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04/19/96 16:35 -&510 842 8252 CHEVRON PRUVUUla <br /> The presence of elevated values Of11dissolded sulfate in wells MW-9 <br /> and MW-2R (35 and 38 - mg/L, respectively) , suggests that tho <br /> formerly impacted portion of the site is presently characterized by <br /> relatively low concentrations of dissolved hydrocarbons. As noted <br /> in Observation No. 3, recent groundwater samples from MW-9 are <br /> collected from a submerged screen, representing aquifer conditions <br /> wholly below the water table. <br /> (b) Dissolved Ferrous Iron - the uniformly low concentrations <br /> of ferrous iron in all sampled wells implies the relative abundance <br /> of the anaerobic electron acceptor ferric iron (see attached Site <br /> Map/Dissolved Ferrous Iron) . The implied presence of ferric iron <br /> suggests that the dissolved hydrocarbon presence is minimal in the <br /> vicinity of all sampled wells, and sufficient electron acceptor is <br /> available to inhibit the migration of dissolved hydrocarbons. <br /> (c) Dissolved Nitrate - the nondetect to minimal <br /> concentrations of dissolved nitrate, in upgradient, downgradient <br /> and on-site wells, indicates that the electron acceptor is locally <br /> depleted in the subsurface (see attached Site Map/Dissolved <br /> Nitrate) . The absence of dissolved nitrate is apparently a <br /> characteristic of the vicinity of the site. <br /> (d) Dissolved oxygen - the concentrations of dissolved oxygen <br /> in all site wells indicate a sufficient presence to facilitate the <br /> aerobic degradation of available dissolved hydrocarbons in the <br /> saturated zone (see attached Site Map/Dissolved oxygen) . The areal <br /> distribution and concentrations of the DD further suggests that the <br /> dissolved hydrocarbons values at the site are minimal. <br /> Please call me at CTN 242-1383 if you would like to discuss this <br /> site further. <br /> l <br /> Sheldon N. Nelson <br /> cc: T.E_ Buscheck <br /> J.N_ Stambolis <br /> J.M. Randall <br /> 4 <br />