Green plastic bait boxes marked “poison” aren’t what residents expect to see on the slopes of the dams at Calero and Chesbro lakes. When people started asking questions about the rodent traps, the answers came from the Community Services District.
The CSD is required to have a pest management program as part of its responsibility for the dams, said Paul Siebensohn, CSD director of field operations.
It’s not the first time pest control measures have been used at the dams, he said. “This is an on-going program. … We look at it as a safety issue.” Ground squirrels and other small, burrowing rodents can cause “catastrophic failure of the dams” by burrowing into the earth walls, Siebensohn said.
The bait stations are located on the slope that faces woods and fields, not the water. This is one is on the dam at Lake Calero.
The CSD meets standards set by the state Division of Safety of Dams for maintaining the dams. The agency conducts annual inspections of the dams.
Calero and Chesbro are two of the community’s three drinking water lakes. Water that’s diverted from the Cosumnes River is stored in the lakes.
Siebensohn said Western Exterminator Co. is performing the pest control work for the CSD. The company installed the traps after first sending out a specialist, he said.
The rodent traps are located on the ground side of the dams, away from the water. They are tethered in place. A warning label on the top of each identifies them as tamper-resistant bait station for the control of rodents. The bait is listed as .005 percent diphacinone, and the chemical’s Environmental Protection Agency number appears. Diphacinone is an anticoagulant commonly used for rodent control. The label also carries the pest control company’s name and contact information.
Small-diameter holes on either side of the trap provide entry for the ground squirrels and rodents that are targeted.
Siebensohn said the animals don’t leave the trap and neither does the bait, according to the pest control company, which reduces the risk to other wildlife.
In addition to setting traps, the exterminators are also releasing a gas into the ground that kills the rodents in their burrows, Siebensohn said.