Funnel/Gate Project
Fort Bragg, California

This project was Geo-Con's first funnel and gate project. The project was performed at the Fort Bragg Mill, which is located in a remote portion of the Northern California coast about 150 miles north of San Francisco. During the previous 40 years, the site was operated by various parties and was used to treat wood that was milled on site. These treatment chemicals contained pentachlorophenol (PCP) which eventually entered the groundwater along with diesel fuel and unleaded gas from underground storage tanks.

The California Regional Water Quality Control Board issued a clean-up and abatement order to Louisiana-Pacific Corporation (L-P) for this work. Geo-Con worked closely with L-P's environmental consultant to produce a funnel/gate which was practical, efficient and constructable. The funnel/gate consisted of a 1,000-foot long by 25-foot deep soil-bentonite slurry wall which was penetrated in four areas by activated carbon gates. These gates collected impacted water through gravel collection trenches and then discharged the water through pipes in the slurry wall into gravel-filled infiltration galleries. This system forced all impacted water to flow only through the activated carbon gates and receive treatment prior to being discharged on the other side of the slurry wall. The slurry wall's minimum permeability of 1x10^-6 cm/sec virtually eliminated any migration of water through the wall.

This project was completed on time and under budget in about six weeks and has met all project-specific requirements.

• Start: 8/15/95
• Completion: 9/15/95