The Washington Suburban Sanitary Commission recently completed a tricky mining procedure for a bi-county water main that will run under Bethesda.
On April 24, WSSC “holed through” the wall of a shaft 200 feet below a spot near Tuckerman Lane and I-270. A Tunnel Boring Machine drilled a 4.5-mile section of what will be a tunnel for a 84-inch diameter water main that will be able to hold up to 100 million gallons of water a day.
WSSC said its Tunnel Boring Machine (TBM) hit its target under Tuckerman Lane a few feet off from dead center.
It was the last leg of the 5.3-mile tunnel and the final step in the mining portion of the Bi-County Water Tunnel Project. The Bi-County Water Tunnel will run along I-270 and I-495, connecting two existing 96-inch water mains and helping to keep up with increasing water demands in both Montgomery and Prince George’s Counties.
A press release on the project said the new main will also increase reserves in case of emergency. It will be completed in 2014.
The scheduled shutdown of several large water mains at the time of the Chevy Chase Lake Drive water main break in March, including a 96-inch main from WSSC’s Potomac filtration plant to Tuckerman Lane, drew scrutiny from Montgomery County leaders.