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110 Second Avenue gMtt,#D7,Pacheco,CA 94553 McCAWBELL ANALYTICAL INC. Telephone:510-798-1620 Fax :510-798-1622 hqp://www.mccaMpbell.com E-mail:main@mccampbell.com OBSERVATIONS, INTERPRETATIONS&CONCLUSIONS General Overall, pH increased from 7.89 to —8.3, while alkalinity, TDS, EC, & Ca+2 decreased in the aquifer water. These effects are consistent with the pptn of CaCO3 in response to the pH increase. The degassing of CO,,g reaction 2a, is probably the dominant reaction that causes pH to increase.These pptn reactions as well as those of Fe&Mn oxides will diminish permeability, although the extent & hence significance is not known. Note that the Initial soil pH = 8.94 measured on DI water in equilibrium with the soil is very different from the pH=7.89 of the aquifer water. ✓�� Water Quality With regard to other water quality parameters,chloride was conserved, as expected. Sulfate increased moderately from 130 to 160 mg/L, perhaps due to reaction I or analogous to 4a except with sulfate as the end product. Unexpectedly, ORP decreased from 419 to 217 my with ozonation,perhaps because the significantly increased dissolved hydrocarbons now control the redox potential. J Hydrocarbons&VOCs Good agreement is generally found between 8260 & 8020/8021 for MBTEX hydrocarbons except for the initial soil values. The data were double checked & no errors were found, extraction surrogate recoveries agreed with stated dilution factors,so the explanation for this defaults to sample inhomogeneity. TPH(g)hydrocarbons were diminished by>--90%in the soil by day 5 of ozonation. Individual hydrocarbon compounds decreased by 10-100x in both 8260& 8020 soil analyses. TPH(g)hydrocarbons in the aquifer water phase increased— 30x after ozonation. This is probably simple mass transfer from the soil to water phase due to the oxidative loss of organic sorption sites in the soil. A decrease of 317 mg/kg TPH(g)occurred in the soil,with an increase of 2.7 mg/L in the aquifer water. Looking at the reaction vessel soil & water as though it comprised a section of the subsurface being ozonated, there was a 340/(33+3) or a 94% decrease in TPH(g) after 5 days, indicating that ozonation is an effective means of decomposing hydrocarbons. MTBE was `absent' from the Initial (& Final) soil presumably due to its high water solubility;MTBE decreased from 91 to<5 ppb in the aquifer water due to ozonation. The amount of hydrocarbon lost to purging by ozone was negligible compared to that oxidized by ozone, as evidenced by the "Ozone degassed front & back samples". As expected, simple purging alone, using a much higher gas to soil ratio in a U-shaped purge&trap sparge vessel,was completely effective. 1200 ppb acetone & 360 ppb MEK were observed in the Final water (but not Final soil) sample & small amounts of MEK were found in the front & back organic liquid traps downstream from the sample reaction vessel. The trace benzene found in the liquid traps may be an artifact of the tygon tubing used to connect them to the ozone destroying cartridges.Our lab has observed trace benzene arising from the degassing of tygon tubing in the past. Trace amounts of acetone & MEK were also found in the "N2 Sparged Sample". This discourages their description as ozonation by- products & their explanation remains unresolved. Acetone is ambient laboratory contaminant, but MEK is not. Acetone's diffusion through Teflon tubing, induced by flowing gas on the receiving side, with its partial breakdown to MEK is a possible explanation. I ; Metals:Major&Trace Elements Water The Initial water contained a fairly high sediment content, 1-3%,but the Final Water had negligible to low sediment, & the sediment content & pptn reactions are believed to be responsible for some difficulties in reconciling some metals data.This led to our reliance on"Total Recoverable"metals(TRM)values,for which data trends were clear. TRM determinations for the Initial & Final aquifer water were performed as follows. The Initial water including its suspended sediment was acidified with--2%HNO3 &remained in contact for a minimum of 16 hours. The aliquot of `►► water withdrawn from the reaction vessel for the Final water was treated similarly. This is --equivalent to "Total i Recoverable Metals" as described by the EPA in method 200.8. This procedure was used because it was found that the VP f _