Building a cavern-style combined sewer overflow pump station

Air handling/conditioning units are located on the roof of the pump station’s superstructure. The superstructure houses electrical equipment, and cranes for servicing the cavern pumps. The facility will be operated remotely from the Easterly Wastewater Treatment Plant.

Benching down in progress. The top 27 feet were excavated in three staggered headings. Once the roof was secured, the remaining 38 vertical feet were excavated down in four 10-foot high, full-width benches. The white reflectors are convergence monitoring points.

The upper mezzanine in the pump room. Pumps are oriented vertically with motors above.

Benching down completed. Bottom concrete floor slab under construction.

The 160 mgd Easterly Tunnel Dewatering Pump Station is 240 feet below ground and 35 feet lower than the nearby tunnel storage system. The underground cavern will be approximately 140 feet long, 56 feet wide, and 65 feet high. Each shaft is 40 feet in diameter and houses discharge pipes, HVAC ductwork, and electrical conduits. Excavation included about 100 feet of overburden soils over bedrock shale. Rendering: MWH Global

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