ARCHIVED REPORTS_XR0012639 - Laserfiche WebLink

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M MJ 11 1 SY 4 and possible drainag4 routes to the excavation. Figure 4 Is a projection of the excavated area, the area of visible contamination found when excavating and locations of Soil Borings 3 and 4 and lonitoring Well 3. This figure is not a true three dimensional projection and was prepared at the request of the AHD to the best of the writers ability. Figure S is a copy of a figure from the Versar report which is appended to the original Hunter & Associates report. This figure is included as a result of di.scussiofso fdisearlieof pit seepage. Figure 6 is an altered fig ureGTI report (also attached to the original Hunter & Associates report) which shows the contamination measure- ments found outside the 4scavated area on a geologic cross section originally prepared by GTI . Figure 7 shows the ;^ , location of the cress section. . Dispcoal of pit Seepage As discussed in the original report of Hunter & Aosocdi tes, the excavation at ane time was "out 45' 5 belov gr At �- o ..k this time, groundwater seeped into the pit t0 a depth Of about 51 . This groundwater was pumped out and into the westerly pcnd shown on Figure 1, using transfer hoses from the pit to the pond. The approximate route of the hoses ns from the westerly edge of the pit, between mw-1 and Spoil File No. 1 to the southerly extension of the westerly pond. prier to filling completely, the groundwater seepage � 9 been tested for hy&rccarbcn contamination and none w�.s I�Ound (see original report and appendices) . Drainage To ??t When Open To -45' Figures i , 3 and c and 7 shoe; the _"el i- c::ship of Boil ri I,gS 3 aIi'd to the excavation. This reviewer has noted that the pit, when water from the water table 14x5 draining *" as an 80' wide observaticr. into it, could be thought o_ , well . This aspect is not good if contamination is found cause it will not delineate the direclion and location of the contamination plume, However, it is-an excellentient test for contamination in general because a large volume of water has moved from ;-he formations intr,-the well from all directions. The cress section Of '�he pit (Figure 3) 4 illustrates the relationship of the bore holes to the excavation. When water drained from the periphery around the excavation towards the pit, it should have moved any contamination into the pit. Tests made on samples of pit later seepage never showed any indication of contamination. - — ain water through the vadose zone, into :also, seepage e r --- ... .... _ the water tG'�le _and--then- ...... -intothe-pit.,shou..l.d.._have bradg L _._.._._. _....._._ _._.__..—.._-- he pit from the vicinity of holes SB-3 contaminates into t ._._. and S^-4 if they had existed in anything other than minor amounts. This lihely path is shown on Figure 3.