ABSTRACT
Liquid Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 8.4.5 Adsorptive Force Affecting Underground Liquid Movement . . . . . . . . . . . . . . . 301 8.4.6 Combination of Capillary and Adsorptive Forces Affecting
Underground Liquid Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 8.4.7 Energy Conservation Affecting Underground Liquid Movement . . . . . . . . . . . . 304 8.4.8 Water Movement in Saturated Zone of Soil Formation . . . . . . . . . . . . . . . . . . . . 305 8.4.9 Water Movement in Unsaturated Zone of Soil Formation . . . . . . . . . . . . . . . . . . 305
8.5 Properties of Gasoline and Its Movement in Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 8.5.1 Properties of Gasoline and the Forms of Release Underground . . . . . . . . . . . . . 306 8.5.2 Fates of Gasoline Underground: Adsorption and Degradation
of Gasoline and the Effect on Gasoline Movement . . . . . . . . . . . . . . . . . . . . . . . 307 8.5.3 Multiphase Movement of Gasoline Compounds . . . . . . . . . . . . . . . . . . . . . . . . . 309
8.6 Management of Tanks and the Environment as Remedial Actions . . . . . . . . . . . . . . . . 310 8.6.1 Tank Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 8.6.2 Tank Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
311 8.6.4 Alternatives for Tank Abandonment and Replacement . . . . . . . . . . . . . . . . . . . . 312
8.7 Control of Contaminants Migration as Remedial Actions . . . . . . . . . . . . . . . . . . . . . . . 312 8.7.1 Gas Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 8.7.2 Control of Plume Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
8.8 Removal of Contaminants as Remedial Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 8.8.1 Removal and Recovery of Free Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 8.8.2 In Situ Biological Treatment of Groundwater Decontamination . . . . . . . . . . . . . 317 8.8.3 Pump-and-Treat Processes for Groundwater Decontamination . . . . . . . . . . . . . 323 8.8.4 Removal of Gasoline from Contaminated Soil . . . . . . . . . . . . . . . . . . . . . . . . . . 338
8.9 Phenomena Related to the Release of DNAPLs and Other Hazardous Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 8.9.1 Chemical and Physical Properties of DNAPLs . . . . . . . . . . . . . . . . . . . . . . . . . . 349 8.9.2 Fate of DNAPL Release Underground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 8.9.3 Site Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 8.9.4 Practical Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
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.
