Bernardin Lochmueller & Associates’ wetland treatment saved Washington, Ind., $26 million and cut projected annual operating costs by $1.6 million, according to the American Council of Engineering Companies.
Because of its “green design” and money-saving features, the engineering trade association has selected BLA’s wastewater treatment project for a 2013 Engineering Excellence Honor Award.
Like many Midwestern cities, Washington’s sanitary and stormwater system were originally combined to save money. However as the city grew, it didn’t have enough storage capacity and as little as 1/10 of an inch of rain caused combined-sewer overflows (CSOs) of sewage mixed with rainwater directly into waterways. The city needed to fix this, but the traditional approaches of separating sewer and stormwater pipes or adding wastewater treatment plant capacity would have cost $53 million, according to one study.
The city’s CSOs flowed into Hawkins Creek, which runs through residential neighborhoods. Between rains, the creek dried, turning gray and foul smelling. A 2001 water quality study found unsafe levels of many contaminants, and the city posted signs warning residents that contact with the creek could make them sick.
Washington asked BLA to develop a water project that would incorporate green design to lower costs. BLA’s engineers devised a system that cost $26 million less to build, when compared with the next lowest-cost alternative.
Now, when it rains, the CSOs flow to a 5 mg storage tank where it’s held until the wastewater treatment plant can process it. When the tank is full, CSOs travel via two 84-inch pipes (pictured) to a 27-acre constructed wetland. There, fine sediment settles in the forebay and then plants filter out contaminants. The effluent passes through a UV disinfection system before being discharged into Hawkins Creek.
In June, the Indiana Department of Environmental Management (IDEM) approved the system, saying it met Washington’s Clean Water Act obligations. The system handled its first major rain events in September. Water quality tests showed that the water being discharged by the wetland system surpassed IDEM’s quality requirements and surpassed the more stringent standards for the city’s wastewater treatment plant.
For the first time in years, Hawkins Creek has minnows, frogs and other wildlife, BLA says.