24054_AJACC Auto_VIMS Mod Request_Rev 1_20230505

Via Email
May 5, 2023 NCDEQ – Division of Waste Management
Brownfields Program 1646 Mail Service Center Raleigh, NC 27699-1646 Attn: Mr. Peter Doorn
Re: VIMS Modifications Approval Request – Rev. 1 Utility Handhole Installation AJACC Auto Brownfields Site
301 Verbena Street Charlotte, Mecklenburg County, North Carolina Brownfields Project No. 24054-20-060 H&H Project No. GSL-004

Dear Pete: On behalf of Greystar Development East, LLC (Greystar), Hart & Hickman, PC (H&H) has
prepared this letter to request that the North Carolina Department of Environmental Quality (DEQ)
Brownfields Program provide approval for proposed modifications to the vapor intrusion
mitigation plan (VIMP) prepared for the Action Jackson Aftermarket and Car Care Automotive
Service and Repair (AJACC Auto) DEQ Brownfields Program property (Brownfields Project No.
24054-20-060) located at 301 Verbena Street in Charlotte, Mecklenburg County, North Carolina
(Site). A multi-family residential apartment complex is under construction at the Site and the
development is known as Elan LoSo.

On March 29, 2022, the Brownfields Program provided approval for the Vapor Intrusion
Mitigation Plan – Revision 1 dated March 15, 2022, related to installation of vapor intrusion
mitigation controls during construction of the Elan LoSo multi-family residential building. In
Mr. Peter Doorn May 5, 2023 Page 2
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accordance with the approved VIMP, a passive vapor intrusion mitigation system (VIMS) is being
installed during construction of the building. The proposed VIMS modification is described in the
following paragraphs.

Installation of Electrical Handhole within Building
The Terrace level electrical room will receive electrical wiring from an exterior substation that
will be pulled through conduit from outside of the building to the interior. Due to an excessive
number of elbows and turns anticipated in the conduit to run directly to the electrical room, it is
necessary for the contractor to install a handhole pull station within the building maintenance room
of the Terrace level building (see Drawing No. 1 below). The purpose of the handhole pull station
is provide an additional location to pull wires to prevent potential issues or damage to the wiring
during installation.

The handhole pull station will be comprised of a 5-foot by 5-foot and 5.5-foot-deep precast
concrete handhole (i.e. manhole) with a circular manhole lid with approximately thirty 4-inch
diameter electrical plastic conduits and associated electrical wires installed in the bottom of the
handhole. A 6-inch thick concrete pad will be poured within the base of the handhole. The
handhole lid will contain an air-tight gasket without holes in the lid to prevent air transfer from
within the manhole to within the building. As the handhole is only necessary for installation of
the wiring during construction, after construction, the handhole is not anticipated to be opened or
entered after construction and no future maintenance activities inside of the handhole are expected.

The proposed VIMS component installation method for this handhole is depicted in Detail 29/VM-
1B (Drawing No. 2) embedded below. The DEQ-approved Raven VaporBlock-20 Plus (VBP-20)
vapor barrier will be sealed to the side of the handhole utilizing manufacturer approved double-
sided tape or other sealants. The vapor barrier around the handhole will also connect to the vapor
barrier installed below the slab to create a continuous layer. Further, Raven Pour N’ Seal, which
is a medium viscosity high strength epoxy designed as by Raven a vapor barrier when cured, will
be poured across the base concrete layer around the penetrations in accordance with manufacturer
Mr. Peter Doorn May 5, 2023 Page 3
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instructions. In addition, the interior space of the handhole will connect to the mitigated sub-slab
stone layer from the passive VIMS using a 2-inch diameter PVC pipe to allow passive venting of
the interior space of the handhole and allow vapors within the handhole to be discharged above
the building roofline.

As an additional precaution, electrical conduits within the electrical room that connect to the
handhole will have the annular space sealed with a spray foam followed by a polyurethane sealant
(Sikaflex or equivalent) to create an air-tight seal after the electrical wires are installed. This
additional measure will further prevent vapors from migrating within the handhole through the
electrical conduits. A placard, or sign, will also be placed on the handle lid, or on the closest wall
to the handhole vault, with “VAULT LID SHALL REMAIN CLOSED WITH AN AIR-TIGHT
SEAL AS PART OF THE VAPOR INTRUSION MITIGATION SYSTEM”

Drawing No. 1 – Proposed location for handhole (depicted with red circle) within the Building Maintenance Room.

Mr. Peter Doorn May 5, 2023 Page 4
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Drawing No. 2 – Proposed VIMS modification for electrical handhole.

The measures described herein regarding the electrical handhold are designed to prevent vapor
intrusion from Site contaminants into the building. Inspections of the installed handhold
components will be completed and documented in the VIMS installation report and as-built
drawings as summarized in the DEQ-approved VIMP. In accordance with the VIMP, a sub-slab
vapor sample is proposed to be collected prior to building occupancy from the room adjacent to
the maintenance room at monitoring point location MP-T4 (see Drawing No. 1). The analytical
data from this monitoring point and other samples in the building will be used to evaluate if any
further measures may be warranted to prevent vapor intrusion in the area of the maintenance room
and the handhole described herein. If additional measures are warranted, DEQ will be notified of
the proposed modifications.

Mr. Peter Doorn May 5, 2023 Page 5
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Engineer’s Certification
According to the DWM Vapor Intrusion Guidance: “Risk-based screening is used to identify sites
or buildings likely to pose a health concern, to identify buildings that may warrant immediate
action, to help focus site-specific investigation activities or to provide support for building
mitigation and other risk management options including remediation.” In addition, this VIMP was
prepared to satisfy the vapor intrusion mitigation condition in the pending Brownfields Agreement.
Per the North Carolina Brownfields Property Reuse Act 130A-310.32, a prospective developer,
with the assistance of H&H for this project, is to provide NCDEQ with “information necessary to
demonstrate that as a result of the implementation of the brownfields agreement, the brownfields
property will be suitable for the uses specified in the agreement while fully protecting public health
and the environment instead of being remediated to unrestricted use standards.” It is in the context
of these risk-based concepts that H&H’s professional engineer makes the following statement.

The Vapor Intrusion Mitigation System (VIMS) detailed herein is designed to mitigate intrusion
of subsurface vapors into the subject building from known Brownfields Property contaminants in
a manner that is in accordance with the most recent and applicable guidelines including, but not
limited to, DWM Vapor Intrusion Guidance, Interstate Technology & Regulatory Council (ITRC)
guidance, and American National Standards Institute (ANSI)/American Association of Radon
Scientists and Technologists (AARST) standards. The sealing professional engineer below is
satisfied that the design is fully protective of public health from known Brownfields Property
contaminants.

Mr. Peter Doorn May 5, 2023 Page 6
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We appreciate your review and of the proposed modifications to the VIMS design. If you have
any questions or require additional information, please do not hesitate to contact me at 704-586-
0007.
Sincerely,

Trinh DeSa NC PE#044470 Engineering Manager
Hart & Hickman, PC (#C-1269)
cc: Mr. Andrew Besu (H&H) Mr. David Kahn (H&H)
Mr. Kelly Johnson (NC DEQ)