HINKLEY Operators of a planned compost recycling plant in Hinkley will install an additional seal to prevent leakage into the groundwater, a company official said.

The California Regional Water Quality Control Board, Lahontan Region, discovered a structural defect in the plant's design that could have led to a spill under extreme circumstances, Operations Manager Chris Seney said.

Mike Plaziak, supervising engineering geologist for the water board, said the concern was that material could spill over during heavy rainfall and seep into the area between the surface and the groundwater. He added that because the groundwater level in the desert was at least 100 feet below ground, it would take a significant amount of rainfall for this to occur.

The problem was "a very, very minor detail," Seney said.

The agency's concern was overblown, Seney said. He said that the plant was already lined on all sides to prevent any leakage but lacked an additional seal at a gap between a metal plate and concrete berm.

Seney said the facility would have two retention ponds that could withstand a "thousand-year rain event" as well as three monitoring wells.

The letter said that the operators could avoid the need for design changes if they installed additional monitoring equipment in the area. Seney said they would install the seal because doing so was simple and inexpensive.

The project is moving forward after a judge approved the company's environmental impact report in December. Construction has been stalled for six years in the face of strong opposition from local environmental activists. Seney said he was unsure when the project would begin construction.

Bob Conaway, Hinkley resident and member of HelpHinkley.org, which has fought against the project, said that he was not familiar with the seal issue but praised the water board for bringing it to the company's attention.

"I encourage them to keep a close eye," Conaway said, adding that his group still had serious concerns with the project.

The 80-acre facility will accept 400,000 tons of waste product per year, half of which will be biosolids, or treated human waste, and half green waste, like tree trimmings and grass clippings.

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