CHICKASHA – The quality of local drinking water and development plans for the new water treatment plant highlighted the City Council meeting recently.
A design team from Freese & Nichols, Clay Herndon and Jason Cocklin, told the City Council on July 1 that the Oklahoma City engineering company is entering the final design phase on Chickasha’s new water treatment plant. Cocklin told Southwest Ledger that F&N estimates completion of that phase “by the end of the year.”
That work will be followed by “regulatory engagement” and requisite state permits, he indicated.
Next will be the bidding phase, which is anticipated for March through May 2025, Cocklin said. After the contract is awarded, construction will take approximately 18 months to complete, from May 2025 until December 2026, F&N predicts.
“We have met every deadline to date,” Cocklin said.
F&N’s “focus is on water quality and reliability,” he said. The plant will be designed to produce 6 million gallons of potable water per day (mgd) of raw water and will be “expandable” to 8 mgd, he said. Production of 6 mgd “should get you out to the horizon, to about 2060-70,” Cocklin estimated.
Water that Chickasha draws from Fort Cobb Lake will undergo a “powdered activated carbon pretreatment process” that “will help with water odor problems,” Cocklin said.
The new plant will utilize a “conventional water treatment process,” he said. “We will plan for the ability to add advanced treatment, such as reverse osmosis, in the future if regulatory or water quality changes require it,” he told the Ledger.
“There’s been a lot of discussion about water quality and pressure, and discoloration,” Mayor Zach Grayson said at the outset of the July 1 council meeting.
The city’s antiquated water treatment plant is “running at maximum capacity, 4.7 million gallons a day, and it’s hot, which stirs up a lot of sediment,” City Manager Keith Johnson replied. Nevertheless, water from the faucet is “still safe to drink,” he said.
Chickasha’s water treatment plant is at least 60 and perhaps 70-plus years old and is incapable of adequately treating water. Regardless of which activation date is accurate, the water plant has already surpassed its design capacity and useful life, and lacks modern technological advancements in water purification.
The new treatment plant, which will cost an estimated $74 million, will have flocculation basins and sedimentation basins, engineering designs show.
Flocculation reduces the number of suspended solid particles as smaller particles combine to form larger ones.
Sedimentation is a common way of treating water. It is a process that removes solids that float and settle in the water. The process relies on use of sedimentation tanks that remove larger solids. Suspended solids that have a specific gravity similar to water remain suspended while heavier particles settle.
The treatment process also will employ two sludge lagoons, Herndon and Cocklin related. Sludge from water treatment is a by-product of water treatment that’s comprised of solid, semisolid, or slurry waste; it’s a combination of organic matter, inorganic solids, microorganisms, and trace chemicals.
Generators will be installed at the new treatment plant as a backup power source in the event the electric grid fails, Cocklin said.
Virtually all structures at the existing water treatment plant will be demolished, he said. However, the chemical feed equipment and generators at the facility will be salvaged, Cocklin said.
City officials have identified the parcel of land on which they want the new treatment plant built “and we’re in negotiations with the owner,” Grayson told the Ledger on June 19. “We are still negotiating with the owner but are confident we’ll reach agreement in the next few weeks,” Johnson told the Ledger on July 2. More testing planned on lakes’ water quality Among the services it is providing, F&N also intends to perform additional water quality testing of Fort Cobb Lake and of Lake Chickasha, a potential backup source of water. “The issue of water quality” is important, Councilman Brian Gerdes told the F&N team.
Chickasha currently receives all of its water from Fort Cobb Reservoir approximately 35 miles northwest in Caddo County. The lake water is conveyed to Chickasha’s water treatment plant on Genevieve Street through a concrete asbestos pipeline.
The city’s metered pump station recorded Chickasha drawing 1.037 billion gallons of water from Fort Cobb Lake in Calendar Year 2022, and 1.093 billion gallons, an average of almost 3 million gallons per day, last year.
The Fort Cobb Master Conservancy District “wants us to find an alternative source of water” to supplement Chickasha’s withdrawals from Fort Cobb Lake, former Mayor Chris Mosley said. Lake Chickasha was a logical source of supplemental water because it’s relatively close – approximately nine miles west of Chickasha, in Caddo County – and the city owns it.
Blending water from Lake Chickasha with water the city buys from Fort Cobb Lake “can meet your needs now and into the future,” Herndon and Cocklin told the city council on Jan. 16.
However, they conceded that Lake Chickasha “has some water quality challenges.” Unless it’s first purified in a treatment plant, water from Lake Chickasha is unfit for human consumption, research performed by the Oklahoma Water Resources Board has shown.
Lake Chickasha was impounded in 1958 and is fed by Spring Creek on its western arm and by Stinking Creek on its eastern arm. The reservoir is located in Caddo County approximately nine miles west of Chickasha.
Most recently the OWRB monitored the lake from October 2017 through July 2018. Agency representatives visited the lake four times during that period and sampled the water at three sites, records reflect.
Turbidity was rated at 10 NTU (nephelometric turbidity units). Environmental Protection Agency drinking water standards for conventional filtration call for less than 0.3 NTU in 95% of samples, and never higher than 1 NTU. Excessive turbidity (cloudiness) in drinking water is aesthetically unappealing and may represent a health concern.
Lake Chickasha is hypereutrophic, meaning it is extremely rich in nutrients and minerals and thus of poor quality. Its trophic state index is 61. The TSI is a classification system designed to rate water bodies based on the amount of biological productivity they sustain.
The lake ranks high in chlorophyll-a, which is a measure of algal biomass that is used to indicate or determine productivity in a lake. “The more chlorophyll-a is detected, the greater the level of algae,” said Robby Short, public information officer for the OWRB.
Lake Chickasha’s most recent chlorophyll-a measurement was 22.6 milligrams per cubic meter. In layman’s terms, that’s high, “indicating Lake Chickasha is a highly productive system,” Short said.
In addition, the levels of nitrogen and phosphorous are such that both nutrients are “readily available for algae to use, thus you get quite a bit of algae” in the lake, Short continued.
Lake Chickasha is listed in the Oklahoma Water Quality Standards as a “nutrient limited watershed,” which means the lake is considered threatened from nutrients.
The lake’s salinity level is “within the range of values seen in this area of the state,” the OWRB wrote. That means it is “hard” water.
Based on water quality data and flow rates from Fort Cobb and Lake Chickasha, Freese & Nichols will develop “a range of blended water quality scenarios for treatment parameters” and will develop recommended treatment design points “based on levels of risk.”