A district crew was marking utility locations when it discovered a major blockage in the system.

In working to solve the problem, large pieces of broken pipe were found that were eventually traced back to the trunk line.

A CCTV inspection of the trunk line that runs under the path alongside Magnolia Avenue between Bon Air Road and Doherty Drive indicated that a section of the pipe had collapsed and much of the pipe was deformed into an oval shape instead of its usual round state, which is generally the last stage before collapse.

Ross Valley Sanitary District General Manger Brett Richards said “Wastewater is still making its way through the damaged section of pipe despite the problem, however, we must repair it immediately.

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“We are fortunate that this was discovered before a major rain event as it is quite likely we could have had a major spill.”

In a unanimous vote by the Ross Valley Sanitary District Board of Directors, the lowest bid from four qualified contractors ranging from $US725,000 to $US1,389,000 for the emergency repair work was accepted.

Maggiora & Ghilotti, based in San Rafael, have begun repair work and plan to complete the job within 60 to 90 days, depending on weather conditions.

The district staff has recently begun using CCTV system to inspect and map the Ross Valley sewer system. Over the last two months, the RVSD Board has been presented with images of 24 pipes that are severely damaged and will also need repair.

“Our CCTV crew has only mapped about 20 per cent of our pipes, but the damage we have discovered supports the grave assessment of the overall system that was made three years ago when I joined the District,” Mr Richards said.

The District has estimated that as much as 85 per cent of the community’s public sewer pipes are at, or beyond, their service lives.