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0I • JM Equipment page 2 1245 W. Charter Way, Stockton. Report comment le er Observation 1: (co tinued) Based on the table on page 6, SJCEHD calculates that a minimum of 86 gallons of liquid was injected into MW-9. If the soil has 50% effective porosity, GTI's point would be well taken, however, clayey soil typically has 4-8% effective porosity - even wit a total porosity of 50%. Using a 5% effective porosity, the volume of water inj cted could reach and affect GP-1 , especially if application of pressure to drive tV e injectant into the aquifer overwhelmed the hydraulic conductivity of the oil and created temporary pathways through the clayey soil by rupturing the cle yey soil fabric. Also, GTI interpret the decline of hydrocarbon concentrations in MW-9 to be due to oxidant being inj acted into the well, which at first glance would seem to be the causative factor. F owever, SJCEHD notes that a similar decline of hydrocarbon concentrations occirred during the summer and fall of 2001, which cannot be attributed to injection of oxidant. SJCEHD questions how to demonstrate that the recent decline is not caused by or greatly influenced by the same factors operating in 2001? Observation 2: Increased oxidation-reduction potential (ORP) in MW-1 and GP-1, interpreted to indicate a 1-foot radius of influence for the injectant. SJCEHD believes that the oxidants were forced from MW-9 to GPA through temporary rupture in the soil fabric caused by applied pressure overwhelming the clayey soil's hydraulic conductivity, bypassing the major portion of impacted water between thE wells and delivering the oxidants directly to GP-1. This was demonstrated by t ie breakthrough at 8 or 10 psi that forced the H2O2 solution up GPA to the surface. SJCEHD believes it quite possible that the observed ORP effect in GPA wa more due to direct migration through temporary ruptures in the clayey soil tha to migration uniformly through the column of soil adjacent to MWA's screened section. The implication is that most of the impacted groundwater in the clayey soil would be bypassed and mostly groundwater immediately adjacent to the walls of the temporary rupture in the clayey soil and to the well casings would be addressed by the oxidants. GTI hypothesizes that the oxidants migrated along fractures in the clayey soil induced during dr Iling, into GPA and recommends investigating the applicability of using fracture t chnology to enhance the permeability of the soil. As fully hydrated clay has high cohesiveness but little rigidity or shear strength, SJCEHD questions whether or not fractures can be maintained in a saturated clay or clayey soil. Please provide documentation of the successful application of fracturing in saturated clay and/or clayey soil to SJCEHD for further evaluation of the recommenda ion.