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City continues upgrades to treatment plant

FARMINGTON — Work is progressing on a multi-million dollar wastewater treatment plant upgrade on Farmington’s east side.

In February of this year the city embarked on a $6.2 million upgrade at the east wastewater treatment plant located off Highway 32. The project, being done by Brockmiller Construction of Farmington, involves expansion of the plant’s footprint, addition of another oxidation ditch, another clarifier with a second new unit to be added in the future, and construction of a control building.

“We are running on schedule and budget. Brockmiller is doing a wonderful job,” said Public Works Director Allen Welshon. He was joined by Plant Manager Mike Harrington for a brief tour of the facility to explain the problems facing the plant before the upgrade, and how the new components are going to be placed and how they will operate to raise the functionality of the plant to a level suitable well into the future.

The existing plant was completed in 1989. Since that time the oxidation ditch, the first major component in a sewage plant, has been full of sewage and functioning non-stop. Upgrades include adding a second oxidation ditch, this time with the latest technology. Once all improvements are completed in the fall of 2010, the old oxidation ditch will be emptied and inspected before being put back into service.

The plant currently is designed with a maximum operating load of 1.3 million gallons per day. For the past several years it has often averaged nearly double the designed load. Over the past month, due to the heavy rainfall and ongoing problems with stormwater infiltration in the sewer system, the plant has been averaging 3.3 million gallons per day.

 Stormwater infiltration is a major concern for sewage treatment plants. In the perfect world, the only liquid to find its way to the sewage plant would be sewage. But in reality, many people and contractors have customarily routed downspouts and sump pump drains into sewage lines.

In recent years education and enforcement have slowed the trend of putting stormwater into sewer lines. Still the problem exists, either through poor design on new construction or older drains not being rerouted.

A third source of stormwater infiltration into sewer lines is through damaged or loose-fitting sewer mains. For the past few years the city has dedicated about $100,000 a year to video exploration and sealing of existing sewer mains in an effort to keep stormwater out.

Doug Smith is a reporter for the Daily Journal. You can reach him at 573-756-8927, or at

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