ARCHIVED REPORTS_XR0007889 - Laserfiche WebLink

Home Browse Search

Ms Mary Meays Page 6 March 2, 1994 feet in width (inclusive of side slope dimensions) In the proximity of the building wall, the excavation was sloped at a minimum 1 1 slope to avoid undermining the building structure For excavation below a depth of seven feet, a substantial seepage of ground water was encountered Further soil excavation and confirmation sarn lin below thi5 depth required dewatering of the excavation tots o approximately 4,500 gallons of ground water was umped from the excavation at Site 2 usin a vacuum-truck oil excavation activities procee a urn eit er the cleanup goals were attained at the excavation sidewalls and bottom or until prevailing site conditions_prevented further excavation The limiting conditions on the excavation were either t e grown wa er seepage creating a spongy, unstable bottom or the proximity of the building wall preventing additional excavation Eighteen soil samples to confirm the cleanup goals were collected from the excavation bottom as well as the sidewalls Prior to backfilling Site 2 with clean dirt, the saturated bottom of the excavation was stabilized by laying out a geotextile fabric (Amoco 4545) covered with a four-foot-thick rock base consisting of one- to two-inch- diameter size rock The remainder of the excavation was backfilled using clean dirt compacted in 6- to 8-inch lifts using conventional construction equipment The soil was compacted to 90 percent to prevent excessive settling The compaction was verified with a nuclear density gauge The backfill operations were completed on 8 October 1993, and the site was subsequently paved with a 4-inch asphalt cover to match the existing grade EXCAVATION CONFIRMATION SAMPLING Confirmation soil sampling was conducted between 7 October 1993 and 19 October 1993 at Site 1 and between 6 October 1993 and 14 October 1993 at Sito amp es were ana yze so ine range H by EPA Method 8015- Modified and BTEX by EPA Method 8020 The confirmation sample locations at Sites 1 and 2 are illustrated in Figures 3 and 4, respectively Samples were collected from the sidewalls as well as the bottom of the excavations The majority of the soil samples were collected with a pre-cleaned brass tube placed directly into the soil in the backhoe bucket However, some sidewall samples were collected by driving a pre- cleaned brass tube approximately six inches into the soil The samples were sealed, labeled, and transported to the TEG mobile laboratory under chain-of- custody procedures The results of the confirmation sample analyses are shown in Tables 1 and 2 The laboratory data sheets are provided in Appendix A All soils containing concentrations in excess of cleanup goals (100 ppm TPHg and 1 ppm BTEX total) were excavated from both sites except for the soils directly adjacent to the building foundation or underneath the building