Alco Pacific Site Removal Action Workplan (RAW)

Alco Pacific Site Removal Action Workplan (RAW)

The soil remedial activities (RA) include excavation, removal, and off-site disposal of approximately 3,600 cubic yards of lead contaminated soils from an industrial site in an industrial area. On-going groundwater monitoring will be conducted following the completion of the soil removal action. The primary chemical contaminate of concern is lead with levels ranging between 2.7 parts per million (ppm) to 3,000 ppm with a small area up to 85,700 ppm. Petroleum aromatic hydrocarbons, polychlorinated byphenyls and volatile organic compounds (VOCs) are found at 4.8, 9.5 and 0.3 ppm, respectively. These secondary Chemicals are collocated with the lead and will be removed with the lead soil removal. The proposed remediation goal for lead is 257 ppm, based on a baseline human health risk assessment for unrestricted/residential use exposure for soil. This cleanup goal for the Site is consistent with that applied previously to other residential and schools sites. Based on the prior site characterization the depth of the excavation will extend two feet below ground surface (bgs) and in three defined areas to seven feet bgs. Also, one isolated area will be drilled out to surgically remove contaminated soil at 41 feet bgs. A backhoe will be used for the shallow soil removal and field activities are expected to last two weeks. A bucket auger drill rig will be used to remove deeper soils and this field activity is expected to last one week. The deeper drill out will be immediately backfilled with bentonite to prevent problems associated with deeper soil removals. The drill rig will stop just above groundwater thereby avoiding water table release of the soil at the bottom of the boring hole. Post-excavation confirmation samples will be collected at the bottom and sidewalls of the excavation and step out locations from the drilled areas. These samples will verify all soil contamination equal or exceeding the targeted clean up goals will have been removed. The site characterization detected VOCs and heavy metals in groundwater under the site. DTSC has determined that a regional VOC plume exists. Onsite groundwater wells will be maintained and three down-gradient groundwater wells will be installed. On-going groundwater monitoring will be conducted as part of additional remedial activities following the completion of the soil removal action. The need for future groundwater remediation has not yet been determined. DTSC plans to begin the RA within four weeks after formal approval of the RAW and associated Health and Safety Plan. Excavation and backfilling activities are expected to last two weeks, drill rig activities are expected to last one week. As soils are excavated, they will be segregated into stockpiles and covered with heavy plastic sheeting until transported offsite for appropriate treatment/disposal in a box type truck trailer. Unauthorized access to the excavation area will be prevented. If the excavated soils contain greater than 350 ppm lead they will be disposed of at a Class 1 landfill, 150 miles away. The disposal trucks will travel approximately one half mile and then enter the 105 Freeway to travel to the designated treatment/disposal area. The excavation will be backfilled with clean imported soils, compacted and topped with chip seal. During the RA, and approved Health and Safety Plan will be enforced. The Site will be marked and access to the excavation area will be limited to prevent unauthorized access. Site access will be monitored during working hours and open excavation areas will be fenced at the end of each day. A Fact Sheet will also be distributed notifying nearby businesses not to enter the excavation areas due to the possible exposure to lead contaminated soils.

Carson

Los Angeles