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The advantage of this system is the elimination of the waste stream handling associated <br /> with GAC. Disadvantages include reduced reliability and higher cost. Capital cost for <br /> this system totals $370,000; operation and maintenance adds about $63,000 per year. <br /> Alternative 3—UV-Peroxide Treatment <br /> This method destroys the hydrocarbon compounds by oxidation. Hydrogen peroxide is <br /> added to the groundwater, which is then subjected to ultraviolet (UV) light. This <br /> creates hydroxyl radicals, which oxidize the hydrocarbons. The products are carbon <br /> dioxide and water. <br /> Advantages to this system are lower maintenance and elimination of contaminated <br /> residual. Problems associated with scale fouling, common to air strippers, are largely <br /> G• eliminated. Disadvantages include high power consumption and the need for pilot <br /> testing. This method is also not as flexible; the system is less adaptable -to different <br /> influent concentrations or flow rates. There are vendors who will lease these systems, <br /> G <br /> providing some flexibility for change. <br /> Capital cost for a UV-peroxide system would be about $265,000, assuming Del Monte <br /> purchases the system at startup. O&M costs are estimated at about $59,000 per year; <br /> f about half of this is for electric power. <br /> i <br /> Summary <br /> Costs for Alternatives 1 and 3 are essentially equal. Alternative 2 is substantially higher <br /> and is not recommended for this site. The O&M for Alternative 1 can be expected to <br /> decrease with time as influent concentrations drop; since carbon replacement is the <br /> largest component of the cost, this may have a substantial effect on long-term cost. <br /> 1 <br /> ' Alternative 2 can be obtained by lease, with service as part of the contract. This can <br /> reduce the initial cost and incidental expense to Del Monte. The UV-peroxide system <br /> is not, however, as adaptable to changing conditions; O&M cost is largely unrelated to <br /> influent concentration. <br /> Because the influent stream to the treatment process is not well-defined and is <br /> expected to change with time, Alternative 1 is recommended for this site. <br /> Recommended Remedial Action Plan <br /> Implementing a remedy in phases will allow remediation of the Disco location to begin <br /> as soon as possible and provides an opportunity to "fine tune" the proposed <br /> remediation system. This Remedial Action Plan (RAP) describes actions for a <br /> "Phase I" to address the near-source area. This will allow for timely action in the area <br /> i of greatest concern and will prevent migration of the most highly contaminated <br /> I . <br /> SF031604\RP1007.51 4-8 <br />