DERR-2024-012441

Kelsey Robinson <[e-mail]>
Enbridge Gas Environmental Covenant Notification Letter
Kelsey Robinson <[e-mail]>Thu, Nov 14, 2024 at 3:48 PM
To: "[e-mail]" <[e-mail]>
Cc: "[e-mail]" <[e-mail]>, "[e-mail]"
<[e-mail]>
Hey Kris,
Perfect, thanks for clarifying on both of those.
We approve of this work that will be performed and let me know if there are any schedule updates.
Are you still planning on the sampling before the end of the year?
Additionally, if any contaminated soils are encountered or managed or the slurry wall is encountered during activities, please notify us.
Thank you,
Kelsey
On Thu, Nov 14, 2024 at 3:42 PM [e-mail] <[e-mail]> wrote:
Thanks Kelsey,

1. Yes, the outlet of the new box will need to be shallow in order to get the right slope to the existing drain box. So instead of
having a deep box with a shallow outlet they’re just going to make the box shallow for less disturbance.
2. SWP-3, SWP-4, and SWP-5 will be installed in the exact same location, so the abandonment is really pulling out and
replacing the existing piezo. SWP-1 and SWP-2 will be moved a few feet from their current location, so the current piezos will
be filled with bentonite and then paved over when the area is paved next year.

Hopefully that makes sense, let me know if additional info is needed.

Thanks again,

Kristopher Benson
Environmental
—

Cell: 801-349-6950
[e-mail]
1140 West 200 South, Salt Lake City, Utah, 84104
Safety. Integrity. Respect. Inclusion. High Performance.

From: Kelsey Robinson <[e-mail]>
Sent: Thursday, November 14, 2024 3:23 PM
To: Kris Benson (Enbridge UWI - 5) <[e-mail]>
Cc: [e-mail]; Todd P Kemp (Enbridge UWI - 5) <[e-mail]>
Subject: [EXTERNAL] Re: Enbridge Gas Environmental Covenant Notification Letter

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Hey Kris,

I have a couple minor questions:

1. Is the drain box only 1-foot deep? Just seems really shallow, so wanted to make sure I was understanding correctly.
2. Can you share the reasoning for the different types of abandonment methods outlined for the piezometers?

Thank you,
Kelsey

On Thu, Nov 14, 2024 at 11:45 AM [e-mail] <[e-mail]> wrote:
Ms. Robinson:
Please find the attached letter notifying Utah Department of Environmental Quality of subsurface excavation work in the
Environmental Covenant Area at the Enbridge Gas Salt Lake Operations Center. These projects are related to the installation of a
stormwater drain box and piezometer installation as part of the implementation of the Updated Operations and Maintenance
Manual – Salt Lake Operational Center North, as detailed in the attached notification.
Please let us know if we can proceed with this work. If you have any questions, please don’t hesitate to call.
Thank you,

Kristopher Benson
Environmental
—

Cell: 801-349-6950
[e-mail]
1140 West 200 South, Salt Lake City, Utah, 84104
Safety. Integrity. Respect. Inclusion. High Performance.

CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and or privileged
and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an

Enbridge Gas
1140 West 200 South
Salt Lake City, Utah 84104
United States

VIA EMAIL

November 14, 2024

Kelsey Robinson
Environmental Scientist
Utah Department of Environmental Quality
Division of Environmental Response and Remediation
168 North 1950 West
Salt Lake City, Utah 84116

RE: Environmental Covenant Questar Gas Salt Lake Operations Center –
Stormwater Drain Box/Line and Piezometer Installation

Dear Ms. Robinson:

Questar Gas Company (Questar), d/b/a as Enbridge Gas Utah (EGU), is providing a 30-
day notification to the Division of Environmental Response and Remediation (DERR) to
conduct excavation activities within the Salt Lake Operations Center Environmental
Covenant boundaries. The excavations will take place as part of the construction and
installation of a new stormwater drain box and line which will tie into an existing drain box
and the abandonment and replacement of five piezometers used for groundwater
monitoring. An overview of the Environmental Covenant boundaries is provided in Figure
1, planned excavation related to the stormwater drain system are shown in Figure 2, and
piezometer locations are shown in Figure 3. Project details are provided herein.

The drain installation will occur on the east side of the property (Figure 2). A new 2-foot
by 3-foot drain box will be installed to a depth of 12-inches below ground surface. A 4-
inch line will then run from the new drain box and tie into an existing drain box
approximately 45-feet away. The trench for the 4-inch drain line will be approximately 1-
foot wide and will go down to a maximum of 36-inches below ground surface. Following
installation of the new drain box and line clean, imported material will be used to backfill
the excavation. These excavation activities will not take place near the slurry wall. If
encountered, EGU will manage impacted soil for off-site disposal. Unimpacted spoils will
be stockpiled for future use.

EGU intends to replace five piezometers to support its Remedial Action Plan and
Operations and Maintenance Plan, approved by DERR on April 15th, 2024 and April 23rd,
2024, respectively. Piezometer installations will be completed by a 3rd party, State of Utah
licensed well drilling company between November 25th and November 27th, 2024. A total
Kelsey Robinson
November 14, 2024
Page 2 of 6

of five new shallow 1-inch piezometers (SWP-1, SWP-2, SWP-3, SWP-4 and SWP-5) are
proposed to be installed within the Environmental Covenant boundaries to a depth of
approximately 15-20 feet.
Existing piezometers SWP-3, SWP-4, and SWP-5 will be abandoned in place by removing
the existing well casing and filling the annulus with 10/20 silica sand below 7 feet and
bentonite chips to the surface. Following abandonment, new piezometers will be installed
within each of the existing well vaults. Existing piezometers SWP-1 and SWP 2 will be
abandoned in place with bentonite chips. The replacement SWP-1 and SWP-2 piezometers
will be installed adjacent to the former SWP-1 and SWP-2 vaults, and completed with
stickup casings and vehicular bollards.

Piezometers will be installed via direct-push using 3.75-inch direct-push rods. The total
depth of piezometers will be based on the depth to the confining layer at each location as
interpreted by the field geologist but is not anticipated to be deeper than approximately 20
feet. Piezometers will be screened from approximately 5-15 feet using 10-20 silica sand,
sealed to the surface with bentonite hydrated with fresh water. Following installation wells
and piezometers will be developed until water is visually clear or until 5 well volumes of
water are removed. Piezometer locations are included as Figure 3. Soil cuttings,
development water, and related wastes will be containerized for characterization and off-
site disposal at a permitted facility.

A EGU Environmental Compliance Coordinator (ECC) will lead a Health Hazard Advisory
(HHA) meeting with all involved personnel to review the property’s history and potential
health hazards for the day’s tasks prior to any work requiring ground disturbance. All
project personnel will be required to attend the HHA meeting and verify that they
understand the information provided. The ECC will remain onsite for the duration of the
ground disturbing work to perform continuous environmental monitoring and to ensure the
slurry wall is not encountered. The ECC will visually inspect excavated soils for signs of
contamination (odor, staining, discoloration, indication of free product or residuals) and
conduct atmospheric monitoring with a field-calibrated photoionization detector (PID), as
necessary. If any contaminated soils are encountered, they will be isolated, characterized,
and managed for appropriate off-site disposal.

The ECC will stop work if Action Levels specified in the Environmental, Health, Safety
and Site Management Plan (2.50 parts per million-volt) are exceeded. Work will re-
commence following the implementation of exposure controls and reduction in exposure
to contaminants in the breathing zone to below prescribed Action Levels. Upon completion
of the work, EGU will submit a report to UDEQ to provide information related to any
impacted materials encountered, laboratory analytical results, and waste generation and
disposal.

If you have any questions or concerns related to this notice, please contact me at 307-371-
0966 or [e-mail].
Kelsey Robinson
November 14, 2024
Page 3 of 6

Sincerely,

Adam Plonsky
Manager, Environmental Compliance
Kelsey Robinson
November 14, 2024
Page 4 of 6

Figure 1 – Salt Lake City Operations Center Overview Map

Kelsey Robinson
November 14, 2024
Page 5 of 6

Figure 2 – Proposed Ground Disturbance Area

Kelsey Robinson
November 14, 2024
Page 6 of 6

Figure 3 – Piezometer Locations