Simple valve keeps odors away

The 36-inch CheckMate valve being prepared for installation by applying a thick coat of lubrication to help the valve slide into place. Like most backflow valves, the CheckMate operates on differential pressure. However, unlike most backflow valves, it’s activated with less than 1 inch of head and seals much tighter. In addition to combined sewers, the design also works on sanitary and storm sewer outfalls and manholes.

Entler Excavating, Decatur, Ill., installed the valve. The project, including the time it took to exchange a 36-inch valve for a 35-inch unit, took about two months. Few citizens are aware of how simple and inexpensive solving the odor problem was. This is one of the most cost-effective solutions to a nagging quality-of-life problem the city’s implemented. Downtown Decatur now looks good and, to complete the last piece of the puzzle, smells good.

An 8-foot-diameter reinforced concrete, closed-lid manhole was built near the Decatur Public Library about halfway down the hill where the historic brick arch sewers downtown feed into a 36-inch sewer interceptor that empties into the 7-foot, egg-shaped main interceptor.

Problem-solving team from Decatur, Ill. (from left): Decatur, Ill., City Engineer Matthew Newell, PE; Public Works Director Richard Marley, PE; and Paul Caswell, PE, formerly the city’s sanitary sewer engineer and now asset manager for the Sanitary District of Decatur.

To install the 36-inch inline backflow valve, the city built an 8-foot-diameter manhole near the public library on East Main Street about halfway down the hill where the 36-inch line feeds into the 7-foot-diameter interceptor on Martin Luther King Jr. Drive.

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