4101_Guilford_CityHigh Point_Riverdale_MSWLF_Seaboard_ReportCommentLetter_FID1773531_20230223

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 23, 2023
Re: Review of 2022 Annual Monitoring Report
Seaboard Group II and the City of High Point, dated December 12, 2022
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 have reviewed the
referenced document submitted to the HWS on December 12, 2022. Based upon our review, we offer the
following comments.
Section 1.2 — Site Geology:
Reference a figure that shows the location of geologic features or identify well locations to orient the
reader to where the features are located. Items in this section where better orientation is needed for the
reader or where incorrect wells appear to be stated in the text include the following:
• Southern Intermittent Stream (SIS) Fault. Does the fault trend (or contain) the open ditched
portion of the SIS from SW-5 to SW-3 as shown on Figure 3? If yes, use these sample locations
or wells near the locations for reference.
• Seaboard Dike. Text indicates that the dike runs from the former Seaboard facility past PW-13i
and then runs north of the Deep River. Does it continue to trend N-NE between the near -vertical
river segment and PW-14D shown on Figure 2?
• PW-5D Dike/Fault. The text references PW-8S on the east side of the Seaboard site. This well is
not shown on the Figures. PW-5D is located south of the river (Figure 2) while the text indicates
that it is located north of the river.
• Regional Fault/Dike. Text indicates that it trends north of the Deep River. Is it inferred to pass
through or by PW-16D?
01-11- 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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Section 2.1— Groundwater Monitoring Network and Figure 2 — Groundwater Monitoring Well Locations
Well PW-SF1 is referenced in the Section but is not shown on Figure 2.
Section 5.0 — Hydrogeological Conditions
The third paragraph references an extraction rate/capture zone test that was completed using well PW-
DRO1. This well is not shown on any of the figures.
Figures 5 and 6 — Iso-concentration maps for 1,4-dioxane and total VOCs
The contaminant plumes for 1,4-dioxane (1,4-D), total VOCs and chlorobenzene in bedrock extend across
the Deep River under the land in the regulated buffer of the Piedmont Triad Regional Water Authority, as
evidenced by concentrations above the NC Groundwater Quality Standard (2L Standards) at MW-15D
and PW-16D. The concentrations for 1,4-D, chlorobenzene and the VOCs in groundwater have decreased
over the last five years after the remediation system became fully operational. However, the
concentrations remain above the 2L Standards. Upgrades to the remediation system were described in
Technical Memorandum E-11 (TM E-11) submitted to the HWS on February 3, 2022 and approved on
March 8, 2022 after additional information was provided. New extraction wells were installed and
operational by June 2022. The Seaboard Group II and the City of High Point (Seaboard Group) submitted
two quarterly progress reports after the extraction wells were started, covering the period June to
December 2022. Data in the second quarterly report, dated February 13, 2023, indicates that total VOCs
and 1,4-D are decreasing at several bedrock wells in the SIS basin area.
Seaboard Group II and the City of High Point should continue to monitor the contaminant concentrations
in wells across the Deep River along with well MW-12b, in the northwest part of the plume. At well MW-
12b, the contaminant concentrations have not decreased as much over the last five years.
Table 1— Well MW-17 (WSW-1) is listed in the table but not shown on any of the figures. Where is it
located?
Please respond to the comments in this letter through submittal of a revised 2022 annual monitoring
report. 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
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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