10-03-1988 Planning Packet - Laserfiche WebLink

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Headspace 1.0 2.0 2.0 0 .•»‘Av '/<:■ smi ■:4 mm►- -- ■! mm Hi mm w. -4i-. •4.■jii MooitoriB»weUiMW-IO»ndMW-llarefreeofEPA«01/602p»niBetera. MoBiu>ri»*w*HMW-10hada coBceBtniiOB of U Biicro»«Bi per liter (u*/l) of beazeoe. This low cooeoBtratioo ij jiapect due to the ubiquitous nature of this compound in our environment. Monitonni well MW-12 contained very low cOBceniratiOBS of xylenes, l.l-dichtofoethylene, 1,1-diehloroethane. and toluene. The __of these parameters are aU below recommended allowable limio for drinkin* water. .aalytical results from MW-10. MW-II. and MW-12 an provided in Appendix C. a n mscUSSlQW t ■>■1 Hy<r«wl»g , . The water table of the unconfined aquifer at the site generelly occurs eight to ten feet below the ground surface. Flow in this surficial aquifer U toward the south-southeast as discussed in our December 23, 19S7 report. Monitoring welU MW -4D, MW-10, and MW-11 are all screened at the same approximate elevation and are 25 feet below the ground surface. Together, these wells show that flow in the 20 to 25 foot interval is toward the north-northwest. This apparent reversal in flow direction is suspected to be due to the influence of the drainage trench and buried sewer Une along the eastern edge of the WSI property line, between monitoring wells MW-10, MW-11, and monitoring well MW-4D and therefore is thought to be very localized (Figure 2). We believe that shallower wells would reflect this same pattern and that ground water flow in the 20-25 foot interval is similar to shallow ground water flow observed across the site. 4.2 Fxfgwt of Soil end Ground Water ContlBliwitiftll Soil and ground water contamination are primarily restricted to the area between monitoring weUs MW- 2 and MW-4. ConU Tunant conditions identified in this area are discussed in our December 23. 19d7 report. The aerial extent of soil and ground water contamination is outlined in Figure 3. The vertical extent of VOC contamination is restricted to the upper 25 feet of the site. Boring logs of monitoring well MW-4D (Delta ’s May 24. 1987 report) show the presence of a sand unit between 21 and 24 feet. It is likely that the contaminants are moving through sand lenses such as this one. Our objective for remediation will be to intersect as many of these sand lenses as possible with the recovery trench. mm-- mi- m-'-'A- mm |L • v4 \l Mm ,.Vr kjl i.l Ceneral Delta recommends concentrations iden trench system wouh out system at the evaluated. Modifi assessed. ^.2 Conceptual Pea The east end of the single total fluids S’ aeration system for into the sanitary se< mass balance of th< 1.3 Wacovgrv Trcnc The recovery trend The total lengt'i of 18 feet. A crcss-s« be dependent on th the bottom of the i coarse washed gravi A plastic liner wil prevent fine grainet clean soil removed < contaminant concer hNu photoionizatio The recovery sump of approximately 11 well cover. The su long slots cut at 45