Cal trans is proposing a geotechnical investigative drilling operation in and
adjacent to the Russian River at State Route 20 in order to obtain subsurface information that would inform design for replacement of the Calpella Bridge. Drilling would be conducted at eight (8) locations in the vicinity of the future bridge abutments. The proposed soil and rock borings would be between 4 to 6- inches in diameter and would be drilled to approximate depths of 50 to 150-feet. A 5.5-inch diameter steel casing may be used at the top of the boring hole to secure drilling fluid circulation. The drilling fluids shall be contained and recirculated through a closed system-drilling fluids and products shall be fully recovered in a mud tank before being transferred to 55- gallon steel drums for disposal. The boreholes would be backfilled with cement grout and/or bentonite.