SANFORD – The $650 million casino proposed by the Passamaquoddy and Penobscot tribes could use all of the extra capacity the Sanford Sewage District is building if it hooks into the system.

The development eventually could generate 1.2 million gallons of effluent per day that would require treatment and disposal.

Casino project coordinator Erin Lehane said the preliminary plan submitted to the Sanford planning department was required to show that the facility could hook into existing sewer and water utilities.

Sebago Technics, which drew up the proposal, is reviewing options that include treating the waste on site, using the Sanford Sewage District, or utilizing a combination of both.

“We’ll negotiate what they want us to do,” Lehane said. “We’ll defer to the planning board.”

The 1.2 million-gallon-per-day projection comes as the Sanford Sewage District’s new treatment plan is under construction.

The new plant, when up and running June 1, 2005, will allow the district to discharge up to 4.4 million gallons of treated effluent per day into the Mousam River from Oct. 1 to April 30, and 3.5 million gallons per day for the remainder of the year.

Sanford residents and businesses now discharge an average of 2.1 million gallons per day year-round.

Sanford Sewage District Superintendent Michael Hanson said the casino projection means the town would have to decide how much of the new treatment plant’s capacity would be allocated for new commercial and residential growth.