by Joe Parzych
On March 2012, Northern Construction of Palmer, MA, began replacing the Factory Hollow Bridge, a bridge built in 1931 to bypass Factory Hollow, once a beehive of manufacturing. During those years, there was a water powered fulling mill where woolen cloth was cleaned and beaten to thicken it. The mill also wove wool, cotton and a combination of the two and there was a dye shop and clothing factory. As part of its history, the town was home to a shoe factory that turned out shoes and boots dating back to the Civil War.
To allow access to Turners Falls, a community on the other side of the river, a small wooden bridge was built in the 1920’s for horse drawn vehicles, where it still exists a short distance upstream from the newer Factory Hollow Bridge, a structure that followed in 1931. The newer bridge, built by the Commonwealth of MA, was built to accommodate motor vehicles and trucks. Interestingly, an earthquake shook the area in 1938 but did no damage to the 1931 bridge. The abutments for the earlier bridge were not disturbed either. As the existing bridge began to deteriorate over time, SPS of Salisbury, MA, made repairs to the existing bridge, patching the deck with a quick setting epoxy concrete.
The job begins
Once the job was under way, Northern Construction first ran into problems when driving H beam piles for new abutments, ten feet back from existing abutments. They encountered huge chunks of shot rock, material remaining from the construction of the 1931 bridge. It seems the builder backfilled the abutments with huge chunks of ledge blasted from a rock outcropping on the north side of the westbound bridge approach.
Northern Construction excavated some of that ledge, but other chunks of the solid igneous rock, halted attempts to drive H beam piles. Northern Construction and MA DOT negotiated a new plan calling for holes to be drilled to accommodate 30-inch diameter steel casings in which to set the H beam piles. Accordingly, Buffalo Drilling of Buffalo, NY, contracted to drill holes for the casings. They used a SD 20E Caterpillar excavator carriage with a Gin Tai Japanese drilling rig mounted in place of an excavator front. The rig, capable of drilling to 200-feet, drilled holes for the 30-inch steel casings, 68-feet deep. A problem arose when the drill encountered unstable soil in which the sides of the hole would not hold up.
To stabilize the sides, Graves Concrete Service supplied flowable concrete fill that set up soft enough to drill through, but firm enough to keep the hole open. Following equipment issues with the earlier unit, Buffalo Drilling rented a Soil Mec drill rig from Hub Foundations of Harvard, MA, to finish drilling the holes.
The bores were initially drilled to bedrock which is 68-feet with continued drilling another five feet to cement the casings and H beam pilings into the bedrock. Once the H-beams were in place, Northern Construction filled the bottom half of the casings with concrete, and surrounded the H beams the remaining way to the surface with crushed rock.
Superintendent Jack Graves, working for Northern Construction said that using crushed rock in the top half of the casings allows the pilings to sway slightly in the event of an earthquake. He noted that all new U.S. bridges have been mandated to be constructed to withstand the shock wave of an earthquake following bridge failures in California quake disasters. This new bridge will stand atop twelve H-beam pilings as if on stilts. “They may wobble a bit but they won’t snap,” he said.
The contract called for replacing the bridge, while maintaining two way traffic during the construction. Graves said that is accomplished by building the bridge in three sections. As construction on the northern third of the bridge nears completion, the plan will be for westbound traffic to use the new section and eastbound traffic will use the outside southern section. Next, the contractor will demolish and rebuild the middle third. Once the middle section is complete, traffic shifts so that the contractor’s crew can demolish and rebuild the remaining southern third section. At the same time, the crew must maintain a walkway for foot traffic, even though there is very little.
As part of the safety regimen, lumber in the form of 4-inch thick x 8-inch wide hardwood planks were placed on the lower flanges of the bridge’s existing I beams to serve as false work. Witch Concrete Sawing Service then cut the existing reinforced concrete deck on the old deck into manageable chunks to be removed. The hardwood tongue and groove false work planks are sturdy enough to catch concrete demolition debris as a demo blanket, without breaking.
Workers also took great care to avoid polluting the Falls River. They used wooden forms rather than galvanized sheet metal corrugated pans as stay in place forms, so that voids, or “rat holes,” would be readily apparent once the forms are stripped. This was required by MADOT.
The first deck pour took place July 1, 2013. Lane Construction supplied a 4,000-pound high performance bridge deck concrete mix design that contained 3/4-inch washed stone. In order to maintain two way traffic, both the Terex Transit-Mix concrete mixer and the Valley Concrete -Alliance Concrete Pump were set up on a terraced staging area where the mixer discharged concrete into a hopper. Following the initial pour, Northern Construction workers covered the fresh concrete with tarps, “shingling” the tarps to shed water without damaging the fresh concrete. This protected the job from an ensuing rainstorm that followed soon thereafter.
As a side note, Atlantic Bridge and Engineering, the steelwork subcontractor for SPS on the Turners Falls-Gill Bridge, is also sub-contracting the re-bar installation and other steel work for Northern Construction on the Rte 2 Bridge, nearby. The two bridge projects are within sight of each other across the Connecticut River. “With all the change orders, the completion date is a moving target,” Northern Construction CEO Dan Hughes said, noting that the original completion date is scheduled for Nov 30, 2013.
by Joe Parzych