NC0080853_Corrective Action Plan_20200130

` ,q_COAI AECOM 919-461-1100 phone
1600 Perimeter Park Drive,Suite 400 919-461-1415 fax
Morrisville, North Carolina 27560
January 30, 2020
NCDEQ/ Division of Water Resources RF
IV
ED
NPDES Permitting FEB 0 3 2020
1617 Mail Service Center
Raleigh, North Carolina 27699-1617NCDFQ IDWR1NPDES
Subject: Corrective Action Plan Update
Salem Business Park Remediation Site#NC0080853
Nokia of America Corporation
3370 Lexington Road, Winston-Salem, Forsyth County, North Carolina
Dear Mr. Coco:
On behalf of Nokia of America Corporation (Nokia), AECOM Technical Services of North Carolina
Inc. (AECOM) is submitting the following Corrective Action Plan Update to fulfill the requirements
of Condition A.(2.) of National Pollutant Discharge Elimination System (NPDES) Permit
#NC0080853 for the groundwater treatment system located at the former Nokia facility, now
known as the Salem Business Park Remediation Site, in Winston-Salem, Forsyth County, North
Carolina.
Background
A groundwater treatment system operates at the Site to remediate groundwater impacted with
volatile organic compounds (VOCs). The primary treatment unit is a shallow-tray air stripper. As part
of the NPDES permit monitoring requirements, effluent samples are collected from a flume (FE-151)
located approximately 100 feet downstream of the air stripper. Between 2015 and 2018, the
tetrachloroethene (PCE) concentration in effluent samples collected from flume FE-151 ranged from
<0.5 micrograms per liter(.ig/L) to 5.6 pg/L, with an average concentration of approximately 2.5
pg/L± 1.8 pg/L. These concentrations have been consistently below the historical permit limit of 17
pg/L.
On August 29, 2018, Nokia received notification from the North Carolina Division of Water
Resources (DWR) that the facility would receive a new NPDES permit that would include a
concentration limit of 6.1 pg/L for PCE at the permitted effluent sample point(FE-151). While the
concentrations of PCE at the permitted effluent sample point have not historically exceeded the
new limit, the average factor of safety will be reduced from nearly ten-fold to approximately three-
fold. Based on the substantial change in permit-required treatment, Nokia requested a compliance
schedule for meeting the new discharge concentration limit. The compliance schedule was
included as Condition A.(2.) of the NPDES permit that became effective on February 1, 2019. The
new PCE discharge limit also became effective on February 1, 2019, along with a requirement to
increase the frequency of PCE sampling from FE-151 from quarterly to monthly. The compliance
schedule provides an additional two years (February 2021) for Nokia to achieve compliance with
the new PCE limit. AECOM submitted a Corrective Action Plan (CAP) on behalf of Nokia to
NCDEQ DWR on August 1, 2019, outlining proactive corrective action activities implemented prior
to the CAP submittal, along with proposed additional corrective actions to ensure permit
compliance by February 2021 (AECOM, 2019).

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Completed Corrective Action Activities
In May 2019, Nokia proactively began corrective action activities to improve air stripper
performance and ensure consistent compliance with the new PCE discharge limit. Between April
2019 and June 2019, AECOM conducted multiple tests and compliance activities, including
instrumentation upgrades, air-to-water ratio optimization, and increased sample QA/QC. These
activities are detailed in the CAP submitted on August 1, 2019 (AECOM, 2019). The following
additional corrective actions were conducted between July 2019 and January 2020.
Continued Evaluation of Sample QA/QC
To evaluate laboratory analytical precision and the reproducibility of PCE concentration results at
low concentrations (<6 pg/L), duplicate samples were collected from flume FE-151 during the
monthly events between April and December 2019. The average difference between parent and
duplicate samples during the nine months of evaluation was approximately 0.1 pg/L. These results
provide confidence that variability in laboratory measurements is unlikely to result in a "false
positive"type of permit exceedance. As a result, AECOM will discontinue laboratory QA/QC
evaluation beginning January 2020.
Air-to-Water Ratio Testing with Normal Influent Concentrations
Air-to-water ratio testing was initially conducted in May 2019 to evaluate if the air stripper
operating conditions could be adjusted to maximize PCE removal. Five operational set points
were evaluated at an average influent concentration of 780 pg/L, and downstream concentrations
were reduced below the laboratory reporting limit(1 pg/L) at all five set points. Although the test
demonstrated that adequate removal could be achieved, an optimum air-to-water ratio was not
identified.
Treatment Testing with Artificially High Influent Concentrations
In December 2019, AECOM evaluated air stripper treatment performance at higher than normal
influent concentrations by extracting groundwater exclusively from the two extraction wells with
the highest PCE concentrations (EW-16 and EW-17). Two sets of influent and effluent samples
were collected. Influent PCE concentrations were 2,470 and 3,020 pg/L and resulting effluent PCE
concentrations were 3.4 and 3.4 pg/L. This testing demonstrated that adequate treatment could
be achieved when influent concentrations are more than two times the normal influent
concentrations.
Air to Water Ratio Testing with Artificially High Influent Concentrations
Because air to water ratio testing conducted on normal influent concentrations did not identify an
optimum air-to-water ratio, AECOM repeated the air-to-water ratio test in January 2020 using
influent derived from extraction wells EW-16 and EW-17. During the half-day test, the
concentration of PCE immediately downstream of the air stripper was between 5.6 and 6.3 pg/L
while influent concentrations varied between approximately 906 and 2,080 pg/L. A correlation
between air-to-water ratio and PCE removal efficiency was not identified.
Conclusions
The primary conclusion from the testing conducted in May 2019, December 2019 and January
2020 is that a relationship among the air stripper operational parameters has not been identified to
predictably optimize PCE removal. Despite the lack of an apparent optimization model, all
samples collected under normal operating conditions indicated that adequate treatment was
achieved. Adequate treatment under artificially high influent concentrations was demonstrated in
several, but not all of the samples collected. No additional corrective action activities are currently

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planned. Nokia will continue to conduct permit-required sampling and monitor air stripper
performance as part of routine operation and maintenance activities.
If you have any questions or require additional information, please contact Erin Stewart at
919-461-1323.
Sincerely,
AECOM
aWliSteitA). CAA--
John Moran, E.I. Christo her Brownfield, P.E. Erin Stewart, P.G.
Staff Engineer Project Engineer Project Manager
cc: NCDEQ/Division of Water Resources-WSRO
References
AECOM, 2019. Corrective Action Plan, Salem Business Park Remediation Site#NC0080853.
Former North Carolina Works, Lexington Road Plant, Winston-Salem, NC. August 2019.