A Tuesday afternoon sewage spill was reported to have dumped less than 100 gallons of wastewater into Wolf Creek in Grass Valley.
A sewage line beneath Highway 49 was obstructed with a foreign object, causing an overflow near the off-ramp onto Highway 20, near the Nevada County Fairgrounds, reported Tim Kiser, Grass Valley’s public works director.
“The blockage has been cleared in the line, and we’re in a cleanup process,” Kiser said. “It was some kind of debris, either a root structure or something that someone flushed inappropriately. We don’t know for sure.”
The blockage was noticed around 2 p.m. Tuesday, said Kiser, who was unable to give a preliminary estimated total amount of spilled sewage as of press time.
“It certainly wasn’t a weather-related spill,” said Bill Lawrence, director of Nevada County’s Environmental Health department.
Kiser did estimate that a small amount, less than 100 gallons, made it past a roadside ditch that caught the bulk of the spill and into the creek.
The overflow was contained within a half-hour, and the blockage was cleared less than 20 minutes afterward, Kiser said.
The Nevada County Environmental Health department notified approximately 830 residents within a quarter-mile to a mile from the spill, instructing them to stay clear of the creek for the next 48 to 72 hours, Kiser and Lawrence said.
“The solution factor will be fairly high, but you are talking less than a percent of the flow,” Kiser said.
“It’s actually less than a 10th of a percent.”
Kiser said the spill is likely to be so diluted by the creek’s flow that he does not expect it to impact any wildlife.
“Overall, it probably is not an issue,” Kiser said. “But we would rather overestimate and put more caution than is necessary over the next couple days.”
A report of the incident will have to be filed with the state of California, Kiser said.
The last time Environmental Health notified residents of a Grass Valley sewage spill was Dec. 2, 2012, Lawrence said.
Such spills often lead to fines for the city such as the $110,000 fine the Water Quality Control Board issued in 2011 after 10,000 gallons of wastewater spilled into the creek (although near a Joyce Street lift station and not at the treatment plant).
The city has blamed Empire Mine, which the city has said accounts for nearly a quarter of the plant’s incoming untreated water, as a contributing factor to its overflows.
Wolf Creek Community Alliance conducted a 10-year study of the waterway.
The results, published in October, indicate that the creek is mostly healthy but that sewage spills create noticeable, though temporary, drops in detectable water quality.
To contact Staff Writer Christopher Rosacker, email firstname.lastname@example.org or call 530-477-4236.