22042 Matheson Ave Dec Memo 20181207

DECISION MEMORANDUM
DATE: December 14, 2018

FROM: Carolyn Minnich
TO: BF Assessment File

RE: Matheson Ave II
2710 Chick Godley Road
Charlotte, Mecklenburg County BF # 22042-18-060

Based on the following information, it has been determined that the above referenced site, whose
intended use is for no uses other than multi-family high density residential, retail, office, and
with prior written DEQ approval, other commercial uses can be made suitable for such uses.
Introduction:
The Brownfields Property is two parcels and approximately 8.33 acres (Mecklenburg County tax
identification numbers 08302101 and 08303115). The Brownfields Property is currently
undeveloped wooded land. It is vacant land with woods, trees, and vegetation over growth. Little Sugar Creek bisects the Brownfields Property. Little Sugar Creek and the land adjacent to
the creek for a total of 6.10 acres are NOT in the Brownfields Property. This portion of land is
being transferred to the City of Charlotte.

Redevelopment Plans: The redevelopment plan for the Brownfields Property is the construction of four apartment
buildings for residential use. The buildings will have walk out base level, showing three levels
from the front and 4 along the back and associated parking and amenities. Approved uses will
include the following: multi-family high density residential, retail, office, and with prior written
DEQ approval, other commercial uses. The Brownfields Property is surrounded by land in industrial, commercial, retail, and residential use. Little Sugar Creek and the greenway will NOT
be included in the Brownfields Property as stated above. Refer to the figure below for proposed
site configuration.

Site History:

For discussion purposes the entire property has been divided into three sections and only the
Northern and Southern parcels will be included in the Brownfields Program. The Northern Third is the smallest with access to Matheson Ave and proposed Building 1, the Central Third (which is NOT in Brownfields Property and is Little Sugar Creek and flood plain being transferred to
City of Charlotte), and the Southern Third is the largest with 3 proposed buildings. The
Brownfields Property has not been previously developed. In the 1970s, fill material was placed
on a significant portion of the property. According to the interviews in the environmental reports, the fill dirt was likely imported from the construction project at Matheson Avenue and 30th Street Bridge, but no official documentation is available for verification.

Potential Receptors:
Potential receptors are construction workers, on-site workers, future residents, visitors, pets, and trespassers.
Contaminated Media:
DEQ has evaluated data collected from the following media at the subject property: groundwater,
soil, and soil vapor. DEQ relies on the following data to base its conclusions regarding the subject property and its suitability for its intended reuse.

Soil Phase II ESA activities were conducted in November 2014 and November 2017. Minor levels of
petroleum related VOCs and chlorinated VOCs were detected in the soil at concentrations below
Residential Preliminary Soil Remediation Goals (PSRGs). Arsenic concentrations exceeded the
residential PSRG of 0.68 mg/kg. Detections ranged from 1.6 to 4.2 mg/kg. The concentrations are consistent with the surrounding area and are considered to be naturally occurring except for a surface sample, SOIL-1-112117, at a concentration of 19 mg/kg. The IHSB’s tabulated generic
residential use preliminary remediation goal (“remedial goal”) for arsenic is 0.68 mg/kg.
However, the IHSB generic preliminary remediation goal conservatively assumes the presence of
additional soil contaminants that have the same health effects, and factor that into the remediation goals when appropriate. The North Carolina Brownfields Program is statutorily required to apply standards at each brownfields site that are only as stringent as necessary to
make the site suitable for the uses specified in the Agreement while fully protecting public health
and the environment. This Agreement’s arsenic remedial goal (“screening level”) was developed
using site-specific factors through a Human Health Risk Assessment conducted pursuant to U.S. EPA risk assessment guidance. The site-specific residential remedial goal for arsenic is 22
mg/kg.

Total Chromium concentrations were detected across the Brownfields Property. The standard for
Total Chromium is the lower threshold for hexavalent chromium. The samples were not speciated for trivalent and hexavalent. There is no source for hexavalent chromium on the
property.

Lead concentrations were detected in Soil 2 sample at 910 mg/kg and the standard for residential
use is 400 mg/kg. Follow-up samples were below the standard of 400 mg/kg. Final grade sampling will be required once grading activities are complete.

Manganese concentrations were detected in two samples above Residential PSRGs at a
concentration of 482 and 401 mg/kg. These are likely naturally occurring and consistent with the
Charlotte Region.
The following two PAHs concentrations were detected above Residential PSRGs:
benzo(a)pyrene and benzo(b)fluoranthene.

There were several other compounds detected but not above Residential PSRGs. The risk calculator was used with highest concentration for all detected compounds. The results are listed
below.

Groundwater
Groundwater samples were collected from SB-1, SB-2, SB-4 and SB-6 in November 2017. The results indicated detections of various contaminants, but only two constituents exceeded the
standards. Bis(2-ethylhexyl)phthalate in SB-2 exceeded the NC 2L standard at an estimated
concentration of 3.2 µg/L and the standard is 3 µg/L (it is also noted that this compound is a
common laboratory artifact and that it was also detected in the method blank). Chromium in SB-
6 also exceeded the NC 2L standard of 10 µg/L at a concentration of 35 µg/L. It was noted that the SB-6 sample was collected from a temporary groundwater monitoring well and had high
turbidity.

Surface Water
Surface water is not located on the Brownfields Property, but Little Sugar Creek and a proposed linear park (greenway) bisect the Brownfields Property. The creek and greenway will be owned
and maintained by the City of Charlotte. Little Sugar Creek surface water samples revealed
chlorinated solvents above 2B surface water standards. DEQ BF sent an email correspondence to
Shawna Caldwell at Mecklenburg County Groundwater and Wastewater Services on 8/10/2018
with the Phase II Limited Site Assessment Report. Redevelopment near the creek will require fencing or landscaping to prevent access to the creek.

Soil Vapor
In September 2018, eight (8) soil gas samples were collected on the Brownfields Property within
the anticipated footprints of the future site buildings. See the location on the figure above.
Compounds were detected, but none at concentrations above the DWM Residential Soil Gas Screening Levels (SGSLs). Please refer to the Soil Gas Assessment Report dated October 30,
2018 prepared by APEX for more details on sampling event. The summary table below shows
risk calculator results.
Sub-Slab Vapor No structures are on the Brownfields Property at the time of assessment. Therefore, no sub-slab
samples were collected.

Indoor Air
No structures are on the Brownfields Property at the time of assessment. Therefore, no indoor air samples were collected.

Risk Calculations

Risk calculations were made site-wide due to no historical use and the lack of identified source areas. Thus the data collected was considered to be representative of the property as a whole.
Both determinations including, and excluding, naturally occurring metals were conducted as
outlined below.

The risk calculations indicated the following based on available data, including the following media: groundwater, residual soil (based on confirmatory soil data), soil gas, air, and soil
samples. Note, HI represents the Hazard Index

Residual Soil Max – with Naturally Occurring Metals includes the highest concentrations of all
compounds or metals detected at the Brownfields Property, including those metals which, based on the sample location, are likely to be naturally occurring (arsenic, manganese, and total
chromium).

The following is more detailed list from the risk calculator. The drivers for exceedances are manganese, total chromium, and arsenic.

Note, if we revise the arsenic concentration to 4.2 mg/kg, the top end of the site specific range (4.2-1.6 mg/kg), the risk is decreased from 2.9 to 2.6 for the calculated non-carcinogenic hazard
quotient.

Residual Soil Max includes the highest concentrations of all compounds or metals at the
Brownfields Property; however, excludes those metals which are likely to be naturally occurring
(arsenic, manganese, and hexavalent chromium). The Brownfields statute only regulates contaminants, thus although there may be in an inherent risk, DEQ Brownfields does not regulate naturally occurring metals.

The following is a summary table for Soil Vapor to Indoor Air for Residential Use per the DEQ
February 2018 Risk Calculator.

Based on the detected concentrations, the Residential Hazard Index for soil gas to indoor air was
0.18 and the carcinogenic risk is 1.4 E -06. When the HI is less than 1 no additional vapor
assessment or mitigation is necessary.
Required Land Use Restrictions: Based on the site-specific data provided to the Brownfield program, the site reuse is suitable for
the site as long as the agreed upon land use restrictions in the BFA are abided by.

• No childcare usage
• No groundwater usage
• No soil disturbance without DEQ approval
• Soil may not be removed from or soil imported without DEQ approval
• EMP required prior to redevelopment
• Annual development summary report required
• DEQ shall not be denied access
• Deed conveyance of Notice
• No use of known contaminants on the BF Property
• Abandonment of on site monitoring wells
• Maintenance of future monitoring wells as needed to remain on site
• LURU submittal