BELLOWS FALLS — The Board of Trustees has heard back from a consulting engineer called in by Bellows Falls' public works wastewater management chief operator Robert Wheeler, following complaints in The Square of escaping sewer gas infiltrating businesses late last month.
Tim Powers of Powers Insurance at 35 The Square told the board on Jan. 25 that several businesses were affected and some employees had to go home as a result. The board was asked to call in an engineer to conduct an investigation paid for out of the sewer fund.
On Feb. 8, Trustees approved $7,000 for Naomi Johnson, PE and Vice President of Dufresne Group Consulting Engineers of Windsor, to investigate. She submitted a 11-page initial report in which she described the likely chronology and causes for the gas leakage in The Square, beginning with improvements in the sewer line done last summer.
“Before the improvements were done, gas was coming down to Mill Street toward the wastewater plant and likely venting through the perforated manhole cover there. When the pipeline was tightened up, the gas could no longer escape,” Johnson said.
She said she listened to the chronology of complaints from citizen business owners and determined that gases started building up at that time.
She noted that on Jan. 31, when a perforated manhole cover replaced the solid cover on Mill Street, business owners smelled an improvement, but later in the day said perhaps they had spoken too soon. Sewer gas could still be detected.
For another week, odors came and went.
Johnson said the cause of sewer odor is septic sewage sulfur hydroxide and can occur when sewer water is sitting in the mains too long; however, chemical tests did not indicate the wastewater to be septic at that point.
Johnson noted that three significantly long septic mains feed in just above Mill Street, two from Walpole and one from the Rockingham Industrial Park, fed through seven pump stations. She said they would take a look at the pump stations next. Sewage can turn septic creating gases if it sits too long.
“Every building has gas vents that feed out through their roofs,” Johnson said. “It's finding its way up and out.”
Since stagnant wastewater is the most likely culprit, Johnson hopes that examination of the pump stations, and perhaps increasing the frequency of pump action, will move the wastewater through more quickly and prevent gas from forming.
Johnson said she thought a short term solution would be to put one of two types of valves at the Mill Street location to prevent gases from escaping back up the lines into the Square.
Besides installing valves that would open to allow the wastewater through and then close to prevent gas from escaping back up the pipes into the Square, Johnson suggested that the sitting wastewater could be treated with a type of oxidant that would stem gas production.
Both Interim Town Manager Francis “Dutch” Walsh, and Wastewater Chief Operator Rob Wheeler, noted that the cities of St. Johnsbury and Claremont, N.H., had experienced similar problems when they had upgraded their sewer mains, so it was not an unusual problem to run into. Once those towns found the source of the leak, the problem was solved.