ABSTRACT
Liquid Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695 18.4.5 Adsorptive Force Affecting Underground Liquid Movement . . . . . . . . . . . . . . 697 18.4.6 Combination of Capillary and Adsorptive Forces Affecting
Underground Liquid Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 18.4.7 Energy Conservation Affecting Underground Liquid Movement . . . . . . . . . . . 700 18.4.8 Water Movement in Saturated Zone of Soil Formation . . . . . . . . . . . . . . . . . . . 701 18.4.9 Water Movement in Unsaturated Zone of Soil Formation . . . . . . . . . . . . . . . . . 701
18.5 Properties of Gasoline and its Movement in Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 18.5.1 Properties of Gasoline and the Forms of Release Underground . . . . . . . . . . . . 702 18.5.2 Fates of Gasoline Underground: Adsorption and Degradation
of Gasoline and the Effect on Gasoline Movement . . . . . . . . . . . . . . . . . . . . . . 703 18.5.3 Multiphase Movement of Gasoline Compounds . . . . . . . . . . . . . . . . . . . . . . . . 705
18.6 Management of Tanks and the Environment as Remedial Actions . . . . . . . . . . . . . . . . 706 18.6.1 Tank Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707 18.6.2 Tank Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707
707 18.6.4 Alternatives for Tank Abandonment and Replacement . . . . . . . . . . . . . . . . . . . 708
18.7 Control of Contaminants Migration as Remedial Actions . . . . . . . . . . . . . . . . . . . . . . . 708 18.7.1 Gas Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708 18.7.2 Control of Plume Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708
18.8 Removal of Contaminants as Remedial Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 709 18.8.1 Removal and Recovery of Free Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 709 18.8.2 In Situ Biological Treatment of Groundwater Decontamination . . . . . . . . . . . . 713 18.8.3 Pump-and-Treat Processes for Groundwater Decontamination . . . . . . . . . . . . . 719 18.8.4 Removal of Gasoline from Contaminated Soil . . . . . . . . . . . . . . . . . . . . . . . . . 734
18.9 Phenomena Related to the Release of DNAPLs and Other Hazardous Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745 18.9.1 Chemical and Physical Properties of DNAPLs . . . . . . . . . . . . . . . . . . . . . . . . . 745 18.9.2 Fate of DNAPL Release Underground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745 18.9.3 Site Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746 18.9.4 Practical Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 752 Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755
Underground storage tanks (USTs) comprise one or a combination of tanks (including the associated underground piping) that are used to contain substances regulated under the RCRA1,2 (Resource Conservation and Recovery Act) or CERCLA3,4 (Comprehensive Environmental Response, Compensation, and Liability Act-Superfund), the volume of which include 10% or more located below ground surface (bgs). Generally, this term does not encompass residential and farm tanks holding 4164 L (1100 gal) or less of motor fuel used for noncommercial purposes, tanks storing heating oil to be used on the premises where it is stored, tanks on or above the oor of an underground area, such as basements or tunnels, septic tanks, and systems for collecting wastewater and stormwater, ow-through process tanks, emergency spill and over ll tanks, and related pipeline facilities.5-7
When the UST program began, there were approximately 2.1 million regulated tanks in the U.S. Today there are far fewer, because many substandard UST systems have been closed.8 According to the U.S. Environmental Protection Agency (U.S. EPA), less than 5% of the current number of UST tanks store hazardous substances.6 The majority of these tanks are used to store petroleum products for retail and industrial purposes. of the regulated tanks, 80% are believed to be made of bare steel, which can quickly corrode, allowing the contaminants to seep into the ground, posing a signi cant threat to the environment. The greatest potential hazard from a leaking UST is that the petroleum or other hazardous substance may seep into the soil and contaminate groundwater, the source of drinking water for nearly half of all Americans.8 A leaking UST can present other health and environmental risks, including the potential for re and explosion.
