DDW-2025-009276

October 2, 2025
Sent via Email Only
Cory Hatch
Manti City
50 South Main
Suite #1
Manti, Utah 84642
[e-mail]:Concurrence, Preliminary Design Report for Manti City Membrane Plant;Manti City, System #20005, File #13620
This is not Plan Approval for construction.Dear Cory Hatch:The Division of Drinking Water (the Division) received the Preliminary Design Report for an ultrafiltration surface water treatment
plant from your consultant Benjamin Coray, P.E., on August 22, 2025. The Division granted the membrane pilot study waiver on April 18, 2024.
Our understanding of the project is that Manti City is planning to construct a membrane surface water treatment plant to treat the flows from the Cold Spring (WS002), Middle Fork Spring
(WS003), Sister Spring (WS004), Milk Creek Spring (WS005), Hougaard Spring (WS006), North Slope Spring (WS007), Big Spring (WS008), and Deer Trail Spring (WS009). Only the Sister Spring
(WS004) and Big Spring (WS008) are determined to be under the direct influence of surface water. However, all the springs combine and run through a hydroelectric power plant. Manti has
made the decision to treat all of their spring flows through the proposed membrane surface water treatment plant. Manti City was granted a pilot study waiver to design the surface water
treatment plant using the Toray or Asahi membrane modules based on operational data from the Mount Pleasant, Monroe, and Garden City water systems.
Based on the Preliminary Design Report, Manti City selected to design the plant with the Toray HFUG-2020HN membrane modules. It is the Division’s understanding that the HFUG-2020HN filter
components are identical to the HFUG-2020AN packaged in a different housing that is rated for higher pressure. The preliminary design report proposes the following for Manti’s new membrane
surface water treatment plant:
The membrane surface water treatment plant will initially be installed with two (2) filtration skids with space for a third future skid.
Initially, forty-three (43) modules will be installed on each of the skids with the possibility of expanding to fifty-six (56) modules per skid in the future. Each module will have a
membrane area of approximately 969 ft2. Based on WesTech reports at 5oC the modules have an instantaneous flux of 39.5 gallons per square foot per day (gfd), a normalized flux at 20oC
of 60.2 gfd, and a maximum normalized flux of 98.5 gfd.
Each skid will initially have a capacity of 1,000 gallons per minute (gpm). That can be expanded to 1,200 gpm with the full fifty-six (56) modules installed. Due to redundancy requirements
in R309-530-8(8)(b)(i), A membrane filtration facility that provides the sole source of water to a water system shall be capable of meeting peak day demand at the lowest feedwater temperature
when the largest membrane unit is out of service by providing either: one redundant membrane unit or multiple membrane units with excess treatment capacity for each unit at maximum design
flux, the membrane treatment plant will be credited with a 1,000 gpm source capacity credit to be used in source and storage capacity calculations.
Based on Westech estimates approximately 1,258 gpm will be required for the backwash flow rate, for a total of 27,120 gallons per day required for backwashing. Using a design production
rate of 1.44 million gallons per day, the expected water recovery is 96.1%.
The preliminary design report establishes parameters for a full-scale treatment facility that meets the requirements of Rule R309-530-8.We hereby concur with the preliminary design report
for the proposed membrane surface water treatment plant for Manti City.
This concurrence is not Plan Approval to construct a full-scale surface water treatment plant. Manti City shall submit plans and specifications for the full-scale plant, and a complete
Project Notification Form to the Division for approval prior to construction of the surface water treatment plant.
If you have any questions regarding this letter, you can contact me either by phone at [phone]or [e-mail].
Sincerely,
Dani Zebelean, P.E.
Environmental Engineer IIIDZ/mdbcc:Eric Larsen, Central Utah Public Health Department, [e-mail] Coray, Sunrise Engineering, [e-mail]
Mitchell Heap, Sunrise Engineering, [e-mail]
Cory Hatch, Manti City, [e-mail]
Kent Barton, Manti City, [e-mail]
Dani Zebelean, P.E., Division of Drinking Water, [e-mail]
Sarah Page, Ph.D., Division of Drinking Water, [e-mail]
John Chartier, P.E., DEQ Central District, [e-mail]
DZebelean 20005 13620 PDR Concurrence