Risk Screening, Evaluation And Assessment
CATEGORY OF SERVICE, LOCATION:
Risk Assessment for Site Closure, Hanford, California
TYPE OF CLIENT:
Major Oil Company
- Client had previously disposed refinery liquid wastes and sludge in a surface impoundment at a municipal landfill. The impoundment was subsequently covered with soil, and the landfill was closed. The impoundment area was sold to a private landowner. Trinity completed site characterization following Regional Water Quality Control Board (RWQCB) direction.
- Risk assessment was utilized in view of the limited extent of impacts and lack of environmental or human receptors in vicinity of site.
CLIENT GOALS FOR PROJECT:
Client goal was to determine cost-effective path to closure for this site.
- Trinity developed a site conceptual model based on previously-performed site characterization. The site conceptual model included developing a list of chemicals of concern using RBCA Tier 1 and California Environmental Screening Levels.
- Based on the site conceptual model, Trinity used RISC4 model to evaluate vadose-zone and saturated-zone fate and transport of chemicals of concern. Site data and conservative assumptions were input to the fate and transport model.
- The fate and transport model indicated no chemicals of concern would reach the theoretical receptor within 100 years. Therefore, no additional risk assessment was conducted
RESULTS, RESOLUTION, NEXT STEPS:
- Trinity’s report included an evaluation of costs of remediation by excavation, and the presentation of the site modeling approach, input parameters, and results.
- Client and property owner are negotiating a deed restriction to prevent future development or groundwater supply well installation within the former impoundment area.
- Submittal of the report to the RWQCB is pending.