ARCHIVED REPORTS_XR0012112 - Laserfiche WebLink

Home Browse Search

E11��t® 1 ' Ms. Margaret Lagorio February 11, 2005 Page 3 ' • Benzene concentrations in zone A well (U-11), zone B wells (U-16, U-18, and U-24) and zone C wells (U-15 and U-25) increased since the last sampling event. 0 Except for well U-19, benzene concentrations remained below laboratory reporting limits in the remaining wells and zone A piezometers (NP-1-22 and NP-2-22) and piezometer (NP-1-111). ' MTBE Concentration • MTBE was not detected above laboratory reporting limits in any of the samples. Ozone Microsparge System Description The Ozone Microsparge system consists of groundwater treatment via two C-SpargeTM systems installed at the site. Each C-SpargeTM system includes an ozone generator, air compressor, and a programmable timer/controller. The C-SpargeTM systems utilizes ozone microsparging: a ' process where ozone is entrained in air and introduced into groundwater. The ozone/air mixture is sparged at rates of 2-6 cubic feet per minute (cfm) through specially designed sparge points to create "microbubbles." As these microbubbles rise within the column of water, dissolved N volatile organic compounds (VOCs) including petroleum hydrocarbons are oxidized. The system cycles between 16 micro-sparge points and sparges an ozonelair mixture into wells SP- 1A&B, SP-1C, SP-2A, SP-2B, SP-3A, SP-3B, SP-3C, SP-4A, SP-413, SP-5A, SP-5B, SP-5C, 1 SP-6A, SP-6B and SP-6C. Ozone sparge wells are located in the areas of highest dissolved VOC concentrations near the eastern property of the Unocal Site. Each sparge point has a dedicated line and is connected to the system by low density polyethylene (LDPE) tubing. The tubing runs through Schedule 40 polyvinyl chloride (PVC) pipe. The system layout is shown in Figure 9. Ozone Microsparge System Operation ' With the exception of scheduled downtime for operation maintenance, the micros ares stem P 9 Y operated continuously during the fourth quarter 2004. ' Effectiveness of Ozone Microsparge System System effectiveness is monitored by assessing groundwater analytical data and concentrations of dissolved oxygen (D.O.) from single-completion zone A well (U-3), zone C well (U-10) and nested piezometers NP-1 and NP-2 screened in zones A, B, and C. (Figure 2). Zone A well (U- 3), zone C well (U-10) and piezometers NP-1 and NP-2 screened in zones A, B, and C are within the raduis of influence of one or more sparge points. D.O. readings are collected periodically, with groundwater samples, from wells U-3, U-10, and piezometers NP-1 and NP-2. Well construction details and D.O. readings are summarized in Table 7 and Table 8, respectively. The microsparge system was operated continuously during the fourth quarter 2004. • ' JAProjectA694010187-3251WorkinglReports10187 4th Qtr 04-QMR RSR.doc ' Celebrating 35 Years of Excellence in Environmental Services