DERR-2024-006294

Stantec Consulting Services Inc.
2890 East Cottonwood Parkway
Suite 300
Salt Lake City UT 84121-7283
April 19, 2024
Project/File: 203721870
Nicole Chavez
Utah Department of Environmental Quality
Division of Environmental Response and Remediation
195 North 1950 West, First Floor
Salt Lake City, Utah 84116
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK
Ms. Chavez,
On behalf of 7-Eleven, Inc. (7-Eleven), Stantec Consulting Services Inc. (Stantec) proposes the following
work plan and budget to conduct an off-site source desktop study and four quarters of groundwater monitoring
at 7 Eleven Store No. 27074 (the Site), located at 3185 Harrison Boulevard, Ogden, Utah (Figure 1). The
Site is eligible for reimbursement under the Utah Petroleum Storage Tank (PST) Trust Fund. The scope of
work proposed herein would be designated as Work Plan and Budget (WP&B) NXK-07.
This work plan presents a technical approach and cost estimate to the Utah Department of Environmental
Quality (UDEQ), Division of Environmental Response and Remediation (DERR), for the following scope of
work: work plan preparation, project management, desktop study of potential off-site petroleum hydrocarbon
sources, four quarters of groundwater monitoring, and reimbursement services.
The purpose of the off-site source desktop study is to assess the need for further investigation of off-site
sources that may be contributing to the unexpected dissolved petroleum hydrocarbon concentration trends
following source area soil removal and well abandonment and replacement activities necessitated by the
Utah Transit Authority (UTA) construction along Harrison Boulevard. The purpose of quarterly groundwater
monitoring is to continue to evaluate dissolved petroleum hydrocarbon concentration trends and seasonal
groundwater level fluctuations at the Site.
BACKGROUND
7-Eleven began leasing the southern portion of the property in 1986 and operated a 7-Eleven convenience
store with former retail sales of gasoline. The former underground storage tank (UST) system was located
in the southeast side of the property (Figure 1) and consisted of three 10,000-gallon gasoline USTs and two
product dispensers formerly used to distribute various grades of unleaded gasoline fuel.
April 19, 2024
Page 2 of 6
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

The northern portion of the property is occupied by an out-of-service automotive service facility, most recently
In’ n’ Out Auto Clinic. The facility was previously operated as a Minit Lube, and a petroleum release from this
facility (Release Site IPT) was discovered during the closure of two 3,000-gallon new oil USTs and one 3,000-
gallon used oil UST on June 24, 1994. The former Minit Lube USTs were in the northwest portion of the
property (behind the automotive service facility) and were closed by removal.
Wasatch Environmental (Wasatch) conducted a limited subsurface investigation (LSI) on April 23, 2020, on
behalf of the Utah Transit Authority (UTA). Residual impacts from Release Site IPT appeared to be present
based on the analytical results of a groundwater sample collected from a temporary well-point within the
former UST basin (west of the current automotive service facility building). The sample contained
concentrations of total petroleum hydrocarbons as gasoline range organics (TPH-GRO) and TPH as diesel
range organics (TPH-DRO) above the Initial Screening Levels (ISLs) developed by the UDEQ-DERR Leaking
Underground Storage Tank (LUST) Section.
Based on the soil and groundwater analytical results of the LSI by Wasatch, a petroleum release from the
7-Eleven UST system was reported to the UDEQ-DERR on May 11, 2020. Soil and groundwater analytical
results presented in the Wasatch report indicated concentrations of petroleum hydrocarbon constituents at
the Site exceeding the ISLs and Tier 1 Screening Levels (TSLs) developed by the UDEQ-DERR LUST
Section. The groundwater samples collected by Wasatch were grab-type samples as only enough
groundwater was purged to improve the sample turbidity; three well volumes were not purged before
collection. Based on these results, the UDEQ-DERR assigned Release Site NXK to the Site and requested
a subsurface investigation
Under WP&B NXK-01, Stantec conducted the subsurface investigation on October 26 and 27, 2020 (with
groundwater sampling conducted on November 12, 2020). Benzene was reported exceeding the ISL in a
soil sample collected from the on-site boring advanced to install monitoring well MW-2. TPH-GRO was
reported exceeding the ISL in a soil sample collected from the off-site boring advanced to install MW-4.
Groundwater analytical results indicated dissolved concentrations of benzene, ethylbenzene, TPH-GRO, and
TPH-DRO exceeded their respective ISLs and/or TSLs in samples collected west and south of the UST basin
(MW-1, MW-2, MW-3, and MW-4), and groundwater impacts extended beyond the property boundaries to
the south.
The UST system was closed by removal on March 2, 2021. A remedial excavation was then completed from
March 3 through 5 under WP&B NXK-03. Petroleum containing soil (PCS) was removed from the UST
excavation as part of UST closure, and the excavation floor was extended an additional 1.5 to 2 feet beyond
the interface of backfill and native soils to remove additional PCS. Excavated soils were screened on site
using a photoionization detector, and PCS was segregated for disposal. Non-impacted soils were used as
backfill, and additional imported fill was also needed to fill and achieve compaction within the UST excavation.
Approximately 180-tons of PCS were disposed of as non-hazardous waste at the ET Technologies Soil
Regeneration Site at the Salt Lake Valley Landfill.
Under WP&B NXK-02, Stantec conducted quarterly monitoring between the second quarter of 2021 and the
first quarter of 2022. Dissolved petroleum hydrocarbon concentrations generally decreased during this time
but remained above ISLs in MW-1 and MW-4 and TSLs in MW-2.
April 19, 2024
Page 3 of 6
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

On April 8, 2022, Stantec oversaw the abandonment of groundwater monitoring wells MW-2, MW-4, MW-5,
and MW-6 to accommodate UTA BRT Project construction. Well abandonment activities were conducted
according to WP&B NXK-04.
As of fall 2022, UTA BRT Project construction had progressed to the point that replacement groundwater
monitoring well locations could be proposed. On February 7 and 8, 2023, Stantec oversaw the installation of
replacement groundwater monitoring wells MW-2R, MW-5R, MW-8, and MW-9 and conducted soil logging
and sampling activities. These activities were conducted according to WP&B NXK-05.
Four quarterly groundwater monitoring events were conducted between April 2023 and January 2024. These
activities were conducted according to WP&B NXK-06.
Due to the impacts of the UTA BRT project to the property, 7-Eleven ceased operations at this store in July
2023. The convenience store building is currently vacant. Stantec retains environmental access to manage
Release Site NXK.
Work conducted under WP&Bs NXK-01 through NXK-06 were previously reported to the UDEQ-DERR in the
following reports.
 Subsurface Investigation Report, 7-Eleven Store No. 27074, dated December 15, 2020.
 UST System Closure and Remedial Excavation Report, 7-Eleven Store No. 27074, dated April 28, 2021.
 Quarterly Groundwater Monitoring Report, 7-Eleven Store No. 27074 documents, dated August 2, 2021,
November 2, 2021, February 2, 2022, and May 2, 2022.
 Monitoring Well Abandonment Report, 7-Eleven Store No. 27074, dated July 8, 2022.
 Groundwater Monitoring Well Installation Report, 7-Eleven Store No. 27074, dated March 30, 2023.
 Quarterly Groundwater Monitoring Report, 7-Eleven Store No. 27074, dated April 24, 2023.
 Quarterly Groundwater Monitoring Report, 7-Eleven Store No. 27074, dated July 24, 2023.
 Quarterly Groundwater Monitoring Report, 7-Eleven Store No. 27074, dated October 24, 2023.
 Quarterly Groundwater Monitoring Report, 7-Eleven Store No. 27074, dated January 24, 2024.
SCOPE OF WORK
Task 1 – Work Plan Preparation
Task 1 includes the preparation of this work plan, including communication and coordination with UDEQ-
DERR. A Site-specific health and safety plan will also be prepared to address hazards associated with the
proposed scope of work.
Task 2 – Off-Site Source Desktop Study
Task 2 includes a desktop review of readily available databases to assess the possibility of off-site petroleum
hydrocarbon sources contributing to unexpected dissolved petroleum hydrocarbon concentration trends at
the Site. Since abandonment of MW-2, MW-4, MW-5, and MW-6 and installation of MW-2R, MW-5R, MW-8,
and MW-9, significant dissolved concentration fluctuations have been observed. These fluctuations are
April 19, 2024
Page 4 of 6
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

further complicated by the significant increase in TPH-DRO across the Site, and TPH-DRO concentrations in
upgradient wells which were previously below ISLs or the laboratory reporting limit. TPH-DRO concentrations
especially warrant research into off-site sources as 7-Eleven has not historically sold diesel at this location.
The recently completed UTA construction along with the accompanying changes to public utility corridors
may have enabled new contaminant migration onto the Site. Potential databases that will be included in the
off-site source desktop study include the UDEQ-DERR interactive map, historical aerial photographs, and
public utilities map resources.
Task 3 – Four Quarterly Groundwater Monitoring Events
Stantec will conduct four quarterly groundwater monitoring and sampling events for all seven on-site
monitoring wells. It is anticipated that seven groundwater samples (MW-1, MW-2R, MW-3, MW-5R, MW-7,
MW-8, and MW-9) and two quality assurance / quality control (QAQC) samples (one trip blank and a field
duplicate) will be collected and analyzed for a total of nine samples per quarter. It is Stantec’s understanding
that QAQC sample analyses are eligible for reimbursement under the Utah PST Trust Fund.
Prior to sampling, static groundwater levels will be gauged to the nearest one hundredth of a foot using a
battery-powered water level meter. Free product is not anticipated in any Site wells as it has not been
encountered during previous monitoring events and the UST system and source area soils have been
removed. A battery-powered product/water interface probe will be on hand incase strong hydrocarbon odors
are encountered during water level gauging. Stantec will not invoice 7-Eleven (and will therefore not seek
reimbursement on 7-Eleven’s behalf) for the product/water interface probe unless product is detected during
a given monitoring and sampling event.
Low recharge rates have been observed in Site wells during previous groundwater monitoring and sampling
events; therefore, Stantec utilized low-flow purging techniques during the execution of WP&B NXK-06.
Stantec proposes to continue low-flow sampling at the Site.
Wells will be purged via peristaltic pump at a rate low enough to limit drawdown within the well to one foot or
less. Groundwater quality parameters will be recorded on the appropriate time interval necessary to fully
replace the volume of the flow-through cell between readings. Purging will continue until three consecutive
readings are within the following stabilization parameters:
 pH +/-0.1
 oxidation reduction potential (ORP) +/-10 millivolts
 temperature 3%
 conductivity 3%
 dissolved oxygen (DO) 10% (or <0.5 mg/L)
 turbidity 10% (or <5 Nephelometric Turbidity Units [NTU]).
Sample tubing will be disconnected from the flow-through cell prior to sample collection. In instances where
a low enough purge rate cannot be achieved to limit drawdown to one foot or less, those wells will be purged
dry and allowed to recharge to at least 75% of the original water column height before sampling. The depth
April 19, 2024
Page 5 of 6
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

to groundwater at the time of sampling will be recorded for each well. Purged groundwater will be thin spread
on the surface near each well location. Groundwater samples will be collected in five 40-milliliter (mL) amber
glass volatile organic analysis (VOA) containers containing hydrochloric acid (HCl) preservative. VOAs will
be filled in a manner to minimize sample volatilization and remove all headspace.
Samples will be labeled with the sample identification, collection date, and time, and placed into an ice chilled
cooler for delivery to the project laboratory under chain-of-custody (COC) documentation. Samples will be
analyzed for TPH-GRO and methyl tertiary butyl ether, benzene, toluene, total xylenes, and naphthalene by
EPA Method 8260B; and TPH-DRO by EPA Method 8015 (the trip blank will not be analyzed for TPH-DRO).
All analyses will be performed by Pace Analytical National located in Mount Juliet, Tennessee.
Task 4 – Reporting
Following completion of each quarterly groundwater monitoring and sampling event, Stantec will prepare one
report documenting the results of the event. The reports will include current and historical groundwater
monitoring and sampling results tabulated in data summary tables, site plan, groundwater elevation contour,
and isoconcentration maps, conclusions and recommendations, and laboratory reports with associated chain-
of-custody documentation. The first quarterly groundwater monitoring report will also include the results of
the desktop study with recommendations for a path forward towards a more complete conceptual site model.
Task 5 – Reimbursement Services
Stantec’s services will include preparation of reimbursement claims on behalf of 7-Eleven. This task includes
assembling invoices paid by 7-Eleven, subcontractor invoices, details of charges, Stantec invoices, proof of
payment documentation, the UDEQ-DERR Standardized Invoice Form, and the UDEQ-DERR Request for
Payment Voucher Summary Worksheet. Stantec assumes at least two reimbursement claims will be
submitted under WP&B NXK-07.
ESTIMATED COSTS
The estimated costs for the scope of work described in this work plan are presented in Table 1. Non-
reimbursable costs, such as subcontractor markup, have been omitted from the cost breakdown. The costs
presented in Table 1 represent Stantec’s estimate of likely charges to be incurred during the implementation
of the scope of work described above. Actual charges to the tasks and activities included in the scope may
vary from those presented in the estimate as activities and tasks require either more or less effort than
estimated. Stantec will contact the UDEQ-DERR project manager if there is significant diversion from the
estimated cost breakdown, or if additional authorization above the total estimated cost of this work plan is
required.

April 19, 2024
Page 6 of 6
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

Should you have any questions or require any additional information, please contact Anna Skinner at
[phone].
Sincerely,
STANTEC CONSULTING SERVICES INC.

Anna Skinner
Project Manager
Certified Consultant #0271
Phone: [phone]
[e-mail]
Attachments: Figure 1 – Site Plan
Table 1 – Estimated Costs for WP&B NXK-07

April 19, 2024
Figure
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

FIGURE 1
Site Plan
MW-1
MW-3
MW-7
3200 SOUTH
HA
R
R
I
S
O
N

B
O
U
L
E
V
A
R
D
FORMER
CANOPY/
DISPENSERS
CONVENIENCE
STORE
BUILDING
AUTOMOTIVE
SERVICE
FACILITY
T
T
ELEVEN
FORMER
PLANTERPLANTER
UE
UE
UE
UE UE UE UE
UTILITY POLE
STREET LIGHT
PL
A
N
T
E
R
STORE NO. 27074
FORMER
UST BASIN
FORMER
SIGN
FORMER
PLANTER
FORMER
PLANTER
FORMER
PLANTER
FO
R
M
E
R
PL
A
N
T
E
R
MW-6
MW-2
MW-2R
MW-9
MW-8
MW-5R MW-5
MW-4
203721870 STA AMS JPW 03/20/23
1SITE PLAN
STORE #27074
3185 HARRISON BOULEVARD
OGDEN, UTAH
FOR:
JOB NUMBER:DRAWN BY:CHECKED BY:APPROVED BY:DATE:
FILEPATH:C:\Users\SAguinaldo\Desktop\2023\SLC\203721870\FIG 2_7-11_27074_SITE PLAN_03-20-2023.dwg | Layout Tab: 1 | Drafter: SAguinaldo | Mar 22, 2023 at 14:43
FIGURE:
No warranty is made by Stantec Consulting Services Inc. as to the accuracy, reliability, or completeness of these data. Original data were
compiled from various sources. This information may not meet National Map Accuracy Standards. This product was developed
electronically, and may be updated without notification. Any reproduction may result in a loss of scale and or information.
N
ELEVEN
PHONE:
2890 E COTTONWOOD PKWY, STE 300
SALT LAKE CITY, UTAH
[phone]
LEGEND
T
UE
MONITORING WELL LOCATION
TELEPHONE LINE
GAS LINE
OVERHEAD ELECTRICAL LINE
BELOW GROUND ELECTRICAL LINE
WATER LINE
0 30 60
APPROXIMATE SCALE IN FEET
ABANDONED MONITORING WELL LOCATION
April 19, 2024
Attachment 1
Reference: Work Plan and Budget for Off-Site Source Desktop Study and
Four Quarters of Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK

TABLE 1
Estimated Costs for WP&B NXK-07
Work Plan Preparation and Site-Specific HSSE
• Work Plan Preparation
Additional Groundwater Sampling 1 NTE @ $650 = $650
• Additional Health & Safety Plan 1 NTE @ $200 = $200
Work Plan and HSSE Subtotal $850
Off-Site Source Desktop Study
PM P103 40 hours @ $118 = $4,720
Field P104 4 hours @ $101 = $404
Off-Site Source Desktop Study Subtotal $5,124
Quarterly Groundwater Monitoring
• Field and Prep
PM P103 2 hours @ $118 = $236
Field Prep P104 2 hours @ $101 = $202
Field P104 7 hours @ $101 = $707
Field Travel P104 1.75 hours @ $101 = $177
• Equipment and Mileage
Mileage - 100 mile round trip 100 miles @ $0.67 = $67
Sampling Supplies 1 day @ $25.00 =$25
Water Level Meter 1 day @ $25.00 =$25
Peristaltic Pump 1 day @ $30.00 = $30
Sample Tubing 175 feet @ $0.50 =$88
Water Quality Meter 1 day @ $40.00 = $40
Traffic Safety Equipment 1 day @ $15.00 =$15
• Analytical
Water - EPA 8260B MBTEXN & TPH-GRO 9 samples @ $46.00 = $414
Water - EPA 8015 TPH-DRO 9 samples @ $28.00 = $252
Individual Groundwater Monitoring Event Subtotal $2,277
Quarterly Groundwater Monitoring Subtotal $9,109
Reporting
• First Quarterly Groundwater Monitoring Report with Summary of Off-Site Source Desktop Study
Senior PM P101 1 hours @ $152 = $152
Professional P102 2 hours @ $147 = $294
PM P103 10 hours @ $118 = $1,180
Field P104 4 hours @ $101 = $404
Drafter P107 2 hours @ $85 = $170
Admin P109 1 hours @ $62 = $62
First Report Subtotal $2,262
• Quarterly Groundwater Monitoring Reports Two, Three, and Four
Senior PM P101 1 hours @ $152 = $152
Professional P102 2 hours @ $147 = $294
PM P103 8 hours @ $118 = $944
Field P104 4 hours @ $101 = $404
Drafter P107 2 hours @ $85 = $170
Admin P109 1 hours @ $62 = $62
Remaining Individual Report Subtotal $2,026
Reporting Subtotal $8,340
Reimbursement
• PST Fund Claim Preparation
Senior PM P101 2 hours @ $152 = $304
PST Specialist P108 12 hours @ $78 = $936
Reimbursement Subtotal $1,240
Total Budget $24,663
c
Table 1
Desktop Study and Quarterly Groundwater Monitoring
7-Eleven Store No. 27074
3185 Harrison Boulevard, Ogden, Utah
Facility ID 1200120, Release Site NXK
Estimated Costs for WP&B NXK-07
c
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