ARCHIVED REPORTS_WORK PLAN TO ESTABLISH BACKGROUND SOIL CONCENTRATIONS

Home Browse Search

GER • GENESIS ENGINEERING&REDEVELOPMENT The groundwater table is shallowest adjacent to the slough on the west side of the Site, and slopes to the east. Groundwater flow beneath the Site is consistently to the east, away from Whiskey Slough, at a relatively steep gradient ranging from approximately 0.028 to 0.033 ft/ft. Groundwater flow direction does not change between high and low tide. A downward vertical gradient has consistently been observed between piezometers P-1 and P-2 and Monitoring Well MW-5. Water levels in the slough show a cyclic fluctuation that indicates that the slough is directly affected by tidal fluctuations. The water level pattern observed in the slough is semi-diurnal, with two high tides and two low tides each day. Well MW-2, located adjacent to the slough, shows diurnal tidal fluctuations. Downgradient wells MW-4, MW-5, MW-6, and the piezometers show no cyclic daily fluctuations, suggesting that tidal influence from the slough does not extend to the eastern side of the Site. 3.0 SCOPE OF WORK This Work Plan includes the following elements: 1. Collecting 13 shallow reconnaissance samples from native soil, and analyzing the • samples for the constituents identified in Section 3.2; 2. Disposal of Investigation Derived Waste; and 3. Preparing a report documenting the field investigation and proposing soil cleanup goals for Clean Closure of the Site. The proposed area for the reconnaissance borings is shown on Figure 3. In selecting this location, GE&R reviewed the topographic map for the Site vicinity(Figure 1), historic images of the area from Google Earth, and the U.S. Department of Agriculture Soil Conservation Service Holt Quadrangle Soil Map. The area surrounding the Site generally consists of farmland, land being used for housing or commercial use, or land that, like the Site, has been filled in, as well as the dikes holding back the surface water. Since construction of dikes in the San Joaquin Delta early in the 20th century, the land has been put into intensive use. As a result, all of the land immediately surrounding the Site has been put to some kind of use, and much has been filled. The lack of fallow land,parks, or otherwise undisturbed land in the surrounding area makes the selection of an area for background soil sampling difficult, as all the land has been modified in some way. There is no area that has not been used for some purpose. That makes proximity to the Site; lack of industrial use and/or imported fill; and similarity in water table elevation the most controllable variables in selection of the background sampling location. William DePaoli Property 2 of 5 Work Plan to Establish Background Soil Concentrations February 2012