State rethinks plant ratings
The Arkansas Department of Health says capacities it approved for the city’s two water treatment plants are too high, an admission prompted by a letter it received from the engineering firm the city has contracted for consultation on its water system and the design of a new treatment plant and distribution system.
A Jan. 31 letter from Crist Engineers Inc. to the department said the Ouachita Plant on upper Lake Hamilton and Lakeside Plant that treats water from the city reservoir at Lake Ricks aren’t capable of meeting their department-approved capacities.
The letter said the department’s calculations don’t allow for time the nine filters at Ouachita and six at Lakeside are offline for backwashing. Crist’s calculations factor in one hour a day for backwashing, or cleaning the filters with treated water, and a filtration rate it said is more in line with plant capabilities.
The Hot Springs Board of Directors appropriated $2.29 million last year to rehab and replace all nine filters at Ouachita.
“The evaluation uses the maximum allowable filtration rate, which is not the actual filtration rate being used at these water plants,” the letter, referring to calculations the department uses to determine plant capacities in its surveys of water systems, said.
Crist said its calculations lower Ouachita’s capacity from 22.33 million-gallons a day to
21 mgd and Lakeside’s from 6.2 mgd to 4 mgd, an adjustment the department agreed with.
“We concur that the maximum sustainable flows are
21 mgd for OWTP and 4 mgd for LWTP based on optimum source water and facility conditions,” the department said in its March 2 response letter.
Deputy City Manager Bill Burrough told the city board earlier this week that the state’s response confirms the need for additional supply and treatment capacity, which the city hopes to realize through a $110 million debt issue that will bring a
23 million-gallon average day allocation from Lake Ouachita on line.
The city’s withdrawal agreement with Arkansas Entergy Inc. provides it up to 30 mgd from upper Lake Hamilton, but usage can’t exceed a 20-mgd average calculated over a three-month rolling period.
The letter encouraged the city to proceed, warning that the state can impose conservation orders and restrict connections and extensions if water systems don’t keep pace with demand. The city said production reached 80 percent of daily capacity more than 50 times in 2012, which, under department guidelines, requires it to begin planning for the future.
The state’s most recent survey of the system in 2016 showed 15.12 mgd of production was needed to meet average daily demand, which, according to the rate analysis from the city’s water and wastewater rate consultant, was 7.8 mgd in 2016.
Leaks in the distribution system and finished water used in the treatment process contribute to the difference in production and water sold.
“I was glad that we received that letter,” Burrough told the board. “It indicates that the action we’re taking is within their guidelines and what they strongly encourage, so we’re moving forward with that.”
Crist told the board last year that a $95 million cost is estimated for the Lake Ouachita project, which includes a 25-percent contingency and engineering fee. Part of the proceeds from the $20.5 million bond issue the board will consider next month will go toward Crist’s fee for designing a raw-water line, distribution and transmission lines, an intake and treatment plant.
The $29.4 million estimate for a more than 20-mile long raw-water line from the intake at Lake Ouachita’s spillway landing area to a treatment plant near Amity Road is the biggest expense of the project, but Crist has said bringing finished water from the south would improve water quality and distribution-system hydraulics.
The city’s two treatments plants are in the northwest and north part of the service area. Crist contends pumping more finished water from that direction would increase pressure on transmission and distribution lines, leading to more leaks and widening the gap between production and water sold.