Bennington wastewater treatment plant repairs ongoing, but long-term fix could cost millions


BENNINGTON >> Short-term fixes to stop smells and compliance issues at the aging wastewater treatment plant are underway, but a long-term solution could cost millions and lead to higher fees.

A state order requires the town come up with interim and long-term solutions for the Harrington Road facility, where equipment failures led to multiple violations and putrid smells in part of town this summer.

Town Manager Stuart Hurd estimated it will cost $200,000 for an engineer to assess the plant's condition and come up with a long-term plan, and to replace broken-down components. While a previous estimate to overhaul the plant was upwards of $12 million, Hurd said he hopes a project could be done with much less.

"We need to get that down to $6 to $8 million, back into a range voters can support," Hurd said on Thursday. "Even then, we may find ourselves having to choose what the highest priorities are for us." That could mean only replacing some components at the 31-year-old plant, he said.

A project will likely affect sewer fees, Hurd said, but it's unclear how much.

A state order issued on Aug. 31 required the town to hire an engineer to assess the treatment plant on Harrington Road, which was built in 1962 and last overhauled in 1985. Aldrich and Elliott, of Essex Junction, submitted a contingency plan to the Department of Environmental Conservation this week; a long-term schedule must be submitted by the end of the month.

Multiple wastewater discharge violations this summer, as well as a putrid sewage smell in parts of town, stemmed from failure of multiple rotating biological contractor (RBC) unit. The units are used after primary treatment and before disinfection. Treated wastewater, or effluent, is discharged into the Walloomsac River.

The plant has four rows of eight large, cylinder shaped units, for a total of 32, The permit requires 24 be used, but only 10 are now online, according to town and state officials. The breakdowns were caused by a combination of structural failures and the failing of motors and gearboxes.

Failure of those RBC units interrupted the whole treatment process and led to sewage not being aerated, according to David DiDomenico, environmental analyst for the Department of Environmental Conservation's wastewater management program. That in turn led to periods of bad smells and violations.

Plant staff reported three violations to DEC three times this summer, according to management division records. Samples of discharged wastewater taken July 5 found elevated levels of E. Coli – 11,000 colonies for every 100 millilitre of effluent, above the permitted 77 colonies. That violation affected an estimated 2.73 million gallons of treated and partly disinfected effluent.

Two separate reports in August, each representing two sequential days, noted violations above the ultimate oxygen demand (UOD) of 1,700 pounds a day: 2,765.8 pounds between Aug. 1 and 2, and 1,840.7 on Aug. 15 and 16. Follow-up tests found the plant in compliance. Plant staff notified DEC that they adjusted other parts of the treatment process to compensate for the lack of RBC units.

The plant's current wastewater discharge permit was issued in 2011 and expires at the end of the month. Compliance issues would not affect the renewal process, which is already underway, according to DiDomenico. The state handles permit applications and violations separately, he said, either through a 1272 order or order of discontinuance.

The contingency plan submitted to DEC on Wednesday calls for bringing RBC units online on a rolling basis. Treatment plant and Water Department staff are expediting structural repairs on 10 units with a goal to have them repaired by Friday. Repair of another eight are expected to be done by early next week. New gearboxes will be installed on another eight units by Nov. 1 and another eight by Dec. 15.

Contact Ed Damon at 802-447-7567, ext. 111.


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