DENVER - Colorado oil and natural gas regulators on Monday approved rules making the state the first to require energy companies to do groundwater sampling both before and after they drill.The sampling is meant to show whether supplies of drinking water have been affected by energy development.Industry and environmental interests both immediately found fault with the new sampling regulations, which the Colorado Oil and Gas Conservation Commission approved Monday as it began a three-day hearing on rule changes. Next, the commission will consider updating how far drilling must be from buildings.The Environmental Defense Fund said the sampling rules approved Monday represented the weakest program in the nation for testing groundwater around oil and gas operations. Meanwhile, the Colorado Oil & Gas Association, a trade group, worried the rules could hamper energy development with excessive requirements.Colorado is requiring sampling of up to four water wells within a half mile of a new oil and gas well before drilling, between six and 12 months after drilling, and between five and six years after drilling.An exception is in the energy-rich Greater Wattenberg Area, one of the state's top areas for drilling with thousands of active wells. Operators there would only have to sample one water well per quarter governmental section, before and after drilling. That angered environmental groups who said the limited sampling would slash the odds of detecting contamination. Energy companies countered that wells are so close together there that it doesn't make sense to require more sampling.The state commission said an existing program in Weld County provides water well testing to any well owner requesting it.Environmental groups also contend the new rules fail to set standards for how groundwater samples are collected and tested, and will allow drilling operators to "cherry pick" which water sources to sample.The Colorado Oil & Gas Association supported building on a voluntary groundwater monitoring program that began in January.Oil and gas drilling accounts for nearly 44,000 jobs in Colorado and brought in $208 million in severance taxes last year. However, residents along the Front Range have expressed concerns about potential health effects from drilling as activity moves closer and closer to more populated areas.Industry groups had sought to limit testimony at the hearing from people who live near drilling sites, saying in part that their comments on their health problems weren't based on medical expertise. The commission, however, decided to allow the testimony.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.