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i 4 i P 09 �r This document appears to contain a similar summary of previous investigation as was presented in the previous PSA documents and therefore comments were already provided for this section and only comments related to the proposed waste excavation are provided. Comments: The section of the "work plan"titled "Proposed Waste Disposal" appears to consist of the proposed waste excavation activities to be conducted. This "work plan" document is incomplete since it does not provide adequate information to indicate that wastes in the area proposed to be excavated (as well as at the entire WDS), have been adequately characterized and delineated. Portions of this document are confusing because of wording, inconsistencies in nomenclature and typographical errors. Some of the information absent from the "work plan" includes but is not limited to the following: absence of information describing the wastes proposed to be excavated, incomplete information on how the lateral and vertical extent of waste excavation will be determined, methods to confirm the adequacy of waste removal, confirmation sampling and analytical testing, management of excavated wastes. Also, was air monitoring conducted during excavation and readings recorded? Tables included in the report summarize only metal analytical data and include samples not shown on Figure 2. In addition, the tables include nomenclature such as "Shallow Pond Sampling" without any reference to what this means. The following are more specific comments (blue) to specific statements included in the"work plan" (italics). During the investigation of the former PNA site, the majority of the trenches demonstrated minor percentages of glass. A set of trenches at the southwest boundary of the property(T46, T48, T50, T58 and T59) demonstrated a differing thickness (topology) of the potentially buried waste. The waste strata over native soil ranged from 18 inches at trench T46 to 10 feet deep at trench T58. Comments: What is meant by "a set of trenches?" According to Figure 2 - Excavation and Sampling Plan, it appears trenches T58 and T59 are actually located close to the western property boundary. The other three mentioned trenches appear to be located within the waste disposal area proposed to be excavated. The "Legend" on Figure 2 indicates a double red line designating the estimated property boundary; however, a single red line only is shown on the figure and the property boundary is not defined. There is no description of the types of wastes encountered in the area planned to be excavated. There were no trench logs accompanying the document and therefore the types of wastes that reportedly were encountered in trenches T46, T48, T50 was not available. Without trench logs, waste thicknesses, depths of underlying native soils, the presencelabsence of soil cover and thickness and the total waste depth are not known in the area proposed to be excavated. What is the rationale to conduct waste excavation in only this area of the waste disposal site and not other areas such as where trenches T1 to T23 were excavated (e.g., the glass waste disposal area to the north). Are the wastes observed in trenches T46, T48 and T50 similar to wastes observed in the earlier trenches T1 to T23? It is likely that based on historical site use, the waste stream would be similar. On Figure 2, what is the nomenclature of "G" or "C following the trench identification? Does this designate "garbage" and "clean"? Tables accompanying the document include borings and trenches not shown on Figure 2. All site investigation borings and trenches should be shown on Figure 2 and be accompanied by information about whether wastes were present and if so, the waste thickness. Ninyo&Moore 1 500 E.Louise Avenue,Lathrop,San Joaquin County,California 1 104690095 1 August 11,2017 40