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' r#0t0 gteal rtelratd 1= Page 12 Dual Phase Extraction Pilot Test Report Project No 723 2 November 12,2004 ' of 35% H202 mixed with 60 gallons of distilled water for a total of 75 gallons This represents 19% of the calculated pore volume ' * Cylinder pore vol = height x area x porosity = 20 feet x rr(4 feet)2 x 0 5= 503ft, 503Y x 7 48 gallons/ftj=3752 gallons ' The TPH-G concentrations in MW-9 have rebounded since the pilot test was completed On August 25, 2004 well MW-9 was sampled as part of a routine quarterly monitoring event and ' found to contain 122,000 ug/l TPH-G This suggests that the amount of water in the pore spaces around MW-9 treated was miniscule in relation to the total volume monitored by the GeoprobeTM observation wells Another consideration in the test was the organic content of the soils The pre-test soil composite samples A & B contained 1900 and 4300 mg/kg total organic carbon (TOC), ' respectively (see Table 1) The TOC concentration added to the TPH-G (6000 mg/kg at 20 ft in GP-2) increases the amount of total organic load that will be oxidized by these chemicals This will result in a slower decline in the groundwater contaminant concentrations since the ' TOC will run competition with TPH-G M7.0 CONCLUSIONS & RECOMMENDATIONS Based on our interpretation of the data collected over the course of this subsurface ' investigation, GTI have reached several conclusions These conclusions are based on the premise that the data we considered, although incomplete, are representative of actual site conditions We acknowledge that there may be undiscovered conditions, which would upon ' their consideration, change our interpretation and thus our conclusions Our recommendations are based on our knowledge of site conditions, and on the state and limitations of subsurface investigative technology The following conclusions are made ' 1 ISCO is a viable technology for reducing contaminant concentrations in groundwater at the site ' 2 The clayey nature of the site's soils inhibits oxidant transport and thereby reduces the efficiency of ISCO or for that matter, any in situ technology A permeability enhancing technology may need to be applied at this site to compensate for this site limiting ' condition 3 Oxidation-reduction potential (ORP) measurements confirm the chemical alteration of the aquifer and thus serve as an indicator for monitoring ISCO effectiveness 4 The five-foot sampling interval utilized in bore hole investigation at the site leaves data gaps for the possible existence of thin (<1 foot thick) sand/silt layers that could act asv�