On Memorial Day weekend, Choctaw Utilities received reports of water quality issues in the system. We are aware of these issues and wanted to provide an update on the cause, and what is being done to remedy the issue.
During normal day-to-day operations, the plant produces water at a rate of 250 gallons per minute (GPM). This is a relatively low rate that doesn’t push water through the main distribution system very hard. A rate of 250GPM creates 360,000 gallons of water per day, which keeps the water towers full.
During holiday weekends, such as Memorial Day, Independence Day, and Labor Day, usage increases. Add in an extended dry period, like we’re in now, and usage increases even more. During these higher usage times, it is necessary to produce water at more than the typical 250GPM. Right now, the plant is currently producing at a rate of 300GPM, which creates 432,000 gallons per day. The graph below illustrates plant production for 2022 and 2023. (2022 in green, 2023 in blue).
Producing at a higher GPM rate pushes the water through the system faster which has the unhappy side effect of stirring up sediment that is in the bottom of the distribution pipes. The calculations below show the effect of higher flow rates through a pipe:
To address this issue, Choctaw Utilities (CU) has retained the service of an engineering firm, CT Consultants, who specializes in distribution system issues. The scope of work between CU and CT Consultants is attached. The scope of work is intended to help guide infrastructure improvements to address quality issues. Specifically, the study will build a Water Distribution Study (WDS) model that will allow system deficiencies to be identified and addressed. The entire scope is in the attachment, but there are a few bullets that are worth pointing out:
- Confirm system peaking factors and apply various flow conditions to the model to identify potential system deficiencies.
- System storage and turnover and pumping will be analyzed through EPS scenarios. This evaluation will include specific attention to the transmission grid and how water flows through the system. Special attention will be paid to mains with low velocity and high water age.
- Provide a holistic review of the distribution system and give recommendations on best management practices for operating the distribution system.
- Develop recommendations for flushing of all silts and solids in the distribution network.
- Immediate Priority: Make recommendations, based upon modeling, for any infrastructure improvements that may help improve & subsequently maintain water quality in the system. Recommendations shall include locations and type of infrastructure recommended.
The report from CT Consultants will include infrastructure recommendations to address items identified by system members and from the WDS model. With engineering data in hand, CU can then take the next step of implementing data-driven recommendations to resolve issues. We anticipate the report to be completed by the end of summer. At that point, CU can cost out what improvements are necessary and how that will impact the rate structure. Note 1: CU has not raised rates in the last 5 years, which included the cost of construction on the new plant. Note 2: The tax savings realized thus far from the Non-Profit conversion allowed this study to be completed at no extra charge.
Click the link below to view CT Consultants scope of work.