With parts of Northern California's scenic hillsides illegally gouged by bulldozers for marijuana grows, frustrated local officials asked the state for help to protect streams and rivers from harmful sediment and the chemicals used on the pot plants.

They hoped to charge growers under federal and state clean water regulations with tougher penalties than the infractions local officials could impose. But they were rebuffed.

It's too dangerous, the state agency in charge of protecting the region's water said in a letter to county supervisors.

"We simply cannot, in good conscience, put staff in harm's way," wrote Central Valley Regional Water Quality Control Board Executive Director Paula Creedon.

As in many rural counties in California, marijuana farms are becoming more and more plentiful. They proliferate in the high Sierra, where armed Mexican cartel operatives clear wilderness areas, divert creeks and poison wildlife. Other smaller gardens are planted by people operating as collectives by pooling dozens of permits under the state's medical marijuana laws, though many of those are traffickers attempting to skirt the law. State law allows a person with a medical permit to grow roughly a dozen plants.

Butte County Supervisor Chairman Bill Connelly _ frustrated that even photos of illegally scraped and terraced hillsides in sensitive watersheds didn't convince the water quality board to act _ accused the board of not applying the law equally.

"My concern is that legitimate business people get harassed (by the agency), but illegal people will not be harassed because they get a pass," he said. "They go after the timber industry and farmers."

Penalties can range from cease-and-desist citations to fines of $5,000 for each day of the violation to more than $1 million, said state water board spokeswoman Kathie Smith.

The issue of large-scale marijuana enforcement and the damage some pot farms cause is not new in a region known as the Emerald Triangle, for the marijuana that has been produced there for decades. Marijuana is the state's biggest cash crop with an estimated $14 billion in legal and illegal sales annually.

California wildlife wardens and hikers in the state's remote backcountry occasionally happen upon gunmen guarding multimillion-dollar pot farms. It's one of the reasons the California Department of Fish & Wildlife recently issued its wardens more powerful weapons.

Those growers, when caught, are charged criminally in federal courts. But at the local level, counties are concerned with growers taking advantage of laws legalizing the growing of marijuana for medical uses. Even the legal farmers must comply with environmental laws.

The state's nine regional water boards are quasi-independent agencies that set their own policies, though all are charged with enforcing the federal Clean Water Act and its California equivalent. The Central Valley board, which focuses on runoff from farming, construction and hundreds of dairies, does not have a policy for investigating violations associated with marijuana grows.

"This is outside of our expertise," said Andrew Altevogt, assistant executive officer of the agency. "It's not the kind of thing that we do."

Yet its sister agency, the North Coast Regional Water Quality Control Board, aggressively seeks out and prosecutes growers who flatten remote hilltops, dam streams to divert water and allow sediment and chemicals to reach waterways.

In 2007 that agency joined an environmental crimes task force made up of county district attorneys and code enforcement agents.

"I initiated this because I thought it was the best way to get action on the things I was seeing," said Storm Feiler, a water board scientist who is part of the task force. "We have taken an active role because we have so many grow sites over here, and since 2007 there has been an astronomical increase. It's a really big issue for us."

The discrepancies in enforcement have come to the attention of Assembly Member Dan Logue, R-Loma Rica, who represents Butte County. He said it's the first time he's heard of a state agency refusing to enforce state laws.

He said that as marijuana farms proliferate, the issue of keeping creeks, streams and rivers free of toxins has become a statewide issue.

Logue sent a letter to the water board's Creedon expressing concern over the "diminishing water quality in this part of my district," and asking the agency to help find a way to enforce the Clean Water Act. He has asked for a meeting with members of Gov. Jerry Brown's staff in an attempt to force action.

"This has to be fixed," Logue said in an interview. "We have an issue in the state where agencies are fearful, and the law isn't being applied equally."