Though federal regulations require offshore drilling locations to be inspected by the Department of the Interior's Minerals Mining Service every 30 days, those inspections have repeatedly not happened since the Deepwater Horizon site was permitted by MMS in 2001 – including one out of every four months since President Obama's inauguration.
ABC News has learned that in the 16 months from January 2009 through April 2010 MMS failed to inspect Deepwater Horizon four times – in May 2009, August 2009, December 2009, and January 2010.
The reasons for the lack of inspections, sources said, were logistic.
In May and August 2009, the proper twin engine helicopter needed to fly to the Deepwater Horizon site was being serviced.
Inclement weather prevented flights to the site for 12 out of 22 work days in December 2009, with maintenance to the helicopter consuming another two days, leaving eight days for the inspection – which was not carried out.
The next month, January 2010, inclement weather prevented flights for eight of the 19 work days, with four days impacted because of maintenance. But even in those seven days available, again, the inspection was not carried out.
Inspections were carried out in February, March, and April of this year.
The lack of regular inspections is not a new development. In the past five years – 60 months -- Deepwater Horizon was inspected 48 times. And in the 104 months since September 2001 when MMS permitted the site, Deepwater Horizon was inspected 88 times.
“It is MMS’s goal to inspect drilling rigs on a monthly basis,” an Interior Department official said, “but there are various reasons why a drilling rig may not be inspected every month, such as if helicopters are grounded because of inclement weather or rig inactivity due to hurricanes; if a rig moves between multiple locations in a month; if a rig is on location and preparing to drill, but not actually drilling; or if a rig is at the end of its work on a location but is preparing to move off.”