Bears and ravens learn to live with new rules at water treatment plant


It doesn’t sound appetizing to us humans, but the Mammoth Community Water District wastewater treatment plant has proven irresistible to local critters—and that has created a problem for the water district.

The wastewater treatment plant contains large, open pit water treatment pools—and a banquet of alluring smells and a steady supply of fats and grease.

It is thus a popular spot for local animals, particularly bears and ravens, presenting a unique challenge for the district.

“Bears are basically 500-pound raccoons with powerful and dexterous hands bent on destruction driven by appetite,” said Rob Motley, plant maintenance and instrumentation supervisor at the district.

For example, one winter morning, the staff arrived to discover a bear had removed a heavy metal grate and tossed it into another tank where it broke expensive machinery.

District staff was forced to drain the tank to perform the repair and the bear’s quest for an easy meal had a toll of 36 hours of district staff time—plus the expense of replacing the broken equipment.

More operational costs can translate to higher water rates.

In addition to the bears, ravens have been an ongoing problem at the wastewater treatment plant. 

“I have seen over 50 at the plant at once,” Motley said. The ravens land in the wastewater tanks to scrounge for food and then take off to roost nearby; making a mess anywhere they go afterward, he said.

After continuous innovation and testing, Motley figured a way to keep bears and ravens from bathing and dining in the wastewater tanks.

For the bears, the district decided to install an electric fence around the perimeter.

This new fence proved to be an effective, non-harmful method of keeping the bears out since they can sense the electricity and won’t even touch the fence, he said.

For the birds, netting has been placed over the wastewater tanks to keep the ravens from dining and dashing. The success of the netting and deterrence of bears has convinced the district to invest in sturdy wire mesh covers for the open tanks.

The results of district staff time and financial investments to maintain a critter-free wastewater plant has increased the plant’s efficiency, decreased employee time repairing damage and cleaning up, kept animals from growing dependent on human food sources, and saved citizens from increased rates, district officials said.