ARCHIVED REPORTS_XR0012626 - Laserfiche WebLink

Home Browse Search

�.a I As was the case with the soil action levels the groundwater cleanup concentrations vary in a case by case scenario based on the site characteristics. 5.0 SITE CONDITIONS 5.1. Site Geology The subsurface geology at the site is characterized by unconsoli- dated sands, silts and clays exhibiting little lateral continui- ty. Although no continuous beds were discernible, a medium to coarse sand with variable silt content was observed at all well locations beginning approximately 20 feet below ground surface (BGS) . This coarser zone extended to at least 35 feet BGS at all well locations. At monitor wells location MW-1 and MW-S, the saturated formation was typified by coarse materials (medium to coarse sands and, at MW--1, fine to medium gravels) . The saturated zones for wells MW-1 and MW-3 were encountered at 28 feet BGS and 26 feet BGS respectively. At MW-2, however, the saturated material was a sandy clay encountered at a depth of approximately 36 feet BGS. in general, the soil observed at all depths at MW-2 was much finer than at the other well locations, with the dominate soil encountered being a silty clay. 5.2 Groundwater Gradient s. Upon completion of the well development the depth to water and top of casing measurements were obtained. This information was used to determine the site groundwater gradient. From this data, it was found that the site gradient (groundwater flow direction) p, is primarily northeast (Figure 4) . 6.0 CONCLUSIONS AND RECOMMENDATIONS Based on the analytical data, hydrocarbon compounds exist within the soils and shallow groundwater at the site in excess of typical cleanup levels. The chemical concentrations present within the soils and groundwater suggest that site cleanup can be accomplished via limited activities based on the following; o For conducting an evaluation of remedial actions at u:_a subject site, the L.U.F.T. field manual ri: .% assessment and [. decision tree flow chart methodologies can be utilized. Figure 5 presents the decision tree flow chart and graphi- cally presents the path followed for the evaluation of the Human Services building site. As can be seen by following the path; soil cleanup .is recommended. o The hydrocarbon presence within the soils appears to be limited to a relatively small area centered around borehole #3. - 10 -