Stalled and busted 320 feet underground near Bothell’s Maywood Hills Elementary School, a tunnel-boring machine may get back to its assigned duty of digging a tunnel for the Brightwater sewage-treatment project sometime next month.

Due to damage to the drill, the machine has sat idle since May. Brightwater Project Manager Gunars Sreibers said recently that after a series of delays, repairs finally got under way last month.

To make those repairs possible, contractors drilled six so-called dewatering wells near the broken machine and adjacent to Maywood School. Sreibers and others said project management has worked closely with the Northshore School District to ensure the wells have not caused any disruption to the school or created any safety hazards.

“We have worked very well with the district,” Sreibers said, adding the original intention was to have work on the drill finished by September. Obviously, that didn’t work out.

“They worked quickly with no problems and we have received no parent or community complaints,” said Northshore Communications Director Leanna Albrecht. She said some additional drilling on the property was completed over the recent winter break.

Sreibers said a number of issues slowed the intended repair time. The initial wells were dug to reduce water pressure around the head of the drilling machine, referred to as BT2.

As the drill head sits so far beneath the surface, just like deep underwater divers, those completing repairs on BT2 would have needed to undergo time-consuming decompression after working on the drill. The wells were designed to remove groundwater and reduce atmospheric pressure around the drill head removing the need for decompression.

The original plan didn’t work as well as the contractor hoped, Sreibers said. To help remove even more groundwater, workers dug 10 additional drainage tunnels that allowed repairs on the drill to begin.

Sreibers noted the drill head is 16 feet in diameter and needs welding work all the way around that surface. Additionally, with the help of the company that produced the machine, workers are installing a new device meant to keep rocks — or cobbles, as Sreibers, put it — from clogging the drill head. That was one of the issues that led to problems with the drill.

As for the wells near Maywood, Sreibers said there is a fairly lengthy decommissioning process. He expects them to be permanently capped by summer.

He added that the contractor has a duty to restore any damage or alterations done to the Maywood grounds.

In the meantime, Sreibers said Brightwater officials are keeping an eye open for any possible problems related to tunnel drilling around the intersection of 90th Avenue Northeast and Northeast 195th Street in Bothell.

According to Sreibers, BT2 passed through the area in June 2008. Nevertheless, homeowners have reported noticing cracks in driveways, sidewalks and home foundations they believe could be related to the tunneling and the resulting settling of the ground.

“We take all these types of things very seriously,” Sreibers said, stating inspectors took a careful look at two properties. He described the problems reported by homeowners as “minor,” but said engineers installed monitoring equipment in the area to look for any signs of ground settling. Sreibers added those monitors will be checked at least weekly.

There is a second Brightwater drill about to undergo repairs at a site outside of Bothell in Lake Forest Park. Sreibers said BT3 is making its way slowly toward dewatering wells set up in that city. While it needs some attention, BT3 apparently did not suffer as much damage as BT2. Repairs will extend past next month mostly because the machine was not in a spot where workers could gain access to it when troubles first appeared.

Sreibers said that as BT3 makes its way to a point where it can be repaired, engineers are testing a new polymer that might make digging through local clay layers a lot easier and quicker. Still, due to the damage suffered by the drills, tunnel boring is way behind schedule, as has widely been reported. Sreibers expects drilling efforts to last into next year adding millions to the cost of Brightwater. Who will be stuck with the tab for the overruns — King County, the contractor or the drill maker — has yet to be decided.