DDW-2024-008804

July 9, 2024
Teresa Gray
Salt Lake City Water System
1530 South West Template
Salt Lake City, Utah 84115
Subject:Operating Permit, Package 1 & 2- Bypass Water Line Installation and Temporary Direct Filtration Conversion to City Creek WTP (TP003), Salt Lake City Water System, System #18026,
File #12494 & 12496.
Dear Teresa Gray:
The Division of Drinking Water (the Division) received a request for an Operating Permit for Package 1 & 2- Bypass Water Line Installation and Temporary Direct Filtration Conversion
to City Creek WTP (TP003) from your consultant Steven Brenchley of Brown and Caldwell on June 29, 2024. The Division issued Plan Approval for Package 1 and Package 2 on June 7, 2023,
and November 21, 2023, respectively. The site visit of the facility was conducted on July 1, 2024, by Division staff. This project has met all the conditions for receiving an operating
permit.
Our understanding of the project is that the Salt Lake City Department of Public Utilities (SLCDPU) took a phased approach to rebuild the City Creek Water Treatment Plant (CCWTP). Depending
upon the availability of funds, different packages were proposed.  Package 1 consisted of the initial phase to divert at a maximum of 4 MGD of City Creek Water via a bypass pipeline
connecting the north flocculation basin to the filter building. Package 1 was approved by the Division on June 7, 2023.
Package 2 improvements included the conversion of the City Creek WTP (TP003) to Direct Filtration by converting 2 of 4 existing filters to flocculation basins, bypass piping of existing
flocculation and sedimentation basins and moving the disinfection compliance point of entry (POE) to downstream at Site 12 (picnic spot) to meet the proper CT.
City Creek is the only source for the City Creek Water Treatment Plant. The water treatment facility design allows for direct filtration (no sedimentation process) if certain water quality
parameters are met for a specified percentage of the year. The project team from Brown and Caldwell analyzed
daily raw water turbidity readings from 1994 to 2018, and hourly raw water turbidity readings from January 2014 to January 2019. Both sets of data confirmed that City Creek meets and/or
exceeds direct filtration facility requirements.
The data sets also confirm that at some point, a direct filtration facility will shut down temporarily during high raw water turbidity events. Certain contingencies are required to avoid
disrupting supply to the City Creek service area. Those contingencies are:Upgrading the North Bench Pump Station. Upgrades are anticipated to begin October 2024 and finish by October
of 2025.Using the existing Morris and Ensign Downs tanks as finished water reservoirs with a total capacity of 10 MG. The existing tanks in this area can provide approximately 18 days
of storage in the Winter and approximately 2.0 days of storage in the summer (at peak day demands)
Operating as a direct filtration facility increases the City Creek Water Treatment Plant’s disinfection requirements because the plant will be regulated differently without sedimentation
basins, and the plant will have less disinfection volume available without the sedimentation basins. Plant operators typically maintain a free chlorine residual of 0.8 mg/L. Two options
exist to maintain typical peak plant production of 8 million gallons per day (mgd), or even reach rated plant capacity of 15 mgd as a direct filtration facility.Increase free chlorine
residual as needed up to 2.0 mg/L (customers may find higher levels objectionable), and/orUse the 3 MG FWR for disinfection volume.
Operating as a direct filtration facility will increase solids loading on the City Creek Water Treatment Plant’s filters. This should not be a problem for filter effluent water quality,
but the increased loading would lead to more frequent backwashes. If raw water turbidity increases above 10 NTU, plant operators may need to reduce plant flow to extend filter runs and
limit filter backwashes to no more than two backwashes per day.
City Creek Treatment Plant Modification
This Package 2 project included modifications to convert the existing City Creek Water Treatment Plant from a conventional filtration facility into a direct filtration facility. This
included bypassing the existing flocculation and sedimentation basins, retrofitting two existing filters into flocculation basins, installing a new disinfection sample location to meet
proper CT that would act as point of entry and installing a plant water disinfection system. Following is the breakdown of the specific works:
Demolition and salvage of flocculators and drives in existing flocculation basins.
Demolition of filter media, piping, underdrains, troughs, and associated appurtenances on Filters 1 and 2.
Modification and installation of salvaged flocculators into repurposed Filters 1 and 2.
Installation of new flocculation and sedimentation basins bypass pipe.
Installation of remote sampling (chlorine, pH, Temp.) 1.46 miles down the canyon from the plant.
Installation of a 3000-gallon water chlorine contact tank for in-plant water use CT, piping, and appurtenances.
All associated electrical and instrumentation work is required to make a complete and operable system.
Flow from the existing south rapid mix basin passes through the existing south floc basin inlet channel into a new 3-foot-wide flocculation inlet channel. The flow is then distributed
through four 16-inch diameter floc inlet pipes equipped with isolation valves. The inlet pipes are sized to minimize headless, while providing even flow distribution between the flocculation
basins.
Source water turbidity analysis:
The pilot study and memorandum on Direct Filtration done by a consultant shows that City Creek meets the requirement of R309-530-5.3. Brown and Caldwell have analyzed historical data
for City Creek and determined that source meets requirement of 75 percent of the measurement below 5 NTU and that plant capability of shutdown automatically when the source turbidity
of 20 NTU lasts longer than three hours or source water turbidity exceeds 30 NTU at any time. The shutdown is accomplished via the SCADA system and by shutting down the raw water inlet
gate, filtered water valves, and chemical feed pumps. 
Continuous turbidity monitoring:
Per R309-530-5, the CCWTP is equipped with continuous turbidity monitoring on the raw water, each filter effluent pipe, and combined filtered water line. CCWTP is staffed by operators
24 hours a day, 7 days a week. The raw water turbidimeter will alarm and the plant shut down automatically.
For the plant shutdown to function, the respective valves and pumps are in Remote or Auto mode. An Automatic plant shutdown occurs whereby the intake valve shall close, the pumps shall
be turned off, and the filter outlet valves shall be closed during raw water turbidity exceedance as mentioned above.
Changes to disinfection strategy.
The modification to direct filtration requires CCWTP to provide additional disinfection to meet microbial removal and/or inactivation requirements. The CCWTP meets the required disinfection
by increasing the free chlorine residual and using the full plant volume for CT.

We have received the following information for Package 1 & 2- Bypass Water Line Installation and Temporary Direct Filtration Conversion to City Creek WTP (TP003) Project:
Certification of Rule Conformance with plan approval conditions by a professional engineer.
As-built or record drawings.
Satisfactory bacteriological results as evidence of proper disinfection and flushing.
Evidence of operation and maintenance manual delivery.
We have determined that all conditions for issuing an operating permit have been met. On this basis, an Operating Permit for Package 1 & 2- Bypass Water Line Installation and Temporary
Direct Filtration Conversion to City Creek WTP (TP003) Project are hereby issued as constituted by this letter. You may now place the facilityin service in your water system.
Monitoring and Reporting
The monitoring frequencies for inorganics and metals, nitrate and sodium sulfate and TDS have been increased to the baseline monitoring frequencies for surface water sources described
in R309-205. The following samples are now due at the following frequencies:Facility with new requirementsAnalyte(s) Required# of samplesSampling FrequencyNext Due DateRule ReferenceTP003
City Creek WTPNitrate1Quarterly07/01/2024-09/30/2024R309-205-5(4)(a)Inorganics & Metals1Yearly07/01/2024-12/31/2024R309-205-5(3)(a)Sulfate Sodium, TDS1Yearly07/01/2024-12/31/2024R309-205-5(3)(a)
The monitoring frequencies shall be re-evaluated upon project completion. The monitoring schedule for this system can be viewed anytime online at waterlink.utah.gov. Please contact David
Kruse at [e-mail] or [phone] with any questions regarding this system's source monitoring requirements.
Please maintain a copy of this letter with your permanent records for future reference.
If you have any questions regarding this Operating Permit, please contact Nagendra Dev, P.E., of this office, at [phone], or Michael Newberry, P.E., Engineering Manager, at (385)
515-1464.
Sincerely,
Russell Seeley, P.E.
Assistant Director
ND/mrn/mdbcc:Matthias Neville, Salt Lake County Health Department, [e-mail] Stewart, Salt Lake City Public Utilities, [e-mail] Stewart, Salt Lake City
Public Utilities, [e-mail] Brenchley, Brown & Caldwell, [e-mail] Jones, Brown & Caldwell, [e-mail]
Nathan Hall, Brown & Caldwell, [e-mail]
Jared Carr, Jacobs Engineering, [e-mail]
Teresa Gray, Salt Lake City Public Utilities, [e-mail]
Michelle Barry, Salt Lake City Public Utilities, [e-mail]
Sarah Page, PhD, Division of Drinking Water, [e-mail]
David Kruse, Division of Drinking Water, [e-mail]
Mark Burger, Division of Drinking Water, [e-mail]
Nagendra Dev, P.E., Division of Drinking Water, [e-mail]
NDev OP 18026 12494_12496 CCWTP