19056_NPP_Decision Memo_20180131

DECISION MEMORANDUM
DATE: January 31, 2018
FROM: Hayley Irick
TO: BF Assessment File
RE: North Point Police District One Office
7836 North Point Boulevard
Winston-Salem, Forsyth County
BF # 19056-15-034
Based on the following information, it has been determined that the above referenced site, whose
intended use is for no uses other than office and related parking, can be made suitable for such
uses.
Introduction:
The property is comprised of one parcel (Forsyth County parcel ID 6827-36-1326.00) totaling
1.3 acres. Historically, the property was used as a gas station. The property was redeveloped in
2016/2017 by the prospective developer, the City of Winston-Salem, with a single -story,
approximately 10,000 square foot, slab on grade office building to be used as the North Point
Police District One Office. Groundwater, that poses a vapor intrusion risk, is impacted at the
property as a result of historical activities conducted on and off site. The surrounding area is
mostly commercial, consisting of office space, restaurants, and a hotel.
Redevelopment Plans:
The Brownfields Property has been redeveloped as the North Point Police District One Office.
As mentioned above, the property was redeveloped in 2016/2017 for this use; the footprint of the
building was placed in an area of the Brownfields Property upgradient of the highest
concentrations of contaminants in the subsurface and not directly on top of that area. During
redevelopment, prior to construction of the building foundation, a GEO-SEAL Vapor Mitigation
Membrane and a sub -membrane depressurization venting system were installed. The
redeveloped Brownfields Property also includes a large, surface level parking lot, which
occupies the space over the area where the highest concentrations of contaminants were
previously detected.
Site History:
Prior to development, the property was undeveloped, wooded land. The property was initially
developed in the 1970s as a gas station called U-Filler-Up #5 which was operated by the
Abercrombie Oil Company of Danville, VA. In April 1978, four Underground Storage Tanks
(USTs), consisting of three 12,000-gallon gasoline USTs and one 4,000-gallon kerosene UST,
were installed on -site. The gas station was in operation until 1996. In 1997, the four USTs were
excavated and removed from the site. Confirmation soil samples were collected beneath the
former tank locations at a depth of 12 feet below ground surface. The tanks were listed with the
UST Section under Incident Number 18165. The UST Section issued a No Further Action letter

on May 1, 2013 and a Notice of Residual Petroleum (NORP) was filed with the Forsyth County
Register of Deeds. This recorded NORP contains the following perpetual land use restriction:
Groundwater: Groundwater from the site is prohibited from use as a water supply. Water supply
wells of any kind shall not be installed or operated on the site.
The property was previously developed with a one-story block kiosk and canopy, two concrete
dispenser islands which formerly maintained five product dispensers each, and concrete and
asphalt access and parking areas. These structures were demolished and removed by the PD in
2016.
In late 2016 and early 2017, the Brownfields Property was redeveloped as described above.
Potential Receptors:
Potential receptors are: construction workers, on -site workers, visitors, and trespassers. Based on
these receptors, non-residential and/or commercial screening levels have been utilized during the
data evaluation process.
Contaminated Media:
DEQ has evaluated data collected from the following media at the subject property: soil,
groundwater, soil vapor, and indoor air. DEQ relies on the following data to base its conclusions
regarding the subject property and its suitability for the intended reuse.
Soil
Soil was assessed originally by Triangle Environmental, Inc. as part of the UST removal
activities in 1997. Soils samples collected from 8-12' below ground surface (bgs) were analyzed
for total petroleum hydrocarbons — gasoline range organics (TPH-GRO) and showed a range of
detections from 5.15 milligrams per kilogram (mg/kg) to 6,720 mg/kg (several above 50 mg/kg
UST action limit) in the immediate vicinity of the removed tanks.
During a 1998 Limited Site Assessment performed by SEI Environmental, Inc., soil samples
were collected from the boring for well MW-1 and analyzed for TPH-GRO. The analytical
results from the samples collected from 15' and 20' bgs indicated a TPH-GRO concentration of
1,190 mg/kg and 4.08 mg/kg, respectively.
TPH analyses were conducted on two other separate occasions, in 1999 and 2000, both
performed by Apex Environmental, Inc. The analytical results of soil samples collected from five
borings collected in 1999 around the original filling station canopy at depths of 3-5' bgs
indicated no detections of TPH-GRO. In 2000, twelve additional samples were taken along the
former product lines and dispenser locations. TPH-GRO was found in exceedance of the UST
Action Level of 50 mg/kg in sample D-1 (2,900 mg/kg) and D-2 (130 mg/kg).
Soil was assessed by Apex in 2012 during a groundwater monitoring event. Total petroleum
hydrocarbon, C9-C 18 Aliphatics were detected in one sample (D-7) at 9.3 mg/kg, above the
IHSB's Non -Residential PSRG (October 2016) of 6.86 mg/kg.
N

The most recent soil assessment was conducted on March 18, 2015 by Griffith Enterprise, Inc.
During this assessment, 12 GeoProbe soil samples were collected at a depth of 5' bgs and were
analyzed for VOCs by EPA Method 8260. 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,
methylene chloride, naphthalene and xylenes were detected in several samples at concentrations
below their respective IHSB Non -Residential PSRG (October 2016).
Groundwater
Groundwater monitoring wells were initially installed at the site following the UST removal
activities in 1997.
In 1998, during their Limited Site Assessment, Apex installed a network of four permanent
wells, three shallow and one deep. Elevated concentrations of benzene, ethylbenzene, toluene,
xylenes, methyl tert butyl ether (MTBE) and isopropyl ether were detected in all wells.
Concentrations were highest in MW-2, installed within a UST basin, with benzene at 9,650 µg/L,
ethylbenzene at 2,290 µg/L, toluene at 225,000 µg/L, xylenes at 13,660 µg/L, MTBE at 243,000
µg/L and isopropyl ether at 1,670 µg/L. These concentrations all exceed their respective 2L
standard and (except for isopropyl ether) non-residential vapor intrusion screening level.
The wells were sampled and analyzed again by Apex in 2012 and naphthalene was detected in
MW-1 at 130 µg/L and MW-2 at 6 µg/L, at or above the 2L standard of 6 µg/L. Ethylbenzene
(250 µg/L) and 1,2,4-trimethylbenzene (210 µg/L) were detected in MW-1 below their
respective 2L standards (600 and 400 µg/L) but above the non-residential vapor intrusion
screening levels of 152 µg/L and 24.3 µg/L, respectively.
During the March 2015 Griffith Enterprises, Inc. assessment, groundwater samples were
collected from three existing permanent wells (MW-2, MW-3 & MW-4 installed in 1998) and
analyzed for VOCs by EPA Method 8260. Naphthalene was detected in MW-2 at 64.1 µg/L,
above the 2L standard of 6 µg/L. Xylenes were also detected in MW-2 at 338 µg/L, below the
2L of 500 µg/L but above the vapor intrusion screening level of 323 µg/L.
Surface Water
Surface water is not located on the site.
Soil Vapor
In March 2015, Griffith Enterprises, collected 11 soil vapor samples from newly installed
temporary soil gas monitoring points and analyzed for VOCs by EPA Method TO-15. Improper
QA/QC methods were employed and all canisters reached 0 inches of Hg final vacuum. For that
reason, DEQ does not accept the sampling results and they are not included in the Exhibit 2 to
the Brownfields Agreement.
Indoor Air
Indoor air sampling was conducted following the redevelopment and furnishing of the property
in 2017. An indoor air building survey was conducted prior to sampling in an effort to reduce
interference from potential indoor sources.

On June 14, 2017, eight 8-hour SUMMA canisters were deployed at strategic locations
throughout the office building at 3-5' above the floor elevation. Samples were analyzed by
Method TO-15 for an abbreviated list of contaminants based on known soil and groundwater
contaminants. Improper QA/QC methods were employed and five of the eight canisters reached
0 inches of Hg final vacuum. For that reason, DEQ does not accept the sampling results and they
are not included in Exhibit 2 to the Brownfields Agreement.
The indoor air was resampled using five 8-hour SUMMA canisters that were deployed on July 5,
2017. Following analysis by Method TO-15 for the abbreviated list of contaminants, there were
no detections above the non-residential indoor air screening level (October 2016).
Risk Calculations
Risk Calculations were performed using Excel worksheets provided by Sandy Mort, NCDEQ
Brownfields Toxicologist. The risk calculations indicated the following based on available data,
including the following media: groundwater, residual soil (based on confirmatory soil data), soil
gas, and indoor air:
Medium
Site Area
Non -Residential
LICR
HI
Groundwater
Sitewide
2.3 x 10-5
0.41
Indoor Air
Sitewide
3.1 x 10-6
0.11
Residual Soil Max
Sitewide
0.0
0.81
Red shading LICR> 1 E-04 or HI> 1.
LICR = Lifetime Incremental Cancer Risk
HI = Hazard Index
Based on indoor air sampling results submitted following the July 5, 2017 Indoor Air
Assessment, the Vapor Intrusion Mitigation System (VIMS) appears to be functioning as
intended for this building. The low-level contaminants detected in on -site air samples may be
due to off -gassing of new building materials or products utilized in construction rather than
vapor intrusion from the subsurface. These compounds have been included in the final risk
evaluation and indoor air risk remains below the target hazard index of 1.
Required Land Use Restrictions:
Based on the site -specific data provided to the Brownfield program and the installation of a
passive VIMS, the site reuse is suitable for the site as long as the agreed upon land use
restrictions in the BFA are abided by:
- No child/adult care centers
- No groundwater use
- No soil use/disturbance other than with an approved EMP
- No building construction without VI consideration
- No redevelopment without an approved EMP in place
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- Yearly redevelopment reports, for as long as physical redevelopment of the property
occurs, detailing soil grading cut/fill, sampling, stockpiling or removal of soils,
groundwater or any other contaminated materials
- DEQ access to the property
- Deed conveyance
- NORP LUR restricting groundwater and water supply wells
- No known contaminants on the property
- Abandon any points of groundwater access
- Monitoring well damages
- LURU including VIMS yearly check
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