Company claims disinfectant used at mushroom farms responsible
in part for perchlorate contamination
Morgan Hill – Chlorine bleach used in municipal water systems and at local mushroom farms is responsible for at least part of the perchlorate contamination in South County, according to the company that released perchlorate here for decades.
“Olin believes that mushroom farms represent an historic and ongoing perchlorate source,” Olin Corp. engineer Rick McClure said. “Both the mushroom farms and well sanitizations are sources of perchlorate to groundwater, but we believe there are others.”
Perchlorate was discovered last month in the retention ponds of three local mushroom farms at levels higher than all but a few wells that border the south Morgan Hill site of Olin’s now-shuttered road-flare factory.
But so far, scientists directing perchlorate cleanup efforts are not yet ready to join the company in linking disinfectant used at mushroom farms to the 9.5-mile perchlorate plume that stretches south through San Martin and east of Gilroy. A surface-level contamination does not necessarily equate to groundwater pollution.
“Just because we detected a certain level of perchlorate doesn’t mean that any of these ponds are contributing to the groundwater impacts,” said Hector Hernandez, an engineer with the Central Coast Regional Water Quality Control Board. “At this point, it doesn’t mean that much.”
The regional board tested only water that had already been used to clean processing equipment, so there is no way to know if there were similar levels of perchlorate in the water when it came out of the ground. And not all of the mushroom farms checked for perchlorate tested positive.
Hernandez said that could be due to variances in the way the farms clean their equipment and store cleaning solutions. There is no link between perchlorate and mushrooms. It’s possible that perchlorate is in the wastewater of any processing plant that uses chlorine bleach.
“At this point we think this is something worth looking into further,” Hernandez said. “Our aim is to target not just mushroom facilities but other operations. This is a beginning step into looking at the pervasive use of bleach.”
Olin’s argument comes as the company is preparing a plan to clean the perchlorate plume. While the company has previously accepted responsibility for the perchlorate – a salt that interferes with thyroid activity – it now says that a number of factors contributed to the plume. And Olin is suggesting that the perchlorate in Morgan Hill’s drinking water supply comes not from its factory, but from mushroom farm runoff and the bleach used to sanitize the city’s supply wells.
“The well drillers who sanitized the Nordstrom Park well used bleach and according to [Olin consultant MACTEC] the volume was substantial,” McClure said.
Mushroom farmer Don Hordness, who owns Country Side Mushrooms in Gilroy and Royal Oak Mushrooms in Morgan Hill, accused Olin of trying to shirk responsibility for the pollution caused by its Railroad Avenue factory from 1955 to 1987. The perchlorate found at the mushroom farms was a tiny fraction of that discovered at the factory site in 2001.
“This is really silly,” Hordness said. “Olin dumped for 30 years and is trying to point fingers at other people. They’re throwing stuff at the wall and trying to see what sticks.”
Perchlorate has shown up in a surprising number of places in recent years. It occurs naturally in some fertilizers and appears to occur naturally in lightning in arid climates. It’s present in fireworks, road flares and rocket fuel, and is believed to have entered the nation’s food supply through water used at California farms.
Olin says that all of those factors may be responsible for the perchlorate in South County. Morgan Hill city manager Ed Tewes dismissed Olin’s claim as another effort to avoid responsibility for the contamination in that city. Olin contends that perchlorate could not have moved north from its factory site and has resisted calls by the city to compensate residents for the monthly surcharge they pay to clean their water.
“The water in those retention ponds is equivalent to a thimbleful of water in a big lake full of water underground,” Tewes said, “It is not possible to draw any link between perchlorate found in wastewater ponds at mushroom farms and perchlorate found in drinking water in Morgan Hill.”
Why you should care
Olin contends that the discovery of perchlorate in mushroom farm wastewater means the company is not solely responsible for contaminating South County groundwater. The discovery could ease pressure on the company to clean the groundwater basin.
