Underground Storage Tanks

The term "natural attenuation" was used in the Preamble to the 1990 Final NCP (National Oil and Hazardous Substances Pollution Contingency Plan; Final Rule) which was published in the Federal Register, Vol. 55, No. 46, dated March 8, 1990. Discussion of natural attenuation as a possible remedy for ground water began on page 8733 and continued to the middle of page 8734. Also, natural attenuation was defined as use of "biodegradation, dispersion, dilution, and adsorption" to "effectively reduce contaminants in the ground water to concentrations protective of human health [and the environment] in a timeframe comparable to that which could be achieved through active restoration.

The term "natural attenuation" was also used in the 1988 Preamble to the 1988 Proposed NCP (National Oil and Hazardous Substances Pollution Contingency Plan; Proposed Rule), published in the Federal Register, Vol. 53, No. 245, dated December 21, 1988. Natural attenuation was mentioned on page 51434 as follows: "In limited cases, natural attenuation, which can involve either the dispersion or actual biodegradation of contaminants, may be the most appropriate remedy for a site."

The term "natural attenuation" was also used in the OERR document: Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites, OSWER Directive 9282.1-2, dated December 1988. This discussion can be found on page 5-7, Section 5.3.3.1 of the guidance, and is consistent with the terminology used in the Proposed NCP. Although the 1988 Proposed NCP was released in December of 1988, it was under development by OERR for many months (or years?) prior to its release.

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