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This document consists of Figure 3—Trenching and Sampling Plan. The figure has a red outlined <br /> area described in the Legend as "Estimate [D] Area Dist[u]r[i]bed (Historical)" and appears to be <br /> the location of previous exploratory trenching and later the general area of waste excavation. An <br /> area to the adjacent north is indicated as "Proposed trenches" and a similarly area is located north <br /> of the power plant in the area of previous trenches T29 to T31; however is not indicated as <br /> "Proposed trenches" however, likely is also an area of proposed additional exploratory trenching. <br /> Comments: Typically proposed trench locations are indicated as opposed to a general area; <br /> however, a general area is OK in some cases; however, for this to be the case, typically, <br /> information at each previous exploratory trench indicating the presence or absence of wastes and <br /> waste thicknesses, when present should be provided on the figure so that it is clear why a <br /> "general area" is proposed for additional work. <br /> This document consists of Figure 3—Trenching and Sampling Plan. The figure indicates locations <br /> of trenches and borings. <br /> Comments: Although not known, there are trenches designated in yellow and as proposed and <br /> therefore this figure is likely indicating where additional trenching is planned to be conducted. <br /> Without information on this figure indicating the results of the previous exploratory trenches <br /> (e.g., at each trench location, were wastes present/absent and waste thickness, when present), it <br /> is not possible to tell whether the proposed trench locations are adequate. In addition, the legend <br /> indicates proposed soil boring (also yellow); however, none are indicated on the figure. The figure <br /> also indicates an area of red outline described in the legend as: "estimate area disturbed <br /> [disturbed] (historical)." Four trenches are proposed north and south of the red outlined area and <br /> four trenches are proposed north of the power plant. All trenches are proposed to be oriented in <br /> an east-west direction and it is likely that other orientations may be required for adequate (lateral) <br /> waste delineation. <br /> twWw"ug i � �,. � � � � , x �, s�� �� r� oilrta. �'' "��11" _ I �� `�= <br /> .; � r ,,, W <br /> This document consists of a schematic figure for a proposed "Soil-Gas Point Design." <br /> Comments: This figure is labeled "Proposed "Soil-Gas Point Design" (terminology is not clear, <br /> since it is not known what is meant by"point"?). Is what is proposed a soil vapor probe or a landfill <br /> gas monitoring well? The boring diameter is indicated as a 3 inch diameter. There are four tick <br /> marks on the right side of the schematic diagram and they are not labeled and this section of the <br /> proposed "soil-gas point' has a wider diameter pipe, which is unclear and not labeled. The depth <br /> to groundwater on the figure is indicated as 20 feet bgs; however, background documents indicate <br /> the depth to groundwater is approximately 14 to 20 feet bgs. Therefore, the well screen could be <br /> in groundwater. <br /> This email stated that AGE has evaluated the LEAs request for the longer soil-gas probe design <br /> across the waste and to install to a depth through soil above the water table. AGE stated that <br /> the cover fill is about 4 feet thick at the proposed location and "media is about 18 inches thick" <br /> more native soil is encountered below six feet below surface grade. AGE stated that they can <br /> Ninyo&Moore 1 500 E.Louise Avenue,Lathrop,San Joaquin County,California 1 104690095 1 August 11,2017 37 <br />