The Clearwater Project evaluates the Sanitation Districts' main sewer system. As part of it, the $630M Joint Water Pollution Control Plant Effluent Outfall Tunnel Project was approved to replace a pair of aging wastewater tunnels with a 7-mile-long tunnel.

If the existing tunnels fail sewage could spill into the surrounding waterways having an effect on public health and the environment. The project will modernize aging infrastructure, address concerns of seismic activity and protect water quality, impacting 5 million people across 73 cities in the LA Basin.

The project consists of constructing 7 miles of 18-ft internal diameter precast concrete segmental lining tunnel from a single heading with a pressurized face TBM and all appurtenant work. This tunnel will be constructed almost entirely underneath streetways.

WBA Tunnel Seal, Omega-shaped was specified as the sealing solution because of its superior watertightness, ability to withstand large multidirectional movements, and 100-year life. Dragados USA began construction in 2021 and is expected to continue until 2027.