DWQ-2024-008704

Central Valley Water
Reclamation
Facility
Board Members
Debra Armstrong, Chair
Don Russell, Vice Chair
Kim Galbraith
Brett Hales
Cheryle Hatch
LeAnne Huff
Keith Lord

General Manager
Phillip Heck, Ph.D., P.E.

800 West Central Valley Road, Salt Lake City, UT 84119-3379  [phone]  [phone]
November 25, 2024

Utah Division of Water Quality
Mr. Dan Griffin
PO Box 144870
Salt Lake City, UT 84114 – 4870

Subject: Notice of UV Disinfection Process Upset – November 21, 2024

Dear Mr. Griffin:

This letter is being submitted to you in accordance with Part VI. H. of our permit, to report an
Upset Condition of the UV system that occurred at the Central Valley Water Reclamation
Facility (CVWRF) on November 21, 2024. The sequence of events that caused the upset and
actions CVWRF took to remedy the process upset are described in the following paragraphs:

The plant was being temporarily operated on backup diesel generator power to accommodate
necessary electrical tie-ins for the Biological Nutrient Removal Process construction. When
switching back to normal cogeneration and Rocky Mountain Power electrical power, the system
experienced a breaker failure on the B Buss power switchgear in the UV Building. One UV
channel (Channel 2) was on A Buss and one channel (Channel 4) was on B-Buss. Channel 2 (A-
Buss) remained on-line without issue, Channel 4 (B Buss) lost power and the UV lamps
shutdown.
The electrical switch gear was investigated, and it was determined that the protective trip unit on
the B Buss was smaller than on the A Buss and the settings on the protective trip unit for the B
Buss breaker were lower. A Buss has an 800-amp trip unit and B Buss has a 600 amp trip
unit. To remedy this potential cause of upset conditions in the future, CVWRF has purchased an
800-amp protective trip unit for the B Buss breaker. It will be installed on Monday November
25, 2024. The settings will also be adjusted to match the settings on the A Buss breaker.
Power for Channel 4 was off from 8:39 am until 8:49 am. It has been calculated that 102,083
gallons discharged through UV channel 4 without the lights on. Samples were collected from the
plant and Millcreek per the UV system failure standard operating procedure (SOP*). E. coli
samples were collected from the UV influent, plant effluent, Millcreek upstream of plant
effluent, and Millcreek downstream of plant effluent. Sampling results are provided below and
indicate that there was a temporary increase in E. coli levels in the plant effluent due to the
outage of channel 4:
UV Process Upset 11/21/2024
Page 2

Sample 1 – UV influent, E. coli – 2,416.6 MPN/100 mL
Sample 2 – Plant effluent, E. coli – 1,413.6 MPN/100 mL
Sample 3 – Millcreek upstream of plant effluent, E. coli – 410.6 MPN/100 mL
Sample 4 – Millcreek down stream of plant effluent, E. coli – 387.3 MPN/100 mL

The weekly geomean effluent E. coli level for this period was 71.7 MPN/100 mL (including the
sample taken during the event) which is in compliance with the permit requirement (157 No./100
mL). Due to the short duration of the event, compliance with the weekly geomean limit, and
lower E. coli levels downstream of the discharge point in Millcreek compared to upstream of the
discharge point, it is very unlikely there were any negative effects on the receiving water.

Please let us know if you have any questions or comments regarding this event.

Sincerely,

CENTRAL VALLEY WATER RECLAMATION FACILITY

Phillip Heck, Ph.D., P.E.
General Manager

cc: Brandon Heidelberger, P.E. Assistant General Manager
Sharon Burton, Plant Superintendent