SITE INFORMATION AND CORRESPONDENCE

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Geweke, FRP 3 - 20 September 1993 smear zone. The wells that are proposed for introducing bacteria into the vadose zone and ground water may not affect the full extent of soil contamination in the smear zone. At the Ukiah site, GeoAudit has inferred that soil bioremediation has contributed to the decline in ground water contamination. However, similar drops in contamination have been noted at sites where the contaminated soil has merely been removed. It appears that the Apple Valley site was an in-situ soil cleanup and that ground water was not involved. Neither case study was an in-situ ground water case. The case studies for the two sites in Ukiah and Apple valley were very sketchy. Neither case study contained information about soil characteristics, depth to water, estimates of volumes of contaminants lost, number of borings used to introduce bacteria to the subsurface, volume of bacterial consortia and media used, contents of the medium, species of bacteria in the consortia, number of bacterial inoculations required, size of the contaminated area and the locations of borings and wells within the area. The results of any laboratory experiments, bench scale tests, and/or feasibility tests conducted for Geweke were not provided. The contents of the bacterial medium, the number of bacteria used, species of bacteria in the consortia, volume of the medium and consortia introduced to the subsurface, and the number of inoculations required, were not provided. The soil characteristics were not provided, including pH, EC, moisture content/water-bearing capacity/moisture retention curves, adsorption/desorption rates, metals toxicity, oxygen demand, nitrogen content, phosphorus content, trace mineral content, porosity, and soil particle size distribution. All of these parameters have an impact on soil and ground water in-situ bioremediation. The number and location of wells to be used to introduce bacteria into the ground water were not provided. There was no mention of whether oxygen must be added to ground water and how this may be accomplished. Introduction and maintenance of adequate oxygen in the contaminated ground water zone may be one of the most difficult aspects of in-situ bio. There was no mention of how putting the liquid medium into wells will affect ground water flow or contamination. There was no mention of ground water monitoring for introduction of medium plus consortia during the soil remediation phase. Without monitoring it will be difficult to determine whether ground water is being affected positively or adversely. Other than monitoring contamination levels biannually, there is no mention of how they propose to determine that the soil treatment system is actually working, if more bacterial inoculations are needed, if more oxygen is needed, if additional nutrients are needed, or if the soil has become desiccated. Maintaining adequate oxygen without causing desiccation may be the most difficult aspect of in-situ bio of soil in the vadose zone. Without additional monitoring, it seems that this is effectively, aeration of the soil. The following information is needed to complete the FRP: 1. Locations and descriptions of GL-3, GL-4, and VW-1 through VW-4; 2. A signed copy of the letter in Appendix C; 3. A proposal to remediate the "smear zone";