Are pipeline problems weighing oil stocks down? There’s some evidence of that, at least for one big energy giant. Enbridge Inc. saw its stock price fall from $42 to $40 per share on Aug. 1, as federal regulators nixed the reopening of a ruptured oil pipeline near Grand Marsh, Wisconsin.

The pipeline company said a day earlier that it had made the necessary repairs to get the Line 14 pipeline line flowing again, but had to hold off after the U.S. Department of Transportation blocked the move. According to the federal government, Enbridge must complete more tests and receive operational clearance from an “independent expert” before it gets Uncle Sam’s approval.

"Pipelines operate safely across the country every single day. That's why accidents, like the one in Wisconsin, are absolutely unacceptable," U.S. Transportation Secretary Ray LaHood said in a statement this week.

"I will soon meet with Enbridge's leadership team and they will need to demonstrate why they should be allowed to continue to operate this Wisconsin pipeline without either a significant overhaul or a complete replacement," LaHood added.

Nobody is making light of a spill that leaked 1,000 barrels of oil out of 318,000 barrels moved through Line 14 from Superior, Wis. to Mokena, Ill. on a daily basis. But the episode is another black eye for Enbridge, which only two years ago suffered a similar pipeline leak in Michigan, that saw 20,000 barrels of oil stream into the Kalamazoo River during a 17-hour period.

The Kalamazoo leak led to a report from the U.S. National Safety Board that called Enbridge officials “Keystone Kops” and said the company was fostering a “culture of deviance” where disaster procedures were lax and employees in the dark about what steps to take in the event of a pipeline leak.

A $2 decline in share price, as Enbridge saw on Aug. 1, isn’t exactly earth-shaking. But what could be problematic is the advent of another review by the U.S. Government that could chill big plans for an expanded $3-billion transcontinental pipeline effort that needs approval from both Canadian and U.S. energy regulators.

Now that pipeline is in jeopardy, as is Enbridge’s share price, as both The Wall Street Journal and Zacks Equity Research both said the Wisconsin pipeline rupture will make approval of the new pipeline problematic.

This from Zacks:

The incident is likely to affect Enbridge Energy’s plans to make expansions in the crude oil mainline pipeline system worth $3.2 billion. The project was proposed to transfer crude from western Canada to the Eastern refineries as well as avoid obstacles in the U.S. Midwest. The initiative would comprise capacity addition to the company's Lakehead System and the Eastern Access Projects with its commissioning scheduled for 2014.

For its part, Enbridge is contrite over the Wisconsin spill. This from a company statement by CEO Patrick Daniel:

At the time of the Marshall (Michigan) incident in July 2010, we immediately accepted full responsibility and committed to do whatever it took to make things right in the community, to fully understand what happened, and to do what was necessary to work with all parties to improve procedures and technology so that this wouldn't happen again. While we deeply regret the incident on Line 14 this past week, our ability to quickly detect and immediately respond to the leak thus limiting environmental impacts is evidence of our ongoing commitment to implement the lessons from 2010 and the enhancements we've made over the past two years. We will continue to carefully examine the report of the NTSB, as well as the findings from the investigation of the Line 14 leak, to determine whether any further changes are required. We apologize to those affected by the Line 14 incident and we greatly appreciate the patience and cooperation of the affected landowners and the community.

Operational safety and reliability are our highest priorities. We are humbled by the incidents we have experienced. Under the framework of our comprehensive Operational Risk Management plan, we are applying our learnings, and have set for ourselves the objective of delivering industry leading performance across all of our existing operations. We will design and build our growth projects to meet and exceed the expectations of our stakeholders for the safe and reliable delivery of energy.

Even so, Enbridge only has itself to blame for giving government regulators a good reason to deep-six the major pipeline proposal. "It makes (regulators) look bad when they approve pipelines or endorse companies that continually do this," says Chad Friess, analyst at UBS Securities, in comments to Reuters. "I can definitely see why they'd be losing patience."

It’s not just pipeline ruptures. Some experts say the way pipelines are actually constructed and managed are impacting pipeline performance, and also impacting the price of oil and gas here in the U.S.

In a July 30 energy industry outlook, Ernst & Young says “mismatches” and ‘bottlenecks” are crimping pipeline productivity. “Growing oil supplies from unconventional fields in the U.S. and Canada have created significant logistics constraints, bottlenecks and considerable investment needs,” says Ernst & Young. “In addition, new supply and demand trends/patterns have revealed widespread infrastructure mismatches, with pipelines being in the "wrong place," carrying crude in the "wrong direction" and/or transporting the "wrong products."  These infrastructure constraints and mismatches are clearly reflected in the price disconnects in the Midwestern region over the last 18 months.”

The problem, the report says, isn’t isolated -- it’s systematic.

"The magnitude of the problem is much greater than reversing one pipeline," adds Marcela Donadio, an oil and gas analyst at Ernst & Young LLP. "Not only do we need more infrastructure, we need different infrastructure."

The pipeline issue is a serious one for energy companies, and for investors, as well.

No matter how well the financials look for a company like Enbridge--and they look pretty good right now--the company’s stock may well be held back over concerns about pipeline safety. Don’t think shareholders won’t notice.