PORTLAND — Officials hope an outside lawyer’s investigation will determine whether the city has any “legal options” for recouping as much as $1.5 million in sewer fees that Shipyard Brewing Co. was never billed for over a 15-year period, Mayor Michael Brennan said Thursday.

Bryan Dench, a lawyer with Skelton Taintor & Abbott in Auburn, has been hired to review the city lawyer’s internal investigation of the billing problem and conduct his own inquiry, Brennan said. Dench declined comment Thursday.

Brennan said Dench will also try to come up with a more definitive estimate of how much revenue was lost. That figure will be useful if the city finds a way to recover some or all of the revenue lost because a sewer account wasn’t set up when a second water line was added to the Newbury Street brewery in 1996.

The company used 201 million gallons of water through the second line until the problem was discovered a year ago. Since then, Shipyard has been paying sewer bills ranging from $17,000 to $41,000 a month higher than they had been, according to Portland Water District records provided in response to a Freedom of Information Act request by The Portland Press Herald.

City Councilor Ed Suslovic called for an independent investigation more than two weeks ago, and the city announced Wednesday that it was bringing in Dench. In 2007, Dench was hired by the Portland School Committee to investigate financial and administrative problems in the school district. His investigation led to the resignations of Superintendent Mary Jo O’Connor and Finance Director Richard Paulson.

Brennan said Dench’s track record was a key reason why the city hired him again.

“We want to assure the public that we take it seriously and will do a complete review,” he said.

But city officials said Thursday that the full story may never be known.

The failure to set up a sewer account was traced to a city employee, senior wastewater technician Dave Peterson, who told water district officials that the new water line would not result in any significant wastewater discharge.

In fact, breweries typically generate two to six gallons of wastewater for every gallon of beer.

Peterson died in 2007, and because he can’t be asked about the apparent billing oversight “we can’t, at this particular point, say we can absolutely answer those questions,” Brennan said.

“We want to bring closure to this as fast as we can, but the public needs to know that closure may never be there.”

Councilor David Marshall said he and his colleagues understand the limitations, but have urged city staff to hire an independent investigator “to figure out what happened and how we can prevent it from occurring again.”

Dench’s experience with the school district “has proven that he can plow through paperwork to help uncover who’s at fault,” Marshall said.

Staff Writer Edward D. Murphy can be contacted at 791-6465 or at:

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