Virginia Capes Range Complex Final Environmental Impact Statement

VACAPES Range Complex FEIS/OEISChapter 3 Affected Environment andEnvironmental Consequences3.1 – Bathymetry and Sediments3.1.3.2 Alternative 1Explosions in the WaterAs shown in Table 3.1-2, Alternative 1 would result in 1,453 explosions in the water each year fromtraining in the VACAPES Study Area. As with the No Action Alternative, explosives would range fromthe 8-lb NEW charges in Hellfire missiles to 944.7-lb NEW charges in MK-84 bombs.Impacts from explosions in the water would be the same as those described for the No Action Alternative.All large, high-explosives bombs would be detonated near the surface over deep water, and would notdamage the ocean floor or disturb deep sediments. Increased numbers of explosions would occur forHellfire missiles and underwater detonations using 20-lb NEW charges but, as described for the NoAction Alternative, all effects from these explosions would be localized and short-term.Deposition of Expended Training MaterialsThe effects of expended materials from training activities on ocean bottom sediments in the VACAPESStudy Area were assessed as the number of items deposited per unit area of bottom surface. About2,249,138 training items would be expended under Alternative 1 (see Table 3.1-2). Based on theVACAPES Range Complex sea space area of 27,661 nm 2 , this would be about 81.3 items per nm 2 . Thedensity would range from less than one item annually per nm 2 in several of the training areas to 20,838items annually per nm 2 in W-50C.Of the 2,249,138 training items, approximately 2,196,730 or 98 percent would be cannon shells (25 or 30mm) or small-arms munitions (.50-caliber or 7.62-mm bullets). After 20 years, the greatest density,which would be in W-50C, would be about 416,770 items, or an average of one item per 88 square feet(approximately equal to a square that is 9 feet per side). Throughout the VACAPES Study Area, thedensity would be much lower, about 1,626 items per nm 2 .In addition to the materials described in the tables, Alternative 1 would include the installation of a mineneutralization training area in the W-50C area. This would consist of two relatively small (about 1 squaremile) training minefields, for use with AMNS, RAMICS, and MK-103. There will be 20-40 shapes in thewater of 40-60 feet in depth, both moored and bottom shapes. Concrete anchors would hold the mineshapes in place, one for each mine shape. Each anchor would measure 2.0 to 2.5 feet on each side.Sediment disturbance would occur during anchor placement and could recur with subsequent anchormaintenance activities or during mine shape deployment or recovery. However, all such disturbanceswould be highly localized and short-term, and would not have any lasting effects on bathymetry orsediments.As described in the No Action Alternative, neither bullets and shells nor larger pieces from other militaryexpended materials would affect sediment stability, and they eventually would be covered with sedimentand incorporated into the ocean floor. Based on the studies at the CFMETR, the volume of militaryexpended materials that would result from Alternative 1 would not measurably affect sediment quality.In accordance with the NEPA, Navy training activities in territorial waters under Alternative 1 wouldhave no significant impact to bathymetry or sediment. In accordance with Executive Order (EO) 12114,Navy training activities in non-territorial waters would not cause harm to bathymetry or sediment.3-9 March 2009