Top federal environmental regulators in California laid out a $630-million plan on Monday to capture and treat sewage-tainted water that routinely flows over the border from Tijuana into Imperial Beach and up the coast.

The blueprint focuses largely on installing a pumping system in the Tijuana River north of the U.S.-Mexico border to suck polluted flows out of the channel before they can foul shorelines in San Diego. Trash booms would be installed directly upstream of the intake.