The Carroll-Boone Water Board learned about Optimum Corrosion Control (OCC) at its April 20 meeting when consultant and engineer Brad Hammond of McGoodwin, Williams and Yates (MWY) explained how slowly adjusting the pH of the water would benefit CBWD customers by reducing solubility of lead and copper in pipes.
Hammond said the plan would over about a year adjust the pH to 8.2 – 8.6, whereas now it’s about 7.5. He suggested lime slurry as the adjusting agent, and showed a sketch of what equipment and space the plant would need and where it would fit in most effectively. He estimated the construction cost to be $250,000 plus engineering fees, contingencies and add-ons, making the estimated total $330,000. The OCC project would incur an annual operating cost of about $55,000, which Hammond translated to about two cents per thousand gallons.
Hammond mentioned the Memorandum of Understanding with the cities [Eureka Springs, Berryville, Green Forest and Harrison] states that water from CBWD does not contribute to scaling or corrosion in pipes. Following OCC protocol would better address this part of the agreement, and adjusting the pH is a recognized corrosion control method.
A result to watch for is a potential increase in total trihalomethanes, which are natural compounds that form when chlorine and other disinfectants react with naturally occurring matter in water. Hammond said, “There should be negligible feed down the line.”
He told commissioners he had already spoken to representatives of each city and there was “a general concurrence on the proposed approach.”
Hammond said if the board approved the project at that meeting, MWY could have the bids for the July 20 CBWD meeting and commissioners could choose a contractor. He projected construction could begin by August 17 and finish in February 2018.
“You can tell customers we’ve done everything you can for OCC,” Hammond stated. He added it would be expensive and impractical for each city take on this project individually. Harrison had already proposed an adjustment to its water supply, but this strategy for the entire transmission line means Harrison can now wait and see.
“If it will help the cities, then we oughta do it,” chair James Yates said.
The board voted to approve a motion moving the project forward as long as the cities agree. They approved another motion to authorize Yates to execute the engineering contract contingent upon review by attorney Dan Bowers.
Keels Creek stabilization
Hammond announced bids had been opened for the Keels Creek stabilization project, and Kesser International that did similar work downstream five years ago, was low bidder. Cost of the reclamation will be $340,000 for which MWY had procured a 75-25 matching grant.
Chris Hall, also an engineer for MWY, commented that for some reason, an arc-shaped section of the creek bank near the transmission line started eroding. Something upstream changed the flow of water around that bend, and the result was that a large mass of soil near the transmission line washed away. The opposite side of the creek is a rock wall. At this point, the arc has grown to 600 ft. long and 85 ft. at the widest.
The plan is for the contractor to add riprap and soil to fill in back to the pre-erosion creek bank and install a series of large rocks to be used as Bendway Weirs, a strategy to control direction and speed of flow down the creek.
Hall said the project could be completed in 30 days or less, and the grant amount could even go up if more of the bank washes away. Commissioners approved the motion to accept the grant.
Hammond also announced the Phase 1 of the Parallel Line Project is “substantially complete.” They are waiting for grass to grow before considering the job finished.
Original cost estimate of Phase 1 was $17.1 million, which included purchase of a generator which did not occur. Hammond estimated the final cost will be $15,095,000.
Manager’s report
Plant manager Barry Connell commented he had slowly over time lowered the dosage of the coagulant in the water. The product is still quality water, and he has seen no drawbacks. There is less sludge, less effect on the clarifier, generally less maintenance, and cost-savings. Connell will continue to monitor.
Connell also reported mouse damage to a capacitor of a transfer switch in one of the generators caused arcing clouds of smoke and expensive repairs. Total replacement cost for damaged equipment will be around $25,000.
“That’s why we keep the vegetation down around the buildings,” Connell said.
He came across the damage while performing a spring preventive maintenance inspection.
Next meeting will be Thursday, July 20, at 10 a.m., at the Freeman-Raney Water Treatment Plant on Beaver Lake.