DENVER (AP) — Colorado regulators are beginning a three-day hearing on rule changes for oil and gas drilling that could determine how to protect water sources amid complaints that industry supporters are trying to block testimony from opponents.

Colorado's proposed new rule to protect water from expanding oil and gas operations would not apply to more than a quarter of wells or tanks, pipelines and other production facilities that are frequent sources of leaks.

Environmental groups that worked with Shell Oil to develop tougher ground water testing rules say the state's proposal is a farce, but industry supporters want testimony from opponents limited on grounds there is no scientific evidence to back up claims that drilling is responsible for environmental contamination.

The Colorado Oil and Gas Conservation Commission is holding hearings starting Monday on new proposed drilling rules.

Several Coloradans who live near rigs have submitted written testimony outlining health problems, with the residents and their supporters saying they have a right to be heard. But the Colorado Oil & Gas Association and others say some of the testimony should be tossed because they represent non-expert medical opinions or hearsay.

Dan Grossman, regional director for the Environmental Defense Fund, said that under the new regulations, Colorado's water sampling would be the worst in the nation. Adoption of the rules as currently proposed would mean that sampling would be less rigorous in the Wattenberg Field drilling zones north of metro Denver, where nearly 18,000 wells exist near communities and companies plan to drill thousands more.

Oil and gas drilling accounts for nearly 44,000 jobs in Colorado and brought in $208 million in severance taxes last year.

Gov. John Hickenlooper has called for a consistent set of state rules, so companies do not face conflicting local regulations that could drive them to other states.

CORRECTION: A previous headline on this story incorrectly identified the Colorado Oil and Gas Association as the Colorado Oil and Gas Conservation Commission.

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  • Oil Pump Jack

    In this Dec. 5, 2012 photo, the sun sets behind an oil pump jack and the Rocky Mountains near Fredrick, Colo. Citizen fears about hydraulic fracturing, a drilling procedure used to pry oil and gas from rock deep underground, have made "fracking" the hottest political question in Colorado. In November, citizens in the Denver suburb of Longmont voted overwhelmingly to ban fracking despite heavy opposition from the oil and gas industry and warnings of lawsuits. Now the fracking debate is rocking small local governments _ and leaving the industry wondering how to proceed in a state that has long embraced the oil and gas industry. (AP Photo/Ed Andrieski)

  • Winter X Games 2012 - Day 4

    ASPEN, CO - JANUARY 29: Opponents to the practice of fracking for oil demonstrate with signs as Matt Ladley soars above the crowd during the men's snowboard superpipe final during Winter X Games 2012 at Buttermilk Mountain on January 29, 2012 in Aspen, Colorado. (Photo by Doug Pensinger/Getty Images)

  • Winter X Games 2012 - Day 4

    ASPEN, CO - JANUARY 29: Opponents to the practice of fracking for oil demonstrate with signs during the men's snowboard superpipe final during Winter X Games 2012 at Buttermilk Mountain on January 29, 2012 in Aspen, Colorado. (Photo by Doug Pensinger/Getty Images)

  • David Neslin

    David Neslin, Director of the Colorado Oil and Gas Conservation Commission, outlines the new fracking rules during the Colorado Oil and Gas Conservation Commission meeting in Denver on Tuesday, Dec. 13, 2011. Colorado regulators approved new rules requiring energy companies to publicly disclose chemicals used in hydraulic fracturing but allowing them to protect trade secrets. Under the regulations, a company that doesn't want to disclose an ingredient that's a trade secret has to explain why it should be protected. In those cases, the company would be required to provide contact information in case of emergencies. Information about the chemicals would be available to health professionals under a confidentiality agreement. (AP Photo/Ed Andrieski)

  • Thomas Compton, Perry Pearce

    Commissioners Thomas Compton, left, and Perry Pearce confer during the Colorado Oil and Gas Conservation Commission meeting in Denver on Tuesday, Dec. 13, 2011. Colorado regulators approved new rules requiring energy companies to publicly disclose chemicals used in hydraulic fracturing but allowing them to protect trade secrets. Under the regulations, a company that doesn't want to disclose an ingredient that's a trade secret has to explain why it should be protected. In those cases, the company would be required to provide contact information in case of emergencies. Information about the chemicals would be available to health professionals under a confidentiality agreement. (AP Photo/Ed Andrieski)

  • FILE - In this April 22, 2008 file photo, a natural gas well pad sits in front of the Roan Plateau near Rifle, Co. The director of the Colorado Oil and Gas Conservation Commission, David Neslin, said Monday, Dec. 5, 2011, that requiring drilling companies to publicly disclose what chemicals they use in hydraulic fracturing is only one tool for protecting public health and the environment. The comment was made during a hearing regarding a proposal to require public disclosures of fracking fluids that aren't trade secrets. More than 100 people packed the hearing. (AP Photo/David Zalubowski, File)

  • Haliiburton

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  • Fracking

    People gather in the doorway at a Colorado Oil and Gas Conservation Commission hearing in Denver on Monday, Dec. 5, 2011. The hearing on a proposed rule that would require oil and gas companies to publicly disclose most of the chemicals they use in hydraulic fracturing drew and overflow crowd (AP Photo/Ed Andrieski)

  • Fracking

    An overflow crowd gathered for a Colorado Oil and Gas Conservation Commission hearing in Denver on Monday, Dec. 5, 2011. The hearing was on a proposed rule that would require oil and gas companies to publicly disclose most of the chemicals they use in hydraulic fracturing. (AP Photo/Ed Andrieski)

  • Anthony Chavez

    Anthony Chavez with Occupy Denver Outreach wears a bandana over his face as he waits to testify at a Colorado Oil and Gas Conservation Commission hearing in Denver on Monday, Dec. 5, 2011. The hearing on a proposed rule that would require oil and gas companies to publicly disclose most of the chemicals they use in hydraulic fracturing drew a large crowd. (AP Photo/Ed Andrieski)

  • Deb Gardner

    State Rep. Deb Gardner, D-Longmont, testifies at a Colorado Oil and Gas Conservation Commission hearing in Denver on Monday, Dec. 5, 2011. The hearing on a proposed rule that would require oil and gas companies to publicly disclose most of the chemicals they use in hydraulic fracturing drew an overflow crowd. (AP Photo/Ed Andrieski)

  • Mark White

    Land owner Mark White of Longmont, Colo., testifies at a Colorado Oil and Gas Conservation Commission hearing in Denver on Monday, Dec. 5, 2011. The hearing on a proposed rule that would require oil and gas companies to publicly disclose most of the chemicals they use in hydraulic fracturing drew a large crowd. (AP Photo/Ed Andrieski)

  • April Beach talks about Erie Fracking Sites

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