands at these locations that will be permanently impacted by remaining with the
maintained right-of-way.
The wetland impacts for this project will be temporary only. No permanent wetland impacts
are proposed for the project within the maintained area for the duct bank. Please refer to
Note 1 on the May 3, 2011 Pre-Construction Notification Form figures for wetlands C, F and
Z. Note 1 explains that the wetland impacts are temporary and that the impacted areas will be
replanted with native tree species.
If you have any questions regarding this information or need additional information, please
contact me at [phone].
Sincerely,
a- fi ?
Sharon A. Myers, L. G.
Environmental Compliance Officer
cc: Dr. Daniel Elliott
Ms. Diane Gillis
Ms. Mary Beth Koza
Mr. Ian McMillan
Mr. Vance Nall
Mr. Kevin Nunnery
Attachments: Pump-Around Detail
Page 2 of 2
The following pump-around detail illustrates the linear extent of temporary stream channel impacts
associated with clean water and sediment sandbag dikes. The pump-around technique is often used
when extending culverts for road widening. These dikes are temporary, and their impacts do not require
mitigation.
APPROVED DEWATERING DEVICE
z- DISCHARGE HOSES
STREAM DIVERSION
PUMP
DEWATERING PUMP
INTAKE
HOSE
INTAKE
HOSE
*12* 18"
CLEAN WATER SANDBAG DIKE DEEP,TO T Di
DEEA.'
rDISSIPATOR OW SEDIMENT SANDBAG DIKE POOL
"now arr -0'
OMEN=
S SHOLD DISCHARGE
A STABLE VELOCITY
MADE OF SANDBAGS
WORK AREA
F WATER PLAN VIEW
IMPERVIOUS SHEETING
O
I
WORK AREA Z
N a FLOW
S
1 1 LL V
APPROXIMATELY 5' FOR
CLEAN WATER SANDBAG DIKE
SEDIMENT SANDBAG DIKE
DIMENSIONS ARE SIMILAR
SECTION A-A'
PUMP AROUND DETAIL
NOT TO SCALE