Piece by piece, what goes wrong with Berkshires bridges
Though individual parts of a bridge fail, their health depends on all the elements working together ...
IN THE NORTHEAST, road salt attacks metal structures. Anchor bolts rust and fall away. Weakened beams can begin to twist.
On a small Monterey Road bridge over Hop Brook in Tyringham, rust is eating away at the north end of the span, inspectors note. Around the corner on Main Road, bolts have rusted off another structurally deficient bridge, which also crosses Hop Brook. On this one, rust is slowly working its way into beam No. 6.
Page after page in the inspection reports show diagrams of beams shaded to indicate “section loss,” a civil engineering term for sections of steel losing their structural integrity.
In North Adams, the Route 2 bridge over the Hoosic River conceals not just rust but the accumulation over time of “pack rust.”
An August 2016 inspection found moderate to heavy rust on that bridge’s stringers – a type of beam that supports the bridge deck – with moderate to severe weakening as a result. Those stringers create a “severe” deficiency with the need for action, the report said. The bridge’s floor beams are only little better off, receiving a “severe” deficiency rating with a recommendation that highway officials “prioritize” the issue for repair.
Shown: The bridge over the Hoosic River on State Road in North Adams, as seen on May 30, 2017.
PEOPLE RARELY STOP to peek under bridges they use. They really can’t, in the case of the Mass Pike bridge that crosses the Williams River in West Stockbridge. The bridge supports the eastbound lanes just south of the town center.
Judging from photos included in that bridge’s recent inspection reports, travelers might have been alarmed to see sections of concrete crumbling away from support columns. An inspector at the scene April 14, 2016, termed this span’s substructure a “severe” deficiency in need of action – which it is now getting.
The inspector said this of the condition of the bridge’s eastern pier: “Throughout the east face, the concrete has numerous areas of severe scaling and spalling, up to 5’ keep, with both primary and secondary rebar exposed.” Rebar is a construction term for metal rods placed inside concrete to provide structural support.
The Eagle visited the site this summer and saw work underway to rebuild the support columns and address other weaknesses noted in the most recent inspection.
In Sheffield, anyone who slows down and looks at the bridge over Schenob Brook on Berkshire School Road can see what concrete looks like when it fails.
That bridge earned its structurally deficient status because of problems up top, with its superstructure, now rated “poor.”
Rebar stand exposed on railings on both sides of the road.
But in most places, concrete weathers and fails out of sight.
Inspectors checking the integrity sometimes note the presence of “honeycombing,” a condition in which bubbles that were not properly smoothed away during construction open up.
Shown: Rebar stands exposed to the elements on the bridge over Schenob Brook on Berkshire School Road in Sheffield.
DECKS LEAK AND DEVELOP HOLES
ONE TURNING POINT for the Meadow Street bridge in Lee came when a hole opened in one lane on the deck, offering a surprise view down into Powder Mill Brook. A town crew quickly brought a metal plate to patch the gap.
But this bridge was already on life support. One lane had been closed, in December 2011, through the placement of Jersey barriers because one beam, No. 5, was suffering from corrosion.
A few months later, the hole appeared. Though patched, the bridge deck earned a C-S-I deficiency in an inspection conducted on Feb. 22, 2012.
In northwest Pittsfield, a small bridge that crosses an inlet popular with anglers at Onota Lake developed a hole on its deck in 2010. An inspector termed the deck condition “severe” and recommended action.
The bridge was closed March 14, 2014. Deck woes and problems with its superstructure placed this Lakeway Drive bridge on the structurally deficient list.
Today, a one-lane replacement bridge known as a “pony truss” sits atop the original structure. But concrete still visible is crumbling away.
When an inspector in 2015 flagged deck problems at another Pittsfield bridge on Route 20 over a CSX Railroad line, repairs were swift. The deck on the busy section of highway, near the Hancock line, was repaired last fall.
It is common for leaking decks to accelerate corrosion underneath, since wet beams rust more quickly.
Shown: The placement of Jersey barriers on a Center Road bridge in Savoy caused ponding that damaged the deck.
CURRENTS UNDERMINE BRIDGE ABUTMENTS
THOUGH MANY BERKSHIRES BRIDGES cross relatively narrow streams, currents can pound down those channels. The force of water “scours” bridge elements and is a key problem noted by inspectors.
The Tannery Road bridge in Otis over the West Branch of the Farmington Road suffers from scour, as did the original Meadow Street bridge in Lee – the crossing now served by a temporary replacement structure. In a February 2012 report, scour affecting the Lee bridge was listed as a severe or major deficiency demanding action “ASAP.”
Special placards are in place in Otis, offering a quick visual measure of water depth. The same signs are posted under bridges throughout the county, including at the Main Road bridge in Tyringham. Problems with that bridge’s substructure earned it a rating of “poor,” placing it on the structurally deficient list.
Shown: Concrete is falling away beneath the Elm Street Bridge in Pittsfield.
BRIDGES FAIL BEAM BY BEAM
IT IS COMMON for beleaguered road crews to place Jersey barriers on top of bridges to prevent vehicles from putting weight on beams found to be weakened by corrosion and the resulting “section loss.”
Though that technique buys time for bridges, it reduces the ability of affected bridges to move traffic.
Jersey barriers went up on the Meadow Street bridge in Lee, until an entire replacement span was set onto the structure. In Sheffield, a barrier was placed on the bridge over the Schenob Brook in June 2016 to lighten weight over beam No. 7, the weakest of the lot due to rust and corrosion below. On the east side of the bridge, an inspection found that holes have opened in that same beam.
Things don’t get much worse than what’s happened to the beams underneath the now-closed timber deck at the Umpachene Road bridge in New Marlborough.
Photos in the report show why this bridge is out of service, after the inspector noted “crushing of the beams” at the span’s west end.
Though the bridge has been closed since 2012, inspectors still stop by. Though vehicles can’t cross, public safety still demands that precautions are in place.
On Oct. 25, 2016, an inspection team found that they were not. “The east at-bridge ‘Bridge Closed’ sign is missing,” a member noted.
Shown: Rust weakens beams on a closed New Marlborough bridge over the Konkapot River.
BRIDGES GET TOUGH LOVE
AROUND THE REGION, unseen by most, pieces of wood known as “cribbing” are jammed into tight spaces on the undersides of bridges, to provide secondary support.
In North Adams, cribbing is in place both on the Route 2 bridge over the Hoosic River, a state-owned structure, and on the city-owned Brown Street bridge near downtown. Both are structurally deficient.
Similar wood supports can be seen underneath the Route 20 bridge in west Pittsfield over a rail line.
Those patches buy time. But the problems that prompted their placement, inspection reports make clear, remain.
Shown: “Cribbing” unseen to passers-by helps keep the Brown Street bridge functioning in North Adams.
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