RA-517_3274_CA_MRP_20180511

May 11, 2018

Mr. Mark Petermann
NCDEQ, Division of Waste Management, UST Section
1646 Mail Service Center
Raleigh, North Carolina 27699-1646

Reference: Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230

Dear Mr. Petermann:

As authorized by your acceptance of ECS Southeast, LLP (ECS) Task Authorization Request #1
dated February 6, 2018; ECS has completed the Groundwater Monitoring Report for the above-
referenced site. Included in this report is a description of the field activities, the results obtained,
and our conclusions and recommendations.

ECS appreciates the opportunity to provide our environmental consulting services to you on this
project. If you have any questions concerning this report or this project, please contact us.

Sincerely,

ECS SOUTHEAST, LLP

Sarah Kordon
Environmental Staff Project Manager
[e-mail]
[phone]

John S. Lair, P.G.
Principal Geologist
[e-mail]
[phone]

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230

SITE INFORMATION

Date of Report: May 11, 2018

Facility I.D.: #0-224946
UST Incident No.: TF-3274
Site Rank: H210A
Land Use Category: Commercial

Site Name and Location: Petro Mart #4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina

Parcel Identification Number: 9776-23-9124

Latitude and Longitude: 35.846815 North, -79.091187 West
Contacts

Property Owner: Jean Williams
PO Box 429
Carrboro, North Carolina 27510
[phone]

Property Owner Legal Representative: Benjamin D. Overby
522 South Lexington Ave.
Burlington, NC 27216-2958
[phone]

Consultant: ECS Southeast, LLP
9001 Glenwood Avenue
Raleigh, North Carolina 27617
[phone]
Attn: Matthew Gillis

Laboratory: Con-Test Analytical Laboratory
39 Spruce Street
East Longmeadow, MA 01028
[phone]
NC Certification No. 652

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230

EXECUTIVE SUMMARY

The subject site is known as the Petro Mart #4 site and is located at 11455 NC Highway 15/501
North in Chapel Hill, Chatham County, North Carolina. The subject site is further identified by
Chatham County Geographic Information Systems (GIS) Parcel Identification Number (PIN)
9776-23-9124. On March 7, 2018, ECS collected groundwater samples from monitoring wells
MW-1, MW-2, MW-4, MW-5, and MW-6. Prior to sampling, ECS gauged each monitoring well
for the presence of free product. Free product was detected in monitoring well MW-3, and was
therefore not sampled. The samples collected were shipped to Con-Test Analytical Laboratory
for analyses for volatile organic compounds (VOCs) by SM 6200B. ECS subsequently deployed
an O-Sox remedial device in monitoring well MW-4.

Laboratory analysis of the groundwater samples collected from monitoring wells MW-1, MW-2,
and MW-4 detected petroleum-related hydrocarbons at concentrations that exceeded their
respective North Carolina 2L Groundwater Quality Standards (NC2LGWQS), but did not exceed
their respective Gross Contamination Levels (GCLs). The groundwater results show similar
concentrations as previous samplings events.

Based on the findings of this Groundwater Monitoring Report, ECS recommends the following:

 Installation, development, and subsequent sampling of two down-gradient monitoring
wells.

 Advance up to twelve soil borings to an approximate depth of 20 ft bgs around the
former UST location to determine the extent of petroleum-impacted soil.

 Collect two soil samples from each of the soil borings. Soil sample intervals will be
determined by continuously screening each soil sample for volatile organic vapors using
a photoionization detector (PID). The former UST excavation basin was excavated to
depths ranging from eight feet below the ground surface (ft bgs) to 12 ft bgs. If volatile
organic vapors are not encountered, one sample will be collected at approximately 12 ft
bgs and one sample will be collected at approximately 20 ft bgs.

 Collect groundwater samples from the site monitoring wells and area water supply wells
WSW-1, WSW-5, WSW-6, and WSW-7.

 Deployment of replacement O-Sox remedial device in monitoring well MW-4.

 ECS recommends that a copy of this report be submitted to the current property owner.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230

TABLE OF CONTENTS
1.0 SITE HISTORY ......................................................................................................... 1
2.0 SITE GEOLOGY AND HYDROGEOLOGY............................................................... 3
3.0 RECEPTOR INFORMATION .................................................................................... 4
4.0 FILE REVIEW ............................................................................................................ 5
5.0 FIELD ACTIVITIES ................................................................................................... 5
6.0 RESULTS ................................................................................................................. 6
7.0 CONCLUSIONS ........................................................................................................ 7
8.0 RECOMMENDATIONS ............................................................................................. 8

FIGURES

Figure 1 Site Location Map
Figure 2 Aerial Site Map
Figure 3 Monitoring Well Location Map
Figure 4 Groundwater Elevation Map
Figure 5 Water Supply Well Location Map
Figure 5 Pantry #294 Site Map
Figure 6 Groundwater Concentration Map
Figure 7 Benzene Isoconcentration Map
TABLES

Table 1 UST Information
Table 2 Summary of Historical Soil Sample Analytical Results
Table 3 Water Supply Well Survey
Table 4 Monitoring Well Construction and Groundwater Elevation Details
Table 5 Summary of Current Groundwater Analytical Results
Table 6 Summary of Historical Groundwater Analytical Results

APPENDICIES

Appendix A ECS Personnel Field Notes
Appendix B Site Photographs
Appendix C Laboratory Analytical Data Sheets and Chain of Custody (COC) Record

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
1

1.0 SITE HISTORY

The Petro Mart #4 site is located at 11455 NC Highway 15/501 North in Chapel Hill, Chatham
County, North Carolina (Figures 1 and 2). According to information provided to ECS by the North
Carolina Department of Environmental Quality (NCDEQ), the site is an active gasoline station that
formerly contained one 2,000-gallon kerosene UST, one 2,000-gallon diesel UST, one 6,000-
gallon gasoline UST, and two 8,000-gallon gasoline USTs. The site currently contains one 12,000-
gallon gasoline UST, one 8,000-gallon gasoline UST, and one 6,000-gallon diesel UST (Table 1).

In August 1986, a release of approximately 25-gallons of gasoline was reported on the site. In
October 1986, two monitoring wells (*MW-1 and *MW-2) were installed at the site to depths of 20
and 30 ft bgs. Laboratory analysis of soil samples collected from the monitoring well borings did
not report petroleum-related contamination. The monitoring wells were determined to be dry and
were not sampled.

In 1987, laboratory analysis of soil samples collected by the NCDEQ reported benzene at 8.6
milligrams per kilogram (mg/kg) and methyl-ethyl ketone (MEK) at 120 mg/kg; however, the
location of these soil borings is not known.

In September 1994, groundwater samples were collected from five off-site water supply wells.
Laboratory analysis of the groundwater samples reported methyl tert-butyl ether (MTBE) at 72 ppb
in the water supply well at the Park & Stay mobile home park (WSW-2) located approximately 800
feet south of the subject site. Water-supply well WSW-2 has subsequently been abandoned and
the Cole Park Plaza Shopping Center has been constructed at that location.

In February 1995, two monitoring wells were installed at the site. Monitoring well MW-1 was
installed adjacent to the current tank basin and monitoring well MW-2 was installed on the
southeast corner of the subject site (Figure 3). Laboratory analysis reported several targeted
analytes at concentrations above their respective NC2LGWQS in the groundwater samples
collected from monitoring wells MW-1 and MW-2.

In March 2001, five USTs were removed from the site. A total of eight soil samples were collected
during closure activities. Laboratory analysis of seven of the eight soil samples reported total
petroleum hydrocarbons (TPH) above the NCDEQ UST Sections Action Levels of 10 milligrams
per kilogram (mg/kg). Monitoring wells *MW-1 and *MW-2 were abandoned.

In December 2008, a receptor survey was conducted for the site. At that time, the site consisted
of an active gasoline station (Petro Mart) and one 20,000-gallon compartmentalized UST
containing regular and premium gasoline and diesel. ECS could not determine the current status
of this UST. The receptor survey did not identify monitoring wells or water supply wells on the
subject site. The site was determined to utilize water obtained from water supply well WSW-1
located on an off-site property approximately 350 feet west and upgradient of the site. Water
supply well WSW-1 is owned by Aqua who indicated that water supply well WSW-1 is sampled
regularly for VOCs. Water supply well WSW-1 is approximately 410 feet deep, has a capacity of
60 gallons per minute (gpm), and has been in service since the late 1970s. Five additional water
supply wells (WSW-2, WSW-3, and WSW-5 through WSW-7) were identified within 1,000 feet of
the site. It was reported that these wells are inactive or have been abandoned.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
2

In April 2010, a review of the active UST system compliance records for the site was conducted.
According to a February 2009 compliance inspection, three new USTs were installed on the site in
May 2001 consisting of one 12,000-gallon gasoline, one 8,000-gallon gasoline, and one 6,000-
gallon diesel UST. The inspection identified five violations consisting of the following:

1) Failure to provide secondary containment on UST systems installed or replaced after
May 1, 2000 near wells and surface waters (the UST system is located within 500 feet
of a public water supply well);
2) No leak detection for tanks;
3) Failure to conduct leak detection properly;
4) Failure to report a suspected release (weeps were reportedly observed beneath three
of the four dispensing pumps); and,
5) Failure to investigate a suspected release.

In the compliance record file, there was a response letter from the property owner (K&M Services,
Inc.) regarding to the compliance report. Included in the letter were line and ELD test results, tank
tightness testing results, copies of invoices for a continuous statistical leak detection system
installed in the existing tank monitoring device, an invoice for seven sensors installed in sump
pumps, and dispenser pans, and tank monitoring tapes. In addition, the letter indicates that all
weeps beneath the dispensers had been repaired and that old filters had been removed from the
containment sump. The 2010 compliance review report concluded that the UST system is in
compliance and that residual soil and groundwater contamination may be present in the areas of
the former UST pit and dispensing pumps. The report indicates that groundwater contamination
beneath the site may be originating from an adjoining leaking UST site (Pantry #294).

On April 15 and 16, 2015, ECS installed monitoring wells (MW-1 and MW-2) to depths of 55
and 54 ft. bgs, respectively. Monitoring wells MW-1 and MW-2 are located near the current UST
basin. ECS collected two soil samples from each monitoring well boring at depths of 3 to 5 ft
bgs (SS-1A and SS-2A) and 8 to 10 ft bgs (SS-1B and SS-2B). Soil samples SS-1A and SS-1B
were collected from the boring for monitoring well MW-1 and soil samples SS-2A and SS-2B
were collected from the boring for monitoring well MW-2. ECS also collected groundwater
samples from monitoring wells MW-1 and MW-2.

Laboratory analysis reported methylene chloride at a concentration above its Soil-to-Groundwater
Maximum Soil Contamination Concentration (MSCC) in the soil sample collected from SS-2A, as
shown on Table 2. Laboratory analysis reported MTBE and lead at concentrations above their
respective NC2LGWQS but below their respective GCLs in the groundwater sample collected
from monitoring well MW-1. Laboratory analysis reported benzene and MTBE at concentrations
above their respective NC2LGWQS but below their respective GCLs in the groundwater sample
collected from monitoring well MW-2.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
3

On August 10-12, 2015, ECS installed four monitoring wells (MW-3 through MW-6) to depths
ranging from 46 to 52 ft. bgs. ECS collected groundwater samples from monitoring wells MW-1
and MW-2 and the four newly installed monitoring wells. On August 24, 2015, Bateman Civil
Survey surveyed the site monitoring wells. Laboratory analysis reported benzene and MTBE at
concentrations above their respective GCLs in the groundwater sample collected from monitoring
well MW-3, which is located adjacent to the former UST basin. Laboratory analysis reported
several additional targeted analytes at concentrations above their respective NC2LGWQS but
below their respective GCLs in the groundwater samples collected from monitoring wells MW-1
through MW-6.

ECS conducted a receptor survey update for the subject site. ECS observed two water supply well
houses (WSW-1 and WSW-6) within 500 feet of the subject site and two water supply wells
(WSW-5 and WSW-7) within 1,000 feet of the subject site (Figure 7). ECS spoke with Ms.
Shonda, a representative of Aqua who confirmed that the subject site utilizes municipal water
obtained from the community water supply well (WSW-1) located approximately 350 feet west
and topographically upgradient of the site. Aqua also confirmed that the community water supply
well WSW-1 supplies water to the residences within Cedar Terrace. Water supply well WSW-1 is
maintained by Aqua who indicated that WSW-1 is sampled regularly for VOCs. ECS spoke with
Ms. Jean Williams, the owner of the properties associated with water supply wells WSW-5
through WSW-7, who confirmed that the water supply wells are active and are sampled regularly
by an unknown agent. ECS was not provided with laboratory reports from this testing.
2.0 SITE GEOLOGY AND HYDROGEOLOGY

As determined from the USGS Topographic Map, Farrington, North Carolina Quadrangle dated
1993 (Figure 1), the site is at an approximate elevation of 550 feet above mean sea level.

The subject site is situated in the Piedmont Physiographic Province. The soils encountered in
this area are the residual product of in-place chemical weathering of rock presently underlying
the site and/or historic depositional events. In general, shallow unconfined groundwater
movement within the overlying soils is controlled largely by topographic gradients. However, as
the groundwater percolates downward, it becomes controlled by the subsurface geologic
conditions. Thus, the direction of groundwater movement in the deeper aquifers may not be
consistent with the reflecting topography.

In general, shallow unconfined groundwater movement within the overlying soils is controlled
largely by topographic gradients. Recharge occurs primarily by infiltration along higher
elevations and typically discharges into streams or other surface water bodies. The elevation of
the shallow water table is transient and can vary with seasonal fluctuations in precipitation.
Movement of shallow groundwater is generally from higher to lower elevations.

ECS measured the depth to groundwater in each of the wells and used this data to create a
groundwater elevation map (Figure 4). It was determined that groundwater generally flows to
the northwest at the site. This conclusion is in general agreement with topographic
observations of this area.
Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
4

3.0 RECEPTOR INFORMATION
3.1 Water Supply Wells

On August 10, 2015, ECS conducted a receptor survey update for the subject site. ECS observed
two water supply well houses (WSW-1 and WSW-6) within 500 feet of the subject site and two
water supply wells (WSW- 5 and WSW-7) within 1,000 feet of the subject site (Figure 5). ECS
spoke with Ms. Shonda, a representative of Aqua who confirmed that the subject site utilizes
municipal water obtained from the community water supply well (WSW-1) located approximately
350 feet west and topographically upgradient of the site. Aqua also confirmed that the community
water supply well WSW-1 supplies water to the residences within Cedar Terrace. Water supply
well WSW-1 is maintained by Aqua who indicated that WSW-1 is sampled regularly for VOCs.
ECS spoke with Ms. Jean Williams, the owner of the properties associated with water supply wells
WSW-5 through WSW-7, who confirmed that the water supply wells are active and are sampled
regularly by an unknown company. ECS was not provided with laboratory reports from this testing.

3.2 Public Water Supplies

ECS contacted Chatham County Public Works Utilities and Water Division to inquire if
municipal water is available for the subject site and surrounding area. According to Chatham
County personnel and the Chatham County GIS website, municipal water supply lines are
located on Manns Chapel Road and NC Highway 15/501 which can supply municipal water to
the subject site and surrounding area. The commercial properties located east of the subject
site and some residences south and west of the subject site are currently connected to the
municipal water supply.
3.3 Surface Water
As determined from the USGS Topographic Map, Farrington, North Carolina Quadrangle dated
1993 (Figure 1), the site is at an approximate elevation of 550 feet above mean sea level.
Surface runoff on the site is generally to the southeast.
3.4 Subsurface Structures

ECS did not identify subsurface structures associated with the subject site.
3.5 Land Use

The subject site is developed with a commercial property and currently operates as a convenience
store and gasoline station. The surrounding area is a mixture of residential and commercial
properties.
3.6 Property Owners and Occupants

The Chatham County GIS website was utilized to identify the adjacent property owners. The
names and addresses of the owners of adjacent properties and properties located within 500 feet
of the site are shown on Table 3.
Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
5

4.0 FILE REVIEW

A separate leaking gasoline UST site, identified as “the Pantry #294” (Incident #22718) (Facility ID
#0-021416) is located across Manns Chapel Road, approximately 270 feet from the subject site.
ECS obtained and reviewed the Withers and Ravenel (WR) May 2013 Groundwater Monitoring
Report and found that WR concluded that several VOCs were identified above their respective
NC2LGWQS. WR reported, “The most concentrated contaminant area appears to be around
MW-3. MW-3 and deep well MW-4 were the only wells with contaminants exceeding 15A NCAC
2L groundwater standards.” Additionally, no analyzed VOCs were detected above their respective
GCL. As shown in Figure 6, off-site monitoring wells MW-3 and deep well MW-4 associated with
the Pantry #294 site are located near the eastern portion of the adjacent site. ECS determined
that it is unlikely that the current and former USTs located at the Pantry #294 have impacted the
subject site based on the eastern plume delineation.

5.0 FIELD ACTIVITIES

5.1 Groundwater Flow Direction Measurements

On March 7, 2018, ECS measured the static water level (SWL) in six monitoring wells using a
decontaminated electronic water level meter. The static water levels and top of casing elevations
were used to calculate groundwater flow direction. The static water level measurements can be
found on Table 4.

5.2 Monitoring Well Sampling and O-Sox Deployment

On March 7, 2018, ECS collected a field blank and groundwater samples from monitoring wells
MW-1, MW-2, MW-4, MW-5, and MW-6. Purging and sampling of monitoring wells were
accomplished using a disposable bailer. ECS collected geochemical measurements at each
well for each well volume purged using a YSI-556 multi-parameter meter. Groundwater
Monitoring Well Sampling Data sheets and Personnel Field Notes are provided in Appendix A.
Site Photographs are included in Appendix B.

After purging the well, the groundwater samples were transferred into sample containers provided
by the laboratory. The sample containers were labeled with ECS project number, sample
identification, sample date and time, and requested analytical analysis. The containers were
placed into protective packaging material and placed into a cooler with ice to maintain the
samples at approximately 4 Celsius (C). The samples were submitted to Con-Test Analytical
Laboratories located in East Long Meadow, MA for chemical analysis for VOCs using Standard
Method 6200B. ECS maintained proper COC procedures throughout the sample collection and
transportation process. Copies of the COC are included in Appendix C.

Before site departure, ECS deployed O-Sox remedial devices in monitoring well MW-4.
Monitoring well MW-3 was not sampled due to the presence of free product.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
6

6.0 RESULTS
6.1 Groundwater Flow Direction

The groundwater flow direction is generally to the northwest across the site as determined
between on-site monitoring wells MW-1 through MW-6. A potentiometric flow map for the
subject site is depicted as Figure 4 and a potentiometric flow map is included for the adjacent
Pantry #294 site, with groundwater shown flowing to the northeast, included as Figure 6.

6.2 Monitoring Well Sampling

Petroleum-related compounds were detected in monitoring wells MW-1, MW-2, and MW-4, at
concentrations exceeding their respective NC2LGWQS, as shown on Figure 7.

Laboratory analysis of the groundwater sample collected from monitoring well MW-1 detected
isopropylbenzene above its respective NC2LGWQS. Diisopropyl ether was detected above
laboratory detection limits; however, the concentration did not exceed the respective
NC2LGWQS.

Laboratory analysis of the groundwater sample collected from monitoring well MW-2 detected
isopropylbenzene above its respective NC2LGWQS. Diisopropyl ether was detected above
laboratory detection limits; however, the concentration did not exceed the respective
NC2LGWQS.

Monitoring well MW-3 was not sampled due to the presence of free product.

Laboratory analysis of the groundwater sample collected from monitoring well MW-4 detected
benzene, diisopropyl ether (IPE), isopropylbenzene, 1,2,4- trimethylbenzene, MTBE, and 4-
methyl-2-pentanone at concentrations exceeding their respective NC2LGWQS. Toluene,
ethylbenzene, n-propylbenzene, 1,3,5-trimethylbenzene, total xylenes, and 2-hexanone were
detected above laboratory detection limits, but concentrations did not exceed their respective
NC2LGWQS.

Targeted analytes were not reported above laboratory reporting limits in the field blank or the
groundwater samples collected from monitoring wells MW-5 and MW-6, which are located north
of the suspected source area.

None of the detected concentrations in the sampled monitoring wells exceeded their respective
GCLs. A summary of the current groundwater laboratory analytical results is included in Table 5.
Historical analytical data from groundwater assessment is included in Table 6. The laboratory data
sheets and COC are included in Appendix C. Using the laboratory analytical results of the
groundwater samples collected from the groundwater monitoring wells, isoconcentration maps
showing the horizontal extent for benzene, which was detected above the NC2LGWQS, is
included as Figure 8.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
7

7.0 CONCLUSIONS

Based on the results of this Groundwater Monitoring Report, ECS concludes the following:

 ECS previously identified four water supply wells within 1,000 ft of the subject site; two of
which are within a 500 ft radius.

 Chatham County Public Works Utilities and Water Division confirmed that municipal water
supply lines are available for connection to the site and surrounding properties;

 Free product was observed in monitoring well MW-3. The extent of the free-product has
not been defined.

 Laboratory analysis reported several additional targeted analytes at concentrations above
their respective NC2LGWQS but below their respective GCLs in the groundwater samples
collected from monitoring wells MW-1, MW-2, and MW-4.

 In 2001, five USTs were removed from the site. A total of eight soil samples were collected
during closure activities. Laboratory analysis of seven of the eight soil samples reported
TPH above the NCDEQ UST Sections Action Levels of 10 mg/kg.

 In 2015, ECS installed monitoring wells (MW-1 and MW-2) located near the current UST
basin. ECS collected two soil samples from each monitoring well boring at depths of 3 to
5 ft bgs (SS-1A and SS-2A) and 8 to 10 ft bgs (SS-1B and SS-2B). Soil samples SS-1A
and SS-1B were collected from the boring for monitoring well MW-1 and soil samples SS-
2A and SS-2B were collected from the boring for monitoring well MW-2. Laboratory
analysis reported methylene chloride at a concentration above its Soil-to-Groundwater
MSCC in the soil sample collected from SS-2A. However, ECS considers the methylene
chloride detection to be related to a known laboratory contamination issue that has since
been resolved.

 After conducting a file review of the cross-gradient, adjacent leaking UST site known as
Pantry #294, ECS determined that it is unlikely that the current and former USTs located
on the adjacent site have impacted the subject site based on the eastern plume
delineation.

Groundwater Monitoring Report – Petro Mart # 4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
NCDEQ Contract: N17006
ECS Project: 49:6230
8

8.0 RECOMMENDATIONS

Based on the findings of this Groundwater Monitoring Report, ECS recommends the following:

 Installation, development, and subsequent sampling of two down-gradient monitoring
wells, as shown on Figure 3.

 Advance up to twelve soil borings to an approximate depth of 20 ft bgs around the
former UST location to determine the extent of petroleum-impacted soil.

 Collect two soil samples from each of the soil borings. Soil sample intervals will be
determined by continuously screening each soil sample for volatile organic vapors using
a photoionization detector (PID). The former UST excavation basin was excavated to
depths ranging from eight ft bgs to 12 ft bgs. If volatile organic vapors are not
encountered, one sample will be collected at approximately 12 ft bgs and one sample
will be collected at approximately 20 ft bgs.

 Collect groundwater samples from the site monitoring wells and area water supply wells
WSW-1, WSW-5, WSW-6, and WSW-7.

 Deployment of replacement O-Sox remedial device in monitoring well MW-4.

 ECS recommends that a copy of this report be submitted to the current property owner.

FIGURES

SOURCE:

USGS TOPOGRAPHIC MAP
FARRINGTON
NC QUADRANGLE
DATED 1993

SCALE: 1 : 24,000

FIGURE 1
SITE LOCATION MAP

PETRO MART #4
11455 NC HWY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
SITE
FIGURE 2
AERIAL SITE MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN
Scale: 1 inch = 170 feet
SITE
COMMERCIAL
SINGLE-FAMILY
RESIDENCES
SINGLE-FAMILY
RESIDENCES
THE PANTRY #294
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN

FIGURE 3
MONITORING WELL LOCATION MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
Scale: 1 inch = 80 feet
MW-1
MW-2
LEGEND

Approximate Location of Monitoring Well

Approximate Location of Proposed Monitoring Well

Approximate Location of Former USTs

Approximate Location of Current USTs

MW-1
MW-5 MW-6
MW-3 MW-4
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN

FIGURE 4
GROUNDWATER ELEVATION MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
Scale: 1 inch = 80 feet
LEGEND

Approximate Location of Monitoring Well

Groundwater Elevation

Groundwater Contour Line

Estimated Groundwater Contour Line

Estimated Direction of Groundwater Flow

* The site vertical datum is based on NAV88 and the
horizontal datum is based on NAD83.

MW-1
MW-6
515.86
515.86
MW-4
516.34
MW-2
516.09
MW-1
516.60
MW-5
516.54
Approximate Location of
Former USTs
516
Approximate Location of
Current USTs
MW-3
516.94
516.5
FIGURE 5
PANTRY #294 SITE MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
SOURCE:

Withers and Ravenel (WR) May 2013
Groundwater Monitoring Report

SCALE AS SHOWN
SITE
COMMERCIAL
SINGLE-FAMILY
RESIDENCES
THE PANTRY 294
MW-3
MW-4
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN

FIGURE 6
GROUNDWATER CONCENTRATION MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
Scale: 1 inch = 80 feet
LEGEND

Approximate Location of Monitoring Well

9.9 Concentrations Above Laboratory Reporting
Limits (µg/L)

160 Bold Concentrations Above NC2LGWQS (µg/L)

MW-1
MW-1
MW-2
Diisopropyl ether 9.9
Isopropylbenzene 130
MW-5
MW-6
MW-3
Free Product MW-4
Approximate Location of
Former USTs
Approximate Location of
Current USTs
Diisopropyl ether 0.6
Isopropylbenzene 53
Benzene 1,200
Diisopropyl ether 160
Toluene 74
Ethylbenzene 3.6
Isopropylbenzene 2,100
n-Propylbenzene 11
1,2,4- Trimethylbenzene 620
1,3,5-Trimethylbenzene 200
Total Xylenes 74
Methyl tert-butyl ether 320
2-Hexanone 47
4-Methyl-2-pentanone 1,730
BRL
BRL
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN

FIGURE 7
BENZENE ISOCONCENTRATION MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
MW-3
Scale: 1 inch = 80 feet
MW-1
BRL
MW-2
BRL

LEGEND

Approximate Location of Monitoring Well

Benzene Isoconcentration Contour (µg/L)

1200 Bold Concentration Above NC2LGWQS

FP Free Product

BRL Below Reporting Limit

MW-1
1,000
MW-3
FP
MW-4
1,200
MW-5
BRL
MW-6
BRL
100
FP
Approximate Location of
Former USTs
Approximate Location of
Current USTs
SOURCE:

CHATHAM COUNTY GIS
DATED 2013

SCALE AS SHOWN

FIGURE 7
WATER SUPPLY WELL LOCATION MAP

PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY,
NORTH CAROLINA
NCDEQ INCIDENT: TF-3274
ECS PROJECT: 49:6230
Scale: 1 inch = 360 feet

LEGEND

Approximate Location of Water Supply Well

WSW-1
500 ft.
Radius
1,000 ft.
Radius
SITE
WSW-1
WSW-6
WSW-7
WSW-5

TABLES

UST ID
Number
Last
Contents
Previous
Contents
Capacity
(in Gallons)
Construction
Details
Tank
Dimensions
Installation
Date
Removal
Date Status
1 Kerosene Kerosene 2,000 Unknown 12.0' x 5.33'11/10/1986 3/7/2001 Removed
2 Diesel Diesel 3,000 Unknown 12.0' x 5.33'11/10/1986 3/7/2001 Removed
3 Gasoline Gasoline 6,000 Unknown 16.16' x 8.0'11/10/1986 3/7/2001 Removed
4 Gasoline Gasoline 8,000 Unknown 20.66' x 8'11/10/1986 3/7/2001 Removed
5 Gasoline Gasoline 8,000 Unknown 20.66' x 8'11/10/1986 3/7/2001 Removed
6 Gasoline Gasoline 12,000 Unknown Unknown May 2001 Current Current
7 Gasoline Gasoline 8,000 Unknown Unknown May 2001 Current Current
8 Diesel Diesel 6,000 Unknown Unknown May 2001 Current Current
Chapel Hill, Chatham County, North Carolina
ECS Project: 49:6230
Table 1
UST Information
Petro Mart #4
11455 NC Highway 15/501 North
NCDEQ Incident: 3274
Sample ID Sample Date Sample Depth
(ft. bgs)Methylene ChlorideSS-1A 4/15/2015 3-5 BRL
SS-1B 4/15/2015 8-10 BRL
SS-2A 4/15/2015 3-5 0.032
SS-2B 4/15/2015 8-10 BRL
0.02
85
763
mg/kg = Milligrams per Kilogram
BRL = Below Laboratory Reporting Limit
Bold = Reported above the Soil to Groundwater MSCC
Soil-to-Growndwater MSCC (mg/kg)
Residential MSCC's (mg/kg)
Industrial/Commercial MSCC (mg/kg)
EPA Method 8260B
All results are listed in mg/kg parts per million.
MSCC = Maximum Soil Contamination Concentration Levels
ECS Project: 49:6230
Analytical Method
Contaminant of Concern (mg/kg)
Table 2
Summary of Historical Soil Sample Analytical Results
Petro Mart #4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: 3274
Water Supply
Well ID Well Owner / Address**Well Address Well Use Well Depth
(ft bgs)Type of Well
Approximate Distance
from Source Area of
Release (ft)
WSW-1
Jean Williams
PO Box 429
Carrboro, NC 27510
Cedar Terrace Chapel
Hill, NC 27514 Potable Unknown Drilled Approximately
380 ft west
WSW-5
Jean Williams
PO Box 429
Carrboro, NC 27510
29 Cedar Lake Road
Chapel Hill, NC 27514 Potable Unknown Drilled Approximately
680 ft west
WSW-6
Cheryl Curl Atwater and Toni Buck Curl
709 Reserve Estates Drive
Wake Forest, NC 27586
Cedar Village Road
Chapel Hill, NC 27514 Unknown Unknown Drilled Approximately
280 ft southwest
WSW-7
Cheryl Curl Atwater and Toni Buck Curl
709 Reserve Estates Drive
Wake Forest, NC 27587
103 Cedar Village Road
Chapel Hill, NC 27514 Unknown Unknown Drilled Approximately
930 ft southwest
** ECS confirmed ownership details via Chatham County GIS on April 17, 2018.
ECS Project: 49:6230
Table 3
Water Supply Well Survey
Petro Mart #4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: TF-3274
Monitoring
Well ID
Date
Measured
Depth to
Groundwater
(ft. btoc)
Date
Installed
Total Well
Depth
(ft. btoc)
Screen
Interval
(ft. btoc)
TOC
Elevation*
Groundwater
Elevation (ft)
MW-1 3/7/2018 36.94 4/15/2015 55 40-55 553.54 516.60
MW-2 3/7/2018 36.56 4/15/2015 54 39-54 552.65 516.09
MW-3 3/7/2018 36.18 8/10/2015 49 29-49 553.12 516.94
MW-4 3/7/2018 35.45 8/10/2015 46 26-46 551.79 516.34
MW-5 3/7/2018 36.95 8/10/2015 52 32-52 553.49 516.54
MW-6 3/7/2018 36.19 8/10/2015 52 32-52 552.05 515.86
ft. btoc = Feet Below Top of Casing
* = Survey performed by Bateman Civil Survey on August 24, 2015. The site vertical datum is based on NAV88 and
the horizontal datum is based on NAD83.
TOC = Top of Casing
Table 4
Monitoring Well Construction and Groundwater Elevation Details
Petro Mart #4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
ECS Project: 49:6230
NCDEQ Incident: 3274
MW-1 3/7/2018 BRL 0.6 BRL BRL 53.0 BRL BRL BRL BRL BRL BRL BRL BRL BRLMW-2 3/7/2018 BRL 9.9 BRL BRL 130 BRL BRL BRL BRL BRL BRL BRL BRL BRL
MW-3 3/7/2018MW-4 3/7/2018 1,200 160 74 3.6 J 2,100 BRL 11 BRL 620 200 74 320 47 J 1,730
MW-5 3/7/2018 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRLMW-6 3/7/2018 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL
Field Blank 3/7/2018 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL
1 70 600 70 20 6 70 70 600 400 400 40 100 500
5,000 70,000 84,500 25,000 20,000 6,000 30,000 70,000 260,000 28,500 25,000 40,000 100,000 85,500
Table 5
Summary of Current Groundwater Analytical Results
Petro Mart #4
11455 NC Highway 15/501 North
Chapel Hill, Chatham County, North Carolina
NCDEQ Incident: 3274
BRL = Below Laboratory Reporting Limit Methyl-tert-butyl-etherSample Date
NC2LGWQS = North Carolina 2L Groundwater Quality Standard as of April 1, 2013
GCL = NCDEQ's Gross Contamination Levels for Groundwater as of April 16, 2012(µg/L) = Micrograms per Liter
Bold = Reported above the NC2LGWQS Diisopropyl etherSample ID
GCL (µg/L)
NC2LGWQS (µg/L)IsopropylbenzeneNaphthalene1,3,5- TrimethylbenzeneStyreneFree Product 2-Hexanone4-Methyl-2-pentanone(MIBKUnderline = Reported above the NC2LGWQS and GCL
Standard Method 6200B
ECS Project: 49:6230
EthylbenzeneAnalytical Method
n-PropylbenzeneToluene1,2,4-TrimethylbenzeneTotal XylenesBenzene
EPA Method 6010
Sample ID Date Collected
*MW-1 2/8/1995 1,800 BRL 3,400 300 BRL BRL BRL BRL BRL BRL 760 1,200 BRL BRL NS
*MW-2 2/8/1995 1.0 BRL 1.6 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL NS
4/16/2015 BRL 0.90 BRL BRL BRL BRL BRL BRL BRL BRL BRL 53.5 BRL BRL 44.0
8/12/2015 BRL 1.2 BRL BRL BRL BRL BRL BRL BRL BRL BRL 76.5 BRL BRL NS
3/7/2018 BRL 0.64 BRL BRL BRL BRL BRL BRL BRL BRL BRL 53 BRL BRL BRL
4/16/2015 73.3 17.3 0.64 2.7 1.7 BRL 1.4 BRL 6.2 BRL 83.8 296 BRL BRL BRL
8/12/2015 BRL 13.5 BRL BRL BRL BRL BRL BRL BRL BRL BRL 250 BRL BRL NS
3/7/2018 BRL 9.9 BRL BRL BRL BRL BRL BRL BRL BRL BRL 130 BRL BRL BRL
8/12/2015 29,900 229 32,800 1,860 50.3 733 188 34.4 1,350 340 9,140 22,700 BRL BRL NS
3/7/2018
8/12/2015 1,410 296 1,680 98.9 BRL 26.2 7.5 BRL 306 124 2,497 4,950 BRL BRL NS
3/7/2018 1,200 160 620 74 3.6 J BRL 11 BRL 200 74 1,730 2,100 320 47 J BRL
8/12/2015 1.3 BRL 2.8 0.53 BRL BRL BRL BRL BRL BRL 2.55 BRL BRL BRL NS
3/7/2018 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL
8/12/2015 2.4 BRL 5.2 0.76 BRL BRL BRL BRL BRL BRL 3.7 0.76 BRL BRL NS
3/7/2018 BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL BRL
1 70 600 600 70 6 70 70 400 400 500 20 40 100 15
5,000 70,000 260,000 84,500 25,000 6,000 30,000 70,000 28,500 25,000 85,500 20,000 40,000 100,000 15,000
NS = Not Sampled
BRL = Below Reporting Limit
GCL = NCDEQ's Gross Contamination Levels for Groundwater as of April 16, 2012
MW-6
Free Product ≈ 0.36''2-Hexanone4-Methyl-2-pentanone (MIBKBold = Reported above the NC2LGWQS or NCDEQ Final and Interim GWQS Styrene1,3,5-TrimethylbenzeneEthylbenzeneTotal XylenesMethyl tert-butyl etherNaphthaleneMW-2
NC2LGWQS = North Carolina 2L Groundwater Quality Standard as of April 1, 2013
MW-4
MW-5 LeadNC2LGWQS (µg/L)
Gross Contamination Level (µg/L)
MW-3
Contaminant of Concern (µg/L)BenzeneToluene(µg/L) = Micrograms per Liter
NCDEQ Incident: 3274ECS Project: 49:6230
* = Monitoring wells were abandoned in March 2001 Diisopropyl etherIsopropylbenzenen-Propylbenzene1,2,4- TrimethylbenzeneUnderline = Reported above the NC2LGWQS and GCL
MW-1
Table 6Summary of Historical Groundwater Analytical ResultsPetro Mart #411455 NC Highway 15/501 North
Analytical Method
Chapel Hill, Chatham County, North Carolina
Standard Method 6200B (or equivalent)

APPENDIX A

APPENDIX B

SITE PHOTOGRAPHS
PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY
NORTH CAROLINA
NCDEQ INCIDENT: 3274
ECS PROJECT NO.: 49:6230

Photograph 1: View of the subject site. View is to the southwest.

Photograph 2: View of monitoring well MW-1. View is to the north.

SITE PHOTOGRAPHS
PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY
NORTH CAROLINA
NCDEQ INCIDENT: 3274
ECS PROJECT NO.: 49:6230

Photograph 3: View of the monitoring well MW-2. View is to the southwest.

Photograph 4: View of the monitoring well MW-3 with free product in bailer. View is to the west.

SITE PHOTOGRAPHS
PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY
NORTH CAROLINA
NCDEQ INCIDENT: 3274
ECS PROJECT NO.: 49:6230

Photograph 5: View of the monitoring well MW-4. View is to the northwest.

Photograph 6: View of the monitoring well MW-5. View is to the north.

SITE PHOTOGRAPHS
PETRO MART #4
11455 NC HIGHWAY 15/501 NORTH
CHAPEL HILL, CHATHAM COUNTY
NORTH CAROLINA
NCDEQ INCIDENT: 3274
ECS PROJECT NO.: 49:6230

Photograph 7: View of the monitoring well MW-6. View is to the west.

APPENDIX C

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