MARYVILLE, Mo. — The Maryville City Council on Monday approved what is slated to be the final price for a new granular activated carbon adsorber and took other steps to stock up for combating water issues through the fall.
At its regular meeting Monday evening, the council OK’d a $651,456 proposal from HDR Engineering to complete the adsorber project. A GAC adsorber binds taste and odor constituents as water passes through a filter, removing the taste and odor particles from the drinking water before it goes out to customers across the area. An existing, unused clearwell tank on the site of the water treatment plant is being repurposed for the job.
Earlier this year, the council locked in a price for some construction materials at up to $472,878 for the rehabilitation of the clearwell tank and for PVC pipe. Combined with Monday’s addition and the $230,460 contract with HDR to serve as engineer on the project, the new GAC adsorber will run about $1.3 million — very near the $1.2 million price tag that had been estimated.
“So to be at $1.3 million with the escalation of prices that we’ve seen in the construction industry I think is a pretty good place to be,” said City Manager Greg McDanel.
In February, the city and Public Water Supply District No. 1, which supplies water to much of the outlying county and is the city’s largest customer, agreed to a cost-sharing arrangement that will see PWSD No. 1 pay $600,000 of the final cost of the adsorber project.
As part of a comprehensive report on the city’s water treatment upgrade options going forward, HDR recommended in January that the city install the GAC adsorber, which was the most effective short-term way on the water treatment side to help mitigate recurring taste and odor issues. The adsorber is set to be ready for the fall, when cyanobacteria — or blue-green algae — blooms are typically at their peak on Mozingo Lake, the city’s water source.
A long-term solution could still include a new water treatment facility, but any decisions on the next steps are on hold until the completion of a new water and sewer rate study — the first since the city began looking into building a new wastewater treatment plant that was completed in 2015. The study, which is scheduled to be completed sometime around the beginning of September, will help determine just how much rates would need to increase to accommodate a potential new facility that could cost between $18-38 million, and where those increases should come from.
The cost-saving alternative included in HDR’s January report was to upgrade parts of the existing water treatment plant, which was constructed in 1956.
The council also approved more powder activated carbon for use in the water treatment plant. PAC applications have been used during the treatment process to better filter out the compound geosmin, which has caused some of the recent taste and odor issues. The applications are helpful, but only removes about 88-90 percent of the geosmin, making it a short-term stopgap designed to last until the GAC adsorber is installed, which should be more effective.
The city previously purchased 30,000 pounds of PAC in December, and on Monday, council members approved the purchase of another 30,000 pounds for $27,000 from Jacobi Carbons.
On the source water side, the council Monday approved the application of more EarthTec algicide to 500 acres of Mozingo Lake through a contract with Estate Management Services for $13,750.
In May, the council approved the purchase of 2,200 gallons of the algicide and a 500-acre application for $53,350. During that application, only 1,100 gallons were used, and the remaining amount will be used for the next application when the algae count rises again.
The city began using the algicide on the lake earlier this year after HDR recommended it to combat the growth of the cyanobacteria on Mozingo Lake that can cause taste and odor issues in drinking water. PeopleService continues to take biweekly samples of the lake to monitor algae counts, and the city applies the algicide when the numbers get too high. The first application on May 10 came after the algae count rose from 10,800 cells/mL at the end of April to nearly 100,000 cells/mL on May 6. By May 13, the numbers had fallen off sharply to less than 40 cells/mL.
McDanel said that currently, lake monitoring shows higher algae counts on the northern half of the lake than the southern half.
Even after the GAC adsorber goes into service, McDanel said in May, the algicide will likely still be necessary because the buildup of cyanobacteria in the lake could affect recreational activities.
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