2903_Lexington_MonitoringPlan_DIN25881_20160309

Water Quality Monitoring Plan

City of Lexington Closed Solid Waste Landfill
State Road 2001
Lexington, North Carolina
Permit No. 29-03

Prepared for:

City of Lexington Public Works
28 West Center Street
Lexington, North Carolina 27292

Prepared by:

Babb & Associates, P.A.
P.O. Box 37697
Raleigh, North Carolina 27627

February 2016

_________________________________
Gary D. Babb, Licensed Geologist

Table of Contents

1.0 Introduction 1
1.1 Site Information
1.2 Site Geology
1.3 Site Hydrogeology

2.0 Water Quality Monitoring Program 5
2.1 Groundwater Monitoring Network
2.2 Surface Water Monitoring Network
2.3 Monitoring Frequency

3.0 Water Quality Sample Collection 7
3.1 Field Sample Procedures
3.2 Field Quality Assurance
3.3 Sample Delivery/Chain-of-Custody

4.0 Laboratory Analysis 9

5.0 Recordkeeping and Reporting 10

Figure 1 Site Location Map
Figure 2 Water Quality Monitoring Sample Locations/Potentiometric Map

Table 1 Well Construction Information/Elevations

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 1

I. Introduction

1.1 Site Information

The City of Lexington Closed Landfill is located approximately two miles northeast of
downtown Lexington, North Carolina on State Road 2001 in Davidson County, North
Carolina (Figure 1). The landfill ceased operation on May 1, 1990 and was closed by
capping the fill with a four-foot thick final cover using native soils. The northern
boundary of the landfill is established by the Southern Railroad which traverses the
property from southwest to the northeast. The eastern, southern, and western portions of
the landfill are bordered by Abbotts Creek which flows in a general southwesterly
direction.

Properties adjacent to the closed landfill are either undeveloped woodland or farmland.
Property usage to the south and east is primarily undeveloped woodland, farmland, and
residential. Undeveloped woodland and residential properties are also present to the
north of the landfill. Properties to the immediate west are undeveloped woodland.
Several industrial/commercial facilities are located along US Highway 64, located
approximately 2,300 feet west/northwest of the landfill.

1.2 Site Geology

The subject property is located in the Carolina Slate Belt, which is part of the Piedmont
Physiographic Province of North Carolina. The geology of the Carolina Slate Belt is
characterized by metavolcanic and metamorphosed intrusive rock sequences. According
to the Geologic Map of North Carolina published by the Department of Natural
Resources and Community Development (Brown, 1985), the rocks underlying the subject
property are metavolcanic rocks consisting of interbedded felsic to mafic tuffs and
flowrock.
City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 2

According to the Geologic Map of The Charlotte Quadrangle, North Carolina and South
Carolina (Goldsmith, Milton, and Horton, 1988), the rocks underlying the landfill are
interbedded felsic and mafic metavolcanic rocks. The metavolcanic rocks are fine to
medium grained with locally coarse grained or agglomeratic rocks of basaltic, andesitic,
and dacitic composition. This report identified a fault located between the landfill
property and US Highway 64 which is oriented in a northeast/southwest direction. The
general course of Abbotts Creek changes from a southwesterly direction to a
south/southwest direction at the landfill following this fault.

1.3 Site Hydrogeology

The observed subsurface conditions at the landfill consist of white to gray/green
metavolcanic bedrock overlain by weathered saprolitic soil. The soil at the site is
comprised of a mixture of clay, silt, and sand. The majority of the original soil profile on
the landfill property has been altered during landfill operations to the extent that it is no
longer recognizable.

The northern section of the landfill is characterized by a layer of silty clay and sandy silt
soil that overlies metavolcanic bedrock. The thickness of the soil varies from greater
than 43' at monitoring well MW-5 to 9' at monitoring well MW-6. The eastern section of
the landfill is characterized by a layer of silty clay and silty sand soil that also overlies
metavolcanic bedrock. The thickness of the soil in this area varies from 18' at monitoring
well MW-8 to 38' at monitoring well MW-7. The southern section of the landfill is
characterized by a layer of sandy clay to clayey silt soil. Fine sandy clay was present
beneath these layers in monitoring well MW-10. Bedrock was not encountered during
well installation activities in the southern section of the landfill.

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 3

A series of rising head slug tests were conducted in nine of the landfill monitoring wells
on October 23-24, 1996. An In-Situ model SE 1000C Hermit Data Logger system with
submersible pressure transducers was used to record the water level changes in each well
during the slug tests. The transducers were first lowered into the well and placed a
minimum of ten feet below the static water level. A disposable bailer was then placed in
the well so that the top of the bailer was just below the groundwater surface. The aquifer
was allowed to stabilize for approximately 30 minutes prior to starting each test. After
stabilization the bailer was quickly removed from the well causing a rapid change in the
groundwater level. The data logger recorded changes in the water table every five
seconds and the levels stabilized. The Bouwer and Rice method was used to evaluate the
results and calculate hydraulic conductivity (K).

The calculated K for the nine wells resulted in the following:

MW-2: K = 0.438 ft/day
MW-3: K = 0.0494 ft/day
MW-4: K = 0.323 ft/day
MW-5: K = 0.0812 ft/day
MW-6: K = 1.04 ft/day
MW-7 K = 0.0127 ft/day
MW-8: K = 0.0565 ft/day
MW-9: K = 2.66 ft/day
MW-10: K = 0.327 ft/day

The hydraulic conductivity (K) represents an approximation of the permeability of the
subsurface materials which transmit groundwater. In the monitoring wells evaluated at
the landfill, the estimated permeability values ranged from a minimum of 0.0127 ft/day to
a maximum of 2.66 ft/day, with the average value of 0.506 ft/day. These values are
within the typical range for saprolitic soil. The variability of the values seen here may
reflect the various geologic features encountered (i.e. drainage features, fractured
bedrock, and flood plain sediments).

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 4

The general direction of groundwater flow, based on prior water quality monitoring
events, is shown on Figure 2. Groundwater flow is generally to the south, toward
Abbotts Creek. Based on observed groundwater elevations at the site, the hydraulic
gradient of the shallow water table from north to south is approximately 0.0136 ft/ft. The
observed vertical hydraulic gradient near the discharge zone (Abbotts Creek) is
approximately 0.021 ft/ft upward.
City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 5

2.0 Water Quality Monitoring Program

The water quality monitoring network at the closed City of Lexington Landfill will be evaluated
on a semi-annual basis, except as provided in Section 2.3 below. The location of the
groundwater and surface water samples collected during the semi-annual monitoring events is
shown on the attached Figure 2.

2.1 Groundwater Monitoring Network

There are thirteen groundwater monitoring wells located at the facility that comprise the
existing groundwater monitoring network (Figure 2). The northern boundary of the
landfill is monitored by five wells; MW-4, MW-5, MW-6, MW-11, and MW-12.
Monitoring well MW-11 is the upgradient sampling point which represents background
groundwater quality. The eastern boundary of the landfill is monitored by four wells;
MW-7, MW-7D, MW-8, and MW-3. The southern boundary of the landfill, along
Abbotts Creek, is monitored by four wells; MW-2, MW-9, MW-10, and MW-10D.
Information regarding the date of installation, construction specifics, formation material
encountered, and Lat/Long location of the thirteen groundwater monitoring wells is
provided on Table 1.

Monitoring wells MW-4, MW-5, and MW-12 are located on the hydraulically upgradient
portion of the property, however, the water quality in these wells may be impacted by
their close proximity to the former landfill disposal areas. As such, these three well are
gauged for water levels only, no sample is collected for laboratory analyses.

The monitoring wells to be evaluated by laboratory analyses during each monitoring
event include:

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 6

MW-2 MW-3 MW-6 MW-7 MW-7D
MW-8 MW-9 MW-10 MW-10D MW-11

2.2 Surface Water Monitoring Network

In addition to the on-site groundwater monitoring wells, two surface water samples are
collected from Abbotts Creek during the water quality monitoring events. A surface
water sample is collected upstream (SW-1) and downstream (SW-4) of the landfill from
Abbotts Creek. The location of the surface water samples is shown on Figure 2.

2.3 Monitoring Frequency

The ten groundwater monitoring wells and two surface water monitoring stations will be
sampled for laboratory analyses on a semi-annual basis, normally in the spring and fall of
each year. Based on a recent evaluation of the water quality monitoring network by the
NC Solid Waste Section (January 21, 2016 correspondence), if the concentrations of
volatile organic compounds (EPA Method 8260B) in all of the on-site monitoring wells
are below the applicable NC 2L Groundwater Standards, the monitoring frequency may
be reduced to annually. However, if volatile organic compounds are detected above the
NC 2L Groundwater Standards in any on-site monitoring wells, the monitoring frequency
must return to a semi-annual evaluation.

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 7

3.0 Water Quality Sample Collection

Samples of groundwater and surface water are collected in accordance with the 2008 NC Solid
Waste Section Guidelines for Groundwater, Soil, and Surface Water Sampling Guidance
Document. A description of the sample collection procedure is provided below.

3.1 Field Sample Procedures

Prior to groundwater sampling, water levels are obtained from all thirteen monitoring
wells using an electric water level meter capable of measuring the depth to water to the
nearest 0.01 feet. This information is later used to determine the elevation of the water
table in each monitoring well relative to surveyed datum (Table 1). The depth to water in
each well is also used to determine the volume of standing water in the well casing. This
information allows for the purging of a minimum of three casing volumes from each well
prior to sample collection to assure a fresh groundwater sample was collected. New
disposable laboratory gloves are worn by sampling personnel and each well is purged and
sampled with a new disposable bailer which is discarded after use.

After the monitoring wells had been allowed to recover from purging, samples are
collected in the following order:

 Volatile organic compounds
 Inorganic compounds
 Field Parameters (pH, Conductivity, Temperature)

The samples are collected directly in the laboratory-supplied containers which are pre-
filled with the appropriate preservative. No filtering of the samples is performed prior to
collection. After collection, the samples are placed in a cooler on ice for overnight
shipment to the analytical laboratory.
City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 8

Surface water samples are collected directly into the laboratory-supplied containers as
grab samples. Sampling personnel wear new disposable laboratory gloves for each
surface water sample collected. As with the groundwater samples, these samples are
stored in a cooler on ice prior to overnight delivery to the analytical laboratory.

3.2 Field Quality Assurance

One trip blank sample is prepared by the analytical laboratory and accompanies the
sample shipment until receipt back at the laboratory. The trip blank sample is analyzed
for volatile organic compounds by EPA Method 8260B. Temperature blanks are also
provided with the sample shipments to assure the proper temperature is maintained until
delivery to the analytical laboratory.

3.3 Sample Delivery/Chain of Custody

All groundwater and surface water samples are stored in coolers on ice immediately after
collection. Individual sample containers for each well or surface water sample are placed
in zip lock plastic bags to reduce the potential for cross contamination. Chain-of-Custody
control documents are prepared and shipped with each cooler. Custody seals are also
used for each cooler to maintain sample integrity until delivery to the analytical
laboratory. The sample coolers are shipped via Federal Express for next morning
delivery to the analytical laboratory.

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 9

4.0 Laboratory Analysis

The samples will be analyzed for parameters specified by the NC Solid Waste Section for
Detection Monitoring at permitted solid waste facilities. The standard Detection Monitoring
Program for groundwater and surface water samples consists of the Appendix I parameters. The
Appendix I analyses consists of volatile organic compounds by EPA Method 8260B and select
inorganic compounds by EPA Methods 6010C/6020A.

The laboratory performing the water quality analysis will be a NC Certified Laboratory. Internal
quality control samples, including matrix spikes/matrix spike duplicates, will be performed by
the laboratory for each set of samples. The laboratory report (including internal quality control
samples) and the data presented in Excel EDD format will provided with the written report.

City of Lexington Closed Landfill Water Quality Monitoring Plan
February 2016 Page 10

5.0 Recordkeeping and Reporting

A report summarizing the monitoring event and the analytical data from the event will be
submitted to the NC Solid Waste Section within 120 days of the sampling date.

Monitoring reports will include the following:

 A discussion of site geology and hydrogeology;
 A discussion of the monitoring event procedures and results;
 A groundwater flow evaluation (including a potentiometric surface map);
 Analytical laboratory reports and summary tables;
 Solid Waste Environmental Monitoring Reporting Form; and
 Laboratory Data (pdf and Electronic Data Deliverable Format).

Monitoring reports will be submitted electronically by e-mail to the NC Solid Waste Section and
a hard copy of the reports will be maintained in the City of Lexington Public Works files.

FIGURES

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