by D. Jay Grimes and Ronald M. At­las — On April 20, 2010, an off­shore oil drilling rig in the north­ern Gulf of Mex­ico, the 'Deep­wa­ter Hori­zon' (DH), ex­ploded from un­de­ter­mined causes. The float­ing rig sunk two days later, break­ing off the well pipe and spilling huge amounts of oil. At the low end of the es­ti­mates, the spill has al­ready eclipsed...