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Construction 75% complete on Marshall water-softening project

MARSHALL — Construction on a project that will allow Marshall’s water to be pre-softened has made good progress at the municipal water plant. Currently, the work is 75% complete, Marshall Municipal Utilities water operations manager Jeff Larson said Tuesday.

“It’s on budget, and approximately one month behind,” due to some unforeseen delays in excavation, Larson said.

Larson gave members of the Marshall City Council an update on the water softening project Tuesday night. The construction is part of years of planning to try and cut down on the amount of chlorides released into the Redwood River from the city’s sewage plant. A state permit placed new, more strict limits on the Marshall wastewater treatment facility starting in 2024.

“The community needs to meet the new chloride limit,” Larson said. A major source of chlorides in Marshall’s wastewater is the salt from home water softeners. However, an engineering study found that instead of working to take salt out of Marshall wastewater, it would be less costly to keep the excess salt from getting into the water in the first place.

The city is working with MMU to build facilities and equipment to pre-soften city water. When the project is operational, Marshall’s water will go from being at 35 grains of hardness down to the 8 to 10-grain range, Larson said.

“If things keep going to plan, the start of the softening process will start this late winter,” he said. It will take a few months to gradually soften the water, he said.

Construction at MMU’s raw water plant began in August 2019. The project has an overall capital cost of $11.6 million. MMU received $7 million in funding for the construction through a state grant, and the remaining $4.6 million in costs will be paid by MMU and the city of Marshall.

The water softening project is separate from the ongoing construction work at the city wastewater treatment plant.

“It’s mostly new equipment and processes,” while the wastewater plant construction is focused on replacing outdated equipment, Larson said.

MMU already does soften Marshall’s water down to about 35 grains of hardness, Larson said.

“The method of softening we use is called chemical precipitation. We add chemicals to the water to raise the pH,” and help dissolve and separate out minerals, Larson said. “The current plant partially lime softens, so we’re using lime now.”

With the new water softening project in place, the plant will use both lime and soda ash to soften the water further, he said.

Larson said the construction on the water softening project includes two major areas: a building addition at the raw water plant in Marshall, and the construction of a piece of equipment called a sludge thickener, which helps settle out the chemical sludge created in the water softening process.

“The walls started and finished installation in January,” Larson said. “The steel and equipment installation has been ongoing since then.”

Larson said there had been some unforeseen delays in the sludge thickener part of the project.

“To date, the only real issue that we’ve had so far is a dump that was found when we were excavating for the sludge thickener,” he said. The dump site included a lot of buried concrete, pipes, around 40 tires and a 10-by-10 foot foundation from a 1930s-era well house.

Larson said the project was extended by a month while debris was removed.

“It took a while to excavate this,” he said.

Once the project is up and running, Larson said MMU will gradually step down the hardness of city water.

“This spring, the word should be getting out for people to turn down their softeners,” he said.

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