Marshall’s subterranean wastewater system continues to be under siege by a nemesis from above: grease.

In the latest effort to contain the problem, Marin County has booted the Marshall Store, one of the town’s two bayside restaurants, off the system entirely. The restaurant is now trucking its wastewater over the hill for treatment, a stopgap that its owner says is costing as much as $4,000 a week.

The root of the problem is the buildups…