Sewer plant work proceeds as deadline approaches
DAILY FORUM STAFF
Crews from David Ross Construction have been pouring massive amounts of concrete at the site of Maryville’s new $13.7 million wastewater treatment plant, which state and federal environmental agencies have mandated for completion this July.
In what is easily the biggest public works project undertaken by the city of Maryville in decades, work continued throughout 2014 on a new $13.7 million wastewater treatment plant just north of Highway 136 on the east edge of town.
With earthwork for the plant completed, concrete pours and work on various structures moved forward despite a historically rainy summer.
Then, under the gun of a state environmental mandate to have the plant operational by July 1, 2015, contractor David Ross Construction kept crews on the job even in the coldest winter weather.
Tasks completed or underway include construction of giant clarifier and aeration tanks along with a new
“force main,” the large underground pipe that will bring effluent into the plant from the city’s east lift station.
Unlike Maryville’s existing lagoon system, which cleans sewage simply by allowing waste materials to settle out as effluent flows through a series of man-made ponds before being dumped back into the One Hundred and Two River, the new plant will be mechanical.
In place of the lagoons, the new facility will have two large, circular clarifier tanks equipped with metal arms that churn through sewage in order to remove particulates and suspended solids. In addition, an aeration basin will force oxygen through contaminated liquid, speeding the chemical processes that eliminate ammonia and other toxins, transforming effluent back into clean water.
Like the drinking water treatment facility on the other side of the highway, the sewage plant is to be operated on a contract basis by Omaha-based PeopleService Inc., which says it can run the operation using current staffing levels.
Public Works Director C.E. Goodall said he has been impressed with the way Ross has gone about construction despite a serious problem that cropped up in July as water leached into the plant site from the nearby lagoons.
Goodall said the leaching caused delays in “de-watering” the site and forced the contractor to raise the level of several large concrete structures about 5 feet higher than called for in the original design.
That in itself wasn’t an insurmountable problem, Goodall said, since the structures were simply dug out at a shallower level, negating the need for extensive earthwork or an increased volume of concrete.
However, the change means that three large pumps at the nearby lift station will have to be replaced with larger machines at a cost of around $180,000.
To keep the project within budget, the City Council accepted Goodall’s recommendation that a planned concrete parking pad be replaced with gravel.
The need to raise structures and install pumps prompted Ross to ask for a 60-day contract extension, which moved the anticipated completion date up to May 10.
Maryville is the largest city in Missouri still using lagoons to treat sewage. Ordered by the state Department of Natural Resources to build a new plant or face punitive fines, the council successfully asked voters to approve revenue bonds to pay for construction. Additional needed revenue was created through a series of water and sewer rate increases.
After the new facility becomes operational, it is expected to have a useful expectancy of 20-25 years. City officials say the plant is designed to accommodate expansion related to more stringent purification regulations anticipated in the future.
