DERR-2025-008928

Stantec Consulting Services Inc.
2890 East Cottonwood Parkway

November 11, 2025
Project/File: CPL VCP Landfill Remediation 203723606
Division of Environmental Response and Remediation
David Bird
P.O. Box 144840
Salt Lake City, Utah
84114-4840
Dear David Bird,
Reference: CPL VCP Groundwater Monitoring
Based on our recent discussion at your offices, Stantec proposes collecting groundwater elevation data at
Cannon Pioneer Landfill. The data will be used to supplement the historical groundwater elevation data
records for the proposed remedial action plan development. This proposed groundwater data will be
expanded to include an additional thirteen former monitoring well locations not included in the September
2024 groundwater elevation mapping of the forty-three environmental monitoring wells. Additionally four
new groundwater monitoring piezometer wells will be installed, as shown on the attached Figure 2A to
address central areas interior to the CPL which do not have current monitoring locations. The intent of this
proposed monitoring of the current and new locations is to provide elevation data as it relates to the
location, extent, and depths of mounding of the shallow groundwater within the CPL particularly in the areas
of potential placement of the proposed new waste repository. This information is provided to you for your
input or comments you may have regarding this proposed collection of groundwater elevation data. We are
interested in doing this as soon as practically feasible.
Thank you,
Stantec Consulting Services Inc.

David K. Cline P.E.
Senior Environmental Engineer
Phone: Direct [phone]
stantec.com
Attachment: Figure 2A Potentiometric Groundwater Contours September 2024
cc. Luke Rothey, PRI;
Loyal Hume, KMC

S
5
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CPL-MW-22
CPL-MW-23
CPL-MW-24
CPL-MW-25
CPL-MW-34
CPL-MW-2
CPL-MW-32
CPL-MW-26
CPL-MW-33
CPL-MW-36
CPL-MW-21
CPL-MW-27
CPL-MW-8E
CPL-MW-6
CPL-MW-37
CPL-MW-30
CPL-MW-28
CPL-SV-4 CPL-SV-5 CPL-SV-6
CPL-SV-2
CPL-SV-1
CPL-SV-3
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MW-16
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MW-14
(B-07)MW-20
(B-08)
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(B-09)MW-15
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MW-7
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CPL-SE8
CPL-SW7
CPL-SE7
CPL-SW10
CPL-SE10
CPL-SW11
CPL-SE11
CPL-MW-44
CPL-MW-45
CPL-MW-40
PZ-07 PZ-06 PZ-05
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CPL-MW-39
CPL-MW-38
CPL-MW-47d
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CPL-MW-31
CPL-MW-9E
PZ-09
PZ-08
CPL-MW-35
MW-5
CPL-SW9
CPL-SE9
CPL-MW-46
CPL-MW-29
CPL-MW-51
CPL-MW-50
CPL-MW-49
CPL-MW-53
CPL-MW-52
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Areas of Ethylbenzene VISL exceedance
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SEPTEMBER 2024 GROUNDWATER
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SEPTEMBER 2024 INFERRED
GROUNDWATER ELEVATION
CONTOURS, FEET AMSL
0 750
1 INCH = 750 FEET
1,500
N
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GROUNDWATER MONITORING
WELLS TO BE SAMPLED
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SOIL VAPOR EXTRACTION
WELLS TO BE SAMPLED
CPL-SV-6
PROJECT SCREEING LEVELS (PSL)
(FOR COMPOUNDS EXCEEDING PSLs)
Arsenic (As) = 10 mg/L
Hexavalent Chromium (Cr6) = 0.11 mg/L
Nickel (Ni) = 390 mg/L
Copper (Cu) = 800 mg/L
Diesel Range Organics (DRO) = 1000 mg/L
Gasoline Range Organics (GRO) = 1000 mg/L
1,4 Dioxane = 0.46 mg/L
Benzene = 5 mg/L
Ethylbenzene = 700 mg/L
Vinyl Chloride (VC) = 2 mg/L
N-Nitrosodiphenylamine = 12 mg/L
BIS(2-Ethylhexyl)Phthalate = 6 mg/L
1-Methylnaphthalene = 0.0063 mg/L
NOTES:
ND = Non-Detect
mg/L = Micrograms per liter
(B) = Detection in method blank
As: 133 mg/L
1,4-Dioxane: 68 mg/L
DRO: 5050 mg/L
As: 42 mg/L
As: 68 mg/LAs: 23 mg/L
1,4-Dioxane: 174 mg/L
DRO: 1370 mg/L
As: 730 mg/L
1,4-Dioxane: 51 mg/L
As: 38 mg/L
1,4-Dioxane: 32 mg/L
As: 17 mg/L
DRO: 1080 mg/L
1,4-Dioxane: 38 mg/L
VC: 6 mg/L
1,4-Dioxane: 40 mg/L
Cr6: 1 mg/L
DRO: 1510 mg/L
Benzene: 7 mg/L
1,4-Dioxane: 39 mg/L
As: 194 mg/L
DRO: 5460 mg/L
GRO: 3640 mg/L
1,4-Dioxane: 256 mg/L
Ethylbenzene: 1490 mg/L
N-Nitrosodiphenylamine: 40 mg/L
Bis(2-Ethylhexyl)Phthalate: 11 mg/L
1-Methylnaphthalene: 0.26 mg/L
As: 366 mg/L
1,4-Dioxane: 37 mg/L
DRO: 1790 mg/L
As: 145 mg/L
1,4-Dioxane: 5 mg/L
1,4-Dioxane: 46 mg/L
DRO: 4150 mg/L
As: 543 mg/L
As: 12 mg/L
1,4-Dioxane: 5 mg/L
DRO: 2330 mg/L
1,4-Dioxane: 44 mg/L
VC: 8 mg/L
As: 154 mg/L
Ni: 569 mg/L
1,4-Dioxane: 2 mg/L
DRO: 3340 mg/L
1,4-Dioxane: 59 mg/L
1-Methylnaphthalene: 0.701 mg/L
As: 313 mg/L
Cr6: 0.3 mg/L
1,4-Dioxane: 14 mg/L
As: 16 mg/L
Cr6: 2 mg/L
1,4-Dioxane: 1 mg/L
1,4-Dioxane: 74 mg/L
DRO: 1080 mg/L
As: 28 mg/L
As: 11 mg/L
As: 358 mg/L
As: 10 mg/L
1,4-Dioxane: 5 mg/L
As: 15 mg/L
1,4-Dioxane: 9 mg/L
As: 58 mg/L
As: 22 mg/L
Cr6: 0.2 mg/L
As: 28 mg/L
As: 22 mg/L
Cr6: 3 mg/L
Areas of higher concentrations
SURFACE WATER
SAMPLE LOCATIONS
CPL-SW11
SEDIMENT SAMPLE
LOCATIONS
CPL-SE11
NORTHWEST AREA
NORTHEAST AREA
SOUTHEAST AREA
SOUTHWEST AREA
Areas of VC VISL exceedance
1,4-Dioxane: 2 mg/L
1,4-Dioxane: 3 mg/L
1,4-Dioxane: 1 mg/L
DRO: 3190 mg/L
1,4-Dioxane: 38 mg/L
As: 622 mg/L
As: 52 mg/L
Cr6: 0.22 mg/L
As: 16 mg/L As: 25 mg/L
1,4-Dioxane: 58 mg/L
As: 101 mg/L
Cu: 81 mg/L
1,4-Dioxane: 2.16/4.31(B) mg/L
1,4-Dioxane: 0.33/6.86(B) mg/L
DRO: 2680 mg/L
1,4-Dioxane: 29 mg/L
1-Methylnaphthalene: 0.081 mg/L
DRO: 1660 mg/L
1,4-Dioxane: 14 mg/L
1-Methylnaphthalene: 0.13 mg/L
Proposed new GW piezometer well
Pre-existing GW Monitoring well