7407_CandDLandfillInc_20170403_LFGPlan_DIN27594

Amec Foster Wheeler Environment & Infrastructure, Inc. Tel – [phone]
4021 Stirrup Creek Drive, Suite 100 Fax – [phone]
Durham, North Carolina 27703 www.amecfw.com
Licensure: NC Engineering F-1253; NC Geology C-247

©2015 Amec Foster Wheeler. All Rights Reserved.

April 3, 2017

Ms. Jaclynne Drummond
Compliance Hydrogeologist
NCDEQ Solid Waste Section
2090 U.S. Highway 70
Swannanoa, NC 28778

RE: Amended Landfill Gas Monitoring Work Plan
C&D Landfill, Inc. (7406-CDLF-2001, Pitt County, NC)

Dear Ms. Drummond:

Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) has prepared
the following modifications to the landfill gas-monitoring program for the referenced facility,
pursuant to your letter January 30, 2017 and Solid Waste Section (SWS) protocols for landfill gas
monitoring. This plan amends an existing Landfill Gas Monitoring program in progress since
2009, discussed below. The SWS requires additional monitoring for landfill gas migration, as it
may be contributing to ground water contamination observed at the site. Please note that, to date,
we have not detected landfill gas migration at the site. This plan amendment includes SWS input
provided in a recent phone conversations, regarding monitoring locations and protocols.

PROJECT INFORMATION

C&D Landfill, Inc. owns and operates an unlined landfill (the Facility) for disposal of construction
and demolition (C&D) debris. The landfill consists of two phases, Phases 1 and 2, separated by
a partially channelized drainage feature. Phase 1 is a 15-acre footprint that opened in 2001.
Phase 2 is a 10-acre footprint that opened in 2009. At present, there are eleven landfill gas-
monitoring locations, labelled GP-1 – GP-11 on Drawing M2. The SWS approved the monitoring
locations and the bar hole-punch gas sampling protocols currently in use for the quarterly
sampling. The premise for using bar hole-punch techniques stems from the site conditions, i.e.,
sandy soils existing in the vadose zone and relatively shallow ground water (typically 3 – 5 feet).
In addition, the both phases of the landfill are “above-ground” facilities that did not involve deep
grade cuts below the mean elevations surrounding the footprints.

However, with the detection of ground water contaminations at a subset of wells, specifically MW-
3s, MW-8, MW-12s and more recently, MW-10, new interest in evaluating the possible effects of
undetected landfill gas comes into focus. A 36-inch thick clay cap underlays portions of the site,
which may restrict gas flow and, hence, limit the effectiveness of the bar hole-punch method.

Amended Assessment Monitoring Work Plan
C&D Landfill, Inc. (7406-CDLF-2001, Pitt County, NC)
March 23, 2017
Page 2

The SWS sent a letter to the Facility dated January 30, 2017 (DIN 27312) that requires the
following:

1. Amendments to the Groundwater Assessment Monitoring Work Plan, which expands the
Appendix II sampling to include all of the Phase 2 monitoring wells and revisiting some of
the Phase 1 wells as a one-time event, is required for submittal in March 2017. This
document meets that requirement. Plan implementation will occur with the May 2017
sampling event. Appendix II sampling will not include the surface water samples.

2. A revised Landfill Gas Monitoring Plan is required in March 2017, which moves away from
the bar-hole punch test previously utilized (per the current Facility permit). Instead, the
SWS is requiring permanent monitoring probes constructed similar to monitoring wells but
terminating above the water table. The SWS is also requiring a change in the gas
detection equipment and sampling protocols, based on the possibility that undetected gas
movement may be influencing the groundwater. This document meets that requirement.

3. An Assessment of Corrective Measures is required for Phase 1, and possibly Phase 2 if
connectivity between the two phases is determined, by June 30, 2017. This work will
proceed in accordance with 15A NCAC 13B .0545 and guidelines published by the SWS,
building upon the results of the Assessment Monitoring. The intent is to delineate the
concentration, extent and rate of contaminant transport, such that would allow evaluation
of appropriate remediation methodologies. The work will result in a report prepared for
review by the SWS. A future Work Plan document will address that requirement.

PLANNED COURSES OF ACTION

On behalf of the Facility, Amec Foster Wheeler will perform the following tasks that correspond to
Items 1 and 2 from the SWS letter, discussed above:

a) Implement the amended Landfill Gas Monitoring Plan, initially consisting of new soil-
gas sampling probe locations at key locations near the monitoring wells that show
contamination. New sampling protocols will help determine is landfill gas is present.

b) Eight new locations will be fitted with permanent, direct-push soil-gas probes, such as
offered by Geoprobe Systems® or equivalent. These devices consist of a stainless
steel screen interval (lengths to be verified in the field), which is attached to a conical
shaped steel driving shoe and pushed to the desired depth (just above the water table)
using a hydraulically powered mandrel (drill pipe) mounted on a conventional drill rig.

c) Installation records documenting the soil-gas probe construction will be kept.

Table 1
C&D LANDFILL, INC., LANDFILL GAS SAMPLING
April 3, 2017

LFG Sample Sampling Device* Nearest well Ground Max. Water
Location Elev. Table Elev.

GP-1 Bar-hole punch MW-9A 20.58 15.46
GP-2 Bar-hole punch MW-17 15.25 11.89
GP-3 Bar-hole punch MW-16 14.33 8.53
GP-4 Bar-hole punch MW-15 14.65 9.32
GP-5 Bar-hole punch MW-14s 16.60 12.70
SG-6/GP-6 Gas Probe MW-12s 16.18 12.03
SG-7/GP-7 Gas Probe MW-5 17.90 13.47
GP-8 Gas Probe MW-2s 21.44 12.14
GP-9 Bar-hole punch MW-4 18.42 12.59
GP-10 Bar-hole punch MW-1s 17.59 15.71
GP-11 Bar-hole punch MW-10 16.61 14.05
SG-12 New Gas Probe MW-13 20.69 12.45
SG-13 New Gas Probe MW-12s 16.18 12.03
SG-14 New Gas Probe MW-11 14.49 12.06
SG-15 New Gas Probe MW-8 21.21 12.80
SG-16 New Gas Probe MW-3s 23.02 12.21
SG-17 New Gas Probe MW-3s 23.02 12.21
SG-18 New Gas Probe MW-3A 21.93 11.81
SG-19 New Gas Probe MW-2s 21.44 12.14
SG-20 New Gas Probe MW-10 16.61 14.05

* Bar-Hole Punch will be used for the next sampling event at all existing locations; this method has been
approved for sampling at this site; future use of this method is to be determined

** Soil-Gas Probes are dedicated downhole screens, set at a depth of interest (i.e., vadose zone just above
the water table), with flexible tubing extending to the surface and equipped with a stopcock; these devices are
installed via direct-push; sampling tube connects directly to sampling meter; devices will be protected by steel
covers and are considered permanent; probes will be sampled side-by-side with bar-hole punch tests where
indicated

Future LFG sampling may be adjusted based on the findings of the next round of testing and concurrent ground
water sampling; the next sampling is intended to support a ground water assessment in progress

Dedicated LFG Sampling Wells may be sited once the assessment is completed

Table 2
C&D LANDFILL, INC., LANDFILL ASSESSMENT SCHEDULE
April 3, 2017

Action Item Completion Date*
Expect SWS plan approval 4-3-2017
Finalize cost estimates 4-5-2017
Schedule subcontract drilling 4-7-2017
Notify laboratory of sampling changes 4-7-2017
Update groundwater data records 4-10 – 4-14
Inspect all sampling locations 4-10-2017
Install low-flow sampling equipment 4-10-2017
Mobilize drill equipment 4-17-2017
Repair/replace MW-5 4-17-2017
Procure GEM 5000 gas meter 4-18-2017
Install LFG probes 4-18 – 4-19
Quarterly LFG monitoring 4-20-2017
Semi-annual groundwater sampling 5-15 – 5-16
Receive laboratory data 6-12-2017
Compile data, prepare report 6-12 – 6-16
Review data with stakeholders 6-16-2017
Develop Assessment Corrective Action 6-12 – 6-29
Finalize Ground Water Monitoring Plan 6-19 – 6-29
Finalize Landfill Gas Monitoring Plan 6-19 – 6-29
Submit Assessment Corrective Action 6-30-2017
Implement GW and LFG Monitoring Plans 6-30-2017

*These estimated completion dates are tentative and are subject to change. The Solid Waste Section will be
notified for any deviations from the schedule. Additional action items may be included as the project
progresses.