Linda Meza, spokeswoman for the beaver advocacy group "Worth a Dam," said the last time all eight beavers were seen was Oct. 23.
Public works employees have been closely monitoring Alhambra Creek in downtown Martinez over the past several days, but so far a dam built by a family of beavers has not caused any flooding, Martinez Public Works Director Dave Scola said today.
The creek was rising Wednesday morning, but water seems to be rushing over the top of the primary dam near Escobar Street, Scola said.
Storm water has already washed away the beavers' three other dams, which were built downstream from the primary dam, said Linda Meza with the beaver advocacy group Worth a Dam.
It was difficult to tell how much of the primary dam had been washed away because there was too much water flowing over it.
Public works employees have been visiting the dam every hour to check on water levels, Scola said. They expected the creek to rise further when high tide occurred around 3:30 p.m. or 4 p.m. today, but had plans in place to quickly remove the dam if necessary, Scola said.
The creek, which is the primary drainage channel for a 17-mile watershed upstream from the dam, used to overflow regularly during big storms and flood downtown Martinez until the city completed a $9.5 million flood control project.
In 2007, after a study showed that the beaver dam was negating the flood control project, the city obtained a permit to kill the beavers, but public outcry caused city officials to reconsider.
The public works department later installed a cable and two boat anchors in the dam so that if emergency measures became necessary, the dam could be yanked out quickly. The cable has since been stolen, Scola said.
The city also hired a beaver expert from Vermont to install a flow control device known as a "beaver deceiver."
The device allows water to flow through the dam without the beavers noticing, which deters them from building the dam higher.
The beavers have, however, continued to pack dirt into the primary dam and it is now a solid earthen bank, Scola said.
Scola said that the cable wouldn't have worked anymore anyway because the dam is too solid.
The public works department plans to remove the dam with a backhoe if water levels in the creek get too high, Scola said.
Meza said that even if the dam washes away or is removed, the beavers will be fine. They will simply rebuild their dams when the storm passes.