The Washington Department of Fish and Wildlife (WDFW) has postponed this year's plans to improve fishing at Spokane County's Silver and North Silver lakes because time is too short to adequately address concerns about drinking water.
"The project is biologically sound and we prepared well in that regard," said WDFW regional fish program manager John Whalen. "But unfortunately we didn't realize the extent of domestic water withdrawals from the lake, and now we don't have time to meet permit requirements to address that issue."
Last month WDFW officials approved "rehabilitation" of Silver and North Silver lakes, along with 10 other eastern Washington fisheries, all of which passed State Environmental Protection Act (SEPA) review as not harmful to local ecosystems.
WDFW's plan was to treat the Silver lakes in late October with the plant-derived chemical rotenone to kill tench, an undesirable exotic fish species that currently makes up over half the fish population of the lakes. Silver Lake would have been restocked with bass, bluegill, and rainbow trout next spring; North Silver Lake would have been stocked with rainbows.
A public meeting on the subject in July yielded about 50 percent support and 50 percent opposition to the project. More concerns were later expressed in petitions to WDFW, so Whalen and other staff agreed to a second public meeting on September 21.
"We realized that we needed to address the drinking water issue and water quality permit requirements for the project," Whalen explained. "We learned that there are at least 22 registered water rights for irrigation or drinking water use at Silver Lake, plus other unregistered water withdrawal use."
The Washington Department of Ecology (DOE) issues water quality variance permits for rotenone treatments, requiring adherence to Environmental Protection Agency (EPA) label requirements for rotenone application. Although EPA has no drinking water standards regarding rotenone use, the label currently prohibits applying rotenone within a half-mile of a drinking water source.
DOE requested a review by the Washington Department of Agriculture, (which oversees use of pesticides like rotenone), of how the application restriction could be addressed. Agriculture officials advised that WDFW would have to ensure that all water intakes were not functional until rotenone was no longer detectable.
WDFW would have to determine who withdraws water from the lake, both registered and non-registered, develop agreements for alternative sources of water during and after the rotenone application (about one to three weeks), and monitor the water until rotenone is no longer detectable.
"Meeting these requirements would delay the project too much for effective and efficient treatment before winter, " Whalen said. "The logistics are now beyond our staff time and resources. We are committed to maximizing public fishing opportunities at Silver Lake and other lakes, and we will continue to pursue ways to do so in the future."