Wastewater Treatment Plant  Improvements
Warrenton, Oregon

Outfall BOD and other demands called for sewage treatment improvements for this Columbia River Estuary site. Improvements included three new diked, lined, and concrete surfaced sequencing batch reactors (SBR’s), ultraviolet disinfection, outbuildings, pumps and piping. A new outfall was also installed with directional boring for over 4,000 feet under the marsh and tidal flats to the diffuser in the Columbia River channel.

GSI's thorough site evaluation included drilled borings, cone penetrometer test probes, and digital instruments around the lagoons and outfall alignment. Our local experience enhanced dike construction sequencing and surcharging, foundation bearing and earth pressures for embedded treatment structures, and construction of a temporary, grid-reinforced access road over wetlands (without vegetation removal to enhance restoration). GSI also provided experienced observation of shoring and dewatering, as well as stabilization for the very soft tidally influenced excavations.