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I 62 / 19 / 02 14 : 29 FAX 916 372 5 Wallace-Kuhl Z002 FEB 1 9 2002 Jeff Wong San Joaquin County Public Health Services 304 E. Webber Avenue, Third Floor Stockton, California 95202 I Remedial Action Workplan Addendum CRYSTAL CREAM & BUTTER COMPANY 404 West Fremont Street Stockton, Calfornia WKA No. 1628. 11 In accordance with our telephone conversations of February 11 and February 19, 2002, we have prepared this cursory workplan addendum for remediation of the above site. The purpose of this addendum is to describe a slight variation on the remedial action Plan previously submitted and approved by San Joaquin County. Based on newly received information, we are proposing a change in the vapor extraction/air sparging plan to .incorporate the use of ozone injection. At this point we would like to reserve the ability to use vapor extractionlair sparging in the event that the ozone injection method does not achieve the desired results. However, it is our opinion that use of this newer method will likely be much more cost effective and achieve a greater reduction of contaminants in a more timely fashion. The proposed method utilizes 10 injection points installed by drilling standard soil borings and placing a porous point at a pre-determined depth. Each point is approximately three fect.long and is connected to the surface via special tubing. The points are surrounded by fine sand then topped with a five-foot thick bentonite seal. The borings are then grouted to the surface to prevent cross contamination. A schematic of the proposed boring locations is shown -on the attached plate. The locations are designed to intercept the "perimeter" of the plume while simultaneously attacking the more concentrated areas. Once plumbed to the surface, each point is connected to the ozone generator via a manifold system. The ozone generator and compressor unit cycles ozone at very low pressure to each injection point. A standard rule-of-thumb is that the radius of influence for each point is 1 .5 times the depth they are set below the water surface. For example, a point set 10 feet below the water surface would have an approximate radius of influence of 15 feet (overall diameter of 30 feet). The fact that ozone is cycled to each point much like a home garden sprinkler system allows ��Q for widespread treatment while minimizing any mounding effect.