Laserfiche WebLink
r <br /> 2.RESULTS FOR SECOND SEMIANNUAL PERIOD 2011 <br /> I <br /> Groundwater Flow J <br /> Groundwater flow depends on the physical characteristics of the subsurface materials and <br /> the groundwater gradients. A detailed analysis of groundwater flow for the fourth quarter J <br /> 2001 groundwater elevation data is presented in the Final Site Characterization Report <br /> (CH2M HILL,2002). In general, groundwater flow occurs in the direction of maximum <br /> potential hydraulic gradient,or perpendicular to the lines of equipotential head. J <br /> Groundwater elevation is highest in the clayey sediments northwest of Whiskey Slough <br /> Road (approximately 0 foot msl) and lowest in the sandy sediments southeast of Whiskey -- <br /> Slough Road (approximately-8 feet msl).The horizontal gradient at the site is characterized J <br /> by the individual gradients across the following three transects for the September 1,2011, <br /> groundwater elevations,all of which are in a west-to-east alignment: <br /> • 0.0033 foot per foot (ft/ft) through clayey sediments from well M-3 to the 0-foot-msl <br /> elevation contour <br /> • 0.16 ft/ft through clayey transition zone from the 0-foot to -8-foot-msl elevation contour <br /> �1 <br /> • 0.0012 ft/ft through sandy sediments from well M-8 to well N-19 <br /> Sitewide,horizontal groundwater flow occurs from the recharge areas of Trapper Slough <br /> and the area with standing water through the clayey sediments northwest of Whiskey <br /> Slough Road toward the sandy sediments southeast of Whiskey Slough Road.The water <br /> table drains from the clayey sediments laterally into the sandy sediments at the band shown <br /> by water table elevation contours 0 and-8 feet msl. This flow results in a focusing effect, _ <br /> where groundwater in the sandy sediments southeast of Whiskey Slough Road is naturally <br /> directed toward a common area in the vicinity of the two former extraction wells,RW-1 and <br /> dA <br /> RW-3. <br /> Locally,the former release area is bounded on three sides by a constant head—to the north <br /> and west by Trapper Slough and to the south by the area with standing water.These <br /> boundaries result in locally focused groundwater flow toward the area between the two f <br /> access roads (of the former pipeline and the bypass pipeline) that then drains to the J <br /> southeast. <br /> Groundwater Analytical Results <br /> Analytical results for groundwater samples collected on September 1,2011, are presented in <br /> Table 3. TPHg and benzene concentration contours for these data are shown in Figures 4 <br /> and 5,respectively.These data are further presented as follows: •� <br /> • Appendix C-Tabulated with most recent eight monitoring events <br /> • Appendix D-Time series concentrations charts for wells with consistently detectable <br /> constituents (wells M-10,N-7,N-8,0-1,N-15,N-61,N-17,and RW-1) <br /> • Appendix E-Long-term trend concentration charts,by expanding the future scale of the J <br /> charts in Appendix D to 2050 to better see the long-term concentration trends <br /> In addition,analytical results comparing the standard purge sample data to the <br /> HydraSleeve sample data from September 1,2011, are presented in Table 4. HydraSleeve <br /> sampling results are discussed in Section 3. <br /> 24 ES102411163308SCO/LW3521.DOCX/112970003 <br />