HomeMy WebLinkAboutWA-1034_12709_CA_RPTS_20150824
August 24, 2015
Ms. Rose Ballance
NCDENR Washington Regional Office
Division of Waste Management, UST Section
943 Washington Square Mall
Washington, North Carolina 27889
Subject: GROUNDWATER MONITORING REPORT
ETHERIDGE OIL & GAS COMPANY
34970 US HIGHWAY 264
ENGELHARD, HYDE COUNTY, NORTH CAROLINA
INCIDENT NO. 12709
MID-ATLANTIC JOB NO.: 000R2394.14
Dear Ms. Ballance:
On behalf of Etheridge Oil & Gas Company, Mid-Atlantic Associates, Inc. submits the
enclosed Groundwater Monitoring Report for the above-referenced site. If you have any
questions, please contact me at (919) 250-9918.
Sincerely,
MID-ATLANTIC ASSOCIATES, INC.
Charles B. Hoffman, P.G.
Project Geologist
pc: Mr. T.J. Etheridge, Jr. – Etheridge Oil & Gas Company
August 24, 2015
Mr. T.J. Etheridge, Jr.
Etheridge Oil & Gas Company, Inc.
Post Office Box 65
Engelhard, North Carolina 27824
Subject: GROUNDWATER MONITORING REPORT
ETHERIDGE OIL & GAS COMPANY
34970 US HIGHWAY 264
ENGELHARD, HYDE COUNTY, NORTH CAROLINA
INCIDENT NO. 12709
MID-ATLANTIC JOB NO.: 000R2394.14
Dear Mr. Etheridge:
Mid-Atlantic Associates, Inc. (Mid-Atlantic) is pleased to present this report of
environmental services performed at the above-referenced site. The purpose of our
services, as described in the attached report, was to perform groundwater monitoring at
the above-referenced site.
A copy of this report has been sent to the North Carolina Department of Environment and
Natural Resources, Washington Regional Office, UST Section. We appreciate the
opportunity to provide environmental services to Etheridge Oil & Gas Company and look
forward to assisting you through project completion. Please contact us at 800-486-7568 if
any questions arise or if we may be of further service.
Sincerely,
MID-ATLANTIC ASSOCIATES, INC.
Charles B. Hoffman, P.G.
Project Geologist
GROUNDWATER MONITORING REPORT
ETHERIDGE OIL AND GAS COMPANY
34970 US HIGHWAY 264
ENGELHARD, HYDE COUNTY, NORTH CAROLINA
INCIDENT NO. 12709
Risk Classification: Intermediate
Ranking: I-140-D
Prepared For:
Mr. T.J. Etheridge, Jr.
Etheridge Oil & Gas Company
Post Office Box 65
Engelhard, North Carolina 27824
(252) 925-4301
Prepared By:
Mid-Atlantic Associates, Inc.
409 Rogers View Court
Raleigh, North Carolina 27610
(919) 250-9918
August 24, 2015
TABLE OF CONTENTS
1.0 INTRODUCTION ..................................................................................................... 1
2.0 BACKGROUND ...................................................................................................... 1
3.0 POTENTIAL RECEPTORS ..................................................................................... 2
4.0 FIELD ACTIVITIES ................................................................................................. 2
4.1 Liqujid Level Measurements .......................................................................... 2
4.2 Monitoring Well Sample Collection ................................................................ 3
5.0 DISCUSSION OF SAMPLING RESULTS .............................................................. 3
5.1 Free Product Thickness ................................................................................. 3
5.2 Summary of Analytical Results ...................................................................... 3
5.3 Description of Current Plume Size and Location ........................................... 3
5.4 Additional Monitoring Information .................................................................. 4
6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ................................... 4
DRAWINGS
Drawing 1.1 Topographic Site Map
Drawing 2.1 Site and Monitoring Well Location Map
Drawing 5.1 Estimated Isoconcentration Map - Benzene in Shallow
Groundwater - May 7, 2015
Drawing 5.2 Estimated Isoconcentration Map - MTBE in Shallow Groundwater
May 7, 2015
Drawing 5.3 Estimated Water Table Contour Map - May 7, 2015
TABLES
Table 4.1 Monitoring Well Construction Data
Table 4.2 Groundwater Elevation Data
Table 5.1 Summary of Historical Groundwater Quality Data for Selected
Compounds Beginning 4/28/10
TABLE OF CONTENTS (CONTINUED)
APPENDICES
Appendix A Mid-Atlantic Field Procedures
Appendix B Laboratory Analytical Report and Chain-of-Custody Record for
Groundwater Samples
Appendix C Hydraulic Gradient Determination
1.0 INTRODUCTION
Mid-Atlantic Associates, Inc. (Mid-Atlantic) has performed groundwater monitoring
activities at the Etheridge Oil and Gas Company facility located at 34970 US Highway 264
in Engelhard, North Carolina (Drawing 1.1). This work was completed under Trust Fund
Pre-Approval Task Authorization Number 12709-14.
2.0 BACKGROUND
The subject site is the Etheridge Oil and Gas Company facility (also referred to as the
Ethco Service Station) located at 34970 US Highway 264 in Engelhard, North Carolina.
The site is currently in use as a convenience store and retail petroleum dispensing facility,
which operates one 8,000-gallon gasoline underground storage tank (UST) and one
4,000-gallon gasoline UST. According to information provided in previous reports and
regulatory databases, the site historically operated one 1,000-gallon diesel fuel UST, one
1,000-gallon gasoline UST and two 2,000-gallon gasoline USTs, which were reportedly
removed from the site in June 1994. The layout of the subject site, along with the
approximate locations of the current and former UST basins, are shown on Drawing 2.1.
Based on available information, a petroleum release was reported to the North Carolina
Department of Environment and Natural Resources (NCDENR) following removal of the
former UST system from the site in 1994. As a result, a Limited Site Assessment (LSA)
and Comprehensive Site Assessment (CSA) were conducted for the release in 1998 and
1999, respectively. During these activities, a total of 12 monitoring wells (MW-1 through
MW-5, MWD-6, MW-7 through MW-9 and MW-11 through MW-13) were installed at the
site (Note: no information was available for monitoring well MW-10). Based on the results
of the LSA, the site was assigned an intermediate risk classification (I-140-D) due to the
presence of surface water within 500 feet of the release area. Additionally, groundwater
appears to be discharging to an adjacent drainage feature located along the northern
property boundary of the site. Therefore, the cleanup standards for groundwater at the
site will be ten times the North Carolina Surface Water Quality Standards (NCSWS)
and/or EPA National Water Quality Criteria, as identified in NCDENR’s NC and EPA
Criteria Table updated on May 15, 2013.
According to the NCDENR, a Corrective Action Plan (CAP) was approved for the site in
April 2001 and implemented in March 2003. The CAP proposed monitored natural
attenuation (MNA) and Aggressive Fluid Vapor Recovery (AFVR) for the remediation of
groundwater; however, based on the available data, it appears that additional remedial
technologies would be warranted in order to reduce groundwater contaminant
concentrations to below cleanup goals. This report documents the May 2015 groundwater
sampling activities, as requested by NCDENR.
The opinions included herein are based on our experience and the information obtained
during the study. This report is based on limited observations made on the dates noted
using the procedures described herein. If additional information becomes available, we
request the opportunity to review the information, reassess the potential environmental
concerns and modify our conclusions, if appropriate.
Groundwater Monitoring Report August 24, 2015
Etheridge Oil & Gas Company Page 2
Engelhard, North Carolina
3.0 POTENTIAL RECEPTORS
Receptor information pertaining to this site is summarized in the Ground Water Monitoring
Report, Update Receptor Survey and Free Product Recovery Report prepared by
Geological Resources, Inc. (GRI) and dated April 28, 2010. The site is currently
classified as “intermediate” risk due to the presence of nearby surface waters. A brief
summary of potential receptors, as identified in the GRI report, is summarized below.
Water-Supply Wells
GRI personnel conducted an updated receptor survey on April 28, 2010. During the
receptor survey update conducted by GRI in 2010, several water-supply wells were
identified within 1,500 feet of the source area of the release; however, based on the
information provided in the GRI report, the wells appear to no longer be in use
Public Water Supplies
The GRI report indicated that municipal water is available to the site and surrounding
properties.
Surface Water
According to the GRI report, the closest surface water body to the site is Far Creek,
located approximately 75 feet to the north, west and northeast of the site. In addition, an
on-site ditch (the depth of which appears to be beneath the water table) also runs along
the north and east property boundaries of the subject site.
According to Classifications and Water Quality Standards Assigned to the Waters of the
Tar-Pamlico River Basin, the portion of Far Creek from its source to US Highway 264 is
classified as Class C, Swamp Waters. A Class C Water is defined as waters protected
for uses such as secondary recreation, fishing, wildlife, fish consumption, aquatic life
including propagation, survival and maintenance of biological integrity, and agriculture.
4.0 FIELD ACTIVITIES
4.1 Liquid Level Measurements
On May 7, 2015, Mid-Atlantic personnel measured the depth to water in site monitoring
wells with an electronic water level indicator in accordance with the procedures outlined in
Appendix A. Monitoring well construction data is summarized in Table 4.1 and a summary
of liquid level measurements from the May 2015 sampling event is provided in Table 4.2.
Groundwater Monitoring Report August 24, 2015
Etheridge Oil & Gas Company Page 3
Engelhard, North Carolina
4.2 Monitoring Well Sample Collection
On May 7, 2015, Mid-Atlantic personnel collected groundwater samples from recovery
well RW-1 and monitoring wells MW-1 through MW-5, MWD-6, MW-7 through MW-9 and
MW-11 through MW-13. Groundwater samples were collected in accordance with the
procedures outlined in Appendix A. The samples were shipped to Con-Test Analytical
Laboratories, Inc. in East Longmeadow, Massachusetts. Samples were analyzed by
methods shown on the chain-of-custody record provided in Appendix B.
5.0 DISCUSSION OF SAMPLING RESULTS
5.1 Free Product Thickness
Free product was not detected in site monitoring wells during the May 2015 groundwater
sampling event. Please note that based on the shallow water table, the static water level
elevations of the site monitoring wells appear to be above the screened intervals of these
wells. Monitoring well construction information and depth-to-groundwater measurements
are summarized in Tables 4.1 and 4.2, respectively.
5.2 Summary of Analytical Results
The laboratory analytical report and chain-of-custody record for groundwater samples
collected in May 2015 are provided in Appendix B and summarized in Table 5.1, which
also includes historical groundwater sampling results for selected compounds. As
summarized, samples collected from several on-site monitoring wells exhibited target
compounds exceeding their respective North Carolina Groundwater Quality Standards
(NCGQS). The samples collected from monitoring wells MW-1, MW-2, MW-7 and
recovery well RW-1 also exhibited target compounds at concentrations exceeding ten
times the NCSWS and/or EPA National Water Quality Criteria. When compared with
historical sampling events, groundwater contaminant concentrations appear to have
fluctuated at the site over time.
5.3 Description of Current Plume Size and Location
Isoconcentration maps for benzene and MTBE in shallow groundwater are provided as
Drawings 5.1 and 5.2, respectively. The extent of the dissolved-phase groundwater
contaminant plume appears to be defined to ten times the NCSWS and/or EPA National
Water Quality Criteria within the existing monitoring well network; however, based on the
depth of the northern adjacent ditch and depth-to-groundwater measurements within the
site monitoring wells, groundwater appears to be discharging to the adjacent drainage
feature. Therefore, the extent of potential surface water contamination to the north of the
release area appears to remain undetermined at this time.
Groundwater Monitoring Report August 24, 2015
Etheridge Oil & Gas Company Page 4
Engelhard, North Carolina
5.4 Additional Monitoring Information
• Proximity of Plume to Nearest Receptor
During the receptor survey update conducted by GRI in 2010, several water-supply
wells were identified within 1,500 feet of the source area of the release; however,
based on the information provided in the GRI report, the wells appear to no longer
be in use. As previously stated, groundwater at the site appears to be discharging
to the adjacent drainage feature located along the northern property boundary of
the site. The potential surface water impacts associated with the release have not
been assessed at this time.
• Estimated Groundwater Flow Direction
Based on measurements collected during the May 2015 sampling event, the
groundwater flow direction at the site appears to be radial with hydraulic
gradients of approximately 0.004 ft/ft to the north (MW-2 towards MW-7) and
south (MW-2 towards MW-4), 0.003 ft/ft to the east (MW-2 towards MW-8) and
0.006 ft/ft to the west (MW-2 towards MW-3). Based on available information,
the water table does not appear to be static and may be tidally influenced.
An Estimated Water Table Contour Map is provided as Drawing 5.3. Water level
measurements and groundwater elevations are provided in Table 4.2. The
hydraulic gradient was calculated using the procedure discussed in Appendix C.
6.0 SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
Based on the monitoring event activities and laboratory analytical results, Mid-Atlantic has
determined the following:
• Free product was not detected at the site. Please note that based on the shallow
water table, the static water level elevations of the site monitoring wells are above
the screened intervals for these wells;
• Samples collected from several of the site monitoring wells exhibited petroleum
fuel-related compounds exceeding the NCGQS;
• Samples collected from monitoring wells MW-1, MW-2, MW-7 and recovery well
RW-1 exhibited petroleum fuel-related compounds exceeding ten times the
NCSWS and/or EPA National Water Quality Criteria (site cleanup goals); and
Groundwater Monitoring Report August 24, 2015
Etheridge Oil & Gas Company Page 5
Engelhard, North Carolina
• The extent of the dissolved-phase groundwater contaminant plume appears to be
defined to ten times the NCSWS and/or EPA National Water Quality Criteria;
however, based on the apparent depth of the northern adjacent ditch and depth-to-
water measurements within the site monitoring wells, groundwater appears to be
discharging to the adjacent ditch. The potential surface water impacts associated
with the release have not been assessed at this time.
Based on these results, Mid-Atlantic recommends the following:
• Sampling of the adjacent surface water body to help determine the extent of
contamination and potential surface water impacts associated with the release;
• Continued periodic sampling of site monitoring wells;
• Evaluation of the need for additional remedial technologies for remediation of
groundwater at the site; and
• Submittal of this report to the NCDENR UST Section.
DRAWINGS
TABLES
APPENDIX A
MID-ATLANTIC FIELD PROCEDURES
APPENDIX B
LABORATORY ANALYTICAL REPORT
AND CHAIN-OF-CUSTODY RECORD
FOR GROUNDWATER SAMPLES
APPENDIX C
HYDRAULIC GRADIENT DETERMINATION