L of a job on demolition in subway tunnel, says MTA

The MTA is already about a third of the way done with the biggest part of its demolition in the L train tunnel.

Crews have removed 2,200 out of 6,800 feet of crumbling concrete duct bank that houses long-abandoned Con Ed power lines on each side of the tunnel’s tubes, said Janno Lieber, MTA capital construction chief.

Neither the concrete nor the cables need to be replaced.

“The demolition work has been going smoothly and according to schedule,” Lieber said Monday.

Trace amounts of potentially dangerous silica dust, which is kicked up during concrete removal, has been detected in the L train tunnel during construction. MTA officials say the amount of dust is too small to affect riders’ health.

“We’ve been able to maintain air quality in the stations at all times while preventing delays to service,” Lieber said.

No demolition work is being done on the tunnel weeknights, and crews did not remove any of the duct bank during the weekend of April 26, the first in which L train service was cut back to accommodate the work. The nearly half-mile stretch of concrete that has already been removed from the span was taken out over a combined six days over the past three weekends.

The duct bank removal is separate from what had been the main part of the L train job — the removal of 35,000 feet of concrete from the tunnel’s bench walls.

That job has been drastically scaled back — the walls will be coated with a polymer instead of ripped out, and the cables within them will be replaced with new cables high on the tunnel walls.