By JOHN HOWELL The full length of Sandy Lane is open to traffic again, and 18 feet beneath the pavement waste water is flowing to the Cedar Swamp pumping station on its way to the treatment plant between Route 95 and the Pawtuxet River. It's all good,
The full length of Sandy Lane is open to traffic again, and 18 feet beneath the pavement waste water is flowing to the Cedar Swamp pumping station on its way to the treatment plant between Route 95 and the Pawtuxet River.
It’s all good, and at least this section of the aging sewer system should be set for another 30 to 40 years, if not longer.
Perhaps by then a new form of technology will have been developed to address a crumbling infrastructure that would cost in the tens of millions of dollars to replace. Both the conventional means of repairing a broken pipe – digging it up and replacing it – and a newer form of technology – cured in place pipe – were used to fix the Sandy Lane sewer line.
D’Ambra Construction started the digging soon after the pipe near Armory Lane collapsed on Thanksgiving eve. Unearthing and replacing a 154-foot section of pipe took more than a month and all told, between bypass pumps and piping, police details and the actual work, cost $750,000. By comparison, a six-man crew from Green Mountain Pipeline Services from South Royalton, Vermont applied 1,400 feet of cured in place pipe in less than a week at a cost of $180,000.
Some days they worked around the clock and this job was not without its wrinkles, but it was done and Sandy Lane reopened sooner than projected.
“It is bad, one of the worst I’ve seen,” said Darren Slack, who knows his way when it comes to being underground.
Slack described the 24-inch concrete pipe installed on Sandy Lane as crumbling from the inside with sections of it being held only by its reinforcement wire. Having dug into its records, the Warwick Sewer Authority has concluded pipes designed for a forced main were used when one for a gravity feed line should have been. The concrete piping used for pressure lines at the time is prone to deterioration from hydrogen sulfide gas that can build up in gravity feed systems. It wasn’t designed to withstand the deteriorating effects of the gas.
Slack, who had inched his way on his elbows down 900 feet of pipe deep underground while pulling a rope, is seemingly fearless when it comes to dropping into a manhole. With a degree of pride, he says he can turn around inside a 36-inch pipe. A 24-inch pipe, however, is just too tight, in which case he has to be pulled back out.
On Thursday afternoon, after suiting up in a pair of neoprene waders, slipping on rubber gloves and pulling on his “good luck” hat, he cinched tight his harness. He then disappeared into the manhole as the rest of the team positioned the equipment to feed the “sock” needed to complete the last 80 feet of the job.
The sock, made of felt and impregnated with resin, is made to fit the inside of the pipe that has been cleaned of debris. It is rolled back onto itself so that when it is pumped full of air or water it unrolls for the length of the pipe. In this case, because of seriously compromised pipe, water was used to carry the liner and pressurize it. Once that is in place, the cold water is replaced by water heated to 180 degrees that is kept in the pipe for up to eight hours. That activates the resin that hardens as the liner for the pipe.
The final step is carried out from inside a truck in front of a computer and a set of screens. A robot on wheels or a sled is sent the length of the pipe. From previously taken video and precise measurements, the robot cuts holes for the pipeline connections. The connections are burnished smooth by a rotating wire brush ball that removes any burr that might disrupt flow from an intersecting pipe.
With Slack 18 feet below Sandy Lane, the sock is fed down the manhole with crew director Zack Scott lying on the pavement, his head in the manhole, listening. With the faint calls, more sock is fed into the hole or water pumped in. Then comes the all-clear signal from Slack. Jason Snelling begins reeling Slack to the surface. It’s a tight fit as now the sock takes up half the manhole. Slack’s hands appear first, then his head. He wriggles out. He’s been down there for about 20 minutes. He takes a moment to catch his breath. He looks exhausted.
The rest of the crew moves into high gear, pumping water into the sock as it extends for the length of the pipe. They’ve done this countless times, working as a team and knowing exactly the next step.
Scott pauses to answer a question between turning valves and securing above ground pipe connections.
“This was it, the last section, right?”
“You won’t see us by tomorrow afternoon.”
This week the crew – five of them from the same town on Vermont and high school classmates – will be in New Jersey.
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