In fall 2013, Baltazar Contractors, Inc. of Ludlow, MA installed 700 feet of sewer line on Millers Falls Road, connecting it to a site on Industrial Drive in Montague, MA. Baltazar’s reputation helped the company win the job on a no-bid, negotiated contract because of an emergency. They were working to correct a problem with a previously install section of pipe that was not properly installed during a project by another contractor.
The job started slowly because of high traffic volume. The projected called for 700 feet of 10-inch SDR 35 PVC pipe, in 14-1/2 foot lengths. During the September project, Montague’s DPW Superintendent said, “They’re getting the job done and they’re doing it right. The crew is installing the pipe in the best possible way in a workmanship like manner under very tough conditions. The town of Montague lucked out in getting such a conscientious and experienced company [that is] working for a permanent solution to a very bad problem.”
The job was challenging from the start for several reasons. The area had a high vehicle traffic volume, there were utility lines overhead, the old sewer trench was still on one side, ready to cave in and the nearby utility poles seemed ready to topple over because of the weight of the cables and wires. As a result, Baltazar’s workers were required to hold up the utility wires with insulated, fiberglass-reinforced plastic poles, so that excavators could work without becoming entangled in the lines. Additionally, existing ground water threatened to cause cave-ins, or to float the pipe upward as it was being installed. Superintendent George Sajdera said the biggest obstacle was contending with heavy traffic, especially when setting the first precast manhole structure in place. That was where they were tying into the old section of functioning sewer.
“We would dig for five minutes,” he said, “And then we would have to wait for 20 minutes for backed up traffic to clear.” That was with two police officers directing the daily, heavy traffic for the duration of the job.
To keep the roadway on one side and the old sewer on the other from caving into the trench that was 19 feet deep, Sajdera’s crew use a steel digging box with added steel plates. The box was 20 feet long and eight feet wide and was externally supported on either side for added protection. During the excavation, Baltazar’s excavator operator made the trench a foot and one half deeper than the pipe elevation, so they could bed the pipe in 3/4 inch washed stone. They covered the pipe with another foot and one half of similar material.
The crew guided the pipe into place with laser equipment set up in a downstream manhole. With this process, a worker targets the end of the pipe as a way to adjust the pipe so that the laser beam confirms the pipe is dead center on line and grade. “For reasons of safety, we send just one experience guy into the trench to set the pipe,” Sajdera said. “And everyone wears a hardhat. Even me.”
Once the pipe is on line and grade, it’s covered with screened stone fed from a Celco Hopper with an under belly conveyer belt. That is mounted on the Cat 345 D excavator digging the trench. The conveyer directs stone into the trench as needed.
That accomplishes two things. First, the stone bedding under the pipe is kept in place, on line and grade. With stone covering the pipe, it weighs the pipe down to keep it from floating. Second, workers place a suction hose in the stone bedding under the pipe then connect it to a pump. That removes ground water during installation, which helps prevent the pipe from floating.
The crew kept the trench backfilled, compacted in lifts with an excavator equipped with a hydraulic compactor. To improve the efficiency of the backfilling operation, Baltazar used a Komatsu WA 389 side dump loader capable of dumping backfill material without disrupting traffic. Since there was no room to cast material as they excavated, Baltazar Contractors use two Mack tri-axle dump trucks to haul material to and from stockpiles. By using two trucks, there was no delay between trips.
A second Caterpillar loader, front dump, refilled the Celco hopper. While this was all going on, a skid steer loader outfitted with a rotary broom cleaned up the pavement as the job progressed.
Retired Montague DPW foreman, Charles Richotte, who worked on the original installation that was now being replaced, recalled how different the work was done back then. “We were working in the dark ages with an old cable backhoe and no shoring down to 19 feet. Nobody wore hardhats. The ground water turned the bottom of the trench to quick sand and your feet would get stuck in it. And the Transite pipe floated. We had a pump but didn’t use any stone under the pipe. The sides caved in every little while, and I got buried to the waist more than once. It was awful dangerous. Lucky nobody got killed. I’m glad those days are over.”