SITE INFORMATION AND CORRESPONDENCE

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CtacIO&AtTacluucrinc Page 2 Work Plan Addendum Project No.507.2 May 16,2005 GTI response: The pilo study design did not have a direct means of verifying that all of the water left the well. However, the water was presumed to have vacated the well casing due to observations after the f t injection of liquid hydrogen peroxide on March 19, 2004. After 3 minutes of applying gase us oxygen at 8 psi the slip cap blew off and water/peroxide erupted out of adjacent well GP-1. GTI therefore concluded that after installing threaded caps on GP-1 through GP-3, the subsequent greater pressures of 10 psi would also cause liquids to leave the well casing of the injecti n well (MW-9) and flow into the formation. A second indicator noted in the field was that affi r the gas injection was terminated and the cap removed, well MW-9 continued to off gas for — 3 minutes as evidenced by feeling the vapor flow with the hand held over the casing and ac mpanied by whistling/gurgling noises coming from the well. This indicated that water& so I vapor were now flowing back into the well and displacing gas out into the atmosphere. 3) SJC PHS/EHD co ent: "What conditions constituted equilibrium." GTI response: After o one injection (8% ozone/92% oxygen by weight) the 100% gaseous oxygen was introduced to purge the well for a period of several minutes to preclude degradation of the PVC casing by a ay residual ozone. The well cap valve was closed, the oxygen line detached, and at this poi staff departed for lunch. The well pressure had decayed to zero psi by the time staff returned bout one hour) and this was deemed an equilibrium condition with excess pressure dissipate I to the formation. Please keep in mind that the oxygen injection after ozone injection is intend(d to protect the well casing, and to protect staff from breathing residual ozone gas once the well ap is opened. The term "equilibrium" as used by GTI was referring to an absence of gas pressui es as a possible hazard to staff that were preparing to perform a second sampling procedure of -9 groundwater and not a term applied to chemical equilibrium or reactions. In summary, GTI used the term "equilibrium" for the period of inactivity, which correlated to APT staff useing the phrase "the well then was allowed to rest for one hour and sampled..." in their repo -page 5, section 2.3. 4) SJC PHS/EHD conin ent: "How were groundwater amples obtained following the ozone/gaseous oxygen injection tests?" GTI response: After the procedure noted in response #3 above, the well cap was opened and a disposable Teflon bailer was lowered into the well to obtain groundwater samples. The sample was subsequently translerred to VOA's and handled in accordance with routine quarterly groundwater monitoring protocols. 5) SJC PHS/EHD conin ent: "Provide justificationfor ..three borings...locations."