Contaminant concentrations groundwater

Surface water information, including drainage patterns (overland flow, topography, channel flow pattern, tributary relationships, soil erosion, and sediment transport and deposition), surface water bodies (flow, stream widths and depths, channel elevations, flooding tendencies, and physical dimensions of surface water impoundments structures surface water/ groundwater relationships), and surface water quality (pH, temperature, total suspended solid, salinity, and specific contaminant concentrations)... 

In some cases, such as areas of lower contaminant concentrations or in remote locations, contaminants stripped from the groundwater may be allowed to attenuate naturally in the vadose zone. 

A full-scale cleanup was performed using in situ bioremediation to treat MTBE and BTEX at a service station in Massachusetts. Soil at the site consists of a layer of sand and gravel underlain by peat, silt, and clay. The in situ bioremediation system consisted of 12 injection wells and two butane injection panels used to stimulate cometabolic aerobic biodegradation of the contaminants in groundwater. The system was operated between October 2000 and January 2001. MTBE concentrations were reduced from 370 to 12 pg/L and BTEX contamination in groundwater was reduced by approximately two orders of magnitude during the 4-month period.74... 

Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 625. Average acenaphthene concentrations reported in water-soluble fractions of unleaded... 

Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from Gainesville, FL with individual fractions of three individual petroleum products at 24-25 °C for 24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method 602. Average benzene concentrations reported in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were 8.652, 0.349, and 0.200 mg/L, respectively. When the authors analyzed the aqueous-phase via U.S. EPA approved test method 610, average benzene concentrations in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were lower, i.e., 1.107, 0.073, and 0.066 mg/L, respectively. 

If required, pump-and-treat groundwater remediation and/ or in situ bioremediation are options, but unlike with soil excavation, it may take years for contaminant concentrations to reach the agreed end point. The postclosure part of the closeout activities plan should contain a well-defined exit strategy for any necessary postclosure remediation, based on a sampling methodology that defines progress and determines when the end point is reached. 

According to the vendor, the following factors can have a significant impact on the cost of remediation. The most important factors are the depth of the groundwater and the contaminant concentration. In addition, soil characteristics, site preparation, and labor rates are important (D10033K, p. 36). 

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