7401_PittCouny_MSWLF_MonitoringRequests_FID1742606_20221108

Groundwater Management Associates, Inc.
GMA 4300 Sapphire Court, Suite 100
Greenville, North Carolina 27834
-- - - Telephone: [phone]
- www.qma-nc.com
October 18, 2022
Sent Via Email - iaclvnne.drummond(a)ncdenr.aov
Ms. Jaclynne Drummond
Hydrogeologist
NCDEQ, DWM, Solid Waste Section
2090 US Highway 70
Swannanoa, North Carolina 28778
Re: Pilot Study Update and Request for an Extension of the Pilot Study at the Pitt County Solid
Waste Municipal Landfill (Permit Numbers 7401-MSWLF- and 7401-MSWLF-1974)
Dear Ms. Drummond,
In June 2021, Pitt County completed a $1.065 million cap improvement project at the Southern
Unit of the Pitt County Landfill. These upgrades were part of an approved pilot study for
corrective action following detections of 1,4-dioxane above the 15A NCAC 02L groundwater
standard. Following completion of the construction project, the County repeated geophysical
testing of the Southern Unit to help document the extensive repairs and to evaluate hydrologic
improvements. A comparison of the pre -repair and post -repair geophysical surveys showed the
areas where cap thickness was increased and where extensive surface regrading was necessary
to ensure proper functioning of the stormwater drainage system.
GMA anticipates that the completed cap improvements will reduce infiltration of water through
the cap and better protect the groundwater from further contamination via leaching from
landfill waste at the Southern Unit. However, it is too soon to see hydraulic improvements
and/or reductions in contaminant levels. Continued monitoring of groundwater levels and
contaminant concentrations are needed to assess the effectiveness of the cap and stormwater
system upgrades. GMA requests that the North Carolina Solid Waste Section extend the pilot
study until July 2023 to allow time for the existing groundwater to drain from the Southern
mound prior to making an assessment of hydraulic improvements. Groundwater flow patterns
at the landfill vary seasonally, and this will also allow the County to better evaluate how the
improvements affect the large seasonal shift in groundwater flow patterns.
The County continues to monitor groundwater and surface water at the Southern Unit on a
semi-annual schedule. The next semi-annual monitoring event at the Pitt County Solid Waste
Municipal Landfill is scheduled for January of 2023 and will include only Appendix I of 40 CFR
Part 258 parameters plus 1,4-dioxane. We provide full details regarding the status of the pilot
study, and the most recent monitoring event at the Southern Landfill Unit in the report that
accompanies this letter.

Ms. Jaclynne Drummond
NC Solid Waste Section
October 18, 202 Page 2 of 2
In addition, GMA requests a slight reduction in the number of monitoring wells that Pitt County
is required to sample for both the Northern and Southern Landfill units. GMA believes that
several monitoring wells are redundant/unnecessary and removal of them will help reduce
ongoing monitoring costs. The wells recommended to be removed from the sampling schedule
are P5, P6, and P9 for the Northern mound, and well P11R for the Southern mound. Figures 1
and 2 show the proposed sampling schedules for the Northern and Southern units, respectively.
GMA will continue to use all existing wells in the monitoring well network for water level
measurements during sampling events.
GMA also requests adding well MW1R to the sampling schedule for the Southern mound.
Historically, off -site wells P4, P5, and P6 have been used to assess background groundwater
chemistry. Inconsistent with historical trends, recent water level data indicate that groundwater
elevations in these wells may be lower than groundwater elevations in the adjacent Northern
mound. Monitoring well MW1R does not have this issue and would serve as a suitable
upgradient well to use for background groundwater chemistry if necessary.
Please contact me if you have any questions or concerns, and thank you for your consideration
in this matter.
Sincerely,
Groundwater Management Associates, Inc.
Cody J. Shell, P.G.
Project Hydrogeologist
Enclosures: Figure 1 Proposed Sampling Schedule- Northern Unit
Figure 2 Proposed Sampling Schedule- Southern Unit
cc: Richard K. Spruill, Ph.D., PG (GMA)
Tim Corley, P.E. (Pitt County)
John Demary (Pitt County)
Z:\GMA\251XX-Pitt County\25101 - Landfill\2022 July\Letter Pitt Co Landfill Pilot Study Request Extension 2022.docx

{
011---
IVI VVtI ry
PO4 �.. - 4' Y•
ifik
r.
...,
Bonn
1
19
{f�. i �• �F ink c
4
I � k
Sr
THIS PRODUCT IS FOR GENERAL REFERENCE PURPOSES ONLYAND SHOULD NOT BE USED, AND IS NOT INTENDED, FOR SURVEYOR ENGINEERING PURPOSES. LOCATIONS ARE APPROXIMATE. sY
GIS SOURCE DATA
ORTHO I MAG ERY O STAI N ED FROM INC ON E MAP, IMAGE DATEFEB RUARY 2020
PARCE L BO INDARIES FROM PITT COUNTY GIS, https'llmap.pittnc.opendata.arcgi,.com '
-LEGEND-
MONITORING WELL DITCHES SCALE IN FEET GMA
SURFACE WATER SAMPLE � APPROXIMATE PARCEL BOUNDARIES 0 �0'
t" TEMPORARY�/PIEZOM`
ETER PONDS GROUNDWATER MANAGEMENT ASSOCIATES, INC.
File: DRAWINGS/25101 PROPOSED SAMPLING SCHEDULE - NORTHERN UNIT DATE: 10/31/2022
FIG 2N
PROJECT 25101 PITT COUNTY LANDFILL, GREENVILLE, PITT CO., NC FIGURE 1

."SW1
IVIW 1 R x' vT :.
4d' I_'..
f i.r y*� •
4.
NORTHERN
TR—
P19 MW6R
.:
P28
SOUTHERN00
P12
� JJJ•
TH 15 PRODUCT IS FOR GENERAL REFERENCE PURPOSES ONLY AND SHOULD NOT BE USED,
AND IS NOT INTENDED, FOR SURVEYOR ENGINEERING PURPOSES. LOCATIONS ARE APPROXIMATE.
GIS SOURCE DATA:
4
_
ORTHOIMAGERY OBTAINED FROM NO ONE MAP, IMAGE DATE: FEBRUARY 2020
PARCEL BOUNDARIES FROM PITT COUNTY GIS, M1t�s:llmap-pilinc.opendala.a�cgis.com
-LEGEND-
GMA
MONITORING WELLS
DITCHES
SURFACE WATER SAMPLE
0 APPROXIMATE PARCEL BOUNDARIES
SCALE IN FEET ,
o `�o
(% TEMPORARY PIEZOMETER
PONDS
GROUNDWATER MANAGEMENT ASSOCIATES, INC.
File: DRAWINGS/25101/
FIG2.mxd
PROPOSED SAMPLING SCHEDULE —
SOUTHERN UNIT
DATE: 10/31/2022
PROJECT 25101
PITT COUNTY LANDFILL, GREENVILLE, PITT CO., NC
FIGURE 2