NC0080853_Plan of Action_20190801

AECOM 919-461-1100 phone
AECOM
1600 Perimeter Park Drive, Suite 400 919-461-1415 fax
Morrisville, North Carolina 27560
August 1, 2019
NCDEQ / Division of Water Resources
NPDES Permitting
1617 Mail Service Center
Raleigh, North Carolina 27699-1617
RECEIVED/NCDEQ/DWI?
AI16 0 b 7A19
Subject: Corrective Action Plan
Salem Business Park Remediation Site #NC0080853 Water Quality
Nokia of America Corporation Permitting Section
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 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 currently operates at the Site to remediate groundwater impacted
with volatile organic compounds (VOCs). The primary treatment unit of the groundwater treatment
system is a six -tray air stripper unit designed for up to 120 gallons per minute of groundwater flow
and 600 standard cubic feet per minute of air flow through the unit. The air stripper was designed to
reduce concentrations of tetrachloroethene (PCE) in groundwater to below the laboratory detection
limit.
As part of the NPDES permit monitoring requirements, AECOM collects system effluent samples
from a flume (FE-151) located approximately 100 feet downstream of the air stripper. In addition to
these permit required samples, AECOM collects monthly air stripper influent and effluent samples to
evaluate the system effectiveness at removing VOCs. Between 2015 and 2018, the PCE
concentration in system effluent samples collected from flume FE-151 ranged from <0.5
micrograms per liter (pg/L) to 5.6 pg/L, with an average concentration of approximately 2.4 pg/L.
During the same time period, the PCE concentration in monthly air stripper effluent samples ranged
from <0.5 pg/L to 8.8 pg/L, with an average concentration of approximately 2.6 pg/L.
On August 29, 2018, Nokia received notification from the North Carolina Division of Water
Resources that the facility would be receiving a new NPDES permit that would include a PCE
discharge limit of 6.1 pg/L, which is significantly lower than the previous limit of 17 pg/L. While the
system effluent FE-151 had not exceeded the proposed limit, the PCE concentrations had been
very close to the proposed limit. Based on the expectation that the air stripper unit should be
capable of reducing PCE concentrations to below the laboratory detection limit, Nokia requested a
compliance schedule for meeting the new PCE 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

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provides an additional two years (February 2021) for Nokia to achieve compliance with the new
PCE limit.
Completed Corrective Action Activities
In May 2019, Nokia proactively began corrective action activities to troubleshoot air stripper
performance and ensure consistent compliance with the new PCE discharge limit. The corrective
action activities already completed are discussed below, along with additional proposed
compliance activities.
1. Flow Instrumentation Upgrades
The air stripper did not have instrumentation to precisely measure the volumetric air or groundwater
flow through the system. Air flow was estimated using the air injection pressure and blower flow
curve, and groundwater flow was estimated from the air stripper sump discharge flow rate. To
improve these measurements, AECOM installed a new influent flow meter and an in -line differential
pressure gage in early May 2019. These instruments allowed more accurate and precise
measurements of air and water flow through the air stripper during operation.
2. Air to Water Ratio Testing
The mass removal efficiency of air strippers is the dependent on the correct ratio of volumetric air
and groundwater flow through the stripper. Higher air -to -water ratios typically increase
volatilization of VOCs and increase system efficiency. However, air -to -water ratios can be set too
high and result in groundwater flooding across trays, resulting in uncontrolled and inadequately
treated groundwater flow through the system.
During May 2019, AECOM conducted multiple tests to evaluate if the operating volumetric air -to -
water ratio was adversely impacting PCE mass removal efficiency. On May 8-9, 2019, following
flow instrumentation upgrades, AECOM increased the groundwater flow rate into the air stripper
and collected water samples from the air stripper influent and effluent. The effluent sample result
was below the detection limit for PCE (Table 1), indicating improved mass removal efficiency.
On May 31, 2019, AECOM selected five air -to -water ratio setpoints and collected influent and
effluent samples to evaluate PCE mass removal efficiency under various flow conditions (Table
1). All five effluent PCE concentrations were below the laboratory detection limit. Based on the
results of the air -to -water ratio testing, an optimum air -to -water ratio that maximized PCE removal
efficiency could not be determined; however, sample results displayed a consistent and improved
PCE mass removal rate compared to results prior to changing the original system setpoint.
Prior to air stripper evaluation activities in May 2019, only three effluent air stripper samples
collected since December 2014 had a PCE concentration below the laboratory detection limit
(Table 2). Since the air stripper evaluation activities, eight samples have been collected from both
the flume FE-151 and the air stripper effluent sample port. PCE concentrations in all eight
samples were below the detection limit. These results indicate the air stripper at its current
operating setpoint is capable of achieving consistent compliance with the new PCE discharge limit
of 6.1 pg/L.
3. Evaluation of Sample QA/QC
Air stripper effluent PCE concentrations are typically between 1 and 5 pg/L, a difference of four
parts per billion. To evaluate laboratory analytical precision and the reproducibility of PCE
concentration results at such low concentrations, AECOM collected PCE duplicate samples from
flume FE-151 during the monthly sampling events between April and June 2019 (Table 2).

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Sample results indicate the laboratory results are consistent, with little variability between the
parent and duplicate samples.
Future Corrective Action Activities
Based on the results of the proactive corrective action activities conducted between April and
June 2019, AECOM proposes the following future corrective action activities:
1. Continue Monitoring System Performance (July 2019 - January 2020)
Sample results indicate consistent compliance with the PCE discharge limit is achievable at the
current system operating setpoint. AECOM proposes to continue collecting monthly influent and
effluent air stripper samples along with air and groundwater volumetric flow data to continue
monitoring system performance. If sample results indicate air stripper mass removal efficiency has
decreased and consistent regulatory compliance is in doubt, AECOM will submit an addendum to
this compliance schedule to perform further evaluation of the groundwater treatment system.
2. Elevated Influent PCE Concentration Analysis (September 2020)
Starting in February 2019, influent air stripper PCE concentration results have been below 1,000
pg/L for the first time since March 2017. Historical PCE mass removal trends do not indicate that
reduced influent PCE concentrations result in reduced effluent PCE concentrations, or vice -versa.
However, with the exception of one effluent sample collected on May 9, 2019 (influent PCE
concentration of 1,570 pg/L), all non -detect effluent samples collected after the air stripper
evaluation activities had influent concentrations less than 1,000 pg/L.
To confirm that the air stripper is consistently capable of achieving compliance with the new PCE
discharge limit when influent PCE concentrations are above 1,000 ug/L, AECOM proposes to
collect an additional test sample with a forced elevated influent PCE concentration at the current
air stripper operating setpoint. The influent concentration will be raised by only pumping on
groundwater extraction wells with PCE concentrations known to be greater than 2,000 pg/L based
on the most recent extraction well sampling results. If the sample results indicate the air stripper is
incapable of achieving compliance, AECOM proposes to repeat the air -to -water ratio testing
conducted in May 2019 under elevated PCE concentration conditions.
If you have any questions or require additional information, please contact Erin Stewart at
919461-1323.
Sincerely,
AECOM
/J�oon Moran Erin Stewart, P.G.
Staff Engineer Project Manager
cc: NCDEQ / Division of Water Resources - WSRO

Table 1
Summary of Air to Water Ratio Testing Results
Salem Business Park Remediation Site #NC0080853
Nokia of America Corporation
Winston-Salem, Forsyth County, North Carolina
PCE Water
Differential
Pressure
TemperaturePCE
Sample Date
Concentration
Removal Flow
Pressure
(Air)
Ratio
Before Stripper
5/9/2019
1570
100.00% 78.0
0.170
0.05
64
..
347 4.45
After Stripper
5/9/2019
<1
Influent-80-100
5/31/2019
858
100,00%
79.0
0.180
0.10
67
356
4.51
Effluent-80-100
5/31/2019
<1
Influent-80-60
5/31/2019
803
100.00%
78.9
0.165
0.09
66
341
4.32
Effluent-80-60
5/31/2019
<1
Influent-80-40
5/31/2019
731
100.00%
78.4
0.115
0.08
66
285
3.63
Effluent-80-40
5/31/2019
<1
Influent-60-100
5/31/2019
668
100.00%
59.8
0.235
0.11
66
407
6.81
Effluent-60-100
5/31/2019
<1
Influent-40-100
5/31/2019
830
100.00%
40.0
0.295
0.13
66
456
11.41
Effluent-40-100
5/31/2019
<1
Notes:
Concentrations reported in microqrams per liter (pq/L)
T - degrees Fahrenheit
gpm - gallons per minute
iwc - inches of water column
PCE - tetrachlomethene
scfm - standard cubic feet per minute

Table 2
Summary of Groundwater Treatment System Sample Results
Salem Business Park Remediation Site #NC0080853
Nokia of America Corporation
Winston-Salem, Forsyth County, North Carolina
Sample Date
12/1/14
1,000 1.8 2.4
3/19/15
-
-
2
4/27/15
1,700
5
-
6/1/15
1,900
3.6
4.2
6/29/15
62
0.91
-
7/27/15
1,400
0.76
8/28/15
1,400
1.5
-
9/29/15
1,200
3.2
3.6
10/27/15
1,100
2.5
-
11/30/15
1,200
3
-
12/30/15
1,800
1.5
3.9
1/20/16
11200
3.8
-
3/7/16
1 48
1.1
1.6
6/6/16
1,300
8.8
5.6
8/1/16
1,100
0.66
-
9/7/16
1,700
3.5
3.2
10/20/16
830
<1
-
11/17/16
870
0.63
-
12/5/16
700
3.1
2.4
1/18/17
910
0.95
-
3/17/17
660
1.5
1.1
6/5/17
1,600
1.2
4.2
8/24/17
1,000
0.57
-
9/8/17
1,100
0.69
<1
10/4/17
1,500
3.4
-
11/10/17
1,000
6
-
12/5/17
1,400
1.6
1.6
1/12/18
1,200
2.7
-
2/9/18
1,100
3.9
-
3/16/18
1,100
3.9
3.9
4/13118
1,000
3.8
5/3/18
1,100
4.8
-
6/8/18
1,000
1.3
<1
7/13/18
1,000
3.7
-
8/24/18
1,500
2.4
9/7/18
-
3.2
10/17/18
1,000
1.8
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Table 2
Summary of Groundwater Treatment System Sample Results
Salem Business Park Remediation Site #NC0080853
Nokia of America Corporation
Winston-Salem, Forsyth County, North Carolina
.- Date
Tetrachloroethene
Before StrippeStripper11/13/18 1,400 5.5 -
12/14/18
1,000
2.7
2.1
1/18/19
1,400
3.3
-
2/12/19
704
3.2
3.6
3/7/19
843
2.9
3.1
4/4/19
815
<1
<1
4/4/2019 (DUP)
-
-
<1
5/3/19
545
1.4
1.7
5/3/2019 (DUP)
-
-
1.2
6/13/19
705
<1
<1
6/13/2019 (DUP)
-
-
<1
Notes:
Concentrations reported in microqrams per liter (Pq/L)
Table does not include results from samples collected during the air to water ratio testing (samples
collected 5/9/19 and 5/31/19)
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