No Business Creek Tunnel and Tunnel Lift Station

Completed in 2010 by Mole Constructors, The No Business Creek Tunnel and Tunnel Lift Station project consisted of five shafts, approximately 16,000 linear feet of tunnel, a 10 MGD pump station and 2 odor control facilities. Three of the five shafts were 24-foot dimeter shafts and were constructed through saturated subsurface conditions using secant piles as the primary support methodology. The rock portions of these shafts were excavated using drill and blast methodologies with rock dowels, mesh and shotcrete as a primary supports. These shafts ranged in depth from 78 vertical feet to 236 vertical feet.
One of the five shafts was 32-feet in diameter and was constructed through saturated subsurface conditions using secant piles as the primary support methodology. The rock portion of the shaft was excavated using drill and blast methodologies with rock dowels, mesh and shotcrete as the primary supports. This shaft was 204 vertical feet in depth. A 10 MGD pump station was constructed in this shaft. The final shaft was sunk utilizing open caisson methods through the 120 vertical feet depth of saturated subsurface conditions. The remaining 20 vertical feet of this shaft was excavated using drill and blast methodologies.
The tunnel consisted of 15,954 linear feet of 12 ft diameter excavation, from one work shaft, through very hard granitic gneiss. Blasting methods were utilized for the starter tunnel, connecting the first two shafts. A 12-foot Robbins High-Performance Tunnel Boring Machine (TBM) was used for the remainder of the tunnel. Rock dowels were used for the majority of the tunnel support. A cast-in-place tunnel lining was installed at the shaft connections. The project is for sewer interception and conveyance.