Chumash Heritage National Marine Sanctuary covers 4,543 mi 2 (3,431 nmi 2) of coastal and ocean waters and the submerged lands thereunder, spanning 116 miles along the central California coast off the counties of San Luis Obispo and Santa Barbara. The sanctuary spans a maximum distance of 60 miles from shore, and reaches a maximum depth of 11,580 feet below sea level. Describing the boundary in a clockwise fashion, the Final Preferred Alternative starts along the coast approximately two miles southeast of the breakwater for the Diablo Canyon Power Plant marina, then runs south along the mean high water line through San Luis Obispo County and northern and western Santa Barbara County to the eastern end of the Naples Marine Conservation Area on the Gaviota Coast. Along this stretch, the harbor areas at Port San Luis and Vandenberg Space Force Base near Point Arguello are excluded from the sanctuary. Offshore, the boundary extends from the western edge of Channel Islands National Marine Sanctuary, around important features like Rodriguez Seamount, most of Arguello Canyon, and about half of the Santa Lucia Bank and part of its escarpment. At a point approximately 55 miles offshore of the Santa Maria River mouth, the boundary extends east 43 miles, then due north for 12 miles to the point of origin south of the Diablo Canyon Power Plant marina. This narrative boundary description is provided to facilitate public understanding, but please refer to the formal boundary description and the precise boundary coordinates in Appendix A to this subpart.