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110 Second Avenue Sou #137,Pacheco,CA 94553 McCAMPBELL ANALYTICAL INC. Telephone:510-798-1620 Fax:510-798-1622 24 http://www.mccampbell.com E-mail:main@mccampbell.com POST-REACTION DECAY STUDY Dissolved ozone concentrations ranged from 0.029-0.066 mg/L during the reaction time interval&are tabulated in the results section. It decreased to ND(<0.005 mg/L)4 days after its generation was stopped. Dissolved hexachrome did not decay during the seven day post-reaction decay study. Its initial value of 7 is roughly equivalent to the 8.4 ppb found in the Final water, as a significant volume of water was removed for Final water testing &200m] DI added back into in the reaction vessel. The post-reaction day 1 to day 7 data scatter(2.1 to 7.0 ppb) is far greater than our —5% precision for hexachrome by 218.6 & this indicates that as yet not understood variables (aliquoting or filtering)are important. DISTLC&TTLC hexachrome remained ND during the post-reaction decay study. IMPROVEMENTS IN FUTURE EXPERIMENTAL TECHNIQUE The following improvements will be made to future experimental technique. 1)Glassware should be pre-ozonated&pre-cleaned to ND<0.2 ppb hexachrome levels. 2)A higher aquifer water to soil ratio should be used to eliminate water volume issues. 2:1 instead of 1:1 appears to be more suitable. 3)Ozone flow rates will be regulated more carefully to prevent changes such as that found on day 5 of the experiments. 4) TTLC hexachrome RL can be lowered to 80 ug/kg & possibly to 20 ug/kg. 800ug/kg was found to not be useful, although the 20-80 ug/kg limits may also not be useful. The DISTLC hexachrome RL may be able to be lowered to 24 ug/kg,which would be much more useful than 20 ug/kg. 5)We could test 5 consecutive days of the experiment next time instead of Days 1,2&5 only 6) The parallel N2 purge experiment should be performed in a 1L reaction vessel instead of 30ml U-shaped sparge vessel & can be purged with 02 or N2 instead of 03. Conditions should be the same as for the ozonated sample except that the ozone scrubber should be placed in front of the reaction rather than behind it. The water should be acidified to pH<2 to prevent bacterial decomposition if 02 is used. Insufficient soil was available for these procedures this time. 7)Aqueous phase metals sampling should be more standardized, in terms of time sample sits unpreserved, exactness in preservative's final acidity, whole container as opposed to aliquot acidification, & if necessary techniques for sediment removal. 8) Aqueous hexachrome sampling should be performed more carefully, taking into account time standing prior to filtration& filtration procedures. Bill,if you have any questions or comments please call. Yours truly, Edward Hamilton,Lab Director for McCampbell Analytical Inc.