Laserfiche WebLink
' Former Manna Pro Site Page 4 <br /> Project No 207 3 <br />' Remedial Feasibility Study <br /> • <br />' 2.0 SITE CONDITIONS <br /> 2.1 Contaminant Distribution <br />' In general, the geologic character of the soil observed during drilling may be summarized as <br /> follows <br />' 0 to 15+ feet <br /> Clay and Silt, reddish brown, semi-plastic to friable <br />' 1 S+f eet to 30+ feet <br />' Sand, fine to very course grained Generally fair sorting Greenish gray to greenish brown <br /> Porous and permeable Generally contains few fines, but silty in some intervals <br />' 30+ feet to 40+ feet <br /> Silty clay, greenish gray to dark gray, plastic to semi-plastic deformation <br /> 1 <br /> 40+ Leet to 50+ feet <br /> Silty sand and sandy silt, dark greenish gray to dark gray Poor to fair sorting <br />' This characterization of the stratigraphy at the site is a generalized composite from all of the <br /> boring logs The most important units as relate to the installation of air sparge and vapor <br /> extraction wells are the lower and upper sand units The lower clay unit appears to be the <br />' boundary of most of the contamination Over the life of the project to date, the groundwater <br /> surface has risen from a depth of over 40 feet bgs, to a recent high of about 25 bgs At the <br /> time of the most recent groundwater monitoring event, the level was about 27 feet bgs The <br /> most intensely contaminated soil lies from 35 to 45 feet bgs in a area near the original point <br /> of release A cross-section depicting the mayor soil lithologic units is attached as Figure 4 <br /> 2.2 Contaminant Mass—Mass Balance <br /> Previous mass balance calculations by GTI estimated that about 31,000 pounds of gasoline <br /> hydrocarbons are present in the subsurface in the sorbed phase and that about 330 pounds are <br /> dissolved in the groundwater Geo-Phase Environmental has revisited this issue and <br /> generated a new estimate (see Appendix A for details) Based on this new estimate, there are <br /> about 22,000 pounds in the adsorbed phase and about 460 pounds in the dissolved phase <br /> Given the uncertainties involved in this type of calculation, we feel the two estimates are in <br /> reasonable agreement Part of the reason that the dissolved phase hydrocarbons are higher in <br /> this recent estimate is probably due to the much higher stand of groundwater available to <br /> contain dissolved gasoline Generally, the vadose zone contains little gasoline-impacted soil <br /> i <br /> 2937 Veneman Ave , #13240 Geo-Phase Environmental Inc Phone(209)569-0293 <br /> Modesto,CA 95356 Fax (209) 569-0295 <br />