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Alternatives A1, A2, and A3 address removal of the soil source that contributes to the petroleum <br /> hydrocarbons detected in the groundwater at this facility. Table 7 presents a comparison of the <br /> cost, mass removed, and cost per pound of TPH removed for each alternative in the October <br /> 2004 CAP and in this Addendum. The most effective alternatives are Al, A2, and A3, as shown <br /> below: <br /> Alternative <br /> Al A2 A3 <br /> Excavation: Removal of Excavation: 5' Into Excavation: 14'-17' Into <br /> TRH to 500 mg/kg 14'-17' Watertable Laterally to Watertable Laterally out to <br /> Into Watertable MW-3 MW-3 <br /> Cost $254,500 to $298,500 $151,000 to$183,000 $276,300 to$322,500 <br /> Pounds TPH (g;d)To 11,300 lbs TPH +d 10,200 lbs TPH 11,600 lbs TPH(9-d) <br /> Be Removed cg ) tg d) )� d) <br /> Cost per Pound of $22.4011b to $26.3011b $14.80/1b to$18A0l1b $23.7011b to$27.7011b <br /> TPH o) Removed TPH(9+d) TPH(g,d) TPH(9-d) <br /> Alternative A2 --Removal of soil at the soil/ground water interface and in the top 5 feet of the <br /> water table-- is the most cost-effective solution as the costs of shoring are avoided and the <br /> hydrocarbon mass removed is comparable to those alternatives with shoring. The removal <br /> efficiency of Alternative A2 addresses the free product and petroleum material at the soil/water <br /> interface and contamination in the five feet of the water table. Alternative A2 removes the mass <br /> reasonably accessible and provides the same remedial action time as the more expensive CAP <br /> Options, such as Alternatives 3, 4 and 5. The addition of calcium peroxide will provide an <br /> oxygen source to enhance degradation of the residual. Alternative A2 is the most cost-effective <br /> with regard to cost per pound of TPH removed because Alternative A2 removes 87% of the TPH <br /> associated with Alternative A 1 or A3 at a much lower cost. The driving factor in the cost <br /> difference between these options is primarily related to shoring costs. Based upon this analysis, <br /> Alternative A2 is the recommend remedial action. <br /> 20 <br /> R:ICONTGRAN\Stockton\CAP\CAP ADDENDUM <br />