DDW-2024-007056

April 5, 2024
Jex Jensen
Pacificorp Huntington Plant
P.O. Box 680
Huntington, Utah 84528
Subject:Exception Request Denied, Exception to Rule R309-515-6(6), Well Materials, Design, and Construction and Huntington Well (WS001) and Huntington Well Backup (WS002)Under the Direct
Influence of Surface Water (UDI);
Pacificorp Huntington Plant, System #08034, File #13626
This is not Plan Approval for construction.
Dear Jex Jensen:
On February 12, 2024, the Division of Drinking Water (the Division) received a request for an exception to R309-515-6(6)for the Huntington Well (WS001) and Huntington Well Backup (WS002).
The specific part of the rule mentioned in the request is R309-515-6(6)(i) Well Sealing Techniques and Requirements. This rulespecifically requires that for all public drinking water
wells, the annulus between the outermost well casing and the borehole wall shall be sealed with grout to a depth of at least 100 feet below the ground surface unless an "exception" is
issued by the Director (see R309-500-4(1)).
Background
Both wells for the Huntington Power Plant water system are drilled to a depth of 80 feet. The Huntington Well (WS001) was drilled in 1980 and has a 30-foot neat cement grout seal. The
Huntington Well Backup (WS002) was drilled in 2016 and has a 30-foot bentonite grout seal.
The microfiltration plant was installed in 1998. A project file was opened in 2015 to permit and approve the treatment plant. This process corresponded with the submission of plans and
specifications for the Huntington Well Backup (WS002). The permitting process for the
Huntington Well Backup (WS002) and the microfiltration plant were never completed. Russell Seeley, the then DEQ Southeast District Engineer, rediscovered the treatment plant during the
2021 sanitary survey.
Exception Request Denied to R309-515-6(6)(i)
You based your request for an exception to rule R309-515-6(6)(i) Well Sealing Techniques and Requirements on the following:
Water samples taken from Huntington Well Backup in 2023 met drinking water standards and historical water quality data have not shown water quality violations.
The main aquifer in the region of the Huntington Power Plant is a shallow, unconfined, alluvial aquifer. Below approximately 100 feet, Mancos Shale is present, which is not known as
a productive aquifer.
Other wells have been granted exceptions to this rule for similar shallow aquifer issues.
Although available water samples taken from the Huntington Well and Huntington Well Backup have met drinking water standards, the bacteriological test for the Huntington Well (WS001)
from 1980 shows an unsatisfactory result without additional source samples submitted to indicate otherwise. Further, it was indicated in the draft operating permit from 2016 that the
Division was planning on declaring both wells to be Low Quality Groundwater Sources.
Both wells only have sanitary seals to 30 feet and the log for the Huntington Well indicates that little to no clay was encountered in the uppermost 30 feet. The Well Driller’s Report
for the Huntington Backup Well indicates that clay was encountered but it was mixed with gravel and cobbles. The other Well Driller’s Reports provided in your request also show little
to no clay in the uppermost 30 feet of the aquifer. Additionally, the Huntington Well Backup has a bentonite grout seal, which does not meet the acceptable materials for a well seal
under the requirements of rule R309-515-6(6)(i)(ii) without prior approval from the Division's Director.
While the Division has granted exceptions to R309-515-6(6)(i) for other well sources in the state, each exception request is unique and based on many factors. Regarding Magna’s Barton
and Haynes’ wellfields, the conditions encountered during drilling do not match the conditions at the Huntington Power Plant. The Magna wells encountered more than 30 feet of impermeable
clay opposite their sanitary seals. In addition, the source protection zones for these wells are almost entirely located within the “discharge zone” as mapped in the report titled Hydrogeology
of Recharge Areas and Water Quality of the Principal Aquifers Along the Wasatch Front and Adjacent Areas, Utah; United States Geological Survey Water Resources Investigations Report
93-4221, published in 1994. In this report, the USGS mapped the secondary recharge and discharge areas based on dominantly clay layers, 20 feet thick or more. If a well and its accompanying
drinking water source protection zone two are completely within the secondary recharge area or discharge area as mapped by the USGS, staff consider that sufficient evidence to demonstrate
the lateral continuity of the clay layer to the extent of source protection zone two. Again, source protection zones one through four for the Magna wells are almost entirely located
within the discharge zone, indicating that at least 20 feet of laterally continuous clay is present in the subsurface. These conditions are not similar to the ones encountered in the
Huntington Well and Huntington Well Backup.
Therefore, the wells, as currently constructed, are not equally protective of public health and an exception to R309-515-6(6)(i) Well Sealing Techniques and Requirements is hereby denied.UDI
Notification
The Division of Drinking Water (“the Division”) has determined that the Huntington Well (WS001) and the Huntington Well Backup (WS002) are under the direct influence of surface water
(UDI). The Division designated the source as UDI based on the shallow grout seal that does not meet requirements of R309-515-6(6)(i) for “...grout to a depth of at least 100 feet below
the ground surface…”
As of the date of this letter, the Huntington Well and Huntington Well Backup(identified as WS001 and WS002 in the Division’s database, respectively) is classified as being under the
direct influence (UDI) of surface water.
This water system is required to take the following actions within the following time frames due to this drinking water source being classified as UDI and posing significant risks to
public health.
Required Immediate Actions
You must take the following actions immediately:Notify your water users per the attached public notice protocol.Enact one of the following temporary measures (until a permanent solution
is implemented):Turn the source out of the drinking water system.Issue a boil order or supply bottled water to your customers.Install and operate disinfection facilities to achieve 3-log
inactivation of Giardia lamblia per federal Surface Water Treatment Rule (40 CFR §141.72).If this water system currently does not have the ability to achieve the treatment goal of 3-log
Giardia lamblia inactivation, this option would require submittal of plans and specifications of a proposed disinfection facility to the Division for review and approval. The design
must be signed and stamped by a professional engineer. The proposed design must identify the degree of disinfection in terms of disinfection CT (Disinfectant Residual Concentration in
ppm × Contact Time in minutes) and inactivation log credit. For example, to achieve 3-log inactivation of Giardia cysts at free chlorine residual of 0.5 ppm, water pH of 7 and temperature

at 0.5 oC, the required disinfection CT is 210, which would require at least 420 minutes of contact time. Such significant contact time sometimes cannot be achieved with a water system’s
existing configuration. In such cases, a water system may need to make costly modifications in order to achieve the required 3-log Giardia inactivation. Please note that modifications
to existing drinking water facilities also need to go through the Division’s engineering review process. The implementation time of this temporary option (Option c) may be similar to
that of a permanent solution.Please contact Dani Zebelean at [phone]for questions related to engineering review.Required Action within 30 DaysNotify the Division in writing within
30 days of the date of this letter what your decisions are regarding this water source.
If your decision is to continue using the Huntington Well (WS001) and the Huntington Well Backup (WS002) for drinking water, you will be required to immediately comply with the following
requirements:
Begin collecting water samples from this source prior to any treatment for Escherichia coli (E. coli) analysis. The E. coli sampling shall be done either once a month for two years or
once every two weeks for one year. A total of twenty four (24) E. coli samples are required per the federal Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). These samples
will be used to determine the bin classification of the source water and the degree of required treatment for Cryptosporidium.
Take monthly bacteriological samples from a representative site in the distribution system.
Take nitrate samples on a quarterly basis from this source.
Submit monthly disinfection reports to the Division.
You may also be required to monitor for disinfection by-products (DBPs). Please contact Mark Berger at [phone] or [e-mail] for DBPs questions.Required Actions within 18
MonthsWithin 18 months of the date of this letter, you must implement one of the following permanent solutions:Abandon the Huntington Well (WS001) and the Huntington Well Backup (WS002)
as a drinking water source permanently by physically disconnecting it from your water system.Have installed and be operating an approved surface water treatment facility that successfully
treats this source and meets the surface water treatment requirements.Complete remediation of the source to eliminate the surface water influence. In some cases, geological conditions
might make it impossible to exclude surface water influence and the expense of the remediation could be futile. We recommend that you consult with a hydrogeologist first before pursuing
this option.Options 2 and 3 must go through the Division’s Plan Approval process including issuance of an Operating Permit. Additional drinking water source protection requirements will
apply if Option 2 is implemented, in accordance with R309-600-3(3) and R309-605-8.
We appreciate your immediate attention to this matter. Please notify the Division in writing, within 30 days of the date of this letter, what your decisions are regarding this source.
If you have questions or need further assistance regarding this letter, please call Dani Zebelean at [phone], or Michael Newberry, Permitting and Engineering Manager, at (385)
515-1464
For more details about this designation, what it means, and its consequences see the attached UDI Definition and Possible Causes.
Sincerely,
Nathan Lunstad, P.E.
Division Director
DZ/DLB/mrn/mdbEnclosure:UDI Public Notice TemplateUDI Definition and Possible Causescc:Orion Rogers, Southeast Utah Health Department, [e-mail] Jones, Hansen Allen and Luce,
[e-mail] Hopkins, Hansen Allen and Luce, [e-mail] Jensen, Pacificorp Huntington Plant, [e-mail] Lewis, Pacificorp Huntington
Plant, [e-mail] Shakespear, Pacificorp Huntington Plant, [e-mail] Guthrie, Pacificorp Huntington Plant, [e-mail]
Huntsman, Pacificorp Huntington Plant, [e-mail] Wheeler, Pacificorp Huntington Plant, [e-mail] Zebelean, Division of Drinking Water,
[e-mail] Federico, Division of Drinking Water, [e-mail] Smith, Division of Drinking Water, [e-mail] Page, Division of Drinking Water, [e-mail]
Source Assessment Team, Division of Drinking water, [e-mail] Yee, Division of Drinking Water, [e-mail] Seeley, Division of Drinking Water, [e-mail]
DZebelean 08034 13626 Exception Denied R309-515-6(6) and UDI Notification WS001 and WS002Instructions for Notice for a UDI Source as Tier 1 Template on ReverseThe Division of Drinking
Water has designated a source used by this water system is under the direct influence of surface water. Continued use of this source has a significant potential to have serious adverse
effects on human health as a result of short-term exposure (R309-220-5(1)(h):. In such cases, you must issue a notice within the next 24 hours. You should also coordinate with your local
health department. You must use one or more of the following methods to deliver the notice to consumers (R309-220-5(3)):RadioTelevisionHand or direct deliveryPosting in conspicuous locationsYou
may need to use additional methods (e.g., newspaper, delivery of multiple copies to hospitals, clinics, or apartment buildings), since notice must be provided in a manner reasonably
calculated to reach all persons served. If you post or hand deliver, print your notice on letterhead, if you have it.The notice on the reverse is appropriate for hand delivery or a newspaper
notice. However, you may wish to modify it before using it for a radio or TV notice or posting. If you modify the notice, you must leave the health effects language in italics unchanged.
This language is mandatory (R309-220-8(4)).Population ServedMake sure it is clear who is served by your water system--you may need to list the areas you serve.Corrective ActionIn your
notice, describe corrective actions you are taking. Listed below are some steps commonly taken by water systems with a source determined to be under the influence of surface water. Use
one or more of the following actions, if appropriate, or develop your own:We have taken the source which is under the direct influence of surface water out of service until appropriate
treatment can be installed.We have abandoned the source which is under the direct influence of surface water.We have installed and are operating disinfection facilities to achieve 3-log
inactivation of Giardia lamblia.Source of the ProblemIf you know why the turbidity is high, explain it in your notice. For instance, unusual conditions, such as heavy rains and flooding,
can overburden the water plant, and treated water may therefore not meet the standards. In addition, run-off from parts of the watershed could contain increased concentrations of sediment
and animal waste.After Issuing the NoticeSend a copy of each type of notice and a certification that you have met public notice requirements to the Division of Drinking Water (PO Box
144830, SLC, UT 84414-4830) within ten days after you issue the notice (R309-105-16(3)). It is a good idea to issue a problem corrected notice when the violation is resolved. It recommended
that you notify health professionals in the area of the violation. People may call their doctors with questions about how the violation may affect their health, and the doctors should
have the information they need to respond appropriately. In addition, health professionals, including dentists, use tap water during their procedures and need to know of potential microbiological
contamination so they can use bottled water.DRINKING WATER WARNING[system] has a source designated as Under the Direct Influence of Surface WaterBOIL YOUR WATER BEFORE USINGThe Division
of Drinking Water has designated a source used by this water system is under the direct influence of surface water. Continued use of this source has a significant potential to have serious
adverse effects on human health as a result of short-term exposure. Because of the surface water influence to your source, there is an increased chance that the water may contain disease-causing
organisms.What should I do?DO NOT DRINK THE WATER WITHOUT BOILING IT FIRST. Bring all water to a boil, let it boil for one minute, and let it cool before using, or use bottled water.
Boiled or bottled water should be used for drinking, making ice, washing dishes, brushing teeth, and food preparation until further notice.Sources under the direct influence of surface
water may contain disease-causing organisms. These organisms include bacteria, viruses, and parasites, which can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.
People with severely compromised immune systems, infants, and some elderly may be at increased risk. These people should seek advice about drinking water from their health care providers.The
symptoms above are not caused only by organisms in drinking water. If you experience any of these symptoms and they persist, you may want to seek medical advice.What happened? What is
being done?[Describe the system future plan for the source, corrective action, and when the system expects to return to compliance.]We will inform you when you no longer need to boil
your water.For more information, please contact [name of contact] at [phone number] or [mailing address]. General guidelines on ways to lessen the risk of infection by microbes are available

from the EPA Safe Drinking Water Hotline at 1(800) 426-4791.Please share this information with all the other people who drink this water, especially those who may not have received this
notice directly (for example, people in apartments, nursing homes, schools, and businesses). You can do this by posting this notice in a public place or distributing copies by hand or
mail.This notice is being sent to you by [system].Water System ID#: ___________. Date distributed: ___________.
UDI Definition and Possible Causes
A groundwater source that is Under the Direct Influence of surface water (UDI) is vulnerable to contamination by pathogens found in surface water. This vulnerability could be because
the sub-surface formation is not sufficiently filtering water as the water percolates through the formation or because the groundwater collection infrastructure is poorly constructed
and allows surface water to directly contaminate the groundwater. The Division of Drinking Water’s protocol determines and classifies a groundwater source as UDI based on one or more
of the following factors:
Physical evidence of source deficiencies that allow, or have the potential to allow, surface water contamination of the source
MPA sampling results indicating surface water influence:
One high-risk MPA sample result
Two consecutive moderate-risk MPA sample results
Inconclusive MPA sample results, such as alternating low-risk and moderate-risk results, along with other water quality data or observations of the source that indicate potential contamination
by surface water
Water quality data indicating contamination by surface water, e.g., E. coli positive source sample results not caused by physical deficiencies, detection of Cryptosporidium or Giardia
in the source water.
An MPA test (Item #2) consists of running the source water through a spiral-wound filter for a period of the time. Particles collected by the filter are extracted in a laboratory, examined
under a microscope, and identified. Particles that are expected to be found only above ground or in surface water indicate a risk of surface water contamination. Such indicators include
chlorophyll-bearing algae, parts of flying insects, plant debris, Cryptosporidium,Giardia lamblia, etc. Some of these indicators are not pathogens, but their presence in the source water
means it is susceptible to contamination by pathogens found in surface water.
An MPA sample is rated as having a low, moderate, or high risk of UDI if the score is 0-9, 10–19, or 20 and above, respectively. When basing the classification of a groundwater source
on MPA results, the Division protocol classifies a source as UDI if any MPA sample is high risk or if any two MPA samples are moderate risk or above.
The path that surface water takes as it flows to a groundwater source can and usually does vary with season and hydrogeological conditions. It is common for the flow path to be directly
influenced by surface water under some conditions (such as during a high surface runoff during spring), but not to be directly influenced under others. So, a surface-water-influenced
water source may have MPA sample results of various risk levels, depending on the timing of the sampling. A true groundwater source that is not under the direct influence of surface
water will always have only low-risk MPA results.