MARSHALL — Residential utility rates are set to go up in Marshall over the next two years. Staff at Marshall Municipal Utilities said the average monthly water bill will increase by over $6 in 2020, and increase again by over $7 in 2021. But the rate increase will also help MMU make softer municipal water possible, said MMU General Manager Brad Roos.

At Tuesday’s meeting of the MMU Commission, MMU held a public hearing on electric and water rate adjustments for the next two years. Commission members then went on to approve separate resolutions setting the electric rates and water rates.

Rates were set to go up for both residential electric and water customers. However, the increase was bigger for water rates. Starting Jan. 1, the monthly base charge for water will go up, from the current rate of $14.67 to $17.90. The monthly base charge for water will go up again in 2021, to $21.87.

Commodity charge rates per thousand gallons of water used will also go up in 2020 and 2021.

A household that uses 4,000 gallons of water a month — about average for residential users, Roos said — would see its water bill go from $31.15 a month to $37.70 a month in 2020. The next year, the monthly water bill would go up again, to $45.59.

The main reason for the changes, Roos said, is the water softening project MMU is starting at its water treatment plant in Marshall. By 2024, the city of Marshall will need to comply with stricter limits on the amount of salt that gets released into the Redwood River from the city wastewater plant. Much of that discharge comes from the use of home water softener salt.

A study found it would be less costly to pre-soften Marshall’s water than to try and take the salt out of the wastewater. When the softening project is complete, MMU will use soda ash and lime to take Marshall’s water down to 6 grains of softness. Residents will likely need to use less softener salt at home.

“This (water rate) change gives us the revenue needed for the treatment process,” as well as to deal with the byproducts of the process, Roos said. The water softening process creates a sludge of minerals, which Roos said can be taken away and applied to agricultural fields or feedlots to change the acidity of the soil.

The water softening project has an estimated construction cost of $11.58 million. MMU received a $7 million state grant to help cover construction costs, and the rest of the construction funding will come from MMU and the city of Marshall.

MMU also set rate adjustments for electricity at Tuesday’s meeting. Starting Jan. 1, the monthly base charge for residential electricity will increase from $20 to $21. Electric rates per kilowatt hour of electricity used will also change, but they will go down.

A residential customer using 1,000 kilowatt hours of electricity a month would see their bill go from $89.56 up to $91.94 in 2020.

But while the average monthly electric bill would see an increase from this year, it would still be lower than residential bills four years ago. In 2015, the average residential electric bill was $110.06 a month, MMU staff said.

Roos said electric bills have been trending downward over the past few years, after MMU changed its wholesale energy supplier. In 2016, MMU started buying electricity from Missouri River Energy Services instead of its previous supplier. The move means MMU now pays less for electricity than it did in the past.