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A solid solution prevents contamination from flood water

Saturday, September 16, 2017

Linda Van Hoosen, Communications

Montauk State Park is a hot spot for trout fishing and canoeing. The park is located on the banks of the Current River near Salem, Missouri. In recent years, the park’s wastewater has been treated by a three-cell lagoon. The treated water is irrigated onto a nearby field.
                                                                                              

Two of the three lagoon cells (Lagoon cells 2 and 3 above) were located directly along the banks of the river. The proximity of the cells was a cause for concern. Flooding could potentially breach the cells’ berms and contaminate the river. The Current River is designated as an Outstanding National Resource Water by the Environmental Protection Agency. The solution was to build a new lagoon cell farther away from the river bank and eliminate the two cells along the riverbank. The State of Missouri hired Olsson Associates to design and help oversee construction of the lagoon modifications to minimize the risk of a breach and the possible contamination of the river.

The two cells near the river were demolished and the walls of the remaining cell and the new cell were reinforced with riprap. Riprap is rock or rubble used to armor shorelines against erosion. The lagoon influent pumps and irrigation pumps associated with the treatment facility were also replaced and set in an area to be protected from floodwaters.

In May of 2017, the improvements were tested. Extreme rains caused record flooding of the Current River. A majority of Montauk State Park flooded and all visitors were evacuated. Although the lagoon modification project was still in progress, the new lagoon cell had already been built and reinforced with riprap. The improved cells operated exactly as designed. The newly reinforced walls held with less than two feet of freeboard remaining on the lagoon berms. This demonstrated the project’s success in protecting the Current River from contamination.

“Olsson’s lagoon modification design achieved the State’s goal of protecting the Current River from wastewater contamination during flood conditions,” said Jerry Jesky, senior engineer for Olsson’s Water/Wastewater team in Springfield, Missouri. “Without these improvements, the risk of a lagoon berm breach during the recent flooding would have been much greater due to the previous close proximity of the lagoon cells.”

Olsson provided survey, mechanical, electrical plumbing, and wastewater services for this project.

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