Remediation includes source removal and ensuring that soil and groundwater meet regulatory cleanup standards. Remediation techniques vary according to site specific conditions including a risk evaluation based on, at a minimum, the proximity of residential areas, public and private water supplies, distance to surface water features and land use. As with the site investigation, the operator should submit the remediation plan that includes a summary of the site investigation data, the results of the risk evaluation, and identifies the remedial processes to be implemented, for review and approval prior to starting work.
For groundwater remediation there are many processes or methods that can be employed, however, a few of the more common techniques are briefly discussed below.
- Air sparging is used for the treatment of groundwater saturated by volatile organic compounds (VOCs).
- Monitored Natural Attenuation(MNA) is a groundwater and soil remediation technique that relies on natural processes to decrease concentrations of contaminants in soil and groundwater. Regular monitoring must be conducted to ensure that natural attenuation is continuing.
- Pump and Treat is a process where groundwater isphysically removed the from the aquifer and treated at the surface. Treatment includes carbon absorption, air stripping or disposal.
- In-situ chemical oxidation.
During closure of an oil and gas facility it is likely that impacts to soil from hydrocarbons, brine and potentially other materials will require remediation to mitigate and manage risks that could be harmful to human health and the environment. Soil remediation techniques are broken down into physical and chemical processes. The selected technique will vary according to the type of impact and overall risk. Common soil remediation practices include:
- Excavation and offsite disposal at a commercial landfill or exploration and production waste management or centralized waste management facility.
- Landfarming where contaminated soil, drill cuttings, pit solids, or sludge is treated in the upper soil zone or in biotreatment cells.
- Solidification and stabilization which refers to a group of cleanup methods that use reagents to prevent or slow the release of harmful chemicals from wastes, such as contaminated soil, sediment, and sludge The most common reagents used in solidification and stabilization include quicklime, lime kiln dust (LKD), fly ash, and cement.
- In-situ chemical oxidation uses reagents (liquid and dry) to create chemical reactions that convert contaminates to more stable or less toxic compounds.
- Soil vapor extraction (SVE) which is the in situ remediation of volatile contaminants. SVE removes contaminant vapors from below ground for treatment above ground. SVE is a well-demonstrated, mature remediation technology and has been identified by the Environmental Protection Agency as presumptive remedy.