RUMFORD — By next week, the June 8 Prospect Avenue sewer failure problem should finally be fixed, according to Andy Russell, Public Works superintendent.
That is, if ongoing efforts to extract water from the site this weekend finally work long enough to allow a crew to replace a broken sewer pipe and manhole that are within a huge aquifer more than 18 feet below street level.
"We can do it, we just need to get rid of that water," Russell told selectmen Thursday night. "We just haven't been successful getting rid of that water."
Because June 8 was a Friday, Russell said the town crew marked the sinkhole off with safety cones, and began work June 11.
They excavated in and around the sinkhole until they found a sewer pipe with a hole in it on the Sunnyside Terrace side of the sewer line.
"As we exposed the lower side toward Sunnyside Terrace, we briefly saw a hole in the pipe before we were inundated with flooding groundwater," Russell said.
Efforts to drain the work site failed, so he rented some trench boxes to keep his crew safe due to the depth of the dig.
"The sewer line is about 18 1/2 feet deep there," he said. "It's much deeper than it is in other parts of town."
Sewer lines in Rumford are generally 6-feet deep, he said. The crew tried unsuccessfully to do the work themselves, and then sought help from engineers June 28.
Russell said the engineers recommended using larger pumps to drain the site, which they brought in and tried, but that didn't work either.
He brought in a contractor that specializes in extracting water from sites, and then dealt with Water District concerns.
"Because we had a large amount of road dug up, they were concerned their 12-inch water main may fail due to the amount of road that was opened," Russell said.
That's when he said Town Manager Carlo Puiia and Russell decided to contact a company to install a cofferdam.
That was done, and then on July 11, the company drilled a 12-inch well on the Androscoggin River side of the cofferdam to drain the area, but that didn't extract enough water. The engineer suggested drilling on the other side of the sewer line, but that didn't pan out either, Russell said.
They continued to work inside the cofferdam to extract more soil and even went below the sewer pipe to pump water out of the pipe.
However, while doing this on Tuesday, groundwater and sand outside the cofferdam suddenly came in, buckling a 6-inch water main. Water District employees had to immediately put a valve on the line to stop the break.
Then on Wednesday, the crew had the hole in the sewer pipe exposed and were ready to connect a new pipe to it when water and mud again poured in.
"It's not your typical water/sewer project," Russell said. "It's just beyond the scope of what we've ever done before."
Selectman Brad Adley asked Russell about the status of the Maine Department of Environmental Protection action against the town.
In June, raw sewage was pumped from the dig site onto Prospect Avenue homeowner Eric Davis's land — not once, but twice. Davis filed a complaint with the DEP, which led to a state investigation that is still in the correspondence stage, Russell said.
"We did pump some sewage, and it wasn't just sewage," Russell said.
"It was 90 percent groundwater from the trench that we didn't want to pump back into our sewer main, because we were afraid we were just going to create another problem further downstream and go through this all over again."
He said it was pumped into a catch basin until that clogged with soil, and then pumped along the edge of grass on Davis's property.
Responding to Davis' question Thursday night about why they didn't install silt fences, Russell said he spoke with DEP and they didn't recommend silt fences.
He said he bought some 10-by-15-foot dirt bags that catch soil and filter out water.
"Those exploded on us the first day we used them," Russell said.
"We're back trying to de-water it again. It may take a day or two to dry the area up. We need to get the pipe in, get the manhole in, and that should be it."