SOURCES: Channels: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics; National Transportation Atlas Databases (NTAD) 2009 DVD, available at http://www.bts.gov/ as of May 2010. Cleaning stations: North Protection and Indemnity (P&I) Insurance Association. Deepwater Horizon Incident – Briefing Notes (May 21, 2010). Available at http://www.nepia.com/ as of May 2010. Ports: U.S. Department of Transportation, Maritime Administration, U.S. Port Calls by Vessel Type, available at http://www.marad.dot.gov/ as of May 2010. Terminals: U.S. Army Corps of Engineers, Navigation Data Center, Ports and Waterways Facilities, available at http://www.ndc.iwr.usace.army.mil/data/datapwd.htm as of May 2010.