Measuring and testing – Borehole or drilling – Fluid flow measuring or fluid analysis
Reexamination Certificate
1999-05-17
2001-11-27
Geist, Gary (Department: 1623)
Measuring and testing
Borehole or drilling
Fluid flow measuring or fluid analysis
C073S152410, C073S152420, C166S252200, C166S252500, C166S310000, C436S027000, C436S029000
Reexamination Certificate
active
06321595
ABSTRACT:
FIELD OF INVENTION
This invention concerns methods of detecting the presence of contaminants located in subsurface formations, methods of determining the composition and/or volume of the contaminants and methods of assessing the performance of remediation designed to treat or remove contaminants from subsurface formations.
BACKGROUND OF INVENTION
In the 1980's, it became apparent that many hazardous waste sites had received organic liquids, such as petroleum hydrocarbons, chlorinated solvents, creosote solutions and coal tars which had subsequently migrated into the subsurface beneath these sites. Once in the subsurface, these liquids dissolved and caused the contamination of ground-water supplies and then proved resistant to their quantitative removal by the remedial approaches available. These liquids are known to environmental scientists and engineers as non-aqueous phase liquids, or “NAPLs”. NAPLs such as petroleum hydrocarbons, which are lighter than water, are identified as “ILNAPLs”, while those denser than water such as chlorinated solvents are known as “DNAPLs”.
NAPLs are generally of sufficiently low aqueous solubility and volatility that their limited dissolution into ground waters or volatilization into gases has resulted in predictions of their residence in the subsurface for tens, hundreds or perhaps thousands of years. However, their toxicity is often such that their solubilities are many times the permitted maximum contaminant levels allowed by the U.S. Environmental Protection Agency in drinking water. For example, the most common NAPL contaminant found in ground waters beneath hazardous waste sites, the metal degreasing solvent trichloroethene, has an aqueous solubility of 1385 milligrams/liter but a maximum contaminant level of 5 micrograms/liter.
Partly because of their ubiquitous use in industry and commerce, low maximum contaminant levels and mobility in the subsurface in dissolved and gaseous states, NAPLs and NAPL constituents, such as benzene derived from gasoline, have come to occupy a central place in the technical and regulatory processes associated with the characterization and remediation of hazardous waste sites. In addition, NAPLs have become the focus of this concern because of the extreme difficulty in detecting their presence. In the context of this discussion, “detection” means the act of inferring the amount, location and/or composition of the NAPL. In recent years, a number of knowledgeable observers have commented on the cost and impracticality of detecting DNAPLs using conventional site-characterization techniques. See, for example, Huling and Weaver,
DNAPL site evaluation, Project Summary
, EPA/600/SR-93/022, U.S. Environmental Protection Agency, R.S. Kerr Environmental Research Laboratory, Ada, Okla., 74820 (1993); Cohen and Mercer,
Dense nonacueous phase liquids. Ground Water Issue
, EPA/540/4-91-002, U.S. Environmental Protection Agency, R.S. Kerr Environmental Research Laboratory, Ada, Okla., 74820 (1989); MacKay and Cherry, “Groundwater Contamination:Pump-and-treat Remediation,”
Environmental Science and Technology,
23(6):630-636 (1993).
However, despite the expenditure of billions of dollars annually by the U.S. Government through the Environmental Protection Agency (for instance, in the implementation of Superfund), the U.S. Department of Energy (implementing the Environmental Restoration Program), the U.S. Department of Defense (implementing the Installation Restoration Program), as well as private corporations, the U.S. Environmental Protection Agency reported in April, 1993 (Cohen and Mercer, 1993) that “relatively little effort has been expended on developing new site-characterization tools or methods for DNAPL sites.” This situation has resulted in substantive problems for DNAPL site characterization, in particular because of the tendency of DNAPLs, due to their density and viscosity, to migrate both vertically and laterally from their point of entry into the subsurface to considerable depth. Consequently, DNAPLs are “largely undetected and yet are likely to be a significant limiting factor in site remediation” (Huling and Weaver, 1991).
It follows from the sparing solubility and volatility of NAPLs that, generally, the vast majority of the mass of an organic liquid released to the subsurface may remain in the NAPL form. Relatively minuscule concentrations will be present in the dissolved and vapor states, but it is these less important phases that are generally monitored for compliance with regulations concerning the performance of the remedial operations at a site (see, Environmental Protection Agency, “General methods for remedial operations performance evaluations-” EPAI600/R092/002, R.S. Kerr Environmental Research Laboratory, Ada, Okla. 74820 (1992)).
SUMMARY OF THE INVENTION
It is now contemplated that one or more problems exist in the area of NAPL remediation, namely the inability to directly measure NAPL location, volume and composition and thereby quantitatively assess the performance of remedial technologies. Thus, the absence of reliable tools for detecting NAPLS, particularly DNAPLs, prevents successful remediation or perhaps even containment at hazardous waste sites because effective methods of remediation or containment or both cannot be focused on the source of contamination when the location, amount and perhaps composition of the source are unknown. Furthermore, without direct quantitative measures of NAPL volume and composition, the performance of remediation technologies cannot be assessed.
The present invention provides a solution to one or more of the needs and disadvantages discussed above. This invention provides a significant development in the context of contaminant remediation by providing a process to, in the first instance, detect whether a NAPL is present. In addition, this invention further supplies a method to assess the performance of an attempted remediation by measuring the volume of NAPL in the subsurface both before and after the attempted remediation. Still further, this invention provides a process for ascertaining the composition of the NAPL located in the subsurface prior to remediation, thereby enabling the design of the remediation which is specifically directed to removal of the thus identified constituents of the NAPL. The several aspects of this invention will now be described.
This invention, in one respect, is a method for detecting the presence of nonaqueous phase liquid in a subsurface formation, comprising:
(A) introducing one or more partitioning tracers and one or more non-partitioning tracers at one or more introduction points located in the subsurface formation;
(B) measuring separation between the one or more partitioning tracers and the one or more non-partitioning tracers from one or more sampling points to determine whether nonaqueous phase liquid is present in the subsurface formation.
This invention, in a second respect, is a method for detecting the presence of dense nonaqueous phase liquid located in a subsurface formation, comprising:
(A) introducing one or more partitioning tracers and one or more non-partitioning tracers into one or more introduction points located in the subsurface formation;
(B) measuring separation between the one or more partitioning tracers and the one or more non-partitioning tracers from one or more sampling points to determine whether dense nonaqueous phase liquid is present.
This invention, in a third respect, is a method for determining a three dimensional distribution of nonaqueous phase liquid located in a subsurface formation, comprising:
(A) introducing one or more non-partitioning tracers into one or more injection points located in the subsurface formation;
(B) withdrawing the one or more non-partitioning tracers and one or more partitioning tracer from one or more sampling points located in the subsurface formation;
wherein the introducing occurs at two or more depths or the withdrawing occurs at two or more depths or wherein both the withdrawing and the introducing occur at two or more depths;
(C) measuring separatio
Jackson Richard E.
Pope Gary A.
Baker & Botts L.L.P.
Board of Regents , The University of Texas System
Geist Gary
Maier Leigh C.
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