The City of Lynden is a community of about 12,000 people in the State of Washington. Most of the state is in a severe drought, with the City no exception. Their main source of water, the Nooksack River, was reported on June 26 to be at its lowest point on that date since records were first kept in 1966.

To make things worse, although their treatment plant had been modified a number of times since the original construction in 1924, it had serious defects and could not meet peak day demands. This forced the City to rely on storage. Extended peak demand would exhaust the storage capacity, resulting in service disruptions for all homes and businesses in the area.

We partnered with the City to design a new 8 MGD plant with easy expansion to 12 MGD. The treatment process has to address raw water turbidity from 60 to 1,500 NTU with greatly reduced alkalinity and includes grit removal and horizontal cross flow sedimentation basins equipped with plate settlers. The facility also features high rate, deep bed, dual media gravity filters; UV disinfection; sodium hypochlorite generation; and residuals handling, including a sludge gravity thickener, backwash treatment, and screw press sludge dewatering. The 0.3 mgd clearwell features two chlorine contact chambers and a pump well for eight vertical turbine pumps.

Construction included deep cell excavation 35 feet below ground and adjacent to a 6 MG reservoir and residential area, as well as over 500 auger cast piles up to 70 feet deep. The construction bid was $2 million below budget.