Laserfiche WebLink
Port of Stockton • -3- �1 October 1987 <br /> water level surface maps submitted in the last report cannot <br /> be accepted as the true representation of water level <br /> surfaces until the magnitude of tidal influences is <br /> determined. <br /> Some piezometers are screened across the water table while <br /> others are not. Whether or not this is a significant problem <br /> in getting true water levels must be determined by a <br /> characterization of the geology in this area. <br /> Water level elevations should be based on a mean sea level <br /> datum. <br /> 2. Stockton Petroleum is shown on figure 2 as being an area of <br /> known subsurface petroleum hydrocarbon contamination. No <br /> basis for this determination is documented in the report. <br /> WCC should describe the type and extent of this known <br /> contamination. <br /> 3. Several areas of known contamination were not included in the <br /> report, and others have been identified since the report was <br /> received. The representation of known subsurface petroleum <br /> hydrocarbon contamination misrepresents the situation as it <br /> was known at the time the report was written. Specifically, <br /> the removal of underground tanks at ST Services and Tesoro <br /> Petroleum in 1986 and April 1987 uncovered ground water <br /> contamination. These were not mentioned in the report or <br /> shown on Figure 2. <br /> 4. A determination as to whether or not fuel is floating on the <br /> ground water cannot be made by observing the piezometer <br /> contents, since many of them are screened only below the <br /> water table. Results reported in the last column of Table C- <br /> 1 of the report may be in error. <br /> 5. We are concerned about levels of contaminants in Water that <br /> cannot be detected by sense of smell. Even though WCC field <br /> personnel were not able to smell fuel in water taken out of <br /> some piezometers there is a likelihood that contamination <br /> exists at concentrations above acceptable levels in these <br /> locations. The full extent of contamination will have to be <br /> defined using standard sampling and analytical techniques. <br /> Analysis of water samples should be according to EPA approved <br /> methods, such as method 602 for purgable aromatics. <br /> III. DETAILS OF PROPOSED INVESTIGATION <br /> 1. No monitoring wells have been proposed. These are necessary <br /> in order to collect representative samples of ground water <br /> for analyses. <br /> 2. A sampling and analysis program for site investigation has <br /> not been fully detailed in the workplan. <br />