FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling April 30, 2012 I:\Tidewater\TW Stockton (P2A)\QMRs\2012\1Q12\1Q12 QSSR QRSR QMR Stockton_FINAL.doc 2.8 2.4 FIRST QUARTER 2012 B-ZONE GROUNDWATER RESULTS 2.4.1 B-Zone Groundwater Gradient B-Zone groundwater elevations at the Site ranged from 6.09 ft below MSL in well MW-47 to 1.13 ft above MSL in well MW-44 (Table 3 and Figure 10). Groundwater gradient during 1Q12 in the B-Zone was calculated to the northeast with an approximate hydraulic gradient of 0.006 ft/ft (Figure 10). The highest B-Zone groundwater elevation (1.13 ft above MSL) was reported in well MW-44, located in the southwest portion of the Site east of Mormon Slough. The overall historic trend of the B-Zone gradient is to the east-northeast. Historical groundwater flow direction and gradient data are summarized in Table 8, and vertical gradients summarized in Table 9. The B-Zone groundwater elevation contour map for the January 17, 2012 monitoring event is included as Figure 10. 2.4.2 B-Zone Groundwater Quality Data During 1Q12, groundwater samples were collected from 15 B-Zone wells between January 17 and 20, 2012 (Table 1). Groundwater analytical results are presented in Tables 4 through 7, and summarized below. TPHg, TPHd, TPHo, benzene, MtBE, and TBA isoconcentration contour maps are included as Figures 11 through 16, respectively. The certified laboratory analytical reports for the groundwater sampling event conducted for the L&M OU are included in Appendix D. 2.4.2.1 Separate Phase Hydrocarbons During 1Q12, measurable SPH or SPH-sheen was observed in eight wells. SPH thicknesses for B-Zone wells are summarized below. Well Identification SPH Thickness (feet) MW-17 Sheen MW-43 0.35 MW-46 Sheen MW-47 Sheen MW-48 0.01 MW-49 0.55 MW-50 7.50 MW-52 Sheen