DDW-2025-005010

June 2, 2025
Sent via Email Only
Matthew Lee MacKay
Zion Canyon Water System
Zion National Park, State Road 9
Springdale, Utah 84767
[e-mail]
Subject:Approval, Discontinuation of Surface Water Treatment and Monitoring and Reporting at Birch Creek-Watercress Treatment Plant (TP001), Lower Grotto Treatment Plant (TP003), and
Upper Grotto Treatment Plant (TP004); Zion Canyon Water System, System #27051,File #21722
Dear Matthew MacKay:
The Division of Drinking Water (the Division) received a request from you on May 12, 2025, to discontinue surface water treatment and monitoring and reporting at the Birch Creek-Watercress
Treatment Plant (TP001), the Lower Grotto Treatment Plant (TP003), and the Upper Grotto Treatment Plant (TP004). The Division issued Plan Approval for the treatment plants on April 12,
2021. The Division then issued an operating permit for the treatment plants on May 13, 2024.
Project Background
The treatment plants were first reviewed under plan review file #11908. Our understanding of the project was that unapproved bag filters were observed during the Zion Canyon Water System’s
(the System) 2019 sanitary survey. The Division’s compliance actions prompted the National Park’s engineers to complete a formal review for the water system. During the review, the National
Park’s engineers proposed the redesign to provide adequate treatment should any of the source waters in the future be classified as groundwater under the direct influence of surface
water (GWUDI). Inadequate bacteriological data was available at the time of plan review to determine if disinfection or surface water treatment was required for the Birch Springs (WS001),
Watercress Springs (WS002), Lower Grotto Springs (WS003), and Upper Grotto Springs (WS004).
At the time of issuing the Operating Permit, the System completed source assessment monitoring for the Birch Springs (WS001), Watercress Springs (WS002), Lower Grotto Springs (WS003),
and Upper Grotto Springs (WS004) which demonstrated that the springs would remain classified as groundwater sources. However, the System voluntarily agreed to comply with surface water
treatment monitoring and reporting requirements. After running the treatment plants as surface water treatment plants for the past year, the System has requested to discontinue surface
water treatment monitoring and reporting.
Approval to Discontinue Surface Water Treatment and Monitoring and Reporting
The System’s plan is to replace the Harmsco HC/170-LT2 cartridges with the Harmsco HC/170-1 prefilters in the Birch Creek-Watercress Treatment Plant (TP001), Lower Grotto Treatment Plant
(TP003), and Upper Grotto Treatment Plant (TP004). Each treatment plant has two trains currently consisting of three filter canisters with one Harmsco HC/170-1 and two Harmsco HC/170-LT2
filters in series. With this approval all three filter canisters for each train will have three Harmsco HC/170-1 filters in series. The Division agrees that this is sufficient for the
System to discontinue surface water monitoring and reporting. As of the date of this letter, the System is no longer required to submit monthly surface water treatment reports. The System
will still be required to do chlorination reports quarterly as discussed below.
Secondary Disinfection Requirements
The Systemis required to demonstrate ongoing compliance with the secondary disinfection requirements outlined in Addendum 1 of this letter as long as the Birch Creek-Watercress Treatment
Plant (TP001), Lower Grotto Treatment Plant (TP003), and Upper Grotto Treatment Plant (TP004) are in operation. The System is required to meet secondary disinfection requirements as
outlined in the letter dated July 3, 2023.
If you have any questions regarding this Operating Permit, please contact Dani Zebelean, P.E., of this office, at [phone], or Michael Newberry, P.E., Permitting and Engineering
Support Manager, at [phone].
Sincerely,
Russell Seeley, P.E.
Assistant Director
DZ/mrn/mdbcc:Jeremy Roberts, Southwest Utah Public Health Department, [e-mail] MacKay, Zion Canyon Water System, [e-mail] Bell, Zion Canyon Water
System, [e-mail] Stout, Zion Canyon Water System, [e-mail] Wright, DEQ Southwest District, [e-mail] Zebelean, Division of Drinking Water,
[e-mail] Page, Division of Drinking Water, [e-mail] Treutel, Division of Drinking Water, [e-mail] Federico, Division of Drinking Water, [e-mail]
27051 21722 Approval to discontinue SWT
Addendum 1 
 Secondary Monitoring and Reporting Requirements 
Chlorine Monitoring & Reporting Requirements
The water system is required to meet secondary disinfection requirements. As a part of these requirements, the water system is required to continuously maintain a minimum free chlorine
residual at each chlorinator Point of Entry (POE) into the system and demonstrate a detectable chlorine residual in the distribution system. 
Please contact Luke Treutel at [phone] or [e-mail] with any questions relating to these disinfection monitoring and reporting requirements.
Secondary Disinfection Requirements and Reporting 
Chlorine Residual ‒ Point of Entry (POE) to Distribution System
The POE sampling locations are identified as EP001 and EP003 in the Division’s database.
EP001 is the online chlorine analyzer for the Birch Creek-Watercress Treatment Plant (TP001).
EP003 is the online chlorine analyzer for the combined water coming from the Lower Grotto Treatment Plant (TP003) and Upper Grotto Treatment Plant (TP004).
Maintain a minimum of 0.2 mg/L residual (measured as free chlorine) at the POE sampling locations. [R309-215-16(3)(b)(iii)(A)(I) and (II)]
The chlorine residual concentration measured at the POE sampling locations shall not exceed the maximum residual disinfectant level (MRDL) of 4.0 mg/L (measured as free chlorine). [R309-200-5(3)(c)(iv)]
Record and report the lowest daily value of chlorine residual measured as free chlorine at POE sampling locations (EP001 & EP003). [R309-210- 8(3)(a)(ii)]
Our records show that your water system serves 3,380 people. Please be aware that R309-215-16(3)(b)(iii)(A)(I) requires water systems serving greater than 3,300 people to continuously
monitor the POE chlorine residuals. Therefore, an online analyzer to continuously monitor the POE chlorine residuals entering the distribution system will be needed.
Chlorine Residual ‒ Distribution System (DS001)

This water system must maintain a detectable residualthroughout the distribution system. It is recommended to maintain the chlorine residual above 0.1 ppm in the distribution system.
[R309-520-5]
The chlorine residual measured in the distribution system shall not exceed the maximum residual disinfectant level (MRDL) of 4.0 mg/L (measured as free chlorine). [R309-200-5(3)(c)(iv)]
This water system must take a minimum of three (3) chlorine residual samples per weekat varying locations throughout its distribution system (DS001). [R309-105-10(1)(c)]
Distribution system chlorine residuals must be taken in conjunction with total coliform sampling. [R309-215-10(3)]
Disinfection Report Submission
To demonstrate ongoing compliance with secondary disinfection requirements, the water system must complete monthly operational reports for each active chlorinator using a template approved
by the Division. 
The monthly operational reports are submitted quarterly. The reports are due to the Division by the 10th day following the end of each reporting quarter (i.e., January 10th, April 10th,
July 10th and October 10th). The reports can be submitted by hardcopy, fax, or by uploading them to the Division’s chlorine residual reporting form which can be found at MRDL.utah.gov.
Please contact Luke Treutel at [phone] or [e-mail] to schedule training regarding proper reporting.
In addition to monthly disinfection reporting, this water system must submit the monthly average of chlorine residual samples taken in the distribution system. Distribution system chlorine
residual monitoring results are due quarterly by the same compliance dates as the monthly disinfection report and can be submitted via an online form found at mrdl.utah.gov. 
Records must be maintained for a minimum of 5 years. [R309-105-17(1)]