Abstract : The purpose of the attached document is to recommend a preferred alternative for remedial action at the KC-135 Crash Site. This decision is based on the results of the Installation Restoration Program (IRP), including remedial investigations conducted in 1992 and 1994, and this remedial action plan (RAP) which supports the use of natural attenuation to reduce long-term risks at the site.

The term `Natural Attenuation` refers to naturally-occurring processes in soil and groundwater environments that act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in those media. These in-situ processes include biodegradation, dispersion, dilution, adsorption, volatilization, and chemical or biological stabilization or destruction of contaminants. In practice, natural attenuation also is referred to by several other names, such as intrinsic remediation, intrinsic bioremediation, natural restoration, or passive bioremediation. The goal of any site characterization effort is to understand the fate and transport of the contaminants of concern over time in order to assess any current or potential threat to human health or the environment. Natural attenuation processes, such as biodegradation, can often be dominant factors in the fate and transport of contaminants.

The intent of this document is to present a technical protocol for data collection and analysis in support of intrinsic remediation with long term monitoring (LTM) for restoration of groundwater contaminated with fuel hydrocarbons. Specifically, this protocol is designed to evaluate the fate in groundwater of fuel hydrocarbons that have regulatory standards. Intrinsic remediation is an innovative remedial approach that relies on natural attenuation to remediate contaminants in the subsurface. In many cases, the use of this protocol will allow the proponent of intrinsic remediation to show that natural degradation processes will reduce the concentrations of these contaminants to below regulatory standards before potential receptor exposure pathways are completed. The evaluation should include consideration of existing exposure pathways, as well as exposure pathways arising from potential future use of the groundwater.