Laserfiche WebLink
eieo41CAt recicnl"Me Page 2 <br /> 1"Quarter 2005 Groundwater Monitoring Report <br /> Project No 507 2 <br /> April 18, 2005 <br /> commented on the field work and requested that a site conceptual model (SCM) be submitted <br /> ' prior to proposing further corrective action <br /> Since there is uncertainty regarding the soil profile at the site due to the 5-foot sampling <br /> ' interval GTI proposes performing several continuous core borings GTI developed our <br /> March 7, 2005 "Site Characterization Work Plan" that includes three continuous core borings <br /> to determine the presence of sand/silt Iayers in the core contaminant area The data generated <br /> ' by this effort will then be used to formulate a site conceptual model desired by SFC EHD <br /> After the site conceptual model issue is resolved GTI will propose further corrective action <br /> work <br /> 1.4 GROUNDWATER MONITORING <br /> 1.1 Hydrogeology of Site <br /> ' The geology of the site is predominately clays and sandy clays with lesser amounts of inter <br /> bedded silts and sands The average groundwater elevation was —10 14 feet below msl on <br /> February 17, 2005, which corresponds to approximately 15 14 feet below grade surface (bgs) <br /> This average elevation represents an increase of 1 59 feet since the December 29, 2004 <br /> monitoring event Groundwater gradient for this monitoring event was 0 0033 ft/ft flowing <br /> ' to the N46°E direction This site consistently exhibits a flat groundwater gradient <br /> The gradient direction for the February 2005 monitoring event is shown in Figure 2, and the <br /> ' historical groundwater directions and gradients are shown in Figure 3, Groundwater Gradient <br /> Rose Diagram The groundwater elevation data are summarized in Table 1, Appendix A <br /> Table 5 provides a summary of monitoring well construction <br /> ' The groundwater gradient is relatively flat and the direction of groundwater flow has varied <br /> during the course of the investigation As evident in Figure 3, groundwater exhibited a strong <br /> ' bifurcated flow regime in 2000, trending predominantly to the southwest or north-northeast at <br /> approximately 180-degree direction reversal Since the installation of wells MW-7 and MW- <br /> 10 in May 2001, the direction has been predominantly to the northeast The site is quite close <br />' to the San Joaquin River and tidal fluctuations may contribute to some of the observed <br /> changes in groundwater direction <br />' Vertical Groundwater Gradients <br /> Under vertical groundwater flow conditions, the water level in a monitoring well is a function <br /> of the length of the well screen and its depth or vertical position in the aquifer As with <br />' horizontal flow conditions, the diameter of the well or piezometer is immaterial <br />