20060_Townsend_Siler_City_Amendment_Decision_Memo_20210205

DECISION MEMORANDUM
DATE: February 5, 2021
FROM: Sharon Eckard, PG
TO: BF Assessment File
RE: Smith Property Amendment
Townsend — Siler City
Siler City, Chatham County
Brownfields Project # 20060-16-019
Based on the following information, it has been determined that the Smith Parcel may be
added to the Townsend Siler City Brownfields Property without adding additional risk to
the Brownfields Property.
The Smith Parcel was primarily used for agricultural purposes. It is divided by three
streams that converge on the Smith Parcel and flow offsite to the south. Soil from the
planned construction storm water ponds (BMP samples), shallow soil across the site (SS -
series), and stream sediment (AOC-series) were collected and analyzed in December
2020 to compliment earlier work that included groundwater and surface water sampling.
The Smith Parcel is planned to be used as an employee parking lot for the adjacent
Mountaire Farms poultry processing plant and will have no enclosed structures.
Risk calculator output is provided below and indicates that none of these types of samples
exhibited volatile organic compounds (VOCs), semi -volatile organic compounds
(SVOCs), and metals concentrations that resulted in an unacceptable environmental risk
for residential, nonresidential, construction worker, and recreator/trespasser scenarios,
except that earlier risk evaluation indicated that residential use of groundwater does pose
an unacceptable carcinogenic risk. However, use of onsite groundwater will not be
conducted with this reuse and would be prohibited by the existing land use restrictions
within the brownfields agreement that the Smith parcel would be added to.
Because this amendment is the addition of a parcel to the Brownfields Agreement, it must
undergo a public comment period after the brownfields documents have been revised to
reflect the addition of this parcel and the data in excess of regulatory standards or
screening levels. The PD is scheduled to acquire this property on February 18, 2021; it
would be preferable to have the acquisition occur prior to public comment so that the PD
will own all the property and therefore would not require an acknowledgement by the
owner of the subject parcel.
The risk calculator output is provided below:

1) Sediment, Surface Water, and Groundwater (trespasser scenario):
Risk for Individual Pathways
Version Date: July 2020
Basis: May 2020 EPA RSL Table
Site ID: 20060-16-009 (Amendment)
Exposure Unit ID: Smith Parcel -Sediment, Surface Water, & Groundwater
DIRECT CONTACT SOIL AND WATER CALCULATORS
Receptor
Pathway
Carciinnogenic
sk
Hazard Index
Riskexceeded?
Resident
Soil
4.1E-06
2.0E-02
NO
Groundwater Use*
2.1E-04
9.1E-01
YES
Non -Residential Worker
Soil
2.2E-07
1.6E-03
NO
Groundwater Use*
9.5E-05
2.6E-01
NO
Construction Worker
Soil
2.8E-08
4.3E-02
NO
Recreator/Trespasser
Soil
2.4E-06
1.1E-02
NO
Surface Water*
8.3E-05
2.8E-01
NO
VAPOR INTRUSION CALCULATORS
Receptor
Pathway
CarcinogenicRisk
Hazard Index
Riskexceeded?
Resident
Groundwater to Indoor Air
1.0E-06
9.7E-02
NO
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
Non -Residential Worker
Groundwater to Indoor Air
2.3E-07
2.3E-02
NO
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
2) Shallow Soil Samples — shallow soil samples only with depths to 2 feet below wade:
Risk for Individual Pathways -
VersionDate: July202O
Basis: May 2020 EPA RSL Table
Site ID: 20060-16-019
Exposure Unit ID: Soil samples Siler City
DIRECT CONTACT SOIL AND WATER CALCULATORS
Receptor
Pathway
Carciinnogenic
sk
Hazard Index
Riskexceeded?
Resident
Soil
7.7E-06
5.1E-01
NO
Groundwater Use*
NC
NC
NC
Non -Residential Worker
Soil
1.7E-06
4.2E-02
NO
Groundwater Use*
NC
NC
NC
Construction Worker
Soil
3.0E-07
2.2E-01
NO
Recreator/Trespasser
Soil
4.3E-06
2.7E-01
NO
Surface Water*
NC
NC
NC
VAPOR INTRUSION CALCULATORS
Receptor
Pathway
Carciinnsogenic
Hazard Index
Riskexceeded?
Resident
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
Non -Residential Worker
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC

3) BMP — deeper soil samples to 4 feet below grade:
Risk for Individual Pathways
Version Date: July202O
Basis: May 2020 EPA RSL Table
Site ID: 20060-16-019
Ex osure Unit ID: BMP-samples - Smith Property
DIRECT CONTACT SOIL AND WATER CALCULATORS
Receptor
Pathway
Carciinnogenic
sk
Hazard Index
Riskexceeded?
Resident
Soil
6.9E-06
3.3E-01
NO
Groundwater Use*
NC
NC
NC
Non -Residential Worker
Soil
1.6E-06
2.4E-02
NO
Groundwater Use*
NC
NC
NC
Construction Worker
Soil
2.7E-07
1.4E-01
NO
Recreator/Trespasser
Soil
3.9E-06
1.8E-01
NO
Surface Water*
NC
NC
NC
VAPOR INTRUSION CALCULATORS
Receptor
Pathway
Carcinogenic
Risk
Hazard Index
Riskexceeded?
Resident
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
Non -Residential Worker
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
4) Sediment Samples - from all segments of streams on the property and downgradient of
the confluence at the edge of the property on the south side below flowing offsite:
Risk for Individual Pathways 1 . -
VersionDate: July202O
Basis: May 2020 EPA RSL Table
Site ID: 20060-16-019
Exposure Unit ID: Sediment Samples - AOC-series
DIRECT CONTACT SOIL AND WATER CALCULATORS
Receptor
Pathway
Carciinnogenic
sk
Hazard Index
Riskexceeded?
Resident
Soil
1.2E-05
4.6E-01
NO
Groundwater Use*
NC
NC
NC
Non -Residential Worker
Soil
2.8E-06
3.3E-02
NO
Groundwater Use*
NC
NC
NC
Construction Worker
Soil
4.9E-07
2.6E-01
NO
Recreator/Trespasser
Soil
6.8E-06
2.6E-01
NO
Surface Water*
NC
NC
NC
VAPOR INTRUSION CALCULATORS
Receptor
Pathway
Carciinnsogenic
Hazard Index
Riskexceeded?
Resident
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC
Non -Residential Worker
Groundwater to Indoor Air
NC
NC
NC
Soil Gas to Indoor Air
NC
NC
NC
Indoor Air
NC
NC
NC