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?9 December 2000 AGF-NC E'rujcct No. 95-01 14 Paque ? of s t he ti6llowins.; is a summary of milestone events at the site. • Threc Ground water monitoring wells MW-1, MW-? and MW-3 were installed at the site in October 1993. • During the development a surge block was lodged �Nithin well MW had consistently failed to produce sufficient ground v-atcr to melt the pre-san�p[in�� pttr�Lr reCluirements. theret«re, Tv,M,'-; ,vas over drilled on 07 December 1995 and "RILIted to surf lu trade with portland cement. Three additional ground water monitoring �Nclls v ere installed in December 1995: MW-')R, MX -4 and MW-�. • Petroleum hydrocarbons ,vcre not detected in soil samples collected durinO the installation of wells MW-4 or MW-5, however, hydrocarbon-impacted ground water vas detected in samples collected Crom MW-3R. Results of installatloll proctdut'es were included in the U!lcuverlr, Rcport - December 1995, prepared by AGE. • ]n .lanuary ?000. bio soil horin-� were advanced at the site and t%V0 "t'ound eater wells (MW-6 and MW-7) were installed. The most intense -[']'11-ss impacted oround water was detected within the former t'ST area. • Soil and around water on the site have been impacted with petroleum llVdrocarbons as Stoddard solvents and BITA, Additionally. tetrachloroetllCne ( P('E), cis 1,?-dichloroethene ( 1? DC.r�) and vinyl chloride were detected in the water samples collected from wells NPA'- 4, MW-5_ MW6 and MW7. • "l'he horizontal extent and stabilitN ofthe petroleum Stoddard hydrocarbon-impacted soil and Uround water has been documented north and east of'file I,61,111cr t1STS- • AGF bclievcS that the srkstainccl rise of the ground waterelevation has signi I icantly decreased the potential Iot' eftective]y miti afro() impacted soil below the. ground Nvater tahlc. The reduction ofthc impacted vadose zone and an increased thickness (approximately 75 Deet) of the impacted saturated zone.which is primarily fine graincd. makes the upward and lateral path ofspar-cd air' (via in-situ air-spar(11ng) tllr01,1011 the saturated zone unpredictable and stripped hydrocarbons potentially unrecoverable. • AGF recommi✓rtds evaluation of IIrotrnd water extraction as an alternative �U'round Water remediation technique at the site. Ground water extraction should be evaluated for site- specitic hydropeologic conditions. Factors controlling effectiveness of �oround vyater extraction are soil hydrogeologic properties, dissolved hydrocarbon mass dish'ihution_ and adsorption aflinit. of the hydrocarbons to the soil matrix. The sial] at the site is a fine-grained matrix and the soil at the site is homo-enous. fostering a high adsorption capacity lur the soil and lo%N permeability limiting mi,-,ration of dissolved hydrocarbons. • Also the limited areal distribution ol1hi1-2h c0nccntrations ofdissolved hvdrocurbons near the soUI-CC ofthe release(UST exCayation) favors a hioh potential liar capturing the major portion of the dissolved hydrocarbons on the site. -0drurrrrr!(�eul:n�rronmentak.1uc.