HomeMy WebLinkAbout22007 S Tryon Commercial Vertical Soil Gas Profile Assessment Work Plan_20190403
Via Email
April 3, 2019
North Carolina Department of Environmental Quality
Division of Waste Management – Brownfields Program
1646 Mail Service Center
Raleigh, North Carolina 27699-1646
Attention: Mr. Bill Schmithorst, PG
Subject: Vertical Soil Gas Profile Assessment Work Plan
S. Tryon Commercial
Charlotte, North Carolina
Brownfields Project No. 22007-18-060
H&H Job No. RMR-006
Dear Bill:
1.0 Introduction
On behalf of Ram Realty Acquisitions V, LLC (Prospective Developer or PD), Hart & Hickman,
PC (H&H) has prepared this Work Plan to conduct vertical soil gas profile assessment activities
at the S. Tryon Commercial Brownfields property (Brownfields Project No. 22007-18-060)
located northeast of the S. Tryon Street and W. Tremont Avenue intersection in Charlotte,
Mecklenburg County, North Carolina (Site). The subject Site consists of two contiguous parcels
totaling approximately 2.4 acres of undeveloped vacant land located in a mixed commercial and
residential area of South End Charlotte. A Site location map is provided as Figure 1.
Proposed redevelopment at the Site includes construction of two commercial buildings (Building
AB and Building C) with associated parking areas and open spaces. The future intended use of
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April 3, 2019
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the new buildings includes retail and office spaces. The proposed redevelopment plan for the
Site is depicted in Figure 2.
The Site received eligibility into the North Carolina Department of Environmental Quality
(DEQ) Brownfields Program via a Letter of Eligibility dated February 18, 2018. The PD
subsequently elected to participate in the Brownfields Program Redevelopment Now option. As
part of this process, a kick-off/data gap meeting with PD, counsel for the PD, DEQ Brownfields
personnel, and H&H was held on March 22, 2018 to conduct a Site walk and to discuss historical
uses of the Site, available environmental information, proposed redevelopment plans, data gaps,
and the proposed schedule for completing the Brownfields Agreement.
Based on discussions with DEQ Brownfields during the kick-off/data gap meeting, H&H
prepared a Brownfields Assessment Work Plan (Work Plan) and revisions to the Work Plan
based on DEQ Brownfields comments. The Work Plan received DEQ Brownfields approval in
an email dated May 8, 2018. A summary of previous Site assessment activities is provided in the
following section.
1.1 Previous Environmental Assessments
H&H completed soil and soil gas assessment activities at the Site in July 2018 in accordance
with the DEQ Brownfields approved Work Plan. Results of the assessment activities are
documented in the Brownfields Assessment Report dated July 9, 2018. The results of
Brownfields assessment activities are shown on Figure 2, and a brief summary of the results is
provided below.
Low levels of volatile organic compounds (VOCs), semi-VOCs (SVOCs), and metals
were detected in soil below DEQ Inactive Hazardous Sites Branch (IHSB)
Industrial/Commercial Preliminary Soil Remediation Goals (PSRGs) and within the
range of naturally occurring metals for soil in the area of the Site. Results of cumulative
risk calculations indicate that grading and movement of soil during redevelopment
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activities at the Site will not present a significant risk to construction workers or future
non-residential workers.
Soil gas sample monitoring points were installed to a depth of 10 feet (ft) below ground
surface (bgs) within the footprints of the proposed commercial buildings. Laboratory
analytical results indicated that low levels of several VOCs were detected in each soil gas
sample at concentrations below the DEQ Division of Waste Management (DWM) Non-
Residential Sub-slab and Exterior Soil Gas Screening Levels (SGSLs). Results of
cumulative risk calculations using the highest compound concentrations detected in soil
gas samples collected at the Site indicate that there is no significant vapor intrusion risk
into the proposed buildings.
H&H completed groundwater assessment activities at the Site in July and August 2007. July
2007 groundwater assessment activities included installation of three (3) temporary groundwater
monitoring wells (DPT-2, DPT-8, DPT-9) and collection of groundwater samples for laboratory
analysis. In August 2007, permanent groundwater monitoring well MW-3 was installed and
sampled to further evaluate groundwater conditions in the area of temporary groundwater
monitoring well DPT-9. Locations of the temporary and permanent groundwater monitoring
wells (denoted by DPT and MW nomenclature, respectively) are depicted on Figure 2.
The 2007 groundwater assessment activities are documented in the Summary of Previous
Groundwater Assessment Activities report dated November 19, 2018. Results of the previous
groundwater assessment activities are provided in Figure 2, and a brief summary of the results is
provided below.
Results of the groundwater assessment activities indicated that low levels of
tetrachloroethene or PCE (up to 1.6 micrograms per liter [µg/L]), trichloroethene or TCE
(up to 14 µg/L), aldrin (up to 0.63 µg/L), dieldrin (up to 0.75 µg/L) and selenium (up to
33 µg/L) were detected in Site groundwater at concentrations exceeding DEQ
groundwater screening criteria. Cumulative risk calculation results using the highest
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compound concentrations detected in Site groundwater samples indicates that there is no
significant vapor intrusion risk for the proposed buildings. This is consistent with results
of the 2018 soil gas sampling activities.
Although cumulative risk calculations do not indicate that there is a significant risk for vapor
intrusion into the proposed commercial buildings, DEQ Brownfields expressed concerns
associated with changes to subsurface vapor concentrations and vapor migration patterns that
may result from placement of paved surfaces and construction of new slab-on-grade buildings at
the Site. To address DEQ Brownfields concerns with the potential for future changes to vapor
intrusion risks, H&H proposes to complete vertical soil gas profile assessment activities to
further evaluate the potential for vapor intrusion. An outline of the proposed additional
assessment activities is provided in the following sections.
2.0 Vertical Soil Gas Profile Assessment Activities
The proposed assessment activities will be performed in general accordance with the DEQ IHSB
Guidelines for Assessment and Cleanup (Guidelines) dated October 2015, the DEQ DWM Vapor
Intrusion Guidance (VI Guidance) dated March 2018, and the most recent versions of the U.S.
Environmental Protection Agency (EPA) Region IV Science and Ecosystem Support Division
(SESD) Field Branches Quality System and Technical Procedures guidance.
Prior to conducting field activities, H&H will contact NC One-Call, the public utility locator, to
mark subsurface utilities at the Site. H&H will also contract a private utility locator to mark
utilities which may not be identified by the public locator. Additionally, each soil gas boring
location will be hand cleared to a depth of approximately 5 ft bgs to further screen the boring
locations for the presence of subsurface utilities.
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2.1 Soil Gas Sampling Activities
H&H proposes to advance five (5) soil borings within the footprints of the proposed buildings
for installation of nested deeper and shallow soil gas sampling points. Three (3) soil borings will
be advanced within the footprint of the proposed building in the southern portion of the Site
(Building AB) and two (2) soil borings will be advanced within the footprint of the proposed
building in the northeastern portion of the Site (Building C). A shallow and deeper soil gas
sample point will be installed within each soil boring. Locations of the proposed nested soil gas
borings are shown in Figure 2.
Water level measurements collected in 2007 during groundwater assessment activities indicated
that water table depths at the Site ranged from approximately 23 to 26 ft bgs. Based on recent
rainfall amounts and drier conditions in the summer of 2007 at the time of the groundwater
assessment activities, it is anticipated that current groundwater depths are shallower than
measured during July and August 2007 groundwater assessment activities. The shallow soil gas
sample points will be installed at depths of approximately 5 ft bgs and the deeper soil gas sample
points will be installed to approximately 15 to 17 ft bgs.
H&H will team with a qualified drilling contractor to advance the proposed soil gas borings
utilizing a track-mounted direct-push technology (DPT) drill rig. Continuous soil samples will
be collected from the borings using acetate lined macrocore sleeves. Soil samples will be logged
for lithological description, observed for indication of potential impacts, and screened for the
presence of volatile organic vapors using a calibrated photoionization detector (PID).
A dedicated six-inch stainless-steel vapor implant screen fitted with ¼-inch diameter Teflon®
tubing will then be installed at the base of the soil boring (approximately 15 to 17 ft bgs for the
deeper soil gas sample). Filter sand will be placed from the base of the boring to approximately
6-inches above the deeper vapor implant screened interval. A hydrated bentonite seal will be
placed from the top of the filter sand to approximately 5.5 ft bgs. A second six-inch stainless-
steel vapor implant screen fitted with ¼-inch diameter Teflon® tubing will then be placed within
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the soil boring for the shallow soil gas sample. Filter sand will be placed from the top of the
bentonite to approximately 6-inches above the shallow screened interval. A hydrated bentonite
seal will be placed from the top of the shallow sample filter sand to the ground surface.
Prior to sampling, a leak check will be conducted at each soil gas sampling point by constructing
a shroud around the sampling system and flooding the air within the shroud with helium gas.
Helium concentrations within the shroud will be measured using a helium gas detector and
maintained at near saturated conditions for the duration of the leak check activities. Using a
syringe and a three-way valve, vapor from the shallow and deeper sampling points will be
purged of a minimum of three sample volumes and sampled outside of the shroud into a Tedlar®
bag and analyzed using the helium gas detector to ensure that helium concentrations are less than
10% of the concentration measured within the shroud.
Following a successful field leak check, soil gas samples will be collected from both the shallow
and deeper soil gas sampling points at each location into laboratory supplied stainless-steel
Summa canisters connected to in-line flow controllers with a laboratory calibrated vacuum
gauge. The flow controllers will be connected to the sample tubing at each soil gas sampling
point using a brass nut and ferrule assembly to create an air tight seal. The flow controller will
be calibrated by the laboratory to regulate the sample intake to approximately 100 milliliters per
minute (mL/min). Once the sample train is assembled, the intake valve on the canister will be
fully opened to begin collection of the soil gas sample. Vacuum readings on the Summa canister
will be recorded prior to and following the sampling period to ensure adequate sample volume
was collected. A vacuum will be maintained within the canisters at the conclusion of the
sampling event.
After sample collection, the Summa canister valve will be closed, and the regulator will be
disconnected from the canister. The canisters will be placed in a laboratory-supplied shipping
container, properly labeled and shipped under standard chain-of-custody protocols to a qualified
laboratory for analysis of PCE, TCE, cis-1,2-dichlroethene, trans-1,2-dichloroethene, and vinyl
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chloride by EPA Method TO-15. The laboratory will be requested to use reporting limits that
are below the DEQ DWM Residential SGSLs.
Upon completion of sampling, the soil gas sampling points will be properly abandoned and the
surfaces will be repaired similar to pre-drilling conditions. Additionally, each soil gas sample
location will be estimated using a hand-held global positioning system (GPS) unit.
2.2 Quality Assurance/Quality Control Samples
Laboratory QA/QC procedures will be employed to ensure appropriate sample handling and
analysis and to aid in the review and validation of the analytical data. QA/QC procedures will be
conducted in accordance with the method protocols and will include regular equipment
maintenance, equipment calibrations, and adherence to specific sample custody and data
management procedures. Samples will be analyzed in conjunction with appropriate blanks,
laboratory duplicates, continuing calibration standards, surrogate standards, and matrix spiking
standards in accordance with approved methodologies to monitor both instrument and analyst
performance. Laboratory reporting limits for each analyte will be at or below appropriate
screening criteria, where possible. Additionally, H&H will request that the laboratory include
estimated concentrations for compounds that are detected at levels above the laboratory method
detection limit, but below the laboratory reporting limit (J Flags).
A copy of the laboratory analytical data report and QA package for each group of samples
submitted to and analyzed by the subcontracted laboratory will be provided in an appendix to the
final report. Laboratory QA data consistent with Level II documentation will be requested for
this project. A copy of the completed chain-of-custody record and shipping receipt will be
appended to the corresponding laboratory analytical report included with the final report.
TITLE
PROJECT
SITE LOCATION MAP
SOUTH TRYON COMMERICAL
CHARLOTTE, NORTH CAROLINA
DATE:
JOB NO:
REVISION NO:
FIGURE:
3-27-2019 0
1RMR-006
SITE
0 2000 4000
APPROXIMATE
SCALE IN FEETN
U.S.G.S. QUADRANGLE MAP
QUADRANGLE
7.5 MINUTE SERIES (TOPOGRAPHIC)
CHARLOTTE EAST, NORTH CAROLINA, 1991
SB-2
SB-1
SB-3
VMP-3
VMP-2
VMP-1
SB-4
VMP-4
VMP-5
VMP-6
VMP-7
SB-5
SB-6
REVISION NO. 0
JOB NO. RMR-006
DATE: 3-28-19
FIGURE NO. 2
SOUTH TRYON COMMERCIAL
CHARLOTTE, NORTH CAROLINA
PROPOSED SOIL VAPOR
SAMPLE LOCATION MAP
LEGEND
SITE PROPERTY BOUNDARY
LIMITS OF BROWNFIELDS AGREEMENT
FORMER BUILDING FOOTPRINT
PROPOSED BUILDING FOOTPRINT
PROPOSED PARKING/ PLAZA AREA
APPROXIMATE LOCATION OF FORMER
GASOLINE UNDERGROUND STORAGE TANK
SOIL BORING LOCATION
SOIL VAPOR SAMPLE LOCATION
MONITORING WELL LOCATION
TEMPORARY MONITORING WELL LOCATION
TEMPORARY MONITORING WELL/ SOIL
BORING LOCATION
PROPOSED NESTED SOIL GAS BORING
LOCATION
2923 South Tryon Street-Suite 100
Charlotte, North Carolina 28203
704-586-0007(p) 704-586-0373(f)
License # C-1269 / #C-245 Geology
MOTOR FRE
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(1950-1950)
S. TR
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FORMER B&B CONTRACTING
COMPANY
W.TREMONT A
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NOTES:
1. AERIAL IMAGERY OBTAINED FROM MECHLENBURG COUNTY
GIS (2017).
2. SOIL SAMPLES COLLECTED ON 5/17/18 AND 5/18/18.
3. SOIL VAPOR SAMPLES COLLECTED ON 5/18/18.
4. TCE = TRICHLOROETHYLENE
BZP = BENZO(A)PYRENE
CF = CHLOROFORM
PCE = TETRACHLOROETHYLENE
μg/L = MICROGRAMS PER LITER
μg/m³ = MICROGRAMS PER CUBIC METER
mg/kg = MILLIGRAMS PER KILOGRAM
NA = NOT ANALYZED
5. J FLAG INDICATES AN ESTIMATED CONCENTRATION
BETWEEN THE LABORATORY REPORTING LIMIT AND THE
METHOD DETECTION LIMIT.
6. NO COMPOUNDS DETECTED ABOVE SCREENING LEVELS IN
SOIL SAMPLES SB-1, SB-2, SB-3, SB-4 AND SB-5.
7. HISTORICAL GROUNDWATER DATA ARE IDENTIFIED IN
PURPLE.
FORMER RESTAURANT
(1949-1959)
FORMER B&B
CONTRACTING COMPANY
FORMER TERMINIX, INC.
(1969-2014)
FORMER AUTO REPAIR SHOP
(1950-1963)
FORMER UST DISPENSER
SOIL VAPOR
VMP-2
TCE 42 μg/m³
CF 69 μg/m³
FORMER FARM MACHINERY
SALES & SERVICE (1959-1963)
ELECTRICAL SUPPLY
WAREHOUSE BUILDING C
(1960-1990)
SAMPLE ID
CONCENTRATIONSCONSTITUENTS
SOIL VAPOR
VMP-2
TCE 42 μg/m³
CF 69 μg/m³
SOIL VAPOR
VMP-1
TCE 66 μg/m³
CF 72 μg/m³
SOIL VAPOR
VMP-3 / DUPLICATE
TCE 52/53 μg/m³
CF 28/27 μg/m³
SOIL VAPOR
VMP-4
TCE 6.4 μg/m³
CF 54 μg/m³
SOIL VAPOR
VMP-5
TCE 70 μg/m³
CF 46 μg/m³
SOIL VAPOR
VMP-6
TCE 8.0 μg/m³
CF 290 μg/m³
SOIL VAPOR
VMP-7
TCE 6.1 μg/m³
CF 360 μg/m³
SOIL
SB-6
BZP 0.17J mg/kg
GROUNDWATER
DPT-08 (7/23/07)
PCE <1.0 μg/L
TCE 2.5 μg/L
DIELDRIN 0.75 μg/LGROUNDWATER
DPT-09 (7/24/07)
PCE <1.0 μg/L
TCE 14 μg/L
DIELDRIN 0.15 μg/LGROUNDWATER
MW-3 (8/9/07)
PCE 1.6 μg/L
TCE 11 μg/L
DIELDRIN <0.050 μg/L
GROUNDWATER
DPT-02 (7/20/07)
PCE <1.0 μg/L
TCE 5.7 μg/L
DIELDRIN NA
GROUNDWATER
DPT-07 (7/20/07)
PCE <1.0 μg/L
TCE <2.0 μg/L
DIELDRIN NA
GROUNDWATER
MW-2 (8/9/07)
PCE <1.0 μg/L
TCE 3.0 μg/L
DIELDRIN <0.050
BUILDING AB
BUILDING C
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