4101_Guilford_CityHighPoint_Riverdale_MSWLF_Seaboard_2023AnnualGWComments_FID1831106_20240229

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
MICHAEL SCOTT
Director
Gary Babb, P.G.
Babb & Associates, P.A.
Seaboard Group II and City of High Point
5506 Bradford Pear Ct.
Raleigh, NC 27606
NORTH CAROLINA
Environmental Quality
February 29, 2024
Re: Review of 2023 Annual Monitoring Report
Seaboard Group II and the City of High Point, dated January 16, 2024
Former Seaboard Chemical and Riverdale Drive Landfill Site
Jamestown, Guilford County, North Carolina
EPA ID# NCD071574164
Dear Mr. Babb,
The Hazardous Waste Section (HWS) of the Division of Waste Management has reviewed the referenced
document submitted to the HWS on January 16, 2024. Babb & Associates, P.A. prepared and submitted the
report on behalf of Seaboard Group II and the City of High Point (SG parties). Both the former Seaboard
Chemical facility and the former Riverdale Landfill were operated adjacent to each other, and past
operations have impacted groundwater and surface water around the property. For assessment and
remediation purposes, the "Site" encompasses the combined footprints of the two facilities. Based upon our
review of the 2023 annual monitoring report, we offer the following comments.
Table 1, Monitoring Well Construction Information and Groundwater Elevations.
Table 1 spans 30 pages and lists groundwater elevations obtained at the site back to 2000. Action Item: In
future reports documenting annual monitoring events, edit the table to list only data from well gauging
events back to 2010. (Most wells appear to have at least a few groundwater elevations from gauging events
between 2010 and 2012, when most site monitoring wells were sampled). At the bottom of the table, include
a note directing the reader to the 2023 report to obtain groundwater level measurements prior to 2010.
Section 5.2.1— Groundwater Analytical Results and Figures 5 through 9
Well PW-SF-1 and its associated contaminant concentrations are not shown on any of the
isoconcentration maps. This well has the highest concentration of 1,4-dioxane and vinyl chloride
among the wells sampled during the 2023 annual event. Action Item: Revise the five
isoconcentration maps to include the results from sampling of well PW-SF-l.
• The isoconcentration maps do not show the results for contaminants of concern (COCs) detected
in the samples from each monitoring well installed as part of a well cluster. A comparison of the
D E Q�� North Carolina Department of Environmental Quality I Division of Waste Management
-
217 West Jones Street 1 1646 Mail Service Center I Raleigh, North Carolina 27699-1646
NORTH CAROLINA
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lab results table with each isoconcentration map indicates that Babb & Associates labeled the well
in each well cluster that had the highest concentration. Action Item: Place a note on each figure
indicating that this approach was used for displaying the results.
The contaminant plumes for total volatile organic compounds (VOCs), chlorobenzene and vinyl
chloride in bedrock extend beneath the Deep River and under the land within the regulated buffer
of the Piedmont Triad Regional Water Authority (PTRWA). This contamination is evidenced by
concentrations above the NC Groundwater Quality Standards (2L Standards) at PW-15D and PW-
16D. The concentrations and total VOCs in groundwater have decreased in the wells since the
remediation system became fully operational in 2017. However, the concentrations for
chlorobenzene and vinyl chloride remain above the 2L Standards.
A November 2007 figure produced by ERM NC, PRC (Figure 2, Site Map and Monitoring
Locations), shows a bedrock monitoring well (PW-19) located about 920 feet east-northeast of well
pair PW-6i/6D. This property is labelled as owned by the City of High Point and the "Former Stone
Property". The PW-19 well location appears potentially downgradient of the northeasterly plume
orientations shown on the maps. Action Item: Document the condition of well PW-19 and access
to the well for potential future sampling.
On December 11, 2023 the HWS requested that the SG parties update the receptor survey for the
Site. The findings from the updated receptor survey are anticipated in late March 2024. Action
Item: In the receptor survey text, document the current occupancy and ownership status of the
properties on the other side of the PTRWA buffer where the former property owners once provided
access to sample monitoring wells PW-18 and PW-19. These wells were last sampled in January
2019 and 2015, respectively.' Total VOCs in the sample collected from PW-18 were measured at
an estimated concentration of 24 J ug/1 ("J" qualified by the lab). A common laboratory
contaminant, acetone, composed 17 of the 24 ng/l. Contaminants were not detected above the
quantitation limit in the sample collected in 2015 from PW-19.
Please respond to the comments in this letter through submittal of revised isoconcentration maps that
include well PW-SF-01. After February 29, 2024, until further notice, please address correspondence to
Kim Caulk, Facilities Management Branch Head along with Jackie Drummond. The remaining action items
may be addressed in the upcoming receptor survey update and future monitoring reports. Please contact us
if you have any questions or comments about this letter.
Eric B. Aufderhaar, Project Manager
Facilities Management Branch, Hazardous Waste Section
Division of Waste Management, NC DEQ
ec: Craig Coslett, de maximis, Inc.
Jackie Drummond, Solid Waste Section
Kim T. Caulk, Facilities Management Branch Head, Hazardous Waste Section
' Documents in the regulatory file and verbal communication with the SG parties indicate that subsequent
requests for permission to sample the well were unsuccessful despite repeated attempts over several
years.
E Q North Carolina Department of Environmental Quality I Division of Waste Management
217 West Jones Street 1 1646 Mail Service Center I Raleigh, North Carolina 27699-1646
NORTH CAROLINA -
DaP.mm.mmEwimnm�lQu.� /� 919.707.8200