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Engineers urge caution on timber restoration; town weighs MassDOT replacement versus costly rehab
Summary
Consultants SGH told the Duxbury Select Board their peer review of Dr. Dan Tingley’s Powder Point Bridge study shows key unknowns about buried pile condition and likely higher costs for timber restoration, while a MassDOT steel-and-concrete replacement would be paid by the state but change the town’s character and maintenance obligations.
Consultants supporting Duxbury presented a cautious assessment on July 6 of whether a timber restoration of the Powder Point Bridge can meet long-term reliability and cost expectations. Chuck Barnes of SGH said his firm’s review of Dr. Dan Tingley’s feasibility work shows important unknowns — particularly the condition of buried piles below the mud line — that make Tingley’s optimistic cost and service-life estimates uncertain.
"We can't say right now if Dr. Tingley’s approach would work or not because we don't have enough information," Barnes said, adding that preliminary pile testing in Dr. Tingley’s field work sampled only a few feet of a very small subset of piles. Barnes told the board his firm estimates timber repair or phased replacement costs in the mid‑millions and that a complete rehabilitation could be much higher depending on what buried-pile investigations reveal.
Barnes and Paul Schuman, who joined remotely, contrasted the town‑funded timber options with MassDOT’s proposed steel‑and‑concrete replacement, which MassDOT and federal funds would initially pay for at no cost to the town. "A steel and concrete bridge is a Cadillac bridge," Barnes said, noting a higher initial life expectancy and lower annual maintenance costs but also fewer piles and a different visual character.
Dr. Dan Tingley, who prepared the timber‑restoration study that prompted the review, defended the feasibility of repairs and lower unit costs. He described two posting methods used to repair piles — a less costly Dutchman’s patch and a larger segment replacement — and said his 310‑pile estimate was built from field techniques scaled across the bridge. "We did 6 piles with digging around them and those were sound under the mud line," he said, urging further design and testing to confirm scale economics.
Board members and residents pressed for clarity on the following points: the true per‑pile unit cost (Tingley’s estimate of roughly $10,000 per pile versus SGH’s $15,000–$20,000 data point), total rehabilitation ranges (SGH estimated $4.7–$6.2 million for partial work up to $8–11 million or $16 million for nearly complete rehab), seasonal limits on in‑water work because of bird nesting rules, MassDOT’s inspection and approval role, and how any town-funded option would affect property taxes.
Several speakers urged the town to pursue more advanced design work and an independent cost estimate to narrow the ranges before committing to a restoration path. "You need to get a more accurate unit cost and better design," Paul Schuman said, recommending a contractor‑level estimate based on developed drawings. The consultants also flagged the need to investigate bacterial attack below the mud line as well as fungal decay in the splash zone.
The board agreed to continue the discussion at upcoming meetings and to press MassDOT for schedule and design details. Multiple speakers urged the town to seek clearer answers before committing to either the MassDOT replacement or an extensive town-funded timber program.
The Select Board asked the Powder Point Bridge Advisory Committee and its technical advisors to return at the July 20 meeting with next steps, including a plan for further testing and independent cost estimating. The board did not take a formal vote on a direction at the July 6 meeting.
