NC0084638_Monitoring Information_20181129

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November 29, 2018
Ms. Julie Grzyb
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North Carolina Department of Environmental Quality DEC 0 4 20t6
Division of Water Resources -
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Water Quality Permitting Section - NPDES Permitting Section
1617 Mail Service Center
Raleigh, NC 27699-1617
- Re: Request for Temporary Suspension of the Treatment System Monitoring Requirements
Former Rhone-Poulenc facility located in Gastonia, NC
NPDES Permit No. NC0084638
Dear Ms. Grzyb,
I'm writing concerning NPDES permit NC0084638 issued to Solvay USA Inc. for discharge from a
groundwater remediation system located in Gaston County, NC. The remediation system has been
extracting groundwater for over 20 years and is close to reaching its cleanup goal. To evaluate the long-
term effectiveness of the remedy, we are currently conducting a 'rebound test'whereby groundwater
extraction rates are gradually reduced and eventually terminated while closely monitoring contaminant
concentrations in observation wells and surface water. This test is being conducted under the
authorization of Ms. Cathy Jacobs/North Carolina Department of Environmental Quality-Division of
Waste Management.
The groundwater extraction system is currently operating at 50% of normal flow rates and to date, no
evidence of rebound has been detected. In accordance with the approved rebound test plan
groundwater extraction will cease at the end of January 2019 and surface water and groundwater will
be monitored for signs of rebound for at least 12 months. The electric motor control units for the
groundwater extraction well pumps will be locked to prevent inadvertent operation.
Since there will be no discharge from the NPDES-permitted outfall for the remainder of 2019, Solvay is
respectfully requesting that NCDEQ consider allowing for temporarily suspension of the permit-required
weekly site visits starting on 2/1/19. During this time, Solvay would continue to submit monthly discharge
monitoring reports to document the zero discharge. However, should conditions require resumption of
groundwater extraction, it is understood that all original permit requirements would remain in effect and
NCDEQ would be immediately notified if the groundwater pumping system is re-activated.
If the rebound test indicates that no further active remediation is necessary, Solvay will submit a request
to terminate the NPDES discharge permit and decommission the treatment system.
Solvay—504 Carnegie Center,Princeton, NJ 08540—USA—T:+[phone]-F:+[phone]
Rhodia tic,Meoiher of the Sot ay Group
www.solvay.com

S O LVAY
Should you require additional information regarding this request, please contact me at [phone].
Sincerely,
' / ' /
Michael Shatynski
Remediation Project Manager
•
Cc:Teg Williams/Jacobs via e mail
Cathy Jacobs/NCDEQ via e mail
Ed Watson/NCDEQ via postal mail
Solvay—504 Carnegie Center,Princeton, NJ 08540—USA—T:+[phone]-F +[phone]
rchodln Inc- Member of the Solvtw Croup
www.solvay.com