4101_Guilford_CityHighPoint_Riverdale_MSWLF_Seaboard_FiveYearReportCommentsResponse_FID1811146_20230719

SEABOARD GROUP HAND THE CITY OF HIGH POINT
July 18, 2023
Eric B. Aufderhaar, P.G., Environmental Program Consultant
North Carolina Department of Environmental Quality
Division of Waste Management
1646 Mail Service Center
Raleigh, North Carolina 27699-1646
Re: Five -Year Review Report - Response to Comments
Former Seaboard Chemical and Riverdale Drive Landfill Site
Jamestown, Guilford County, North Carolina
Dear Mr. Aufderhaar:
In response to correspondence from NCDEQ dated May 26, 2023, please find summarized below
responses related to the review comments on the Five -Year Review Report. A revised Five -Year Review
Report is attached to this correspondence as requested.
Comment 1: Section I (Page 3), Site Background and other sections. Property lines should be displayed
on a figure, either the Site Feature Map (Figure 2) or an additional figure. At a minimum, reference the
figure with property lines in the Site Background section, Site Related portion of Section II (page
6) and Treatment System portion of Section II (page 7).
Response: Property lines have been added to Figure 2 which is included with the revised Five -Year
Review Report.
Comment 2: Section I (Page 4), second full paragraph. The text indicates "...the parties then entered into
an Administrative Order on Consent (AOC) dated January 30,1996 with the State to perform the
Remedial Investigation (RI)." Please clarify which parties completed the RI - due to limited staffing and
economic resources the DEQ rarely completes assessment activities for regulated responsible parties.
Instead, DEQ reviews workplans, provides guidance when applicable and reviews reports.
Response: The "Parties", as discussed in the referenced paragraph, refers to the Seaboard Group II and
the City of High Point. Language has been added to the referenced section to clarify the author of the RI.
Comment 3: Section II (Page 6), Site Related section. Add "locked gates" after fencing. Please clarify if
security cameras are in use by the Materials Recycling Facility (MRF) or in the area of the
mechanical treatment system controls.
Response: The words "locked gates" have been added after fencing in the "Site Related" section of the
revised Five -Year Review Report. There are no operational cameras at the site.

SEABOARD GROUP HAND THE CITY OF HIGH POINT
Five -Year Review Report - Response to Comments
Former Seaboard Chemical and Riverdale Drive Landfill Site
July 18, 2023
Page 2
Comment 4: Several acronyms used in the report are not defined when first used or included on the
acronyms list. These include "SCADA" in Treatment Systems (Section II, page 7) and AOP+ in Status of
Implementation (Section II, page 9).
Response: The acronyms "SCADA" and "AOP+" have been spelled out in the text and added to the
acronym list in the revised Five -Year Review Report document.
Comment 5: Section II (Page 8), Natural Treatment System section and Figure 2, Site Features Map. The
text refers to tree stands but not "phytoremediation" which would tie the discussion with Figure 2 more
effectively. We suggest adding "phytoremediation" in the sentence: "an irrigation system for the tree
stand is divided into 16 approximately two -acre phytoremediation zones". In addition,
add "West Lobe" and "East Lobe" to Figure 2.
Response: These comments have been addressed in the revised Five -Year Review Report document.
Comment 6: Section II (Page 9) fourth bullet. A short discussion of the AOP+ system and why it was
determined to not be effective should be included in the revised report.
Response: A brief description of the decommissioning of the AOP+ system has been added to the revised
Five -Year Review Report. Note for reference the full description is provided with Technical
Memorandum E10.
Comment 7: Section IV (Page 12), Five -Year Review Process. The Soil Residue Mound is mentioned in
the third paragraph. Mention in the text when the synthetic liner and overlying soil were installed over the
mound.
Response: The date of the synthetic liner installation (May/June 2010) has been added to the referenced
text in the revised Five -Year Review Report.
Comment 8: Section IV (Page 12), Five -Year Review Process and Figure 5, 1,4-Dioxane Trend Graphs.
Monitoring well MW-15A near the Soil Residue Mound is stated elsewhere in the report as outside the
radius of influence for the remedy. The graph for 1,4-dioxane indicates that the concentration has reduced
over time; however, it is about 1,000 ug/L — several orders of magnitude greater than the North Carolina
Groundwater Quality Standard of 3 ug/L. The remediating parties should consider an alternative remedial
approach to reduce the 1,4-dioxane concentrations in groundwater more quickly.
Response: The Soil Residue Mound (SRM) was closed in -place by grading the surface of the mound and
placing a synthetic cap over the top to eliminate exposure and eliminate rainfall infiltration. There is no
liner beneath the SRM. It was anticipated that these actions would reduce groundwater contaminant
concentrations downgradient of the SRM. As the approved remedy for the Site is containment of

SEABOARD GROUP HAND THE CITY OF HIGH POINT
Five -Year Review Report - Response to Comments
Former Seaboard Chemical and Riverdale Drive Landfill Site
July 18, 2023
Page 3
contaminated groundwater and protection of surface water, active remediation of this source area was not
a part of the approved remedy. The statement "outside the radius of influence" was intended to note that
no extraction wells are located immediately downslope of the SRM. Groundwater flow from the SRM
enters the SIS drainage valley where it is captured by the shallow SIS extraction wells (RW-SIS 2/3/4).
Comment 9: Section IV (Pages 14 and 15), Surface Water 1,4-Dioxane Data. The table on pages 14-15
and the related text on page 15 indicates that the increased 1,4-dioxane concentrations at SW-2 is related
to above average rainfall and runoff from the phytoremediation zone at the time of sample collection.
Describe the rainfall amounts as measured at an onsite or local rainfall gauge associated with the
sampling dates. Include evidence of erosion or seep(s) on the slope in the phytoremediation zone above
the SW-2 location. Finally, determine if there are other sources for 1,4-dioxane near the SW-2 location.
Response: Surface water monitoring station SW-2 is normally dry as noted on the surface water
analytical summary table on page 15. The sample collected on November 7, 2018 occurred after a 0.92
inch rainfall on November 5/6/7, 2018. The sample collected on October 19, 2022 occurred after a 0.64
inch rainfall on October 17/18, 2022.
There is no evidence of erosion or seeps from the phytoremediation zones. The contaminant source is
likely from overland flow of rainfall as observed during sample collection. Also, there are no know
sources of 1,4-dioxane upgradient of the phytoremediation zones as the area is primarily residential.
Comment 10: Section IV (Page 15), Surface Water 1,4-Dioxane Data. In the third paragraph, a sentence
notes that "...at least two known sources of 1,4-dioxane in surface water are located on Richland Creek
upstream of this confluence." Identify these known sources by name and when 1,4-dioxane was
determined to be associated with the sources. This information should also be included in the text below
the "Monitoring" issue category box (Section VI) on Page 28.
Response: The two know sources of 1,4-dioxane upstream of surface water monitoring station SW-
DRP 11 are:
Waste Industries of High Point C&D Landfill: Permit No. 41-16
Former Jackson Lake Road Landfill: Permit No. NONCD0000820
The NC Solid Waste Section is aware of these sources as groundwater/surface water assessments have
been conducted. Note that the former Jackson Lake Road Landfill site is regulated under the Pre -
Regulatory Landfill Program.

SEABOARD GROUP HAND THE CITY OF HIGH POINT
Five -Year Review Report - Response to Comments
Former Seaboard Chemical and Riverdale Drive Landfill Site
July 18, 2023
Page 4
Comment 11: Section IV (Page 19), Operational Data. On the Flow Comparison Chart, change the
"Phyto Disch" curve legend text to "Discharge to Phyto". This change will clarify that the curve
represents the total discharge of water to the natural (phytoremediation) system.
Response: Edit to referenced chart has been made and included with the revised Five -Year Review
Report.
Comment 12: Section IV (Page 21), Operational Data. The two Y axes on the graph are confusing,
especially because the scales differ so widely. To aid the reader, change the left-hand Y axis title to
"Influent, VOCs" and the right-hand Y axis to "Effluent, VOCs".
Response: Edits have been made to referenced graph and included with the revised Five -Year Review
Report.
Comment 13: Section IV (Pages 23 and 24), Operational Data. In the paragraph below the bullets,
restate that the increase in VOC removal and 1,4-dioxane removal in the natural system as shown in the
graphs is due to the additional recovery wells brought online in the Summer of 2022 (i.e. use similar
words to the text on Page 22).
Response: Comment added to referenced paragraph after the bulleted items on page 23 and included with
the revised Five -Year Review Report.
Comment 14: Section IV (Page 25), Site Inspection, Operational Data. Correct the paragraph listing the
parties present at the inspection. Use semi -colons instead of commas after each affiliation and replace the
commas with "of' and "from" between the last name and the affiliated group.
Response: Comment addressed in revised Five -Year Review Report.
Comment 15a: For the Comparison of Surface Water Standards table, mention the applicable surface
water classification for Deep River/Randleman Lake for the section abutting the facility.
Response: Comment addressed in paragraph following Comparison of Surface Water Standards table.
Comment 15b: In the current standard column, note that the values for 1,1-DCE, 1,2-DCA and trans-1,2-
DCE are from the EPA National Recommended Water Quality Criteria List and are not established North
Carolina Surface Water Quality Standards. Finally, there is a typographical error in the third row of the
compound name column for 1,1-DCE.
Response: Edits included with revised Five -Year Review Report.

SEABOARD GROUP II AND THE CITY OF HIGH POINT
Five -Year Review Report - Response to Comments
Former Seaboard Chemical and Riverdale Drive Landfill Site
July 18, 2023
Page 5
Comment 15c: The EPA Guidance in the Five -Year Review Recommended Template, OLEM Directive
9200.0-89 indicates that TBC ("to be considered") items should be mentioned if they may call into
question the protectiveness of the remedy. On March 13, 2023, the Solid Waste Section (SWS) of the
DWM issued a memorandum to operators and owners of active and former landfills advising them that
PFAS testing would be required by the SWS starting July 1, 2023. After PFAS testing is implemented at
the site, the results might require augmenting the mechanical treatment system or remedy in general. This
section should mention the SWS memorandum and the possibility that the remedy may require
augmentation.
Response: Please note the referenced SWS memorandum was issued in March 2023, after the five-year
period the report covers (through August 2022), and thus not being incorporated at this time. Therefore,
no changes to the Five -Year Review Report have been made in response to this comment. We will, of
course, comply with any applicable legal requirements regarding PFAS sampling at the Site. Under the
RASA this would be accomplished under the Technical Memoranda process.
Comment 16: Appendix A — Reference List. Update the reference list as needed in support of changes
made for the Five -Year report revision.
Response: Reference List is updated in the revised Five -Year Review Report.
If there are any questions regarding these response items, please contact me at [phone].
Respectfully,
Seaboard Group II and City of High Point
R. Craig Coslett, Project Coordinator
de maximis, inc
Attachment
CC: Jackie Drummond - NCDEQ Division of Solid Waste