6301_Moore_MSWLF_CAP_DIN28745_20180131

Golder Associates Inc.
5B Oak Branch Drive
Greensboro, NC. 27407 USA
Tel: [phone] Fax: [phone] www.golder.com
Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation
January 31, 2018 0739615017.403
Ms. Jaclynne Drummond, Hydrogeologist
Department of Environmental Quality
Division of Waste Management
Solid Waste Section
2090 US Highway 70
Swannanoa, NC 28778
[phone]
RE: GROUNDWATER CORRECTIVE ACTION MILESTONE SCHEDULE
MOORE COUNTY LANDFILL, PERMIT NO. 63-01
ABERDEEN, NORTH CAROLINA
Dear Jackie:

On behalf of Moore County (the County), Golder Associates NC, Inc. (Golder) is submitting this response
to your September 28, 2017, letter, which requested the completion and submittal of the North Carolina
Solid Waste .0500 Groundwater Corrective Action Application, the selection of a new groundwater remedy
and two contingencies, and the submittal of a plan and timeline to address landfill gas (LFG) migration
concerns at the Moore County Landfill, solid waste permit no. 63-01. The North Carolina Solid Waste .0500
Groundwater Corrective Action Application has been completed and is included as Attachment 1 to this
letter. A preliminary milestone schedule for groundwater corrective action at the facility is outlined below.
The groundwater remediation schedule outlines the County’s proposed remedies as listed on the
groundwater corrective action application. The proposed groundwater remedies have been selected to
address volatile organic constituents (VOCs) in groundwater samples at the facility. The LFG migration
concerns are addressed in detail in the LFG Remediation Plan, which has been submitted under separate
cover. Should the proposed groundwater remedies and preliminary milestone schedule be acceptable to
the North Carolina Department of Environmental Quality (NC DEQ), then the remedies will be presented in
more detail in a Corrective Action Plan (CAP) within 90 days of approval of the North Carolina Solid Waste
.0500 Groundwater Corrective Action Application.
Phase I: Proposed Groundwater Remedy
As presented in the LFG Remediation Plan, the County intends to construct a LFG cut-off trench to a depth
to encounter the top of groundwater to the south of MW-15 (the groundwater monitoring well located along
the northern property boundary). In the recently approved Assessment Monitoring Work Plan, the County
proposed to install MW-15R as a replacement monitoring well for MW-15. As Phase I of the newly selected
groundwater corrective action remedy at the site the County would like to combine these two activities.
LFG has been suspected as a potential source of VOCs in groundwater at the MSW landfill as documented
in the original Assessment of Corrective Measures, and subsequent submittals. To summarize, Phase I
would include the following activities:
 Installation of the methane cut-off trench to the south of MW-15 (as shown on Drawing 1)
 Replacement of MW-15 with MW-15R
 Conversion of MW-15 to a compliance methane monitoring well
 Continuation of monitored natural attenuation (MNA).
As documented in our October 16, 2017, Corrective Action Evaluation Report (CAER), with the exception
of the northern property boundary, the groundwater contaminant plumes are stabilized and contained within
Ms. Jaclynne Drummond, Hydrogeologist January 31, 2018
NC DEQ, DWM, Solid Waste Section 2 0739615017.403

the facility property boundary. In the CAER, Golder evaluated MNA as described in Phase II below, and it
continues to be a viable and appropriate remedy for this facility. In the 2017 CAER, it was noted that VOC
concentrations are declining at the facility. The majority of VOCs historically detected at the facility are
broken down readily by the process of anaerobic biodegradation. Strong anaerobic conditions exist at the
facility and foster a subsurface environment conducive to anaerobic biodegradation. Three VOCs, which
were listed in the recent CAER (e.g., benzene, 1,4-dichlorobenzene, and 1,2-dichlorobenzene), may
actually break down faster under aerobic conditions. Installation of the methane cut-off trench will
accomplish two things with respect to groundwater quality in the area of MW-15; the trench will reduce the
influence of LFG on groundwater and it will allow natural conditions in the area of MW-15 to return to aerobic
conditions faster, likely breaking down these COCs through the process of aerobic degradation.
After the installation of the methane cut-off trench (which is proposed to be completed by September 15,
2018) and the replacement of MW-15 (which will also be completed by September 15, 2018), the County
would like to request until November 15, 2019 to evaluate these actions as a groundwater remedy. This
period would allow the County the opportunity to complete two semi-annual water quality monitoring events
on the newly installed replacement monitoring well (MW-15R). If the second semi-annual groundwater
quality monitoring results in 2019 for replacement monitoring well MW-15R do not show a declining trend
of VOCs, the second phase of groundwater corrective action will be implemented. If the selected cut-off
trench remedy is successful in reducing VOC concentrations in the replacement monitoring well MW-15R,
then the remedy will be evaluated for other areas of the site along the northern property line (e.g., MW-6).
Phase II: Proposed Groundwater Remedy
Golder used industry-standard methods to evaluate multiple active groundwater remedial options specific
to the constituents detected in groundwater at this facility. In this review, we considered the performance,
reliability, ease of implementation, and potential impacts of potential remedies, including safety impacts,
cross-media impacts, and control of exposure to any residual contamination, the time required to implement
each remedy, the costs of implementation, and the institutional requirements (such as State and Local
permits and other environmental or public health requirements that may affect implementation of the
remedy). Based on these evaluations, we are providing the following contingency options, if needed.
The second phase of proposed groundwater corrective action at the facility will consist of the following
activities:
 Installation of an injection monitoring well (IW-1) south of the LFG cut-off trench in the area
of MW-15R (as shown on Drawing 1)
 Commencement of a pilot test for enhanced bioremediation via super-aerated water (SAW)
injections in the area of MW-15R (as an initial pilot study)
 Continuation of MNA.
If Phase II is initiated immediately following the second semi-annual water quality monitoring event in 2019,
the injection monitoring well will be installed prior to December 31, 2019, and a pilot test for SAW injections
will begin before the end of the first quarter in 2020 (i.e., March 31, 2020). The SAW injections will continue
on a quarterly basis in the area of MW-15R for a period of three years. At the end of each year a CAER
will be completed and submitted to NC DEQ. Should the SAW injections succeed in reducing VOC
concentrations below the NC 2L Standards at MW-15R, the remedy will be considered at other VOC
impacted areas. Should the SAW injections fail to reduce VOC concentrations below the NC 2L Standards,
Phase III will be initiated.
Phase III: Proposed Groundwater Remedy
The third phase of proposed groundwater corrective action at the facility will consist of the following
activities:
 Commencement of a microcosm study to evaluate bacteria and carbon sources in the
subsurface in MW-15R
 Injections of SAW and bacteria or additional carbon (e.g., lactate, etc.) in IW-1