ARCHIVED REPORTS XR0008208 - Laserfiche WebLink

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PRELIMINARY ASSESSMENT INTRODUCTION Sample results obtained from the tank excavation revealed high levels of benzene and gasoline range hydrocarbons at the 15 foot depth. These levels prompted the Health Department for the County of San Joaquin to request the excavated soil to be classified to whether or not it is non-hazardous or hazardous waste. A self certification as a non-hazardous waste was accomplished by Western Ciao-Wigineers, see report dated December 8, 1989. Two soil boxings and four monitor wells were used to investigate the site to the 60 foot depth. The borings and monitor wells were r drilled under W8GE#s C-57 license and the supervision of western Seo-Engineers using Rogate Drillingfe Mobile Dri11 H-40 with 8" and 10" hollow stem augers, see Boring and Construction Logs- Appendix A and Peraaits-Appendix D. During excavation of the tank area, the excavated soil was field screened -using a MW Model PI 101 Photo ionising detector. The excavated soil was segmented into four separate piles based upon the degree of positive response during the testing of the excavated soil.. These segments were noted as SP1, SPI, SP3, and SP4. Chemical results of the soil piles indicated that SP2, SP3, and SP4 could be aerated an site, see Table 2. Permits to aerate were obtained from the San Joaquin County Air Quality and aeration proceeded in accordance to the specifications outlined in the permits, see Appendix D. As stated earlier, excavated soil BPI was used to classify the soil as non--hazadorus waste and has been covered with polyethylene liner, see Table 3 ar_d Appendix E. This soil will be treated on site with a controlled aeration system that is in the process of being submitted to the appropriate regulatory agencies, see Figures 3A, , 7A, 7$, and 7C. GEOLOGY AND GROUND HATER OCCURRANCE Regional Geomorphology And Hydrogeology The site lies within the northestern edge of the San Joaquin Valley, which 2.s the southern half of the Great Central Malley geomorphic province of California. The Coastal Range province is the western boundary and the Sierra Nevada province is the eastern boundary of the Great Central Valley. All three of the above mentioned provinces trend in a northwesterly direction along with the major faults which are associated with the province boundaries. The Central Valley provsnce represents the low position basin separating the Sierra Nevada and Coastal Range mountain masses. Erosion of the mountain masses produce sediments 9