DDW-2024-011198

September 24, 2024
Clint McAffee
Park City Water System
P.O. Box 1480
Park City, Utah 84060
Subject:Conditional Concurrence, PFAS and TDS Blending Plan, Park Meadows Well (WS005) and Divide Well (WS010); Park City Water System, System #22011, File #14923
This is not plan approval for construction.
Dear Clint McAffee:The Division of Drinking Water (the Division) received a blending plan for per-and polyfluoroalkyl (PFAS) and TDS compliance from you on May 31, 2023. The Division
informed you on June 28, 2023, that approvals of blending plans for PFAS would be delayed until the Environmental Protection Agency (EPA) passed the final regulation. A TDS blending
plan was approved by the Division on June 29, 2020, and amended on September 12, 2023. The contents of this letter do not modify the approval issued on September 12, 2023.
Background Information
On April 26, 2024, the EPA issued the first-ever national drinking water standard to protect communities from exposure to six PFAS compounds (PFOA, PFOS, PFHxS, HFPO-DA, and PFNA) through
the issuance of Maximum Contamination Levels or MCLs. The PFAS MCLs are legally enforceable limits for community and non-transient, non-community water systems. Water systems must complete
initial monitoring by April 26, 2027, and must be fully in compliance with the MCLs by April 26, 2029.
It is our understanding that the Park Meadows Well (identified as WS005 in the Division’s database), Middle School Well (WS007) and Divide Well (WS010) have PFOS and PFOA concentrations
ranging from 4 to 8.3 parts per trillion (ppt), above the MCL of 4 ppt for these compounds. The Division’s understanding is that the Middle School Well (WS007) is not included in the
proposed blending plan and will fall under the standard monitoring and reporting requirements of the PFAS MCL, with the initial monitoring deadline of April 26, 2027.
Park City Water System’s PFAS treatment and blending compliance was evaluated by your consultant, Water Quality and Treatment Solutions, Inc. Blending water from the Park Meadows Well
(WS005) and Divide Well (WS010) at the Creekside WTP (TP004) with the 3Kings WTP (TP015) sources, Judge Tunnel (WS001), Spiro Tunnel (WS006) and Thiriot Spring (WS001) that have no detectable
PFOS or PFOA, can be accomplished in pipe at the Boothill Vault before discharging into the Boothill Tanks (ST004, ST017), prior to any service connections.
Operational Strategy
The Creekside WTP (TP004) treats the Park Meadows Well (WS005) to meet surface water treatment rule requirements and provides chlorination to the Divide Well (WS010). The flows from
these two sources are metered and pumped into a dedicated transmission line to the Boothill Vault upstream of the Boothill Tanks. 3Kings WTP (TP015) is metered at the plant and pumped
into a dedicated line to the Boothill Vault as well. These two dedicated transmission lines connect inside of the Boothill Vault, where blending occurs, before the combined flows enter
the two Boothill Tanks (1-MG and 2-MG), which are hydraulically connected.
The PFAS blending compliance calculations take into account flows and concentrations, which will change based on plant production and which sources are operating. The blending mass balance
will be programmed into SCADA and will be monitored on the SCADA PFAS Calculator screen to ensure blending achieves PFAS levels below the MCLs. At the time of compliance monitoring,
the higher concentration measured of PFOS or PFOA will be used for the calculations below:
(Creekside WTP flow * Highest PFAS Compound Concentration) + (3Kings WTP flow * Highest PFAS Compound Concentration) = Combined Flow * X ppt (sampled at Boothill Vault blending location)
Estimated Blended Concentration:
PFOS
(1,000 gpm * 7.5 ppt) + (1,500 gpm * 0 ppt) = 2,500 gpm * X ppt
XPFOS = 3.0 ppt (below the MCL of 4.0 ppt)
PFOA
(1,000 gpm * 6.6 ppt) + (1,500 gpm * 0 ppt) = 2,500 gpm * Y ppt
YPFOA = 2.6 ppt (below the MCL of 4.0 ppt)
The Division has reviewed the PFAS Blending Plan for conformance with EPA’s PFAS National Primary Drinking Water Regulation published on April 26, 2024, and the applicable portions of
Utah’s Administrative Rules for Public Drinking Water Systems in R309 and conditionally concurs with the plan with the following stipulations:
The Division will be drafting a Utah PFAS rule. After the drinking water board approval, the Division will apply for primacy from the EPA. This process is anticipated to last approximately
two years. Monitoring and reporting requirements are subject to change based on the final adopted rule approved for primacy. In the absence of an approved final rule in Utah, the following
requirements are anticipated, but not guaranteed, to meet future requirements.
Per EPA’s PFAS National Primary Drinking Water Regulation published on April 26, 2024, monitoring schedule requirements and compliance with the MCLs will be determined based on the most
recent sample results obtained as of the April 2027 initial monitoring deadline.
Compliance with the PFAS standards will be based on the samples collected from the PFAS blending compliance point representing the combined flows of water treated at the Creekside WTP
(TP004) and the 3Kings WTP (TP015). The compliance point has been given a facility ID of TP016 and is named “Boothill Tank TDS/PFAS Blend.” The Boothill Tank TDS/PFAS Blend is the sample
tap located within the boothill vault shortly downstream of the blend point, prior to entry into the boothill tanks. Please label all samples collected from this location as TP016 for
both the facility and sample point ID.
The water system must take one PFAS sample at the Boothill Tank TDS/PFAS Blend (TP016) and at the effluent of the Creekside WTP (TP004) at a minimum of once per quarter for a year.
The water system must keep accurate weekly water produced data for both the Creekside WTP (TP004) and the 3Kings WTP (TP015).
Using the water-produced data, the water system shall submit a quarterly report to the Division documenting how much water was produced from each treatment plant using the enclosed template.
The quarterly report is due by the 10th day following the end of each quarter (i.e. January 10th, April 10th, July 10th and October 10th). Please send the report to [e-mail].

After completion of a year of data collection as outlined above, the Division will evaluate the data and issue a formal approval of the blending plan if the results are satisfactory.
Ongoing monitoring and reporting requirements will be determined at that time. Park City Water System is responsible for completing the required initial monitoring prior to the April
2027 deadline established in the EPA’s PFAS MCL requirements.
Please maintain a copy of this letter with your permanent records for future reference.
For questions regarding PFAS monitoring and reporting, please contact Sarah Romero, P.E., of this office at [phone].
If you have any questions regarding this concurrence, please contact Julie Cobleigh, P.E., of this office, at [phone], or me at [phone].
Sincerely,
Michael Newberry, P.E.

Permitting and Engineering Support Manager
JJC/SEP/mrn/mdbEnclosures –Quarterly Blending Reports Templatecc:Nathan Brooks, Summit County Health Department, [e-mail] DeHaan, Park City Water System, [e-mail]
McAffee, P.E., Park City Water System, [e-mail] Cobleigh, P.E., Division of Drinking Water, [e-mail]
David Kruse, Division of Drinking Water, [e-mail]
Sarah Page, Ph.D., Division of Drinking Water, [e-mail]
Sarah Romero, P.E., Division of Drinking Water, [e-mail]
John Steffan, Division of Drinking Water, [e-mail]
jcobleigh 22011 14923 Blending Plan