U. S. Department of the Interior

This document is the final report for U. S. Department of the Interior, Minerals Management Service (MMS), Gulf of Mexico Outer Continental Shelf (OCS) Region, contract number 1435-01-01-CT-31065, "The SO2 and NO2 Increment Analysis for the Breton National Wilderness Area (BNWA)". This section provides background information about the study, a discussion of increments for Class I areas, as defined in the Clean Air Act, a summary of objectives, and summaries of the methods and findings from the episode-type study.

At approximately 9:50 p.m. on the evening of April 20, 2010, while the crew of the Deepwater Horizon rig was finishing work after drilling the Macondo exploratory well, an undetected influx of hydrocarbons, commonly referred to as a "kick", escalated to a blowout. Shortly after the blowout, hydrocarbons that had flowed onto the rig floor through a mudgas vent line ignited in two separate explosions. Flowing hydrocarbons fueled a fire on the rig that continued to burn until the rig sank on April 22. Eleven men died on the Deepwater Horizon that evening. Over the next 87 days, almost five million barrels of oil were discharged from the Macondo well into the Gulf of Mexico.

Lease OCS G-1569 covers approximately 5,000 acres and is located in South Timbalier Block 185, Gulf of Mexico, off the Louisiana coast. The lease was issued effective July 01, 1967; LL&E became the designated operator of the lease on December 09, 1996. Burlington Resources (Burlington) has assumed operatorship of this lease because of a merger with LL&E; however, MMS records do not reflect Burlington as the designated operator