The challenge before Antea Group was to install a remedial system at a client’s petroleum terminal facility. A subsurface investigation had previously defined the extent of petroleum hydrocarbons present. Investigative tasks included a drilling program consisting of soil boring and monitoring well installations, a soil and groundwater sampling program, and the evaluation of historical site data.
Antea Group assumed responsibility for the maintenance and monitoring of a monitoring well network. It also installed an interim remedial action system consisting of four recovery wells with pneumatic pumps, a free product or water separation system, and an air stripper. Free product was removed from off-site wells using passive skimmer units as an additional interim measure.
Antea Group decided that a bioremediation feasibility study was needed to evaluate the potential for biodegradation as a remediation alternative. Based on this study, a future course of action would be mapped out. The study served the following purposes:
- Examined various organic and inorganic parameters in groundwater and identified factors potentially limiting biodegradation activity for Antea Group’s client
- Evaluated options for remediating soil and groundwater
- Identified those portions of the site where biodegradation processes passively controlled the rate of contaminant migration
- Revealed an area requiring active remediation efforts to control the rate of free and dissolved phase product migration
Based on the bioremediation feasibility study results, Antea Group prepared a corrective action plan. Plan elements were as follows:
- Incorporation of a remediation design based on the extent of contamination, performance of the interim remedial action system, and results of an exposure to pathways analysis and biofeasibility study
- Installation of a groundwater interceptor trench at the downgradient property boundary. The trench was designed to prevent additional off-site migration of dissolved and free phase petroleum hydrocarbons
- Extraction and transfer of water to a separator tank designed to retain free phase petroleum hydrocarbons. Water then passed through a diffused aeration tank prior to discharging to the local sanitary sewer
Future project activities will include evaluating existing treatment system performance with respect to off-site petroleum hydrocarbons, along with developing a plan for addressing vadose zone hydrocarbons on-site.