LAS VEGAS -- Work must begin as soon as possible to seal the closed Sunrise Mountain landfill, according to the Environmental Protection Agency.

Republic Services of Southern Nevada must stabilize while the federal organization develops a comprehensive final plan for the 440-acre former municipal solid waste dump 3 miles east of Las Vegas, EPA officials said.

During storms in September 1998, trash from the landfill was swept into the Las Vegas Wash, which contaminated Lake Mead, officials said. At the time, the EPA cited Republic Dumpco and the Clark County for violations of the Clean Water Act and the Resource Conservation and Recovery Act.

Some remediation work has been done, the EPA said, but they hold the company responsible for failing to install drainage controls to minimize erosion during major storms, or install an adequate groundwater monitoring system.