UPDATE: 1:45 p.m. Dec. 4 Ross Valley Sanitary District officials said the overflowing manhole is part of a 18-inch diameter line that is in Broadmoor Avenue, goes south, crosses Sir Francis Drake Blvd., then heads east on the south side of Sir Francis Drake Blvd.
Camera crews have discovered a significant root blockage in the line, where debris caught on the roots and caused the spill. The blockage was on the southern side of Sir Francis Drake Boulevard, where the 18-inch diameter trunkline goes under the sidewalk.
Heavy weekend rains caused a large sewage spill in San Anselmo, prompting officials to briefly close a lane on Sir Francis Drake Blvd. on Sunday while emergency work was done.
Ross Valley Sanitary District (RVSD) Engineer Randell Ishii said the district’s preliminary “draft numbers” estimate that roughly 30,000 galloons of sewage spilled out of a manhole at 16 Broadmoor Drive in San Anselmo.
RVSD officials found the overflowing manhole around 7:55 a.m. on Sunday, Dec. 2.
The overflow was stopped by 10:30 a.m., according to district officials, around the same time a flash flood warning was lifted in San Anselmo, where San Anselmo Creek came within inches of flooding around 9 a.m. on Dec. 2. Fairfax Creek also nearly caused flooding throughout Fairfax.
Sleepy Hollow Creek was overflowing on Sunday, especially near the area of the Broadmoor sewage spill, Ishii said.
Ishii said some sewage did “comingle” with creek water that had overflowed onto Morningside Drive and creek testing is underway.
Crews were cleaning the affected area yesterday and today, investigating the extent of the overflow and working to determine the cause. Warning signs have been posted in the affected area, according to RVSD officials.
On Sunday, crews focused on cleaning sewage that was released onto streets, front yards and sidewalks in the area. On Monday, a private contractor helped officials clean any homes affected by sewage water, Ishii said.
Police staff from the Twin Cities Police Department and San Anselmo Police Department, as well as officials with the San Anselmo Public Works Department, helped the RVSD officials contain the spill and briefly detour traffic when one lane of Sir Francis Drake Blvd. was closed for sewer-related repairs.
The sanitary district, which has seen multiple recent spills, didn’t have any other sewage spills throughout the recent series of storms — largely because it had a 24/7 “storm control” crew patrolling problematic manholes. “They were able to circumvent possible overflows by cleaning out lines and relieving any restrictions in those lines,” Ishii said.
He added that the money was better spent on personnel than the district paying fines and damaging the environment with additional spills.
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