The 17,000-acre USA Aberdeen - Edgewood site is a military ordnance installation in Edgewood, Maryland. The 4.5-acre Old O-Field site, which is the focus of the Record of Decision (ROD), is a fenced hazardous waste and ordnance disposal area. From 1949 to the mid-1970's, several decontamination and clean-up operations were conducted as a result of munitions explosions. These operations included the application of 1,000 barrels of decontaminating agent non-corrosive containing chlorinated hydrocarbons; soaking the field with several hundred gallons of fuel oil and setting the field ablaze; dispersing lime into the surrounding trees to further reduce the amount of mustard present; and using supertropical bleach, lime, and sodium hydroxide to destroy chemical agents. The ROD provides an interim remedy for contaminated ground water and its effect on surface water. The primary contaminants of concern affecting the ground water are VOCs including benzene, PCE, TCE, and toluene; and metals including arsenic. The selected remedial action for this interim remedy includes installing a downgradient extraction well network; and pumping and onsite treatment of contaminated ground water using chemical precipitation.