NC0084638_rescission_20210902

Weaver, Charles
From: Weaver, Charles
Sent: Thursday, September 2, 2021 12:52 PM
To: '[e-mail]'
Cc: 'Brown, Daniel/CLT'; Watson, Edward M
Subject: rescission of NPDES permit NC0084638 / Rhodia remediation site
Importance: High
Tracking: Recipient Delivery
'[e-mail]'
'Brown, Daniel/CLT'
Watson, Edward M Delivered: 9/2/2021 12:52 PM
The Division received your request to rescind the subject permit. We do not object to this request.
NPDES permit NC0084638 is hereby rescinded, effective immediately. This message is to close the
permit file for the Division, and for your records.
If in the future you wish to discharge wastewater to the State's surface waters, you must first
apply for and receive a new NPDES permit.
Regarding the decommissioning of the wastewater treatment system, you are required to maintain
the wells associated with the system. They must be intact as they are to be used for a Monitoring
by Natural Attenuation study for the next year. After that period, these wells will likely be used as
injection points for additional remediation action at the site.
While the wells are not to be abandoned as part of the system decommissioning, the Division
approves removal of the air stripper and Carbon Absorption canisters, and removal of the outfall
line.
If you have any questions concerning this matter, contact Ed Watson [[e-mail]]
in the DEQ Mooresville Regional Office.
PLEASE NOTE: as part of the Division's conversion to paperless communication, this email is the
only notification you will be sent regarding the permit rescission. No hard copy will be mailed.
Charles H. Weaver
Environmental Specialist
N.C. DEQ / Division of Water Resources
919-707-3616
[e-mail]
(mailing address) 1617 Mail Service Center, Raleigh, NC 27699-1617
Email correspondence to and from this address is subject to the North Carolina Public Records Law and may be disclosed
to third parties.
1

ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
MICHAEL SCOTT
Director
Mr. Mike Shatynski
Solvay USA, Inc.
504 Carnegie Center
Princeton, New Jersey 08540
NORTH CAROLINA
Environmental Quality
August 11, 2021
RE: Response to Proposed Performance Monitoring Plan
Former Rhone-Poulenc Facility
207 Telegraph Drive, Gastonia, NC
IHSB ID# NCD986182582
Dear Mike:
This correspondence is in response to your request to reevaluate the groundwater and surface water
conditions following the implementation of the rebound study conducted at the above -mentioned
Rhone-Poulenc facility.
Review of the data from the 2019 - 2020 Groundwater and Surface Water Sampling Results
indicates an overall lack of migration of contaminant mass within the monitoring well network for
four consecutive quarters since cessation of active pumping. Subsequently, further active pumping
would not be expected to provide sufficient reduction of contaminant mass to warrant restarting the
existing treatment system.
Therefore, the IHSB concurs that the groundwater extraction and treatment system remain shut
down permanently and decommissioned. Furthermore, the NPDES permit was issued by the Division
of Water Quality (DWQ), so you must correspond with the DWQ concerning termination of the permit.
After evaluating the proposed Performance Monitoring Plan (PMP), IHSB approves the following:
• Sampling of monitoring wells in locations where concentrations exceeded the 15A NCAC 2L standards
for chlorinated compounds, and/or benzene and MTBE, and to monitor concentration trends.
• Semi-annual groundwater sampling in March and September should be conducted in the following
monitoring wells: MW-1A, MW-1B, MW-4A, MW-4B, MW-7B, MW-10A, MW-11, MW-13, MW-15A, MW-
15B, MW-15C, MW-16A, MW-16B, MW-17B, MW-17C, MW-20B, MW-22B, MW-33, MW-38, MW-41,
CP-1, EW-2, EW-3, and EW-4.
• Annual groundwater sampling in September should be conducted in sentinel wells MW-39 and MW-
40.
• Semi-annual surface water sampling in March and September at locations SW-1 and SW-8 to monitor
upstream and downstream surface water quality.
• Concentrations of the contaminant vinyl chloride have been reported in the laboratory data but have
not been included in the groundwater analytical data tables since implementation of the rebound
study. Concentrations of this contaminant in the groundwater is significant to the PMP. Ensure this
data is added to future report tables.
NORT£H CAROLINA
DE
oeparoaent of Eommamemai Quaint-. /` '
North Carolina Department of Environmental Quality I Division of Waste Management
Winston-Salem Regional Office 1450 West Hanes Mill Road, Suite 300 I Winston-Salem, North Carolina 27105
336.776.9800

Mr. Mike Shatynski
August 11, 2021
Page 2 of 2
• Groundwater monitoring well MW-41 should be surveyed for top of casing (TOC) and top of ground
elevations. The drop in head indicated by the water level measurements between 50% reduction of
pumping and system shutdown, suggest a more significant hydraulic connection with the site well
network.
• The figures and tables in the annual report should be focused on showing only the monitoring wells
and data relative to the approved PMP. The annual report will be due no later than December 1st each
year.
Consideration for the proposed Well Abandonment Plan will be revisited after the first year of implementation
of the approved PMP.
Please contact me at [phone] or by email at [e-mail] if you have any
questions.
Sincerely,
h JA5
Cherine Jacobs, PG
Senior Hydrogeologist
Superfund Section
Inactive Hazardous Sites Branch
cc: Daniel Brown, Jacobs
Teg Williams, Jacobs
w—_f\ North Carolina Department of Environmental Oualitv I Division of Waste Manaaement

From: Shatynski, Mike
To: Jacobs, Catherine S
Subject: [External] Request for permanent shutdown of the Solvay Gastonia groundwater treatment system and
cancellation of the NPDES Permit
Date: Wednesday, May 26, 2021 11:44:59 AM
Attachments: FIG 01 Extraction Well 2020 vl.pdf
FIG 02 Site Map 2020 vl.pdf
FIG 14 1,1-DCE Historical Data 2020 vl.pdf
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Hello Cathy
You are in receipt of the most recent set of Solvay Gastonia groundwater
monitoring data which continues to demonstrate MNA is occurring.
Below is a summary of efforts taken to date which have significantly
reduced the COCs concentration identified in the Consent agreement.
The groundwater extraction and treatment system (system) installed at
the subject site in 1998 was designed to create a hydraulic containment
zone along the southern (downgradient) and eastern (side gradient,
adjacent to residential properties) portions of the site to prevent off -site
migration of dissolved volatile organic compounds (VOCs) (Figure 1). The
system was also designed to depress the water table near the unnamed
creek to reduce groundwater discharge and protect surface water
quality. Figure 2 illustrates the hydraulic containment zone boundary and
unnamed creek. Performance monitoring data collected over the last two
decades during system operation, have shown significant reductions in
VOC concentrations in treatment system influent as well as groundwater
samples collected from individual monitoring and extraction wells,
gradually developing asymptotic trends. In May 2017, due to the site -wide
decreases of VOCs, with the majority of concentrations having fallen to at
or below North Carolina Groundwater Quality Standards (NCGWQS),
NCDEQ granted Solvay permission to temporarily cease groundwater
extraction and treatment to evaluate the potential for VOC concentrations
to rebound in the absence of pumping.
On February 1, 2019, following a 6-month staggered reduction in
groundwater extraction rates, the extraction and treatment system was
shut down and monitoring was conducted to detect potential rebounding
concentrations of VOCs in groundwater and surface water. In accordance
with the approved rebound monitoring plan, comprehensive monitoring
events were conducted on May 30, September 26, and December 30,
2019, and on April 29 and July 14-16, 2020. Data from these monitoring
events, reported to NCDEQ in October 2020 in the 2019-2020
Groundwater and Surface Water Sampling Results report, did not show
indications of the migration of VOC-impacted groundwater in areas of
historical pumping or near the containment zone boundary. Additionally,
monitoring of surface water quality detected only low concentrations of
1,1-Dichloroethene (DCE) and 1,1-Dichloroethane (DCA) at levels below

their respective North Carolina Surface Water Quality Standards.
Given the foregoing, it is apparent that concentrations of VOCs did not
increase following system shut down and do not exceed their respective
NCGWQS near the containment boundary. Consequently, continued
operation of the system to maintain a hydraulic containment zone is no
longer considered necessary, and would not be expected to result in
further reductions of the isolated areas of 1,1-DCE (Figure 3) and other
VOCs that remain in the western portion of the site, furthest from the
extraction system.
Therefore, Solvay respectfully requests permission to decommission the
treatment system and for NCDEQ to rescind the NPDES permit. Going
forward, Solvay proposes to monitor groundwater and surface water in
accordance with the performance monitoring plan described in the
previously referenced October 2020 report, as summarized below.
Summary of Performance Monitoring Plan
Sample
Media
Frequency
Locations
Rationale
Surface water
Semi-annual
SW-1 and SW-8
Monitor upstream and
downstream water quality
Groundwater
Semi-annual
MW-10A, MW-11, MW-
13, MW-15A, MW-15B,
MW-16A, MW-17B,
MW-17C, MW-22B,
MW-33, MW-38, MW-
39, and MW-41
Monitor locations that exceed
NCGWQS for chlorinated
compounds (primarily 1,1-
DCE, 1,1-DCA, and TCE)
and/or petroleum -related
compounds (primarily
benzene).
Monitor downgradient sentinel
wells
Annual
MW-1A, MW-4B, MW-
7B, MW-8, MW-10A,
MW-11, MW-13, MW-
15A, MW-15B, MW-
16A, MW-16B, MW-
17B, MW-17C, MW-
20B, MW-22B, MW-33,
MW-38, MW-39, MW-
40, MW-41, and EW-2
Same as semi-annual rationale
with expanded peripheral
monitoring

Best Regards
Mike Shatynski
732-718-2283
www.solvay.com
Please note: We have moved our corporate offices. Effective January 25th 2015, our new address is 504
Carnegie Center, Princeton, NJ 08540
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