Bi-County Water Tunnel

Completed in 2015 by Southland Contracting, the Bi-County Water Tunnel Project consisted of the construction of a new 5.3-mile water pipeline to meet the future water requirements for Montgomery and Price George’s counties resulting from economic development and growth. The pipeline will connect two existing water mains: the first near I-270 and Tuckerman Lane and another in Rock Creek Park at Stoneybrook and Beach Drives. The construction of a 10 foot diameter, 28,000 feet long Tunnel Boring Machine (TBM) rock tunnel for an 84-inch diameter steel pipeline with sanded grout annulus backfill. The tree construction access shafts were excavated by drill and blast methods. The main construction shaft at Connecticut Avenue, 35 feet in diameter by 165 feet deep, was supported by liner plates in the overburden and by rock bolts and shotcrete in rock. The 25-foot diameter Tuckerman shaft was 138 feet deep, supported by secant piles and overburden. The Stoneybrook shaft is 16 feet in diameter and 150 feet deep. The tunnel was excavated with a Robbins 10 feet Hard Rock TBM. The 10 feet diameter tunnel runs 150 feet to 300 feet below ground in bedrock. Muck handling ventilation was more difficult due to the small excavation diameters of about 10 feet. Consist of two drives, one extending 4, 125 feet and the second running 4.3 miles without intermediate access shafts. This will be a dependable, high pressure clean water source during high-use periods, droughts, and emergencies.