A 30 inch sewer main that conveys wastewater from Tamalpais Valley to the south Sausalito-Marin city sanitary district treatment plant was punctured while the road contractors were installing a new guardrail along the roadway.

As a result, thousands of gallons of raw sewage were spilled into an adjacent wetland. 

Following the incident, traffic was stopped for several miles. 

Earlier that week, contractors working on the same stretch of highway punctured the same sewer pipe twice with a boring unit as they were drilling holes for new posts. 

During the pipe repair and cleanup, a traffic lane was closed. Officials estimated direct costs to be around $10,000.

Cause: Puncture due to drilling operation

Damage: 5,000 -10,000 USD, spill of raw sewage

Injuries: None

Sewer pipelines, Spills (environmental pollution), Traffic/flight delays, Drill