3606_GastonMSW_Unit2Ph2DesignHydroReview_DIN26776_Sept2016

PAT MCCRORY
Governor
DONALD R. VAN DER VAART
Secretary

MICHAEL SCOTT
Director

September 29, 2016

Ed Shuffler, P.E.
HDR Engineering
440 South Church Street, Suite 1000
Charlotte, NC 28202

Re: Permit No. 3606-MSWLF-1997
Gaston County Landfill
Design Hydro Report and Monitoring Plans Review – Unit II Phase 2
DIN 26776

Dear Mr. Shuffler,
Solid Waste Section (Section) has completed the technical review of the Design Hydrogeologic Report
(dated June 30, 2016) for the proposed Unit II Phase 2 landfill expansion. The Design Hydro report was
contained in the Construction Permit Application (DIN 26713) prepared by HDR Engineering on behalf of
Gaston County and subsequently received by the Section on September 1, 2016. The Design Hydro Report
was prepared on behalf of HDR by Mr. Ross Klingman, P.G. of Buxton Environmental. Unit II Phase 2
covers approximately 11 acres and will be a contiguous expansion of the currently active MSW Unit II Phase
1 landfill area. A review of the proposed Water Quality Monitoring plan, which is presented as Section 13.0
of the Design Hydro report, was also conducted.

Design Hydrogeologic Report – ref. 15A NCAC 13B .1623(b)
Based on our review, the Design Hydro Report for the Unit II Phase 2 landfill expansion meets the criteria
required in .1623(b)(3) for construction, including the top-of-bedrock datum and seasonal high groundwater
table determinations for vertical separation requirements for construction [15A NCAC 13B .1624(4)].
Therefore, the design hydrogeologic portion of the Permit to Construct is approved.

Landfill Gas Monitoring Plan – ref. 15A NCAC 13B .1626(4)
No specific Landfill Gas Monitoring plan was submitted for review. The most recent approved LFG
(Methane) Monitoring Plan is contained as Section 11.0 within the Operations Plan (DIN 21693) approved
by the Section on September 16, 2014. Based on our review, the updated Landfill Gas Monitoring Plan
(submitted as Appendix 8 of the Design Hydro Investigation report) meets all the requirements [per .1626(4)
and Section guidance] for monitoring of explosive gases at the facility, including proposed Phases 3 and 4.
The Section approves the LFG Monitoring Plan.

Page 2

Water Quality Monitoring Plan – ref. 15A NCAC 13B .1623(b)(3)
The Unit II landfill has been planned to be constructed in phases. Currently Phase 1 is active and operating.
The Water Quality Monitoring plan currently approved for Unit II Phase 1 is presented as Section 9.0 of
Permit Renewal Application for the landfill (DIN 21352, June 2014). The proposed WQ Monitoring plan,
presented in Section 13 of the proposed Phase 2 Design Hydro report, addresses compliance monitoring for
the Phase 2 expansion only.

To account for Phase 2 expansion of Unit II, four (4) additional shallow groundwater monitoring wells are
proposed (MW-28, -29, -30, and -31) for compliance monitoring. These wells will be constructed prior
issuance of the permit to operate for Phase 2. Existing monitoring well MW-23 lies within the footprint of
Phase 2 and will be abandoned. Also, an existing French drain (FD-1) discharge pipe within the Phase 2
footprint will extended under the proposed Phase 2 footprint to discharge beyond the new waste boundary.
Sampling will be conducted at this newly extended discharge point per the current plan. The two existing
surface water sampling locations will continue to be sampled per the existing WQMP. No additional surface
water sampling locations are proposed.

Phase 2 is considered an expansion of the existing Unit II facility and not a separate unit. The proposed
WQMP is presented as a separate plan from that of Phase 1. The proposed plan for Phase 2 meets all the
technical and design requirements to adequately monitor for any release of contaminant to the shallow
groundwater aquifer. However, since Unit II is permitted as a single solid waste facility unit (constructed in
phases), the WQMP be presented as one plan and reflect monitoring for the entire unit, both Phase 1 and 2.

Together with existing Phase 1 wells (MW-24, -25, -26, and -27), and the additional wells for the proposed
Phase 2 (MW-28, -29, -30, and -31), the monitoring well network for Unit II would be comprised of eight
shallow compliance monitoring wells, plus one background monitoring well MW-1. Two surface water
locations (US-1 and DS-1) and one French drain (FD-1) outlet discharge will also be monitored.

The proposed Phase 2 expansion detection monitoring wells will be installed prior to construction and
sampled for baseline data according the Water Quality Monitoring Plan. The initial baseline sampling
requirements will be also included in the Permit‐To‐Construct to be issued at a later date. Guidelines for
water quality sampling and electronic data submittal can be located at the Section’s web site.
http://portal.ncdenr.org/web/wm/sw/envmonitoring

Prior to final approval of the updated WQ Plan, please submit a plan that includes both Phase 1 and Phase 2
into one Water Quality Monitoring plan for Unit II. Ideally, a separate, stand-alone document added as an
appendix. However, updating Section 13.0 of the Design Hydro is also acceptable. Also, include an updated
figure 2 depicting the Unit II water quality monitoring plan monitoring network (wells and surface water
sample locations).

Page 3

Well Abandonment
Any existing piezometers and/or monitoring wells within the footprint of the proposed landfill expansion
must be properly abandonment prior to construction activities commencing for the landfill expansion.
(Piezometers, groundwater monitoring wells, and borings, located in proposed expansion may be abandoned now or after a
Permit‐to‐Construct is issued by the Solid Waste Section). Please adhere to the following conditions:

Prior to construction of cell(s), all piezometers, ground‐water monitoring wells, and borings, located in
the proposed cell(s), shall be properly abandoned by over drilling first (exception for non‐cased borings)
and sealed with grout in accordance with 15A NCAC 2C .0113, entitled “Abandonment of Wells”.

a. In areas where soil is to be undercut, abandoned piezometers, monitoring wells, and borings
must not be grouted to pre‐grade land surface, but to the proposed base grade surface to
prevent having to cut excess grout and potentially damaging the wells.

b. Well abandonment records (GW‐30 form) for each decommissioned piezometer, boring, and
groundwater monitoring well must be certified by a Licensed Geologist in accordance with rule
.1623(b)(2)(1) and submitted to the Solid Waste Section in accordance with 15A NCAC
02C.0114(b).

NOTE: The Permit-to-Construct to be issued at a later date will include Geologic, Ground Water, and other
Monitoring Requirements.

We understand the tight schedule for constructing Phase 2 and will work with you to revise the WQMP in
an expedient manner. Since the requested changes are not technical or regulatory in nature, there is no
reason that engineering design and planning should be held up. The design hydro requirements for the
proposed Phase 2 expansion have been met and are approved. If you would like to call to discuss further,
please, please do not hesitate to contact me via email [e-mail] or phone [phone].

Sincerely,
Perry Sugg, PG
Permitting Hydrogeologist
Solid Waste Section

Cc: Ed Mussler, SWS Permitting Branch Head
Larry Frost, SWS Permitting Engineer
Ross Klingman PG, Buxton Environmental