Pacific Gas and Electric : PG&E and Forest Service Biologists Create Innovative Ramp to Help Wildlife Escape Canals

By Paul Moreno

Canals that are part of hydroelectric systems like PG&E's can trap small or young animals, especially when the canals are dry and empty during maintenance. The straight-walled concrete canals can be too deep for smaller or young animals to jump out of.

Over the years, solutions to create various ramps, steps or directional cables to help animals escape have met with mixed results. That prompted biologists from PG&E and the U.S. Forest Service to collaborate to find better ways to allow animals to escape canals.

After a bobcat kitten tries the ramp, a second one follows to escape the canal.

A canal that is part of PG&E's Crane Valley Project near North Fork in the Sierra Nevada Range in Madera County was the test location for the various designs, as it had previously been found to have trapped fawns. From 2011 to 2018, the biologists tested hay bales and ramps at various angles and materials. Water crews from PG&E's Hydro Yard in Auberry built, installed and removed the ramps each year.

Wildlife trail cameras were used to gauge the success of each design solution. The cameras provided observations that allowed the team to modify structure designs. Although primarily geared toward helping mule deer escape, other wildlife also used the escape structures, including bobcat kittens.

Trial and error, then success

PG&E biologists Gina Morimoto andLaura Burkholder and Forest Service biologist Anaé Otto authored an article detailing their study, which was published in November in the California Fish & Wildlife Journal, a scientific periodical by the California Department of Fish & Wildlife.

The effort required an escape ramp that met these criteria: 1) would be easy to deploy and remove during/after the annual summer maintenance period 2) would not affect the structural integrity of the canal and 3) would be economical (inexpensive to construct, deploy and maintain).

Escape ramp deployment was timed with annual canal maintenance, generally a period of six weeks beginning in July and ending in August. The canal was mostly dry during this period, but puddles of water could entice thirsty wildlife.

In 2011, biologists started with hay bales stacked in a step configuration within the canal. Four to six wheat hay bales were stacked at each site.

After trial and error, jute netting, dirt and plants were placed on the ramp to mimic natural terrain and wildlife began using the ramps.

However, cameras never detected any fawns using the bales to escape in 2011. For 2012, a different temporary escape structure designed by PG&E engineer Eric Doswald, an aluminum stage platform covered in neoprene rubber sheets and secured to the canal with galvanized steel to increase traction was tested.

At the beginning of the 2013 monitoring period, a deceased fawn, two live fawns and a cottontail rabbit were found trapped in the canal. One fawn and the cottontail rabbit were manually captured and released from the canal by Forest Service staff, while the other fawn escaped the canal on its own. Upon reviewing the photos, biologists found that the fawns investigated the base of the ramps several times over three days but did not use the ramps. Instead, a fawn tried to jump out of the canal at the base of one ramp.

Thinking like a fawn

After this discovery, the biologists hypothesized that the fawns did not recognize the ramp as a means of escape due to the black surface. The ramp surfaces were then covered with jute netting, dirt and plant material. Three days later, cameras recorded the first successful use of the temporary escape ramps by mule deer fawns.

"Deer may be more amenable to using bridges and escape ramps covered with materials that mimic native ground cover," the researchers wrote. "That finding is similar to our observed change in ramp utilization after the jute netting and debris were added to the ramps."

Over the course of the study, researchers were able to test the effectiveness of the new temporary escape ramps by adaptively making changes and conducting camera trap monitoring.

"We developed a new temporary wildlife escape ramp designed to allow mule deer fawns to self-rescue from a dry vertical-walled canal. Our temporary escape ramp design for small canals appears to be novel and may be applicable in other areas. It is a relatively low-cost solution compared to fencing or covering the canal," they concluded.

PG&E continues to utilize these ramps for dry canals at the study location.

View the full article detailing the study here.

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