DERR-2024-013239

6952 South High Tech Drive, Suite B
Midvale, Utah 84047
P [phone]
Terracon.com
November 25, 2024
Salt Lake City Corporation
Department of Sustainability
451 South State Street, Room 148
Salt Lake City, Utah 84114-5470
Attn: Ms. Catherine Wyffels
Air Quality & Environmental Program Manager
P: [phone]
E: [e-mail]
Re: Status Report
The Other Side Village, VCP Site C121
1850 West Indiana Ave, Salt Lake City, Utah
Terracon Project No. 61237263
Dear Ms. Wyffels :
This letter presents the status of activities conducted to date to remediate documented
impacts at Phase I of the Other Side Village. Remediation activities have followed the
procedures set forth in the Remedial Action Plan (RAP), dated June 21, 2023, and approved
by the Utah Department of Environmental Quality (UDEQ) Voluntary Cleanup Program (VCP)
on August 15, 2023. The RAP was designed to achieve the following objectives:
■remove or control the potential exposure risks posed by the presence of
benzo(a)pyrene, arsenic and cadmium in fill materials, and arsenic in native soils;
■control exposure to groundwater;
■mitigate the potential for vapor intrusion of chloroform in soil gas to structures built
on the site; and
■secure access to the site by installation of a fence.
Impacted Fill and Soil Removal
In order to remove risks posed to construction workers during development and to site
occupants after development, all impacted fill material and soils were removed from the site
and properly disposed. Impacted soil excavation procedures were initiated in September
2023. Previous investigations identified six locations where fill materials exceeded a
regulatory screening level: Test Pits TP-33, TP-36, TP-37, TP-38, TP-40, and TP-42. Native
soils along the north ditch, located in the northern portion of the site, reported elevated
concentrations of arsenic compared to the site-specific action level. These areas were
Status Report
The Other Side Village | Salt Lake City, Utah
November 25, 2024 | Terracon Project No. 61237263
2
excavated in preparation for site development and confirmation samples were collected at
the extents of each excavation.
Table 1 presents the confirmation sample results after impacted soil excavation and removal
from the impacted Test Pits. The table shows the original samples that identified an
exceedance and the confirmation samples that document conditions at the north, south,
east, and west sides of each excavation as well as the floor of the excavation (the native
soil / fill contact). The sample name shows the test pit number and the distance and
direction from the original sample where the final extent-of-excavation sample was
collected. As shown, sample results indicate remaining materials did not exceed a screening
level with the exception of fill material on the east side of test pits TP-40 and TP-42. At
these locations, fill material was excavated to the eastern property boundary and the
confirmation samples were collected at that location, TP-40E-20, collected 20 feet east of
the original sample, reported an exceedance of arsenic and benzo(a)pyrene. TP-42E-15,
collected 15 feet east of the original sample, reported an exceedance of benzo(a)pyrene.
These samples indicate elevated levels of these contaminants are likely present on the east-
adjoining property; however, off-site fill material was not handled during development and
will similarly not be encountered by residences post-development.
Table 2 presents the sample results from the north ditch native soils excavation. As per the
RAP, a trench was excavated along the north ditch alignment approximately 10 feet on
either side. Samples were collected on the north and south sides of the ditch centerline,
beginning at the point where the ditch crosses the north property line and moving south at
50-foot intervals. If a sample reported an exceedance of arsenic, the excavation was
expanded 3 to 5 feet in the direction of the failed sample and a new confirmation sample
was collected. A sample was also collected at the floor of the excavation at the
corresponding 50-foot interval. The sample name indicates the north ditch (ND), the
distance from the north property line trending roughly southeast along the ditch (50 foot to
330 foot), and the direction from centerline (north or south), such as ND – 250 N. As shown
by the sample results, native soils with arsenic concentrations exceeding the site-specific
screening level of 10.8 milligrams per kilogram (mg/kg) were successfully removed.
Approximately 675 tons of soil or fill materials were removed during the initial impacted soil
excavation event. The asphalt pad that was in-place at the south end of the site was not
removed during the soil excavation event and was used as a staging area for soil stockpiles.
When soil excavation was complete and the asphalt pad was no longer needed, the fill
material beneath the asphalt pad was removed. Prior to excavation, two samples were
collected from the approximate center of the asphalt pad and analyzed for arsenic,
cadmium, and benzo(a)pyrene to determine if impacts above screening levels were present.
The two soil samples did not report an exceedance and as such, the excavated material was
handled as non-impacted fill material as described in the RAP. The material, approximately
8 tons, was excavated on August 14, 2024, stockpiled onsite and sampled and was then
transferred to the west-adjoining property. All impacted fill/soil was disposed of at the Salt
Lake County Landfill as “Cover Fill” after receiving prior approval from the Landfill.
Construction debris, such as large pieces of concrete, timbers, scrap metal, rebar, etc, that
was not suitable for cover fill was disposed of at the Landfill as municipal waste.
Status Report
The Other Side Village | Salt Lake City, Utah
November 25, 2024 | Terracon Project No. 61237263
3
Control of Exposure to Groundwater
Exposure to groundwater was controlled during construction by requiring workers involved
in dewatering activities be provided with OSHA 40-hour HAZWOPER training. Exposure to
groundwater after development will be controlled by recording an Environmental Covenant
that prohibits access to and use of groundwater at the site.
Vapor Intrusion Mitigation
A vapor intrusion mitigation system (VIMS) has been designed for each type of building to
be constructed at the site to address potential exposure to elevated levels of chloroform in
soil gas. Terracon used the EPA’s Vapor Intrusion Screening Level (VISL) calculator to
estimate the risk associated with the concentrations of chloroform in the soil gas and
designed a mitigation strategy accordingly. Based on the risk level and the specific building
plan, three approaches to vapor intrusion mitigation will be used at the site:
vapor barrier only;
vapor barrier with passive venting; and
vented foundation.
Exhibit 1 shows the building plan and where each type of VIMS will be used. To date, the
Pavilion structure in the northern portion of the site has been constructed. As shown on the
exhibit, it uses a slab-on-grade foundation and had a vapor-barrier-only VIMS installed.
The remaining slab-on-grade foundations and vented crawl space foundations in the
northern portion of the site under construction and are scheduled to be completed by the
end of 2024. Terracon is providing third-party oversight during installation of the VIMS to
ensure the approved design is followed. Prior to any structure being occupied the developer
will provide documentation that the appropriate vapor mitigation has been implemented.
When all of the systems have been installed Terracon will prepare a VIMS Installation
Observation report that summarizes the observations made during installation. The report
will note any deviations from the plans and will provide documentation that the alternate
installation was approved by the design engineer.
Site Access
As part of the development, fencing will be installed along the eastern site boundary and
around the residential areas as shown in Exhibit 2. This will restrict site access to residents
and authorized guests, in accordance with the development’s stated objective of providing
safe, supportive housing, as well as preventing access to the adjoining landfill. The
developer anticipates permanent fencing will be constructed along the east and south
property boundaries by the end of 2024, and temporary construction fencing will be utilized
along the west and north sides to accommodate construction of the future Phase II
development.
Status Report
The Other Side Village | Salt Lake City, Utah
November 25, 2024 | Terracon Project No. 61237263
4
Currently, the work conducted to date has conformed to the requirements of the RAP.
Terracon is aware that additional development is planned for the site and will be conducted
according to the provisions in the RAP.
Sincerely,
Terracon Consultants, Inc.
Nancy Saunders Amy Austin
Project Manager Authorized Project Reviewer
Attachments:
Table 1 – Test Pit Confirmation Sample Results
Table 2 – North Ditch Confirmation Sample Results
Exhibit 1 – Vapor Mitigation Systems
Exhibit 2 – Site Diagram with VCP Site Boundaries
Amy Austin
Table 1 - Test Pit Confirmation Samples Results
Redwood Road Dump VCP Site C121
1850 West Indiana Avenue, Salt Lake City, Utah
Terracon Project No. 61237263 Task 6
TP-33
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 13.2 0.661 2.55 6.51 1.46 5.63 3.34 J 1.25 4.83 4.03 0.735 2.84 6.17 0.771 2.98 4.1 0.592 2.29
6010B CADMIUM mg/kg 7.1 0.999 NA NA NA NA NA
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.0802 NA NA NA NA NA
TP-36
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 6.95 0.579 2.23 NA NA NA NA NA
6010B CADMIUM mg/kg 7.1 0.889 0.0526 0.559 NA NA NA NA NA
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.134 0.02 0.067 0.00721 J 0.00226 0.00759 0.0562 0.022 0.075 0.0594 0.020 0.0672 0.0805 0.00253 0.00848 <0.00730 0.00218 0.0073
TP-37
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 6.07 B 0.626 2.42 NA NA NA NA NA
6010B CADMIUM mg/kg 7.1 0.649 0.0569 0.604 NA NA NA NA NA
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.211 0.0399 0.134 0.0068 0.002 0.007 0.0771 0.002 0.00671 0.0382 0.00204 0.00683 0.0805 <0.00202 0.00202 0.00678
TP-38
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 15.9 0.553 2.13 7.74 0.561 2.17 7.81 0.566 2.18 7.07 0.589 2.27 10.6 0.59 2.28 6.54 0.567 2.19
6010B CADMIUM mg/kg 7.1 13.6 0.0503 0.534 2.16 0.051 0.542 0.905 0.0514 0.546 0.711 0.0535 0.568 0.949 0.0537 0.57 0.729 0.0516 0.547
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.0342 0.00955 0.032 NA NA NA NA NA
TP-40
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 12.2 0.794 3.06 NA 13 0.605 2.34 5.93 0.634 2.45 10.4 0.667 2.57 5.95 0.639 2.47
6010B CADMIUM mg/kg 7.1 8.42 0.0722 0.766 4.06 0.0604 0.641 5.91 0.055 0.584 NA 2.93 0.0606 0.644 0.293 0.0581 0.617
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.369 0.0137 0.046 0.0351 0.00229 0.00769 0.237 0.0105 0.035 0.0425 0.00219 0.00734 0.00891 0.0023 0.00772 <0.00221 0.00221 0.00740
TP-42
Method Analyte Units Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
6010B ARSENIC mg/kg 10.8 15.1 0.655 2.53 4.75 0.678 2.62 NA 5.61 0.633 2.44 9.18 0.631 2.44 8.91 0.649 2.5
6010B CADMIUM mg/kg 7.1 2.94 0.0595 0.632 NA NA NA NA NA
8270C-SIM BENZO(A)PYRENE mg/kg 0.11 0.0776 0.00226 0.00758 NA 0.196 0.00207 0.00693 NA NA 0.0279 0.00224 0.00751
J: The identification of the analyte is acceptable; the reported value is an estimate.
mg/kg:Milligrams per kilogram
NA: Not Analyzed
Qualifiers:
Site-Specific Screening Level = EPA RSL: Environmental Protection Agency Regional Screening Levels for
Residential Soils for cadmium and Benzo(a)pyrene (November 2022; TR=1E-06; THQ=1.0)
and 10.8 mg/kg for arsenic.
Color shaded value exceeds screening level; gray shading indicates value exceeds RDL.
Lab Sample ID Site Specific
Cleanup
Level
L1557295-30 L1592638-37 L1665547-12 L1592638-39 L1592638-41 L1665547-13
Client Sample ID TP-42 FILL TP-42N-10 TP-42-E15 TP-42S-10 TP-42W-15 TP-42 FLOOR
Date Collected 11/10/2022 03/06/2023 10/11/2023 03/06/2023 03/06/2023 10/11/2023
TP-38S-10 TP-38W-10
L1665547-09L1665547-10 L1668439-01
Client Sample ID TP-140 FILL*TP-40N-20 TP-40E-20 TP-40W-20TP-40S-20 TP-40 FLOOR+3
Lab Sample ID Site Specific
Cleanup
Level
L1557295-35 L1665547-07 L1665547-08
Date Collected 11/10/2022 10/11/2023 10/11/2023 10/11/202310/11/2023 10/19/2023
TP-36W-15 TP-36-FLOOR
TP-38-FLOOR
Date Collected 11/10/2022 03/06/2023 03/06/2023 03/06/2023 03/06/2023 10/10/2023
03/06/2023 10/10/2023
Lab Sample ID Site Specific
Cleanup
Level
L1557295-18 L1592638-24 L1592638-25 L1592638-26 L1592638-49 L1664839-01
Client Sample ID TP-138 FILL*TP-38N-10 TP-38E-10
L1665547-02
TP-37E-20
10/11/2023
L1664839-04
Client Sample ID TP-33-FLOOR
Date Collected 10/10/2023
L1592638-02
TP-33E-10
03/06/2023
L1592638-03 L1592638-04
TP-33W-10
03/06/2023
L1557295-01
TP-33 FILL
11/10/2022
L1592638-01
TP-33N-10
03/06/2023
Site Specific
Cleanup
Level
L1594306-03 L1664839-02
TP-33S-10
03/06/2023
L1557295-11 L1664839-03 L1592638-10 L1592638-11
11/10/2022 10/10/2023 03/06/2023 03/06/2023
TP-36 FILL TP-36-N20 TP-36E-10 TP-36S-10
Lab Sample ID Site Specific
Cleanup
Level
Client Sample ID
Date Collected
Lab Sample ID
Lab Sample ID Site Specific
Cleanup
LevelDate Collected
L1592638-01
TP-37N-10
03/06/2023
L1557295-15
TP-37 FILL
11/10/2022
Client Sample ID
L1668439-05
TP-37 FLOOR+3
10/19/2023
L1762797-01
TP-37S-20
8/1/2024
L1594306-03
TP-37W-15
03/06/2023
Table 2 - North Ditch Confirmation Samples
Redwood Road Dump VCP Site C121
1850 West Indiana Ave, Salt Lake City, Utah
Terracon Project No. 61237263
Depth
Analyte Method Units
SS
Screening
Level
Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
ARSENIC 6010B mg/kg 10.8 10.5 0.602 2.32 10.6 0.635 2.45 7.00 0.615 2.38 5.50 0.629 2.43 4.48 0.617 2.38 5.56 0.622 2.40
Depth
Analyte Method Units
SS
Screening
Level
Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL ResultQ MDL RDL
ARSENIC 6010B mg/kg 10.8 5.46 0.63 2.42 5.60 0.64 2.46 7.71 0.63 2.43 12.50 0.72 2.79 9.12 0.696 2.69 7.59 0.65 2.53 8.02 0.671 2.59
Depth
Analyte Method Units
SS
Screening
Level
Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL ResultQ MDL RDL
ARSENIC 6010B mg/kg 10.8 14.3 0.702 2.71 10.0 0.670 2.59 6.06 0.64 2.48 9.04 0.65 2.52 4.39 0.609 2.35 5.61 0.621 2.4 4.73 0.641 2.48
Depth
Analyte Method Units
SS
Screening
Level
Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL Result Q MDL RDL
ARSENIC 6010B mg/kg 10.8 8.93 0.634 2.45 6.02 0.593 2.29 3.34 0.617 2.38 2.58 0.619 2.39 6.43 0.624 2.41
J: The identification of the analyte is acceptable; the reported value is an estimate.
mg/kg:Milligrams per kilogram
Qualifiers:
Site-Specific Screening Level = 10.8 mg/kg for arsenic.
Color shaded value exceeds screening level
Date Collected 10/11/2023 10/11/2023 10/11/2023 10/10/2023
10/10/2023 10/10/2023 10/11/2023
10/10/2023
0-1 ft 0-1 ft 1 ft 1 ft 0-1 ft
0-1 ft 0-1 ft 0-1 ft 0-1 ft 0-1 ft 0-1 ft 1 ft
Client Sample ID ND - 330 N ND - 330 S ND - 330 Floor ND - 1500 Floor ND - 1500 S
10/11/2023 10/11/2023
Lab Sample ID L1665547-14 L1665547-15 L1665547-16 L1666599-01 L1666599-02
Date Collected 10/10/2023 10/19/2023
Client Sample ID ND-250 N ND - 250 North +3'ND-250 S ND-250 Floor ND - 300 S
10/10/2023 10/10/2023
Lab Sample ID L1664839-17 L1668439-03 L1664839-18 L1664839-19 L1665547-04 L1665547-05 L1665547-06
Date Collected 10/10/2023 10/10/2023 10/10/2023 10/10/2023 10/19/2023
ND - 300 N ND - 300 Floor
ND-200 Floor
0-1 ft 0-1 ft 1 ft 0-1 ft 0-1 ft 0-1 ft 1 ft
L1668439-04 L1664839-15 L1664839-16
Client Sample ID ND-150 N ND-150 S ND-150 Floor ND-200 N ND - 200 North +3'ND-200 S
Lab Sample ID L1664839-11 L1664839-12 L1664839-13 L1664839-14
Date Collected 10/10/2023 10/10/2023 10/10/2023 10/10/2023 10/10/2023 10/10/2023
0-1 ft 0-1 ft 1 ft 0-1 ft 0-1 ft 1 ft
Client Sample ID ND-50N ND-50S ND-50 Floor ND-100 N ND-100 S ND-100 Floor
L1664839-10Lab Sample ID L1664839-05 L1664839-06 L1664839-07 L1664839-08 L1664839-09
N
DESIGNED BY:
SCALE:
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FIGURE 1
001
61237263
10/28/24
1" = 80'
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LEGEND:
SLAB-ON-GRADE FOUNDATION WITH VAPOR
BARRIER MEMBRANE
VENTED CRAWL-SPACE FOUNDATION
SLAB-ON-GRADE FOUNDATION WITH VAPOR
BARRIER MEMBRANE AND SOIL GAS COLLECTORS
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