Mushroom composter busted for stormwater discharges

The San Francisco Bay Regional Water Quality Control Board has ordered Monterey Mushrooms Inc. to pay $911,800 for discharging polluted stormwater into Fisher Creek, harming water quality and threatening aquatic life, the board said.

The company, which is the largest grower of fresh mushrooms in North America, discharged more than 650,000 gallons of polluted water from its Morgan Hill facility into Fisher Creek. Nearly half of the penalty – $440,364 – will fund a Santa Clara Valley Open Space Authority project to restore 3.5 acres of habitat along the creek, downstream of the Morgan Hill facility.

“This penalty sends a clear message that Monterey Mushrooms must improve their operations and protect the aquatic life in Fisher Creek and drinking water uses of the underlying groundwater,” said Lisa Horowitz McCann, assistant executive officer of the control board.

The board’s investigation found that in March 2016, Monterey Mushrooms discharged 258,000 gallons of polluted stormwater from one of its compost storage areas to a ditch that flowed into Fisher Creek. Inspectors found deficiencies in stormwater management practices that resulted in stormwater coming into contact with compost, becoming polluted and then running off the facility.

The investigation also found that in February 2017, Monterey Mushrooms pumped 400,000 gallons of polluted water from a pond to Fisher Creek. The discharge contained ammonia more than five times the U.S. EPA’s water quality criterion intended to protect aquatic life.

A copy of the order is available on the San Francisco Bay Board’s enforcement website.

Fisher Creek flows into Coyote Creek, which flows into San Francisco Bay. These waters provide habitat for aquatic life. When improperly managed, compost waste can degrade water quality with nutrients, pathogens, and other pollutants, the control board said. Excess nutrients can lead to conditions that suffocate fish or cause toxic algal blooms. If released to groundwater, nutrients can also harm drinking water supplies.

As a result of the board’s enforcement action, as well as a separate action brought by the Santa Clara County District Attorney’s Office, Monterey Mushrooms has improved its compost management by increasing process water storage and minimizing the amount of process water on-site.