A ruptured underground pipe leaked about 48,000 gallons of raw sewage into the Redwood Shores Lagoon last week, according to city officials. That's nearly 10 times the amount originally estimated.
The initial estimate of 5,000 gallons was based on preliminary information given to the San Francisco Bay Regional Water Quality Control Board by first-responders who were sent to fix the broken pipe, located near Davit Lane and Anchor Circle, Redwood City spokesman Malcolm Smith said in a statement.
The leak was reported at about 3 p.m. on Wednesday.
The city estimated that 300 gallons of sewage was flowing into the lagoon each minute, and that the flow could be halted in 20 to 30 minutes, Smith said.
However, further investigation at the site revealed that what was presumed to be a broken valve was actually a ruptured pipe, meaning a much higher flow and a longer repair time. The city is required to report a sewage spill and estimate the extent of it to the water quality control board within two hours.
In a report filed with the board by city staff on Monday, the revised spill amount was accompanied by test results from the lagoon water, which continues to show "high levels of coliform bacteria including E.coli."
A warning to residents to avoid all forms of contact with the water -- including swimming, boating and kayaking -- will remain in place indefinitely.
"Redwood Shores residents will be informed as soon as it's determined the lagoon water has returned to normal condition," Smith said.
City officials are developing a lagoon cleanup plan, the San Mateo County Environmental Health Department and the water control board, Smith said. Cleanup measures are expected to get under way this week.
An estimate of cleanup costs and repairs has not been made.