1.1 This provisional guide describes a process for expedited site characterization (ESC) of hazardous waste contaminated sites to identify all relevant contaminant migration pathways and to determine the distribution, concentration, and fate of contaminants for the purpose of evaluating risk, determining regulatory compliance, and designingremediation systems (when required). Generally, the process is applicable to larger scale projects, such as CERCLA (Superfund) remedial investigations and RCRA facility investigations. It is also applicable to other contaminated sites where contaminant characteristics and heterogeneities in the geologic and hydrologic system create a risk that other site characterization approaches will fail to identify relevant contaminant migration pathways. ESC has been successfully applied at multiple sites in different states and EPA regions (Table X1.1). It typically achieves significant cost and schedule savings compared to conventional site characterization (see X1.2 and X1.3).

1.2 The ESC process operates within the framework of existing regulatory programs. It focuses on collecting only the information required to meet clearly defined objectives and ensuring that characterization ceases as soon as the objectives are met. Central to the ESC process is on-site decisionmaking by a multidisciplinary core technician team using the clearly defined framework of a dynamic work plan which provides the flexibility and responsibility to select the type and location of measurements to optimize data collection activities. Other essential features of the ESC process include: intensive compilation, quality evaluation, and independent interpretation of prior data to develop a preliminary conceptual site model, use of multiple complementary site appropriate geologic and hydrologic investigation methods, rapid site-appropriate methods for data collection and interpretation, rigorous quality control for all aspects of data collection, daily on-site reduction and archiving of field data, and daily integration, analysis, and interpretation of data to support on-site decisionmaking. (See Table 1 and Section 5).

1.3 The process described in this provisional guide is based on good scientific practice but is not tied to any particular regulatory program, site investigstion method or technique, chemical analysis method, statistical analysis method, risk evaluation method, or computer modeling code. The appropriate specific site investigation techniques in an ESC project are highly site specific, whenever feasible noninvasive and minimally invasive methods , are used in Appendix X3. Appropriate chemical analysis methods are equally site specific and may be conducted in the field or laboratory depending on data quality requirements, required turnaround time, and costs.

1.4 Generally, the ESC process is not applicable to individual petroleum release sites, real estate property transactions, and sites where contamination is limited to the near-surface and there is no basis for suspecting that contaminant movement through the vadose zone and ground water is a matter of concern, or where the cost of remedial action is likely to be less than the cost of site characterization. Guide PS 03-95 addresses accelerated site characterization (ASC) for petroleum release sites, and Guide E 1739 addresses use of the risk-based corrective action (RBCA) process used at petroleum release sites. Section X1.6.1 describes the ASC process, and X1.6.2 discusses the relationship between ESC and the RBCA process. Practices E 1527 and E 1528 addressreal estate property transactions, and X1.6.3 discusses the relationship between the ESC process abd investigations for real estate property transactions. Classification D 5746 addresses environmental conditions of property area types, for Department of Defense Installations and Practice D 6008 provides guidance on conducting environmental baseline surveys in order to determine certain elements of the environmental condition of Federal property.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.6 Provisional standards achieve limited consensus through approval of the sponsoring subcommittee.