Town engineers say siphon adjustment quelled high BOD/TSS readings; grease blockage likely caused Alpine Court overbilling

Town engineering staff briefed the Water and Sewer Advisory Committee on elevated biochemical oxygen demand (BOD) and total suspended solids (TSS) readings that had been appearing in billing and monitoring data. Staff described how daytime high flows were overflowing a 10-inch siphon into a 14-inch siphon; during lower-flow periods solids settled and later produced concentrated 'slugs' of high BOD/TSS when flows resumed.

To reduce that effect the staff temporarily closed the 10-inch siphon so the 14-inch line could carry low flows. "So what we ended up doing is we closed that 10 inch. And so the 14 is now able to handle the low flows," staff said, and reported that subsequent BOD and TSS readings returned to the normal range, pending a planned siphon station upgrade.

Committee members also reviewed an Alpine Court billing discrepancy. Bedford's 5-minute flow meter consistently recorded about 300,000 nd 500,000 gallons for a month-long period, while Manchester's totalizer showed roughly 2,000,000 gallons. On inspection crews found a large grease blockage in a metering manhole; cleaning the blockage produced an immediate drop in observed level from about 4 inches to under 1 inch at the Manchester meter. Staff said Manchester has verbally indicated it would consider a credit if Bedford can demonstrate the meter discrepancy with paired data.

Staff outlined operational follow-ups: continue flow metering (a broader 2026 study), provide paired meter data to Manchester to support any credit claim, increase manhole cleaning frequency (quarterly scrubbing was proposed), and resume targeted CCTV inspections to identify I&I that may require lining or reconstruction.

The committee requested that flow-metering results and any billing-credit actions be reported back to the advisory committee and council as needed.