20190564 Ver 1_More Info Received_20190806

3TC
ENVIRONMENTAL • GEOTECHNICAL
BUILDING SCIENCES • MATERIALS TESTING
August 6, 2019
Sue Homewood Via email: [e-mail]
Division of Water Resources, Winston Salem Regional Office
Department of Environmental Quality
336 776 9693 office
336 813 1863 mobile
450 W. Hanes Mill Rd, Suite 300
Winston Salem NC 27105
CC: David E. Bailey, PWS
Regulatory Project Manager
US Army Corps of Engineers
CE -SA W -RG -R
3331 Heritage Trade Drive, Suite 105
Wake Forest, North Carolina 27587
Phone: [phone], Ext. 30.
Fax: [phone]
2725 East Millbrook Road
Raleigh, NC 27604
Telephone [phone]
Fax [phone]
www.atcgroupservices.com
Via email: David. [e-mail]
RE: Elon College Landfill Mitigation
Second Request for Additional Information: Elon College Landfill Remediation
3016 Amick Rd., Elon, Alamance Co.;
SAW -2016-02022 (UNCLASSIFIED)
Dear Ms. Homewood:
Below please find response to the request for additional information quoted below in your email of July
16th, 2019. ATC comments to address the concerns in Red.
"I have reviewed your responses and have a follow up concern. You state that "the gabions will be
placed up to or behind the limits of the existing north bank of Travis Creek" and "they will be placed in
an excavated trench behind the bank and placed in the wet so no dewatering is proposed". Condition
11.9 of 401 Water Quality General Certification #4134 states that "All work in or adjacent to streams shall
be conducted so that the flowing stream does not come in contact with the disturbed area". Since the
trench will be in contact with the natural stream flow and at water level and below it, constructing it in
the wet would not meet the requirements of this Condition. Please provide either a dewatering
sequence which isolates the trench area from the natural stream flow (I understand that groundwater
will be present within the trench and you may not propose to pump groundwater out of the trench but
rather install the gabion basket in the groundwater that fills the trench), or provide a justification for
why diverting the natural stream flow is not feasible, and what additional measures will be taken to

August 6, 2019
Page 2 of 2
ensure that water quality standards, particularly turbidity, are not violated during the construction of
the gabion wall."
We have revised to plans to show the gabions will be installed behind the stream bank. We have
specified that the excavation will begin a minimum of two (2) feet back from the existing stream bank.
This will be accomplished by excavation of the slope above the stream bank to the proposed 3H:1V
slope and then excavating the trench into the landfill soils or the residual clayey silts at the site and
placing the gabions in a continuous operation to prevent caving on the stream side.
A geotechnical engineer will be on site during this operation to observe the soils and recommend the
proper procedure to prevent contact with the stream on a continuous basis. The engineer will make
recommendations for excavating stable slopes and immediately backfilling the excavations to prevent
soil from collapsing into the stream as much as is possible. The excavation will be conducted without
pumping to prevent undue migration and disposal problems for of contaminated groundwater as well as
destabilization of the excavation due to pumping.
These changes are shown on the revised Drawing No 10. Attached.
Please email or call if you have any changes or questions.
Respectfully
ATC Associates of North Carolina, PC
Benjamin V. Wilson, P.E.
Principal Engineer
[e-mail]
Cell No 919-697-5446
Attachment: Revised Plan Page 10 - 11x17 (reduced size)

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