ARCHIVED REPORTS XR0004320 - Laserfiche WebLink

Home Browse Search

Additional Site Assessment and Second Quarter 1999 Monitoong and Sampling Report 5 7-Eleven Inc,Store#19976,1399 N Main St,Manteca,California July 15, 1999 Fourteen sod samples were selected for analysis of BTEX, MTBE, and TPH-G by EPA methods ' 8020/8015 modified, and for the oxygenates MTBE,TBA, DIPS, ETRE, and TAME using EPA method 8260 ' 34 Groundwater Monitonng Well Installation/Surveying Between May 11 and May 17, 1999,four groundwater monitoring wells were Installed in four of the five sod borings (MW-4,MW-4A,MW-5,and MW-5A) at the locations shown on Figure 2 The groundwater monitoring wells were constructed of 2-inch-diameter, Schedule 40 polyvinyl chlonde casing with flush ' threads, and 0 020-inch-slat well screen The well screen was installed in the two bonngs, MW-4 and MW-5, from 10 feet to 30 feet BGS The well screen was installed in the other two bonngs, MW-4A and ' MW-5A, from 45 feet to 50 feet BGS Sand was placed in each well annulus from the bottom to approximately two feet above the top of the well screen The well annulus was sealed with approximately 2 feet of bentonite pellets saturated in place on top of the sand pack, and neat-cement grout to approximately 10 inches BGS The wellheads are protected at the surface by locking, water-tight well caps and traffic-rated street boxes (with watertight bolted lids)set in concrete Well Nconstruction details are shown on the dnll logs in Appendix A The top of casing and nm of each well box was surveyed in June 1998 by Morrow Surveying for ' horizontal position and elevation relative to mean sea level datum using the City of Manteca benchmark #16 (Elevation 33 00) located at the northwest corner of Northgate Drive and North Main Street as a ' reference The resultant map is included in Appendix B Field notes from the well installation are included in Appendix C 3.5 Groundwater Monitoring and Sampling On June 6, 1999,depth to water in each well was measured to the nearest 0 01 foot from the top of the well casing using an interface probe Field data sheets are provided in Appendix C S, A potentiometnc surface map was prepared using the groundwater elevation data collected on ' June 6, 1999 (Figure 3) No separate-phase hydrocarbons (SP)were observed in the eight groundwater monitoring wells during this monitoring event The groundwater monitonng results from the June 6, 1999 monitoring and sampling event are presented in Table 2 ' 19976g2sar