Norwich — Norwich Public Utilities will continue to supply 450,000 gallons of water per day to the Mohegan Tribe for the next 10 years under a contract extension approved by the Norwich utilities commission Tuesday.

The agreement is an extension of the agreement that took effect Aug. 31, 2009, and calls for the Mohegan Utility Tribal Authority to pay the same water rates as other Norwich customers, NPU officials said Tuesday.

The Mohegan utility is one of the top 10 NPU water use customers, NPU Water Integrity Manager Mark Decker said.

The agreement calls for NPU to supply the first 450,000 gallons of water per day to the Mohegan utility, with any additional supply delivered from the Groton water supply through the town of Montville’s water system. The utility often exceeds the 450,000 gallon per day provided by Norwich, with usage varying somewhat by season, Decker said.

Provisions in the agreement allow for deviation from the 450,000 gallons based on “temporary conditions within either the Norwich or Groton/Montville systems,” NPU officials said in a news release issued after the approval by the Board of Public Utilities Commissioners. Deviations could occur during major water maintenance projects in Norwich, Montville or Groton, emergencies such as major water main breaks or other unusual events, Decker said.

“NPU has enjoyed a great working relationship with the Mohegan tribe and MUTA for the past 10 years,” NPU General Manager Chris LaRose said in the news release. “We look forward to working with our friends and neighbors in the years ahead.”

c.bessette@theday.com