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Ms. Anne P. Conner 10 10/9/2007 Pacific Gas&Electric Company In addition, other geochemical and statistical methods will be used to evaluate the data. For example, leaching potential can be established by geochemical analysis of soil data. Also, comparisons can be made between consolidated groundwater data under Pond 3 and groundwater data outside the Pond 3 footprint to establish whether concentrations under Pond 3 are significantly different from those outside the footprint. Comparisons can also be made between different vertical and horizontal groundwater sampling locations under Pond 3, and between different vertical and horizontal soil sampling locations within the Pond 3 footprint. 5.1 FALCON Method The FALCON method is specifically designed for identifying the source(s) of contamination plumes. FALCON combines concentration data for several parameters to develop a distinctive graphical fingerprint, or multi-parameter chemical signature. The FALCON method is effective when a contaminant source area contains a unique proportion of two or more contaminants. If the proportion of these contaminants is not affected by degradation, adsorption, precipitation, volatilization, or transformation reactions, and remains constant along the groundwater flow path, then the proportion at the source area serves as a fingerprint that can be traced along the flow path. If these conditions are met, or if the effects of these processes on contaminant concentrations are properly understood, then the fingerprint pattern can be used to characterize the source of a contaminant plume, differentiate the contaminant plume from background conditions at the source, and monitor the migration of the plume from its source along a groundwater flow path. It can be applied to both organic and inorganic contaminants, and is effective over a wide range of contaminant concentrations. 5.2 PCA Method The PCA method is a multivariate technique that extracts one or more "principal components" that identify the analytes that are responsible for variance in the compositional data. Like the FALCON approach, PCA is based on normalized data so it is not sensitive to dilution or concentration (evaporation) processes. If one or more contaminants are present in a set of water analyses at different relative proportions with respect to the other analytes, then PCA will identify them as major contributors to variance in the composition. The technique works with anthropogenic contaminants as well as with naturally occurring constituents such as chloride and sodium. PCA will also identify non- contaminants as contributing to variance if their relative proportions in the samples vary due to natural processes such as dissolution-precipitation or adsorption-desorption reactions. The effects of these processes can be accounted for when interpreting the results as long as they are properly understood. An advantage of the PCA approach is that it is more quantitative than the FALCON method, but it is also more mathematically complex. 5.3 Reporting The above evaluations will be detailed in the 2007 Annual Report. Conclusions and recommendations from these evaluations will also be included in the 2007 Annual Report. Additionally, he 2007 Annual Report will include data analysis from the two 2007 semiannual sampling events. This analysis will be performed consistent with conclusions and recommendations from the Groundwater Monitoring Program Evaluation Report (MSE, 2007a).