Rains send Sonoma County compost operators scrambling
Most government officials in Sonoma County welcomed the rains that began drenching the region Friday as a much-needed midwinter boost to reservoir levels following an unusually dry January.
But when big winter storms make the barometer fall, Henry Mikus’ blood pressure rises.
The executive director of the Sonoma County Waste Management Agency is under strict orders from state water quality regulators to reduce runoff from the 25-acre composting operation atop Sonoma County’s central landfill.
Rainwater that seeps through the open-air compost piles historically has been allowed to mingle with stormwater from other parts of the landfill, and in significant storms both get discharged into Stemple Creek.
But Mikus, under the threat of fines from the North Coast Regional Water Quality Control Board and a Clean Water Act lawsuit filed by neighbors, is overseeing an unusual effort to keep the wastewater out of the creek this winter by hauling it via tanker truck to local treatment plants.
“The truth is, it has gone better than anybody expected,” Mikus said of the work to date.
By combining two smaller sedimentation ponds into one 2-million-gallon lined basin, reducing the size of the compost area by 18 percent and aggressively pumping the water out of the pond before, during and after storms, the compost operation hopes to avoid big fines that threaten to shut it down.
If that happens, the waste management agency would be forced to haul 90,000 tons of yard waste every year out of the county, increasing costs and putting its longtime local contractor, Sonoma Compost Co., out of business.
So Mikus casts a wary eye on any approaching storm that has the potential to dump rain faster than it can be pumped out of the pond. The current storm, which triggered flash-flood warnings for Friday afternoon and evening, appeared to carry that risk.
About 2 inches of rain fell on the Santa Rosa Plain through 4 p.m. Friday, according to AccuWeather. With a total of 4 inches forecast over four days, Mikus thinks that, barring a torrential downpour, discharges to the creek can be avoided.
“It should be manageable,” he said.
December was a different story. About 5 inches of rain fell on the landfill on Dec. 11 and 12, about 3 inches’ worth in the early morning hours of Dec. 11.
The pumping system at the facility involves a modified farm tractor powering a pump than can move about 700 gallons per minute. A 5,000-gallon tanker truck can be filled in about seven minutes, Mikus said. At the moment, only one truck can be filled at a time.
Pumping began that morning as soon as allowed by the permit, at 6:30 a.m., but the wastewater reached the overflow pipe around 9 a.m. and stayed there for about three hours, Mikus said.
“It was like the Dutch boy with his finger in the dike,” Mikus said.
About 550,000 gallons of wastewater made it out of the pond and into the landfill’s stormwater system, with an unknown quantity making it into Stemple Creek. Two smaller releases on Dec. 12 and 16 brought the total to date to about 600,000 gallons, he said.
That compares to 5.3 million gallons that have been trucked from the site since late October, most to the Laguna treatment plant with a lesser amount heading to Petaluma and the East Bay, Mikus said.
That’s more than anyone ever expected they would be able to haul, said Alan Siegle, co-owner of Sonoma Compost. Instead of the expected 60,000 gallons per day, they’ve been able to dump closer to 250,000 gallons per day at the Laguna plant, Siegle said.
The increase has been made possible in part by upgrades to the system’s holding ponds, which allow plant operators to better control the treatment rate of the wastewater, which has organic material in it that if not managed properly can interfere with the plant’s UV disinfectant system, he said.
While regrettable, the releases were limited, he said.
“It’s way more than we’d like, but compared to what could have been discharged, it’s a small portion,” Siegle said.
Water board spokesman David Leland agreed that facility’s efforts have resulted in a “significant improvement” in the amount of wastewater reaching the creek.
“We continue to encourage them to implement a robust interim plan and to complete the steps needed to achieve zero discharge in the long term,” Leland said.
Neighbor Roger Larsen thinks the water board hasn’t encouraged them enough. Last year, he and a group called Renewed Efforts of Neighbors Against Landfill Expansion filed a federal Clean Water Act suit against the waste agency; Sonoma County, which owns the landfill; and Sonoma Compost. He’s heard officials refer to the discharge as “minimal” and “isolated.”