Under pressure from the oil industry, Interior Department Secretary Sally Jewell has extended the comment period on a controversial final "fracking" regulation by 60 days, promising two more months of maneuvering over a rule that, in its earlier incarnations, drew more than 177,000 public comments. The bulk of those appeared to be the product of letter-writing campaigns by environmental groups, according to analysis of comments on Sunlight's Docket Wrench and conversations with agency officials.

The American Petroleum Institute official hailed the Thursday decision, saying the proposed new regulation could slow domestic energy production. But environmental groups don't like the  most recent version of the regulation either. They say it caters to concerns raised by the oil and gas companies during the comment process.

Hydraulic fracturing, or "fracking," is a process in which liquid is pumped underground into fractures in rock near oil and gas wells, thereby releasing more oil and gas to flow. It has significantly boosted U.S. energy production, and proponents tout fracking as a means to reduce the nation's reliance on foreign energy sources. Environmental groups, however, have raised concerns about toxic chemicals used in the process and the possibility of groundwater contamination.

The most recent version of the proposed regulation, released May 16, appeared to address some of the concerns raised by oil producers during the comment period. Docket Wrench picked up comments on the potential cost of the regulations, as well as on technical definitions of such as "usable water" from a number of companies including:

In addition, the proposed regulation would rely on a state-based voluntary database known as FracFocus that petroleum companies have promoted. Environmental groups charge that the system contains loopholes that would allow companies to avoid reporting some of their activities.

But the American Petroleum Institute (API), the oil industry trade group that successfully led the push for an extension of the comment period, argues that states already regulate the fracking process. "States have led the way in regulating hydraulic fracturing operations while protecting the communities and the environment for decades," the API's Erick Milito said in a statement.

Environmental groups spearheaded massive letter writing campaigns on the earlier version of the regulation, which sets out the rules for fracking on public lands managed by the Bureau of Land Management. The National Parks Conservation Association (NCPA) was active during the first commenting period in the summer of 2012. Nicholas Lund, manager of the landscape conservation program at the National Parks Conservation Association says his group not only prepared official remaks but also organized campaigns in which its more than 750,000 members and supporters were invited to participate, including this letter writing campaign that was identified by Docket Wrench.

Lund noted that more than 21,000 people clicked from the group's page through to the comment submission page on the government website regulations.gov, indicating that NPCA supporters were responsible for at least several thousand comments received by the agency. The NCPA is particularly concerned to fracking conducted near national parks, and is advocating that the National Park Service be involved in decisions of whether or not to drill. He said that the group would remain active during the new comment period.

One leading environmental group, the Natural Resources Defense Council organized a letter-writing campaign. Based on analysis of similarity of text of the comments submitted to BLM as displayed on Docket Wrench, so did the Western Organization of Resource Councils.

There was no indication that industry groups had orchestrated letter writing campaigns, although many oil and gas companies submitted highly technical comments. However, it is difficult to draw definitive conclusions, as an agency staffer confirmed that not all comments are posed publicly on regulations.gov; the policy is to not post all letters that appear to be identical or share a great deal of common text. For this reason, only a small fraction of the 177,000 comments are posted for public viewing.