Increased sewer rates for Greater Augusta Utility District customers in Augusta and Hallowell, and a drop in water rates for those and other customers, face public scrutiny Thursday.

In Augusta, a typical customer who relies on the district for water and sewer services will pay $36.54 more per year than he or she does now, starting in October.

Augusta residential customers will also see a higher flat fee charged for storm water, from $16.15 to $23 — a 42 percent increase.

Overall, water and sewer costs for Greater Augusta Utility District utilities customers would have been larger if the district were not also retiring $1.4 million in financing debt for its former water treatment plant, which district officials say will reduce the district’s cost of providing customers water.

Augusta’s sewer rates are going up 38 percent. But that sewer rate increase is partially offset by a 31 percent decrease in the water rate for customers who use Greater Augusta Utility District for both sewer and water.

But in Hallowell, where most customers get their water from the Hallowell Water District — and have their sewer services provided by the regional Greater Augusta Utility District — the impact of the new rates on a typical homeowner will be larger: About $115 a year.

That’s because those customers won’t have the benefit of the decreasing water rates offsetting the increasing Greater Augusta Utility District sewer rates.

Customers can hear about, and comment on, the rate changes Thursday at public hearings in Augusta and Hallowell. The public hearing in Augusta will take place in the lecture hall at Augusta City Center at 4 p.m. At 7 p.m., another public hearing will occur in Hallowell City Hall council chambers.

“The most common question we get, what folks really want to know is, ‘What does this mean for me?’ ” Greater Augusta Utility District General Manager Brian Tarbuck said.

Tarbuck said customers who are curious about the impact the new rates will have on their bills can contact the district. He said an estimate of a rate increase can be generated based on a customer’s prior use.

People unable to attend Thursday’s public hearings may also call the district directly, at 622-3701, to comment or ask questions.

“Hopefully, people will attend the hearings,” Tarbuck said. “If they can’t, our phones work, our email works, and we’d be happy to do our best to explain the need for our rates and answer those questions.”

The main factor driving the rate increase is a major sewer and storm-water system upgrade under way in Augusta.

The $17.3 million project is meant to prevent overflows of human waste into Bond Brook. Currently, during some major storms, water combines with sewage to overwhelm the capacity of the sewer system, with the combined sewer and stormwater then overflowing into Bond Brook and, ultimately, the Kennebec River.

District trustee Ken Knight said the project will benefit all residents of Kennebec Valley, in cleaner water.

The project will boost the system’s capacity to handle sewage and storm water by 1 million gallons by adding two, 670-foot-long, 10-by-10-foot concrete storage tanks beneath Mill Park next to the Kennebec River.

Several years in the planning, construction is expected to take place year-round and be largely complete in December 2012.

The utility district is independent of the city.

The new sewer rates must be approved by the Greater Augusta Utility District Board of Trustees, while the new water rates are subject to the approval of the state Public Utilities Commission.

In Manchester, where some customers get water from the Greater Augusta Utility District, a typical residential user will see a $106 decrease in their yearly water costs.

Keith Edwards — 621-5647

kedwards@centralmaine.com