Opponents of a new plan to open the Delaware River basin to natural gas drilling renewed their attack on the proposal, saying it fails to determine whether public water supplies will be contaminated by gas extraction.

Environmental groups said the Delaware River Basin Commission, an interstate regulator charged with maintaining water quality in the four-state basin, has ignored their calls for a cumulative impact study on whether aquifers would be polluted by toxic chemicals used in hydraulic fracturing (“fracking“), a process that has facilitated the current boom in obtaining gas from shale beds in many U.S. states.

The commission on Tuesday released a revised draft of its plans to regulate the industry, which is expected to drill thousands of wells in the basin if the commission votes on Nov. 21 to approve the plan, lifting a current moratorium.

Weighing The Risks

Vast US reserves of shale gas – which burns with only about half the greenhouse gas emissions of coal – are estimated to be sufficient to meet national gas needs for a century, providing a major new domestic source for energy needs including power generation, and cutting heavy U.S. dependence on foreign oil.

Watch an interview with leading natural gas economist Sara Banaszak about development opportunities in the US here.

Critics say allowing the industry into the 13,500-square-mile Delaware watershed would expose 15 million residents of the New York, New Jersey and Pennsylvania portions of the area to carcinogenic chemicals such as benzene and toluene that are used in or produced by fracking.

“They are continuing down this irresponsible path because they are not permitting any cumulative impact analysis,” said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network, an environmental group that has sued the DRBC in pursuit of a full study on the impact of gas drilling. “They are ensuring that our aquifers are going to be polluted.”

Some residents who live near shale-gas wells in areas of Pennsylvania outside the Delaware basin, and in other states, blame the industry for health complaints ranging from headaches and nausea to arsenic poisoning and neurological problems.

But the industry insists there has never been a proven case of water contamination as a result of fracking. The chemicals used in gas-well completion are injected through steel and concrete casings that prevent any contact with aquifers, and then released thousands of feet below drinking-water sources, industry spokespeople say.

Keeping It Local

Kathryn Klaber, president of the Marcellus Shale Coalition, welcomed the DRBC’s proposal that state regulators should continue to oversee well construction and operation but said the industry group has concerns about “what we don’t know” about the regulations.

“We look forward to continuing to work with the DRBC and other stakeholders to craft common sense regulations,” Klaber said in a statement.

In its 104-page revised Natural Gas Development Regulations, the commission made some changes to an earlier draft, released in December 2010. The new provisions include higher financial assurance requirements for well operators, going up to $25 million for accidental spills and releases, and a requirement that groundwater sampling is conducted for all natural gas projects, not just for high-volume hydraulic fracturing projects.

The EPA recently released a report on water impacts from fracking that was attacked by the industry for its lack of transparency. Read more here.

The revisions were guided in part by comments from almost 70,000 people made between the release of the original draft and April 15, 2011, but no further comment period is being allowed, said the DRBC, which consists of the governors of New York, Pennsylvania, New Jersey and Delaware, and the federal Army Corps of Engineers.

The new plan drew a fresh attack from New York State Attorney General Eric Schneiderman who in May sued the DRBC for failing to conduct an environmental impact study of gas drilling.

“Though modified, these regulations still lack the benefit of a full environmental impact study, which is required by law and dictated by common sense,” Schneiderman said in a statement.

Read an interview with former New York governor George Pataki here about fracking in the state.