Episodic remediation is a cost-effective approach to remediating petroleum contamination at sandy sites. This remedial approach combines the use of proven remedial technologies including air sparging, soil vapor extraction, and dual phase extraction applied in short-term episodic treatments. Mobile episodic remediation is the use of short term remedial events, usually less than 44 hours per event, to physically remove petroleum contamination from the soil and groundwater and stair step petroleum contamination to the remedial objective. EWE has successfully remediated 32 of 39 sites to site closure levels over the past three years using this method of remediation.

During one project, EWE treated 20 sites for an energy company over a period of eight months. The episodic treatments averaged from 8 hours to 24 hours in duration completed every two to three weeks. All treatments were completed by a single mobile treatment unit equipped with an air sparge/soil vapor extraction system. Air sparge and soil vapor extraction was concentrated at the identified source area of contamination at each site. Groundwater samples were obtained prior to and after each of the treatments to determine the effect of each treatment episode on the removal of hydrocarbon concentrations in the groundwater. Work was continued at each site until closure or progress had stopped. Regulatory approval for final site closure was achieved at 15 of the 20 sites treated.

The results of this episodic remedial program demonstrated that at sites with moderate to high permeable soils, contaminated with petroleum hydrocarbons, episodic remediation can effectively clean soil and groundwater at sites to closure levels. These site closures were obtained quickly and cost-effectively because construction and permitting costs were minimal compared to permanent installation or soil excavation. The overall estimated cost savings to the energy client during this project was approximately $1,000,000. The Florida Department of Environmental Protection is now recommending use of this technology at selected sites throughout the State of Florida.

The following case studies demonstrate the effectiveness of episodic remediation.

Case Study 1
Summary - Case Study 1
  • Treated on ten separate occasions over a six month time period totaling 209 hours of treatment.
  • BTEX plume was reduced from 16,000 µg/L to below site rehabilitation limits (<1 µg/L benzene, <50 µg/L BTEX, <50 µg/L MTBE).

Case Study 2
Summary - Case Study 2
  • Treated three times over two months, totaling 36 hours of treatment.
  • Dissolved BTEX plume reduced from 1,000 µg/L to below detectable limits (<1 µg/L Benzene, <6 µg/L BTEX, <3 µg/L MTBE).

Case Study 3
Summary - Case Study 3
  • Treated eight times over five months totaling 271 hours of treatment.
  • Dissolved benzene plume was reduced from 72 µg/L to below No Further Action levels.

Case Study 4
Summary - Case Study 4
  • Treated five times over a period of four months totaling 175 hours of treatment.
  • The dissolved BTEX plume was reduced from 842 µg/L to below detectable limits (BDL).