Attachment 3: Geotechnical Activities Categorical Exclusions

Geotechnical Activities Categorical Exclusion
Project Name
Winchester Creek Bridge Replacement
Project Number (FLH Accounts Table)

Project Manager

OR FLAP DOUGLAS 251(2)

Wendy Schmidt

Project Description (Briefly describe the geotechnical activities and attach any relevant maps.) The project’s purpose is to replace the seismically vulnerable Winchester Creek Bridge, which has substandard bridge rail and sidewalk width, and no approach guardrail. The bridge carries Salmon Harbor Drive over Winchester Creek in Winchester Bay, Oregon. The replacement bridge will be a single-span, wider structure that meets current roadway design standards and current seismic design criteria. The action covered by this CE is the geotechnical drilling. Two geotechnical borings at locations (BH26-01, BH26-02) will be drilled to investigate the subsurface soil, rock, and groundwater conditions throughout the project site within the road right-of-way. Depending on the type of drill rig and method, the borings will be advanced using a combination of large-diameter solid flight auger, hollow stem auger, rotary wash, and/or rock core drilling techniques to total exploration depths between 50 and 130 feet below the ground surface. Additional drilling details include: Boring locations will be finalized in the field by a WFLHD Geotechnical Engineer or Engineering Geologist with the driller after contract award, but will remain within the roadway prism. Water will be used to advance holes when using rotary wash and rock coring, as well aswhen mixing grout for vibrating-wire piezometer installation. Generally, return water from the borehole is recirculated and reused for drilling. Excess drill water and drill cuttings will be drummed and disposed of at a location approved by Douglas County personnel, if a government provided waste area is identified. Otherwise, the cuttings and drilling fluids will be disposed of off-site. Borings will be backfilled in accordance with State of Oregon regulations and resurfaced to match surrounding conditions, including cold patch in paved areas. Borings with installed instruments drilled in paved areas will be completed at the surface with 12-inch diameter flush-mounted, traffic rated monuments. The estimated time for each geotechnical boring, including mobilization to and from the drill location, instrument installations, and ground surface completions, is between approximately 6 to 7 full days, with a total investigation duration of between one to two weeks.