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06 February 2004 AGE-NC Proicct No 01-0865 Page 6 of 9 screened monutoring wells MW-1 through MW-5, MW-9 and MW-10, and from a deeper, sand interval at approximately 50 to 60 feet bsg (MW-6, MW-7 and MW-8) l The laboratory analysis indicated that ground water at the site has been impacted dominantly by TPH-g and the fuel additive MTBE, lower concentrations of BTEX compounds and the fuel additives TAME and TBA also have been detected The highest concentrations of TPH-g and MTBE are concentrated in the area of wells MW-2,MW-3 and EW-1,immediately east of the present above ground fuel storage tanks (Figure 2),the highest concentrations recorded were 110,000 µg/1 TPH-g in September 2002 and 190,000 µg/1 MTBE in June 1999, from well MW-2 The highest concentrations of BTEX compounds and the fuel additives TAME and TBA were also detected from well MW-2, at 540 µg/1 benzene, 930 µg/1 toluene, 40 µg/l ethylbenzene and 750 gg/l xylenes, (March 2001),and 1370µg11 TAME(March 1999)and 2,700µg/1 TBA(September 2002) Laterally, petroleum hydrocarbon-impacted ground water extends from the levee area of the former USTs east to approximately the location of well MW-10, and extends northward to the approximate location of well MW-14,the lateral extent is not defined towards the south,in the area between the HHM site and the island drainage canal (Figure 2) The vertical extent of petroleum hydrocarbon-impacted ground water is not defined, discrete grab ground water samples collected at total depth(between 90 and 105 feet bsg) from three soil borings advanced on 16 December 2003 detected TPH-g, BTEX compounds and MTBE at maximum concentrations of 1,500 µg/1 TPH-g, 320 gg/l benzene, 700 µg/1 toluene, 140 µg/1 ethylbenzene, 560 µg/1 xylenes and 120 µg/l MTBE 24 Potential Impact Of The Wastewater Discharge On The Containment And Rate Of Movement Of The Ground Water Plume Contaminants will be removed from the water to be discharged, discharge into the agricultural drainage ditch is anticipated to have mammal infiltration Furthermore, it is anticipated that the amount of contaminants in ground water migrating down-gradient towards and into the drainage ditch as well as the island drainage canal should decrease as a consequence of the ground water pump and treat operation 25 Effects Of The Ground Water Extraction System On The Gradient And Plume Generally, ground water gradient at the site vanes from a steep 0 25 ft/ft at the levee to 0 02 ft/ft on the plain(flat land) Once the groundwater pump and treat system is initiated,AGE anticipates local groundwater flow direction to be directed towards the area of groundwater extraction The proposed interim ground water extraction and treatment system is designed to implement hydraulic control, limit the off-site migration of hydrocarbons, especially MTBE, and remediate petroleum Advanced GeaEnv►ronmental,Inc