DSHW-2024-006021

WASATCH ENVIRONMENTAL, INC.
ENVIRONMENTAL SCIENCE AND ENGINEERING

2410 WEST CALIFORNIA AVENUE
SALT LAKE CITY, UTAH 84104
PHONE [phone]
FAX [phone]
e-mail: [e-mail]
www.wasatch-environmental.com

SUB-SLAB DEPRESSURIZATION FAN INSTALLATION PLAN
ARMS TECHNOLOGY MACHINE SHOP
2779 WEST DIRECTORS ROW
SALT LAKE CITY, UTAH

PROJECT NO. 2619-003D

PREPARED FOR:

MR. DOUG HANSEN
UTAH DEPARTMENT OF ENVIRONMENTAL QUALITY
DIVISION OF WASTE MANAGEMENT AND RADIATION CONTROL
195 NORTH 1950 WEST, 2ND FLOOR
P.O. BOX 144880
SALT LAKE CITY, UTAH 84114-4880

PREPARED BY:

WASATCH ENVIRONMENTAL, INC.
2410 WEST CALIFORNIA AVE
SALT LAKE CITY, UTAH 84104
801-972-8400
FAX: [phone]

APRIL 23, 2024
Arms Technology Machine Shop
Sub-Slab Depressurization Fan Installation Work Plan Project No. 2619-003D
Wasatch Environmental, Inc. Page 1

TABLE OF CONTENTS

Section Page No.
1. INTRODUCTION AND OBJECTIVES ............................................................................................. 2
2. SITE BACKGROUND ...................................................................................................................... 2
3. SUB-SLAB DEPRESSURIZATION SYSTEM INSTALLATION ACTIVITIES .................................. 4
3.1 Installation of the Systems .................................................................................................. 4
4. REPORTING .................................................................................................................................... 4

FIGURES

Figure 1 – System Design
Figure 2 – Proposed Sub-Slab Depressurization Fan Location Map

Arms Technology Machine Shop
Sub-Slab Depressurization Fan Installation Work Plan Project No. 2619-003D
Wasatch Environmental, Inc. Page 2
SUB-SLAB DEPRESSURIZATION FAN INSTALLATION WORK PLAN
ARMS TECHNOLOGY MACHINE SHOP
2779 WEST DIRECTORS ROW
SALT LAKE CITY, UTAH

1. INTRODUCTION AND OBJECTIVES

Wasatch Environmental, Inc., (Wasatch) has prepared this work plan for installing sub-slab
depressurization fans at the Arms Technology machine shop (Site), owned by ATI Corporation, located at
2779 West Directors Row in Salt Lake City, Utah. This work plan has been prepared to mitigate potential
volatile organic compound (VOC) intrusion into the on-Site building.

The objectives of this work plan are to install two sub-slab depressurization systems (Systems) as
mitigation measures at the Site to mitigate the potential vapor intrusion risks.

This work plan describes the procedures that will be used for installing the Systems at the Site.

2. SITE BACKGROUND

Wasatch completed a Phase I Environmental Site Assessment (ESA) dated September 21, 2023, for the
Site on behalf of Buchalter (the legal representative for the potential purchaser). This report identified the
following recognized environmental conditions (RECs) and recommended additional investigation be
completed:

 There is a potential for releases to the Site from the long-term use of the sump located near the
southwest corner of the Site.

 There is a potential for releases to the Site from the long-term use of chemicals, lubricants, and
oils on the Site.

The Client requested that investigations be completed to evaluate the identified RECs.

On October 24, 2023, Wasatch completed four soil borings (GP-1 through GP-4) at the Site. Wasatch
advanced borings GP-1, GP-2, and GP-3 in the areas hydraulically downgradient of the building to
evaluate for impacts migrating away from the building, and boring GP-4 was advanced adjacent to the
sump to evaluate for potential releases in this area. Additionally, Wasatch collected six sub-slab soil gas
samples (SG-1 through SG-6) from beneath the on-Site building.

Based on the data collected Wasatch concluded the following:

 The suspected source area soil sample collected from boring GP-4 did not exhibit analyte
concentrations that exceeded their applicable United States Environmental Protection Agency
(U.S. EPA) Regional Screening Level (RSL) for Residential or Industrial Soil, except for arsenic.
Based on Wasatch’s experience the detected arsenic concentration is within the typical
background range of 20 to 30 mg/kg for this area. Therefore, it is Wasatch’s opinion that the
detected concentration of arsenic in soil is representative of background concentrations and is not
considered to be the result of a release.

 Chloroform was detected in all soil gas samples at concentrations ranging from 1.2 micrograms
per cubic meter (µg/m3) to 18 µg/m3. Chloroform is a common laboratory contaminant and is also
a breakdown compound of chlorine which is commonly observed in soil gas samples due to the
use of municipal water for irrigation or from leaking municipal water pipes in the area. Chloroform
Arms Technology Machine Shop
Sub-Slab Depressurization Fan Installation Work Plan Project No. 2619-003D
Wasatch Environmental, Inc. Page 3
is not considered to be a constituent of concern resulting from the suspected release of
chlorinated solvents, petroleum hydrocarbons, or metals at the Site.

 Soil gas samples SG-4 and SG-5 exhibited trichloroethene (TCE) concentrations that exceed the
applicable U.S. EPA Vapor Intrusion Screening Level (VISL) Residential and Commercial Target
Sub-Slab and Near-Source Soil Gas Concentrations (TSSGCs). The TCE concentrations in soil
gas indicate a release of TCE has likely occurred near soil gas samples SG-4 and SG-5. These
samples were collected near the sand trap and the former paint booth features which may be the
release point(s). Given the detected TCE in soil gas concentrations, there is a potential that the
rate of vapor intrusion into the building may result in TCE indoor air concentrations that exceed
the U.S. EPA RSL for Industrial Air.

 The arsenic concentrations detected in groundwater exceed the U.S. EPA MCL. Given the
elevated background concentrations of arsenic in soil, it is Wasatch’s opinion that the arsenic
concentrations detected in groundwater are within the typical background concentration range for
this area. No other metals were detected at concentrations that exceed their applicable U.S. EPA
Maximum Contaminant Levels (MCLs).

 TCE was detected in all groundwater samples analyzed for volatile organic compounds (VOCs) at
concentrations ranging from 12.3 micrograms per liter (µg/L) to 75.4 µg/L. These concentrations
exceed the U.S. EPA MCL for TCE. These samples were collected hydraulically downgradient of
the on-Site building. Based on these data, it appears that a release of TCE may have originated
from the on-Site building.

 Based on the data obtained from boring GP-4, it does not appear that a release from the sump
has occurred.

 Given the totality of the data, it appears that a release of TCE has occurred at the Site and may
be located near the sand trap/paint booth features. Wasatch recommended that this release be
reported to the Utah Department of Environmental Quality (DEQ). Wasatch also recommended
that additional investigation be completed to define the nature and extent of these impacts.

On January 4, 2024, Wasatch completed eight additional borings (GP-5 through GP-12) at the Site to
further evaluate the on-Site VOC impacts to soil and groundwater. Based on the data Wasatch
concluded the following:

 Several soil samples were collected above the water table in suspected source areas. Low
concentrations of TCE were detected in the GP-11 (at 5 feet bgs) and GP-12 (at 6 feet bgs)
borings above the water table. This indicates that a minor surface release has likely occurred in
this area. However, these detected TCE concentrations are below the U.S. EPA RSL for
Residential and Industrial Soil and the U.S. EPA Protection of Groundwater Soil Screening Level
(PGWSSL).

 No chlorinated solvents (including TCE and cis-1,2-dichloroethene [CIS]) were detected at
concentrations exceeding their applicable U.S. EPA RSLs for Residential or Industrial Soil in the
soil samples collected. However, soil samples GP-9-10, GP-10-10, GP-10-15, GP-11-10, GP-11-
15, and GP-12-12 (all collected at or below the water table) exhibited TCE concentrations that
exceed the U.S. EPA PGWSSL. This indicates there are soil impacts below the water table at
sufficient concentrations to result in impacts to groundwater at concentrations that exceed the
U.S. EPA MCL.

 TCE was detected in all groundwater samples at concentrations ranging from 4.88 to 47.3 µg/L.
These concentrations exceed the U.S. EPA MCL for TCE, except for groundwater sample GP-7-
17 (4.88 µg/L). Additionally, TCE is the only VOC that has been detected at a concentration
Arms Technology Machine Shop
Sub-Slab Depressurization Fan Installation Work Plan Project No. 2619-003D
Wasatch Environmental, Inc. Page 4
above the U.S. EPA MCL. Based on the groundwater data, TCE impacts to groundwater appear
to be present across the Site.

 Based on the totality of the groundwater data, TCE was detected along the northern, western,
eastern, and southern boundaries of the Site. This indicates that TCE impacts may be migrating
onto the Site, as the local groundwater flow direction is unknown but was assumed to be to the
north or northwest.

 Groundwater sample GP-11 exhibited the highest TCE concentration detected under the building.
Given this and that TCE was detected in the soil above the water table in this boring, it is
Wasatch’s opinion that this area likely represents a minor TCE source area under the building.
Groundwater monitoring wells should be installed to verify the groundwater flow direction.

 One groundwater sample (GP-9-30) was collected from a depth of 30 feet bgs. TCE was
detected at a concentration of 20.1 µg/L, which exceeds the U.S. EPA MCL. This indicates that
TCE impacts have migrated to at least 30 feet bgs at the Site.

 Given the totality of the data, it appears that a release of TCE has occurred at the Site and may
be located near the sand trap/paint booth features. Additionally, it appears that TCE impacts are
migrating onto the Site from an off-Site source, likely resulting in co-mingled plumes. Wasatch
recommends that this release be reported to the Utah DEQ. Wasatch also recommends that
additional investigation be completed to define the nature and extent of these impacts under the
guidance of the Utah DEQ.

Wasatch submitted a Division of Waste Management and Radiation Control (DWMRC) application to
enter into regulatory oversight with the Utah DWRMC on February 20, 2024. The Site was accepted into
the DWMRC Corrective Action program. DWMRC requested that additional environmental investigations
be completed.

Based on the VOC-impacted soil gas and groundwater beneath the on-Site building, ATI has requested
that Systems be installed as mitigation measures to mitigate the potential vapor intrusion risk at the Site.

3. SUB-SLAB DEPRESSURIZATION SYSTEM INSTALLATION ACTIVITIES

3.1 Installation of the Systems

Two Systems would be installed along the eastern building wall in the areas where the highest VOC
impacts to soil gas were detected. The conceptual design for the Systems is shown in Figure 1. The
affected building areas and approximate location of each of the two systems is shown in Figure 2. Each
System would be powered by a Fantech FR-150 6” duct fan rated at 230 cubic feet per minute (CFM) and
mounted on the building exterior. The fans would each be wired directly to a dedicated circuit breaker
installed in the existing circuit breaker panels. The systems would be plumbed using 4-inch schedule 40
polyvinyl chloride (PVC) pipe. The pipe would be installed so as to fully penetrate the concrete floor slabs
and draw vapors from beneath the slabs. All wall and floor penetration will be sealed with calk or
expanding foam sealant to form air-tight seals. Sample ports with removable plugs will be installed in the
vent stack on the building exterior to facilitate monitoring of soil gas removal if desired. Vent stacks will
be extended up the exterior walls to a minimum height of two feet above the roof line.

4. REPORTING

A brief letter report presenting the results of the System installation would be prepared and submitted to
the Client and the Utah DWMRC.

Arms Technology Machine Shop
Sub-Slab Depressurization Fan Installation Work Plan Project No. 2619-003D
Wasatch Environmental, Inc. Page 5
Sincerely,

WASATCH ENVIRONMENTAL, INC.

Blake Downey, P.G.
Vice President and Senior Project Hydrogeologist

Distribution: (1) Electronic - Addressee
(1) Electronic – Scott Farber (ATI Corporation)

Fantech FR-150 Fan
Existing concrete footing and
foundation wall
Flexible Reducer Coupler
4” x 6” (2 places)
Sample port with removable
plug to be located on building
exterior and to be accessible
from ground level
½” EMT Electrical Conduit (on interior)
½” Liquitite Flexible Electrical
Conduit (on exterior)
(as required to protect all electrical wiring)
Fully penetrate concrete floor slab such
that 4” pipe extends into gravel under
the slab
All wall and floor penetrations are to be
sealed using urethane calk or urethane
expanding sealant as appropriate to form an
air-tight seal
Existing Breaker Panel (fan to be wired to
a new, dedicated circuit breaker with lock-out,
label breaker panel position “Sub-slab
Ventilation System, Do Not Turn Off”)
Existing Roof Structure
Existing Concrete Floor Slab
Existing Exterior Wall

Free Flow Exhaust Cap
(to be located a minimum of 2’
above roof line)
4” Schedule 40 PVC Pipe and
Vent Stack
4” Pipe Clamps and Unistrut
(as required to secure vent stack
and system piping)
Drawing is not to scale
Typical configuration for
each of five systems
Building Interior Building Exterior
The use or reuse of this information is restricted to the referenced document unless otherwise authorized.
Wasatch Environmental Copyright 2005
Precision Technology - Sub-Slab Depressurization System Conceptual Design WEI 2419-001E
System Design Figure 1
The use or reuse of this information is restricted to the referenced document unless otherwise authorized.
Wasatch Environmental Copyright 2006
ARMS TECHNOLOGY MACHINE SHOP WEI 2619-003D
Proposed Sub-Slab Depressurization Fan Location Map Figure 2
Directors Row
Sand Trap
w/ Discharge
Floor drain
Capped
floor drain
Paint Booth
Soil Gas Sample Location
Approximate Location of Site
*All concentrations are reported in micrograms per cubic meter.
**All concentrations in exceed the U.S. EPA Vapor Intrusionred
Screening Level Commercial Target Sub-SLab and Near-Source
Soil Gas Concentration.
SG-1
TCE - <0.95
SG-2
TCE - 2.0
SG-4
TCE - 230
SG-3
TCE - 1.8
SG-5
TCE - 690
SG-6
TCE - 4.0
Wasatch Sub-Slab Fan Location
LEGEND