The City of O’Fallon (Missouri) Wastewater Treatment Plant has two rectangular equalization basins: a 75- by 200-foot sized basin with a 3-million-gallon capacity, and 100- by 250-foot basin that holds 4 million gallons.

A challenging aspect of maintaining retention basins is cleaning them after they fill with stormwater. Basins need to be cleaned soon after large rainstorms to control issues with overflow.

Equalization basin cleanup at the O’Fallon treatment plant was an arduous and time-consuming task, usually taking two to three days. The facility team solved the problem by installing hydrants at strategic locations around the basin perimeters.

Stressful and risky job

Before the hydrants were installed, basic cleanup involved two workers hooking up and dragging a 1.5-inch-diameter firehose while slowly and methodically spraying the debris off the sides into a catch basin in the basin floor. It was a physically demanding job that involved hauling a 100-foot-long hose containing about 15 gallons of water with a dead weight of 125 pounds.

In addition, to remove all the sediment on the basin sides and floor, workers had to step down the steeply sloping basin walls. Sometimes they slipped and slid, causing injuries. The exhausting and dangerous operation had to be done weekly or more often.

Simple resolution

For a solution, the plant team turned to The Kupferle Foundry Company, a 157-year-old supplier of water hydrants, sampling stations and flushing devices based in St. Louis. Working together, they deployed a new method of equalization basin washdown.

First they retrofitted the basins with an engineered piping system around the perimeters. Next they located and tapped strategic connection points for the installation of a monitor hydrant system. Finally, they installed six pre-engineered MainGuard #7500M washdown hydrants that connected directly to the piping system at the strategic points.

The freeze-less hydrants drain to ground and can be used year-round in cold climates. Additionally, the city purchased two monitor assemblies (for two workers) designed to attach to each hydrant using a quick disconnect. The hydrants and quick disconnects allowed workers to move the monitors from station to station, saving the city money.

Major improvement

After installing the hydrants, the treatment plant team reduced the time to clean the retention basins from two to three days to two to three hours, an 87 percent reduction. This significantly reduced costs and allowed plant workers to attend to other tasks. In addition, the monitor hydrants’ deployment ended workplace accidents related to cleaning the equalization basins, reducing costs and eliminating lost-time injuries.

“Safety for the crew was the main factor in installing these hydrants, and by installing them we accomplished that,” says Dave Scherer, assistant treatment plant superintendent. Savings on labor costs, the prevention of injuries and the quicker and more efficient cleaning process offset the initial cost of hydrant installation (about $52,000) within two years.

“At first I was skeptical about the hydrants being able to accomplish what they were intended for,” says Scherer. “But seeing them in action removed all doubts.”