Uses

OCS Lease Blocks and BOEM Protraction Diagrams

  The ocean is a vast place with seemingly countless resources. The Bureau of Ocean Energy Management (BOEM) has regulatory authority to manage submerged lands of the outer continental shelf (OCS). In terms of wind energy development, BOEM regulates and manages this use by conveying leases within designated lease blocks. Each whole block is approximately 3 nautical miles (nm) by 3 nm. For renewable energy purposes only, blocks can be leased down to the 16th of a block. Oil and gas leases also use the block and protraction system, but leases are initially leased at the whole block level and then portions of the lease can later be relinquished for resale. In the Atlantic and Pacific, all boundary areas are computed in metric units. Because the Gulf of Mexico has had leases and boundaries for oil and gas existing since the 1950s, all units are English and boundaries and maps, while similar to the rest of the U.S., have a more complicated system of leasing maps, protractions, and projections.   So why should you pay attention to the OCS lease blocks and BOEM protraction diagrams?

  1. OCS Lease Blocks can help when planning for future wind leases. Knowing that BOEM will be leasing whole or portions of blocks allows a planner to identify and analyze blocks that are already leased or that overlie areas deemed suitable or unsuitable for wind project development. A planner can start reviewing blocks that meet favorable criteria for wind development and from those, start to eliminate areas of potential use conflicts because of economic, military, cultural, or environmental concerns. The remaining blocks can then be assessed further for their potential for wind project development. For example, BOEM and the U.S. Coast Guard use the block data along with Automatic Identification System (AIS) data to determine which blocks may have too much shipping traffic to be candidates for wind projects. The analysis is then combined with other block-related analyses to determine areas that may not be the best locations for energy development. What is usually made available for further study, are those whole and partial (1/16ths) blocks that were not eliminated from consideration. This is usually only the first or second analysis. Actual leasing and construction comes much later in the process.
  2. BOEM protraction diagrams help communicate locations of lease blocks. In the MarineCadastre.gov National Viewer, protractions are simple outlines used in mathematically delineating the OCS lease blocks, but these are also downloadable map products from BOEM that at one time were produced as paper charts. They are now available as PDFs. This image shows that the actual protraction diagram includes the blocks, the Submerged Lands Act Boundary, and the Limit of ’8(g)’ Zone, as well as land and water features. Blocks are related to their parent protractions.

Most of the OCS protractions cover an area of 2 ° longitude by 1° latitude and contain up to 1,200 blocks. Since each protraction starts with the same block numbering system starting with block 6,000, each block should be referred to along with its parent protraction number. For instance, NJ18-02 block 7036. Protractions are computed using the International UTM Zone Numbering system, so the protraction name tells you how far from the equator the map is, what UTM zone it is in, and which of 12 maps in that zone it represents. So NJ is North (N); Lat 36-40° (J); 18 is UTM zone 18; and 02 is the 2nd of 12 possible maps. It is important to pay attention to the names of each protraction area so that you can effectively communicate which lease blocks you are interested in leasing. Protractions in most cases also have a name based on the closest large feature, similar to U.S. Geological Survey Quad Sheets.

Quick Caveats. For more information about jurisdictional boundaries, visit Zones, Limits, and Maritime Jurisdictions.

For questions, please contact info@marinecadastre.gov.