Year – Plants Eradicated – Number of Sites – Arrests

2012 – 22,428 – 10 – 4

2013 – 18,229 – 6 – 4

2014 – 25,626 – 5 – 3

2015 – 2,799 – 2 – 0

2016 – 15,887 – 6 – 0

Researchers, law enforcement and others are raising alarms about toxic chemicals used on illegal grow sites in mountain forests and foothill areas of California where people grow and process marijuana, including Calaveras County and the Stanislaus National Forest.

There’s concern for more damage to watersheds, wildlife and water supplies, more damage than was previously known about. Dead animals poisoned by banned pesticides and fertilizers are an especially troubling indicator of how toxic materials pose potential threats to water supplies and public health.

“The days of a few marijuana plants and a box of Miracle Grow are gone,” says Stephen Frick, assistant special agent in charge of Forest Service law enforcement and investigations for the Pacific Southwest region that includes all of California.

Investigators in the Stanislaus National Forest and other Sierra Nevada forests now find pesticides and fertilizers that are banned in the U.S. by the federal Environmental Protection Agency, including the presence of Carbofuran/Furadan, in about one-third third of the marijuana grows they entered this year.

One-eighth of one teaspoon of Carbofuran/Furadan “is deadly enough to kill an adult bear,” Frick said this week.

“In addition to Carbofuran we are seeing Malathion, Aluminum Phosphide, Zinc Phosphide and other restricted-use pesticides which are responsible for contaminating the state’s water supply and killing off wildlife,” Frick said. “The people growing the marijuana used to shoot and eat the wildlife. Now they kill it with pesticides and it goes to waste.”

The increasing presence of dead wildlife at marijuana grow sites in California forests over the past five years helped trigger the realization that more research is needed, Frick said.

“Officers/agents began to find unidentified chemicals and several more dead animals within the growing areas,” Frick said. “These animals included, but were not limited to, foxes, fishers, deer, bear, rabbits, squirrels, chipmunks, several types of birds and a big horned sheep.”

Cannabis in Calaveras County

Calaveras County currently operates under an urgency ordinance adopted last year that regulates commercial cannabis growers operating before May 10, 2016.

More than 700 registered pot farms made marijuana growing the largest industry in the county last year, according to one study, with estimates of an annual economic impact of $339.2 million, 3,404 jobs and income to workers of $172.2 million.

At the same time, the sheriff of Calaveras County estimates there are as many as 600 illegal farms operating in the shadows.

Between Jan. 1, 2016, and Sept. 7, 2017, the Sheriff’s Office eradicated 59 grow sites, made 54 arrests and destroyed 108,476 cannabis plants in Calaveras County, sheriff’s Capt. Jim Macedo said Thursday.

“We currently have about 910 marijuana complaints, 457 have been closed by either sheriff's or code enforcement,” Macedo said. “We are currently receiving 15 new complaints a week.”

Macedo said he could not provide estimated acreage of eradicated grow sites.

Tracking toxins

Asked if anyone with Calaveras County is tracking or trying to track how much toxic waste is coming off illegal and legal, registered grows in Calaveras County, Brad Banner, the county’s environmental management administrator, said, “We're trying to get a handle on that,” he said.

He said the registered grows his staff inspects don’t use a lot of toxins.

“I think it's the ones the sheriff is going to, the sheriff’s department is going to those sites. They move on without making sure the sites are cleaned up and safe,” he said. “It really hasn't been tracked. It should be.”

He said he wants his department to begin working with the Sheriff’s Office.

“We want to make sure those sites get restored,” he said. “It will need to go to the board if we want a person in charge of this. There's an initial list of larger abatement sites, under investigation. There are probably sites that need to be added to the list.”

Banner called The Union Democrat back later to clarify his comments.

“I don't want it sound like the sheriff hasn't been doing their job,” Banner said. “They have been doing their job very conscientiously. It's just that a different department working on this could focus in on one aspect of the abatement and work collaboratively with the sheriff’s department who can focus in on legal enforcement.”

The sheriff's department is doing abatement on “really large” grow sites, Banner said. They're going in there and they're removing cannabis.

“And they have a contractor that can clean up hazardous types of situations, hazardous materials and such, so they do have a contractor on board,” Banner said.

The distinction Banner was trying to make, he said, was that sheriff’s personnel focus on eradication of cannabis plants and then tracking their enforcement activities to make sure people get properly charged with crimes.

“The angle that we're working at with environmental health is to try to track what's on the ground itself and maintain a record of those things,” Banner said. “Instead of tracking individual cases from beginning to end we're tracking more of the materials there from beginning to end. So it's collaborative with the sheriff’s office and it's supportive of them and supportive of code enforcement.”

Hazardous waste

An example of how sheriff’s personnel dealt with toxic materials tied to illegal cannabis processing came to light in early April. The incident was not at a grow site and it did not involve pesticides or fertilizers, but it showed sheriff’s personnel acted quickly to initiate cleanup.

On April 5, deputies in San Andreas discovered nine 55-gallon drums of hazardous waste and close to 1,000 butane canisters, which they described as remnants of a discarded honey oil lab dumped near Calaveras High School.

The discovery came on a tip to the Sheriff’s Office six days after deputies found 44 butane canisters illegally dumped at Calaveras High School, near the lower parking lot on High School Street.

County code compliance and environmental health staff were recruited to coordinate cleanup. They called a hazardous waste cleanup company to remove debris.

According to the Sheriff’s Office, deputies and environmental health staff are treating butane honey oil lab and lab dump cleanups the same as they treat methamphetamine lab cleanups.

Sheriff’s Office staff described butane extraction processes as extremely volatile, and they said the labs often explode or catch fire, creating temperatures in excess of 500 degrees.

Macedo said Thursday he could not comment for other county departments or other agencies, but he emphasized, “We regularly communicate with environmental health and code enforcement as it relates to cleanup concerns. If it’s a hazardous materials event, then we get a hazmat team and contractors to come out and clean up.”

Operation Terminus

In larger crackdowns on illegal cannabis grows like Operation Terminus in late July and early August, the Sheriff’s Office also coordinates with state agencies including Fish and Wildlife, Cal Fire, the State Water Resources Control Board and the Central Valley Regional Water Quality Control Board, Macedo said.

Over four days, deputies with Operation Terminus executed 23 search warrants, arrested 35 people, seized 25 tons of marijuana and destroyed 27,000 marijuana plants in Calaveras County.

Sheriff Rick DiBasilio issued a warning to illegal growers thinking of plying their trade in Calaveras County: “Don't come. You're not welcome, and we will come for you.”

Macedo said at a press conference some marijuana growers have come from across the United States to commit crimes and cause “significant environmental damage.”

DiBasilio cited cooperation with the environmental agencies, unprecedented compared to previous investigations, as a way to combat the “land use issue” of marijuana grows.

Photographs displayed by law enforcement showed squalid and unsanitary living conditions, heaps of garbage, haphazard chemical or fertilizer preparation areas, open drainage systems, electrical generators and slipshod structures.

Environmental damage included human waste and draining in close proximity to stream beds, illegal grading, illegal stream crossings, water rights issues, damming streams and allowing chemicals into waterways, Macedo said.

Illegal pesticide and herbicide use was found at many of the properties, Macedo said. Other environmental violations included “substandard electrical connections, or the use of generators in areas “with dried grasses or fire fuels.”

Stanislaus National Forest

Detection and investigation of marijuana grow sites in the Stanislaus National Forest depends on staffing levels, and over the past five years law enforcement staffing in the 1,400-square-mile forest has been reduced.

“Please be aware that detection and investigative efforts for marijuana gardens are directly related to staffing levels,” Frick said this week. “In most cases, the more LEOs/agents in an area results in more marijuana detection/investigations.”

Statewide, federal Forest Service law enforcement officers found a 52 percent increase in marijuana plants grown in national forests in California, Frick said.

“All indications support another increase in 2017,” Frick said.

Federal law enforcement officers began noticing changes in marijuana growing operations in national forests that included large amounts of restricted pesticides and banned pesticides, Frick said. The presence of dead animals at illegal grow sites was the red flag that spurred investigators to call for more extensive research.

Trying to quantify

Mourad Gabriel with the nonprofit Integral Ecology Research Center in Humboldt County is trying to track quantities of banned, restricted pesticides and illegal fertilizers in forests in northwest California, Northern California and the Central Sierra.

“We are trying to track Lassen, Plumas, Klamath, Shasta Trinity, Six Rivers, Mendocino and Sierra and Sequoia national forests,” Gabriel said. “We're limited budget-wise to northern and northwest California. If we get more funding, Stanislaus and some others in Southern California would go on the list.”

Gabriel said 99 percent of Integral Ecology Research Center funding comes from state or federal grants IERC staff write themselves.

Gabriel said he works extensively with Forest Service law enforcement.

He and his staff have documented more than 200 grow sites so far in California, and they all have the same environmental footprints, including the presence of banned pesticides and fertilizers that can kill mammals and contaminate waterways.

Gabriel estimates California forests hold 41 times more solid fertilizers and 80 times more liquid pesticides than Forest Service investigators found in 2013, he told Reuters earlier this month.

Neurotoxicant rodenticides, which can kill mammals such as the weasel-like Pacific fisher, are among the toxic chemicals used on illegal marijuana crops scattered throughout the state’s public and tribal lands, Gabriel said in an April 2017 summary of clean-up operations in Six Rivers National Forest.

“I do know of numerous sites up in the Stanislaus National Forest,” Gabriel said this week. “I can’t freely disseminate information about locations based on our MOU (memorandum of understanding) with law enforcement. We have more than 200 sites in California documented. They have all the same footprints, regardless of location.”

Contact Guy McCarthy at or (209) 588-4585. Follow him on Twitter @GuyMcCarthy.