Citizens Energy Group customers face double-digit-percentage rate increases for water and sewer service under a request filed Thursday with the Indiana Utility Regulatory Commission.

Monthly rates for the average residential customer would rise 10 percent, from $31 to $34.

Harder hit would be monthly wastewater bills, which would eventually rise 47 percent,  from $30 to $44.

The Indianapolis-based utility said the increases will fund a $114 million upgrade to the water system and a $444 million tunnel system being bored beneath the city  to capture raw sewage that now overflows into streams.

“In order to continue investing in projects that remove raw sewage from our rivers and streams and that improve the quality of our drinking water, rate increases are necessary,” Carey Lykins, CEO of Citizens Energy Group, said in a statement.

Citizens acquired the city’s water and sewer systems more than a year ago in a deal worth $1.9 billion. The gas and steam utility claims that the acquisition has allowed it to achieve $112 million in annual savings.

The tunnel project is aimed at stopping the frequent overflowing of sewage into streams during heavy rains. The combined stormwater/wastewater system had to be remedied under a consent decree between the city and federal regulators.