7407_CandDLandfillInc_20170403_GWAssessmentPlan_DIN27593

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 Ground Water Assessment 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 ground water monitoring program for the referenced facility,
pursuant to your letter January 30, 2017 and Solid Waste Section (SWS) protocols for
Assessment Monitoring. This plan amends an Assessment Monitoring program in progress since
late 2009, discussed below. The SWS requires additional data prior to entering the next stage of
evaluation, the Assessment of Corrective Measures. We understand the SWS will begin placing
emphasis the inorganic parameters, e.g., metals and ionic species, many of which are naturally
occurring background constituents, in addition to organic compounds that have been the
traditional focus of ground water monitoring. This plan includes SWS input provided in recent
phone conversations, regarding specific wells and monitoring parameters.

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 17 active monitoring
wells. The entire set of wells is monitored for detection-stage Appendix I parameters, and
Appendix II parameters are monitored at MW-3s, MW-3A and MW-12s. The SWS requested a
round of Appendix II assessment sampling at wells MW-2s and MW-5, in addition to the Phase 2
wells, MW-9A through MW-17. The Facility will perform Appendix II sampling at MW-8.

Ground water flow is toward the southwest. Drawing M1 shows that wells MW-3s and 3A are
located southwest of Phase 1 (downgradient). Well MW-12s is located southwest of Phase 2.
Well MW-8 is slightly north of Phase 1 (cross-gradient) but south of Phase 2 (downgradient).
Sampling of MW-3s began in November 2007, replacing old MW-9s, which did not show organic

Amended Ground Water Assessment Monitoring Work Plan
C&D Landfill, Inc. (7406-CDLF-2001, Pitt County, NC)
April 3, 2017
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constituents prior to 2007. Well MW-3A sampling commenced with the Assessment at the south
property line in 2009. Wells MW-5 and MW-2s are located south of Phase 1, to the south and
east of MW-3s. Well MW-12s sampling began in early 2010 and began showing detects of
organic constituents within approximately a year. SWS regulations require surface water
monitoring with the 2L standards applicable. So far, no surface water detects that can be
attributed to the landfill have occurred. Constituents and areas of concern include the following:

Benzene: Semi-annual monitoring began detecting benzene at concentrations slightly above the
2L groundwater standard (15A NCAC 2L) at MW-3s and MW-8 in 2007. Benzene is present at
MW-12s beginning in 2011, where concentrations are below the 2L standard prior to 2012 and
typically above 2L afterward. Concentrations of benzene are increasing at MW-8 and MW-12s
but decreasing slightly at MW-3s, as of Nov 2016. Benzene has shown twice below the 2L
standard at MW-14s in 2013 and 2014. At MW-3A, benzene is present sporadically at
concentrations below the 2L standard beginning in 2010, with one value above the 2L standard
detected in November 2015.

Vinyl chloride: This constituent showed up twice at MW-3s above the 2L standard in November
2007 and November 2008, but the data have been “non-detect” since, except for one occurrence
above 2L in November 2014. Vinyl chloride is present above the 2L standard at MW-12s, with
concentrations increasing slightly after May 2012, but the November 2015 value is “non-detect.”
This constituent shows above the 2L standard once each at MW-8 in November 2014 and at MW-
6 in November 2015. The data for MW-3A do not show vinyl chloride.

Cis-1,2-Dichloroethene: This constituent is present in the data consistently below the 2L
standard at MW-3s from November 2007 to May 2011, then it becomes “non-detect.” Likewise,
MW-8 shows concentrations varying from less than 2L to “non-detect” in this same period, with
only one detection in May 2011. Cis-1,2-dichloroethene is present above the Solid Waste Section
Limit (SWSL) but below the 2L standard at MW-12s between 2011 and November 2016. This
constituent does not show in the data for MW-3A.

Toluene: Data for 2007-2008 show toluene below the 2L standard at MW-3s, continuing with
“non-detect” values before then and since through November 2016. This constituent does not
show at MW-3A or MW-8. Toluene is present in the data at MW-12s, below the 2L standard once
in 2012 and twice in 2014-15. Toluene appears at MW-14s below the 2L standard once in 2013.
The surface water data show toluene both above and below the SWSL, including the upstream
background samples, but below either the 2L standard for groundwater or the 2B standard for
surface water.

Other organic constituents are present sporadically at various wells, but no clear trends have
emerged. Inorganic constituents detected with regularity above the 2L standard at this Facility
include cobalt and vanadium, both of which appear above 2L in the background wells. Arsenic is

Amended Ground Water Assessment Monitoring Work Plan
C&D Landfill, Inc. (7406-CDLF-2001, Pitt County, NC)
April 3, 2017
Page 3

present below 2L in the background wells but showing an increasing trend above 2L at MW-3s,
MW-8, and MW-12s. Barium is present below 2L in the background wells and widespread above
2L. Chromium is present in the background wells and increasing above 2L at MW-7 and MW-
12s, although the current monitoring reports total Cr, not the more toxic variety, Cr(VI). Zinc is
present with a decreasing trend in the surface water and increasing at MW-14s.

Factors that influence the monitoring results include lower ground water standards and regulatory
reporting limits implemented by the SWS in mid-2007, which made certain concentrations
reportable (flagged with “J”) below the levels formerly considered “non-detect.” Prolonged
drought and associated ground water fluctuation can affect concentrations of both organic and
inorganic constituents. Many inorganic constituents are present in the background geochemistry,
and elevated turbidity is a known factor at this Facility. At other unlined landfills, migration of
landfill gas is a known contributor to groundwater contamination, but gas migration so-far is not
detectable at this Facility. Past agricultural uses of the property are possible factors at this Facility.

An Alternative Source Demonstration was completed in 2016 (by others) working on a premise
that some type of spill, perhaps in the drainage feature between the phases, is responsible for
the organic constituents observed at MW-3s, MW-8 and MW-12s. The study was inconclusive in
identifying a source of contaminants other than the landfill. 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. A Work Plan meeting that requirement is
addressed in a separate document

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

Amended Ground Water Assessment Monitoring Work Plan
C&D Landfill, Inc. (7406-CDLF-2001, Pitt County, NC)
April 3, 2017
Page 4

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
Item 1 from the SWS letter, discussed above:

a) Implement the amended Groundwater Assessment Monitoring Work Plan described
in this document, beginning with the May 2017 sampling event. Drawing M1 depicts
the locations of the monitoring wells. Table 1 presents a schedule of Appendix I and
Appendix II sampling for the various wells.

b) Well MW-5, damaged and repaired at an earlier time, will be replaced with a new well.
Form GW-1 will be completed and provided (Permit Conditions 10 and 40). The old
well abandoned. A well abandonment record form, GW-30, will be completed and
provided within 30 days (Permit Conditions 11 and 40). This activity meets a SWS
requirement for a new well installation to facilitate delineation of the contamination. A
local drilling firm will perform the well installation and abandonment under the
supervision of Amec Foster Wheeler staff.

c) Environment-1, Inc. will perform the sample collection and analysis. The sampling and
analysis will follow SWS protocols outlined in various guidance documents and
incorporated into the Facility Water Quality Monitoring Plan. Up to now, Environment-
1 purges and samples the wells by bailing. For the upcoming May 2017 sampling
event, the sampling crew will switch to low-flow sampling techniques.

d) Amec Foster Wheeler will compile the new data along with historic groundwater data
for the Facility, update the groundwater contour map and evaluate trends for organic
and inorganic constituents. We will review the results with Facility management and
the SWS. A monitoring report for this event will be submitted to the Solid Waste
Section within 120 days of the sample collection date (Permit Condition 42 and 15A
NCAC 13B .0544(b)(1)(H).

e) Based on the data for the May 2017 sampling event, we will further amend the
sampling schedule and/or recommend changes to the sampling program. Future
revision of the Facility Water Quality Monitoring Plan, as appropriate based on the
findings, will follow.

Table 1
C&D LANDFILL, INC., GROUND WATER SAMPLING LIST
April 3, 2017

Phase 1 wells May ‘17 Nov ’17 May ‘18 Nov ‘18 May ‘19
MW-1d background Appx II
MW-1s background Appx I
MW-2d Appx II
MW-2s Appx II
MW-3d Appx II
MW-3s Appx II
MW-3A Appx II
MW-4 Appx I
MW-5** Appx I
MW-6 Appx I
MW-7 Appx I
MW-8 Appx II

Phase 2 wells
MW-9A background Appx II
MW-10 Appx II
MW-11 Appx II
MW-12s Appx II
MW-13 Appx II
MW-14d Appx II
MW-14s Appx II
MW-15* Appx II
MW-16* Appx II
MW-17* Appx II

Surface water
SW-1 background Appx I
SW-2 Appx I
SW-3 Appx I
SW-4 background Appx I

* Activate these existing wells
** Repair this well prior to May sampling

Sampling beyond May 2017 is subject to finalization after the results for May 2017

MW-3s, MW-3A, MW-8 and MW-12s are the current wells in assessment
There is no MW-12d

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.