ARCHIVED REPORTS_XR0006202 - Laserfiche WebLink

Home Browse Search

1 4 RESULTS ' 4.1 SITE GEOLOGY AND HYDROGEOLOGY The soils encountered during drilling of UVB-MW1 consisted of interbedded layers of lean clay ' with sand, silt with sand, and sand with silt A detailed description of lithology is presented in the soil boring log in Appendix A Water was first encountered at approximately 20 feet bgs during drilling and stabilized at 18 62 feet, measured from the top of the well casing ' Based on gauging data from the first uarter of 1997 the groundwater flow direction at the site is ' to the northeast with a gradient of approximately 0 007 4.2 SYSTEM START-UP AND OPERATION ' Following verification of proper operation during start-up troubleshooting, the UVB system was started on 6 February 1997, and 736 hours of operation were accrued as of 14 March 1997 The ' UVB system was shut down briefly for the installation and development of the UVB monitoring wells from 11 to 14 February and from 25 to 27 February 1997, respectively ' A total of 167 53 pounds of petroleum hydrocarbons were stripped from groundwater during the period from 6 February to 14 March 1997, as shown in Table 3 The mass of stripped petroleum hydrocarbons was calculated from UVB off-gas stream flow rate measurements and laboratory analysis of air samples collected on 6, 17, and 20 February 1997, and 7 and 14 March 1997 i The groundwater sample collected from monitoring well UVB-MW 1 on 28 February 1997 had a ' concentration of TPH-g equal to 99,000 gg/L, benzene equal to 7,200,ug/L, toluene equal to 18,000 jtg/L, ethylbenzene equal to 2,000 ktg/L, and xylenes equal to 11,000 µg/L The groundwater sample collected from UVB-MW 1 represents the UVB groundwater influent ' The groundwater sample collected from monitoring well UVB-MW2 on 28 February 1997 had a concentration of TPH-g equal to 9,400 Azg/L, benzene equal to 200µg/L, toluene equal to ' 1,100,ug/L, ethylbenzene equal to 190,ug/L, and xylenes equal to 1,700 ,ug/L ' Laboratory analytical reports are provided in Appendix C Based on the laboratory analytical results for the groundwater samples collected on 28 February ' 1997 (Appendix C), the UVB system stripping efficiency for TPH-g is 90 5 percent, for benzene 97 2 percent, for toluene 93 8 percent, for ethylbenzene 90 5 percent, and for xylenes 84 5 percent The UVB percent stripping efficiency is defined as (1- Co,,, / C,n) x 100, where C.Ut ' is the concentration of volatile and semivolatile hydrocarbon constituents in grounawater leaving the upper screen of the UVB well, and C,,, is the concentration of volatile and semivolatile hydrocarbon constituents in groundwater entering the lower screen of the UVB well ' WP61 73942 801347 3 12