Aging infrastructure on the North Slope could cause oil spills and "warrants increased vigilance, corrective actions and oversight," a  draft of the state's long-awaited Alaska Risk Assessment says.

But the study of prior North Slope oil spills and incidents doesn't anticipate any significant change in state oversight, and calls for "incremental improvements in current operations and regulatory oversight" rather than a revamping of regulations or a substantially different scrutiny of North Slope operators and Alyeska Pipeline Service Co.

The Legislature in 2007, at the urging of then-Gov. Sarah Palin, originally agreed to spend $5 million to evaluate possible problems along the length of the 800-mile trans-Alaska pipeline, the Valdez port and tanker operations, as well as Cook Inlet oil and gas production facilities.

The study, led by the state Department of Environmental Conservation, was implemented because of a number of small spills and leaks on the North Slope as well as a major spill in 2006 that shut down the pipeline and much of Prudhoe Bay for weeks. Corrosion has been a serious issue for the pipeline and production facilities, which are more than 30 years old.

But in the last year, the full-blown TAPS study has been reduced to an analysis of the oil spill risk on the North Slope only. DEC officials have said the refocusing was partly due to the fact that the oil companies weren't willing to share necessary information with the state and the state did not want to pursue legal action to get it. The state also asked for help from the National Academy of Sciences which reviewed the state's proposed study and said it likely wasn't going to be able to answer the questions it was asking including figuring out where future problems might occur, many of which had to do with oil-field management. The NAS also cited lack of industry cooperation as a problem.

DEC had planned to release the North Slope analysis earlier this year, but the time frame has been slipping. A few weeks ago DEC officials working on the study said a draft was circulating among top DEC executives.

And in fact DEC still hasn't officially released the draft, which was obtained Monday by Alaska Dispatch. DEC Commissioner Larry Hartig still has not signed off on the draft report, which could change before a final report is released. Hartig was not available to discuss the report Monday, his spokeswoman said.

Some critics of the effort have suggested the report was being held up until after the Nov. 2 election, but Gov. Sean Parnell, who is also the GOP candidate in the race, told Alaska Dispatch last week that was not the case and said he did not know the status of the report or where DEC is in the process.

The draft analysis identifies the causes of spills, trends in spills, and what effect aging has on the pipes, equipment and production facilities on the Slope. The study included wells, flow lines, process centers, storage tanks and crude oil transmission lines, the draft says.

"The data does not indicate that the petroleum infrastructure is nearing its 'end of life,' " the draft report says. "There is no significant change in spill trends which would indicate an increase in random failures."

However, that doesn't mean that the state should not take steps to increase monitoring, the report says.

It identified pipelines -- and in particular flow lines that carry a mix of oil, gas and water -- as the most susceptible to leaks and spills and, the report said, those should be a high priority for attention. There are more than 800 miles of flow lines on Alaska's North Slope, and the study documented a "slight increase" in spills over 1,000 gallons from flow lines. Corrosion is the most frequent cause, the study said.

Although the draft report emphasizes that a "paradigm shift" in oversight is not necessary, it does include several proposed actions that mainly are couched as evaluating the effectiveness of current regulations and possibly leading to new regulations at some point.