22040_Metromon Concrete Decision Memorandum 20191004

DECISION MEMORANDUM
DATE: October 4, 2019 FROM: Bill Schmithorst TO: Metromont Concrete Facility BF File
RE: Metromont Concrete Facility 4101 Greensboro Street Charlotte, Mecklenburg County BF # 22040-18-060
Based on the following information, it has been determined that the above referenced site, whose intended use is for no uses other than high density residential, multi-family residential, office, retail, light industrial, open space, recreation, parking, and with prior written DEQ approval, commercial, can be made suitable for such uses.
Introduction: The Brownfields Property is 18.51 acres and portions of the property are being used for construction materials storage and the remainder of the property is currently vacant. The Brownfields Property is located in a commercial and industrial area, and bordered to the
north by Little Sugar Creek. Redevelopment Plans: The PD plans to construct apartments and commercial buildings on the Brownfields Property.
Site History: The Brownfields Property was predominantly undeveloped wooded land until the 1950s when the Site was developed with concrete manufacturing buildings. The Site was
operated as a concrete manufacturing facility by multiple tenants from the early to mid-
1950s until approximately 1997. The Brownfields Property was occupied by Exposaic Industries, Inc until 1995 and has most recently been occupied by the Metromont Corporation (Metromont) for structural
pre-cast concrete manufacturing operations until February 2019.
The southwestern portion of the Brownfields Property is currently being used as a construction materials staging area by Johnson Brothers, Inc., a contractor for the City of Charlotte working on the nearby light rail system. Remaining portions of the site are
currently unoccupied.
The UST Closure Report (1995) indicates that one gasoline underground storage tank and three fuel oil USTs were located on the Brownfields Property. The report indicates that Tank No. 1, Tank No. 2 and Tank No. 3 were removed in August 1995. Tank No. 4 was
closed in-place in August 1995 by filling the UST with concrete (NCDEQ UST Incident No. 15459). The NCDEQ issued a Conditional Notice of No Further Action for UST
Incident No. 15459 on April 23, 2019 requiring that a Notice of Residual Petroleum be filed with the Register of Deeds in Mecklenburg County restricting groundwater use. Potential Receptors: Potential receptors are: construction workers, on-site workers, and future residents. A
receptor survey was conducted and no water supply wells were located within 1,500 feet of the Brownfields Property. Contaminated Media: DEQ has evaluated data collected from the following media at the subject property:
groundwater, soil, and soil gas. DEQ relies on the following data to base its conclusions regarding the subject property and its suitability for its intended reuse. Soil Laboratory analytical results indicate that low levels of medium range aliphatic fractions
(up to 5.5 J mg/kg) were detected above the laboratory reporting limits, but below the Residential PSRG of 20 mg/kg in soil samples collected in the area of the former diesel tank (Tank No. 1), the former gasoline tank (Tank No. 2), and the former heating oil tank (Tank No. 3). In addition, low levels of high range aliphatic fractions (50 mg/kg) and medium range aromatic fractions (13 mg/kg) were detected in the TW-1 soil sample at
concentrations below the Residential PSRGs of 47,000 mg/kg and 22 mg/kg, respectively. No other aliphatic or aromatic hydrocarbon fractions were detected above the laboratory method detection limits in soil samples collected at the Site. Groundwater
A groundwater environmental assessment was conducted at the Brownfields Property in January and February 2019. Nine temporary groundwater monitoring wells were installed and sampled for VOCs, SVOCs, volatile petroleum hydrocarbons and extractable petroleum hydrocarbons (VPH/EPH), and two were sampled for RCRA metals.
Laboratory results indicated an exceedance of 15A NCAC 2L.0202 North Carolina
Groundwater Standards (NCAC 2L) for tetrachloroethylene (TW-2, 2.6 ug/L), cis-1,2-dichloroethene (TW-7, 160 ug/L), and vinyl chloride (0.95 ug/L, TW-7). Results from laboratory metals analyses did not exceed NCAC 2L. In addition, laboratory results indicate exceedances of North Carolina Groundwater Vapor Intrusion Screening Levels
for trichloroethene (2.8 ug/L, TW-7), vinyl chloride (3.3, GW-1), and aliphatic
compounds (TW-1, TW-2, TW-3 and TW-4).
Previously, a groundwater environmental assessment was completed in 1996 and laboratory results indicated that groundwater samples collected from monitoring well
MW-1 exceeded naphthalene and 2-methylnaphthalene for NCAC 2L.

Soil Vapor
Laboratory analytical results for the soil gas samples indicate the presence of several VOCs above the laboratory method detection limits in each of the soil gas samples. No
compounds were detected at concentrations exceeding the Residential or Non-Residential SGSLs in soil gas samples collected at the Site. Risk Calculations Risk Calculations were performed using Excel worksheets provided by Sandy Mort,
NCDEQ Brownfields Toxicologist. For the purposes of looking at the highest possible risk, the highest concentrations were used in the risk analysis from groundwater (temporary monitoring wells TW-1, TW-2 and TW-3), soil (TW-1) and soil gas samples (SG-2). The risk calculations indicated the following based on available data, including the following media: groundwater, residual soil, and soil gas:

PRIMARY CALCULATORS - TW-1 GROUNDWATER AND SOIL
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded?
Resident Soil Combined Pathways 0.0E+00 1.4E-01 NO
Groundwater Combined Pathways 0.0E+00 2.7E-01 NO
Non-Residential Worker Soil Combined Pathways 0.0E+00 2.2E-02 NO
Groundwater Combined
Pathways
0.0E+00 5.0E-02 NO
Construction Worker Soil Combined
Pathways
0.0E+00 6.6E-02 NO
VAPOR INTRUSION CALCULATORS - TW-1 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded?
Resident Groundwater to Indoor Air 0.0E+00 3.6E+01 YES
Non-Residential Worker Groundwater to Indoor Air 0.0E+00 8.6E+00 YES

PRIMARY CALCULATORS - TW-4 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded?
Resident Groundwater Combined Pathways 0.0E+00 1.1E-01 NO
Non-Residential Worker Groundwater Combined Pathways 0.0E+00 2.2E-02 NO
VAPOR INTRUSION CALCULATORS – TW-4 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded? Resident Groundwater to Indoor Air 0.0E+00 1.6E+01 YES
Non-Residential Worker Groundwater to Indoor Air 0.0E+00 3.7E+00 YES

PRIMARY CALCULATORS - TW-2 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded? Resident Groundwater Combined Pathways 3.2E-07 1.8E-01 NO
Non-Residential Worker Groundwater Combined Pathways 8.5E-08 3.8E-02 NO
VAPOR INTRUSION CALCULATORS – TW-2 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded?
Resident Groundwater to Indoor Air 1.8E-07 1.6E+01 YES
Non-Residential Worker Groundwater to Indoor Air 4.1E-08 3.8E+00 YES

PRIMARY CALCULATORS - TW-7 GROUNDWATER
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded? Resident Groundwater Combined Pathways* 5.6E-05 5.4E+00 YES
Non-Residential Worker Groundwater Combined Pathways* 3.2E-06 9.9E-01 NO
VAPOR INTRUSION CALCULATORS – TW -7 GROUNDWATER
Receptor Pathway Carcinogenic
Risk
Hazard
Index
Risk
exceeded?
Resident Groundwater to Indoor Air 8.8E-06 5.6E-01 NO
Non-Residential Worker Groundwater to Indoor Air 7.6E-07 1.3E-01 NO

VAPOR INTRUSION CALCULATORS – SG-2
Receptor Pathway Carcinogenic Risk Hazard Index Risk exceeded?
Resident Soil Gas to Indoor Air 2.5E-06 1.6E-01 NO
Red shading LICR> 1E-04 or HI> 1. LICR = Lifetime Incremental Cancer Risk HI = Hazard Index Risk assessment results indicate risk exceedances from petroleum compounds and VOCs in groundwater to residents and non-residential workers. In addition, risks from VOCs
and petroleum were exceeded for groundwater to indoor air for residents. In order to
mitigate risks to onsite workers and construction workers, all construction work will be
completed under an approved Environmental Management Plan. In addition, the Prospective Developer will install appropriate building vapor mitigation measures to
prevent unacceptable contaminant compound levels from impacting the interior of the buildings planned for construction. Arsenic concentrations were detected in soil above risk levels; however, these detections are comparable to concentrations found in background samples.
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 PD/land owner complies with the agreed upon land use restrictions. A summary of the land use restrictions is provided below.
1. No use other than for high-density residential, retail, office, hotel, parking, restaurant, and, subject to DEQ’s prior written approval, other commercial uses. 2. No groundwater use 3. No disturbing soil without DEQ approval or for landscape/mowing/pruning/repair of
underground infrastructure (written notice to DEQ)/work for EMP. 5. Soil Import/Export must be approved by DEQ. 6. No new buildings until PD demonstrates to the DEQ that indoor air is safe/no VI issues/ or VI protection installed as determined to be required by DEQ. 7. DEQ approved EMP
8. Access to Brownfields Property for environmental assessment. 9. NBP reference in deed. 10. No contaminants (as included in Ex. 2 to the BFA) on property except for de minimis amounts, fluid in vehicles, fuels for generators/equipment. 11. Ongoing maintenance of vapor mitigation systems.
12. Final grade soil sampling for RCRA metals, SVOCs, and VOCs will be conducted in exposed areas. 13. LURU submission January 1st