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Finding a way to repair decaying sewer infrastructure beneath streetcar tracks without disrupting service has become more than just a traditional boring project – pun intended – for workers at Emery & Sons Construction; it’s a way to test a new tunneling technology.

The company last week began work on a $2.3 million Portland Bureau of Environmental Services project to repair several aging segments of sewer line in Northwest and Southwest Portland. Workers plan to repair infrastructure in seven areas around the city in an effort that should continue through early August.

Most of the work will be performed the traditional way – digging out damaged pipe and replacing it. However, for the sections around Southwest Park Avenue and Southwest Market Street, the process grew a little more complicated because of the Portland Streetcar, said Bill Theiss, the BES construction manager on the project.

“At that area and Mill Street, we need to go under the streetcar without disturbing it,” Theiss said. “There’s also a storm sewer and other things under the ground there that we don’t want to hit. We have to be very precise – and the technology we’re working with is very controllable.”

The company and city decided to use the Vermeer AXIS boring machine at the site. A guiding laser is used to dig smaller pipe tunnels than possible with normal micro-tunneling techniques, and it also allows workers to pull a single, long piece of flexible piping backward through the hole, rather than push pipe through in several segments.

And because of specifications for the area, it was the only way to fix that part of the sewer infrastructure without digging up the tracks, said Dale Bettencourt, project manager with Emery & Sons.

“It’s pretty slick,” Bettencourt said. “The machine comes up in one lane, and then it pulls the pipe back through. On paper it’s supposed to be cheaper than the other options, although I guess we’ll see.”

Representatives from Vermeer Corp. and the Australian inventor of the product are in Portland to operate the machine for Emery & Sons as a demonstration, Bettencourt said.

“They’re hoping to do the whole process in one day,” he said.

Workers from Emery & Sons are nearly done digging two pits on either side of the tracks to serve as the starting and stopping point for the machine. The boring will take place today or Wednesday. Installation of the high-density polyethylene pipe will follow, Bettencourt said.

This is the second time the city has experimented with the technology. The first was for a sewer project on Yamhill Street, Theiss said.

“Micro-tunneling generally only goes down to 36-inch pipe, and this goes down to 10-inch to 14-inch pipe,” Theiss said. “At Yamhill it was only a quarter to a half inch off when it came out – that’s very straight. It’s very accurate and that’s important because we can’t have any low spots.”

The city investigated several parts of the sewer system before selecting the segments for the Northwest and Southwest Portland sewer rehabilitation projects, Theiss said.

“Every year we go out and do a whole series of these underground TV reports, where we run a camera down pipes and look at the condition they’re in,” Theiss said. “The pipes in this project were chosen two to three years ago, and they were starting to collapse, or we found holes or something else was going wrong.”

Most of the sewer pipes across the city were installed nearly 100 years ago, and others were installed in the 1950s, so the city checks segments fairly frequently, and runs cameras through the pipes systematically at least every five to 10 years, he said.

“Usually 40 to 60 years after installation we still have good service on those pipes, but after 60 years we start to have problems,” Theiss said. “After 100 years we start looking real close.”

The bundling of projects into a larger contract is something the city started about a year and a half ago, he added.

“The whole thought was we’d try to build enough of a project so we could group them together to get a better price – if you do smaller projects individually, the price goes up,” Theiss said.

A lot of the oldest pipes are made of reinforced concrete or fired clay – which in some places is patched together using unusual methods, he said.

“In general, the clay they used would be in one solid segment, but in some spots they stuck pieces together with grout, and every now and then we discover more of those,” Theiss said. “Sometimes that’s still serviceable, but sometimes it’s not.”

Fired clay is an old sort of material, but it’s regaining appeal, Theiss added.

“We’re starting to go back to it because of its longevity – it holds up well against the corrosive gases,” Theiss said. “And let’s face it, the clay we’d consider a green project. We also find it’s a way to get away from the oil industry and PVC pipe, and at some point we’re going to need to do that.”

The bundle of repairs in the Emery & Sons project won’t use clay-fired pipes, but it’s something the city has tested and might use in future projects, said Stephen Sykes, a spokesman for the BES.

“For this we’re using both PVC and HDPE pipe, and we’ll also use reinforced concrete pipe in one of the larger sections,” Sykes said.

The replacement pipes also will be larger than the original ones to allow for future city development, he said.

“Since these pipes are 70 to 90 years old, and since there’s been a significant amount of development, it makes sense to upsize,” Sykes said.