API Publ 4699-2000 pdf free download

API Publ 4699-2000 pdf free download.S TRATEGIES F OR C HARACTERIZING S UBSURFACE R ELEASES O F G ASOLINE C ONTAINING MTBE.
The greatest concerns associated with gasoline releases have traditionally been non-aqueous phase liquids (NAPL) and dissolved-phase benzene, toluene, ethylbenzene, and xylenes (BTEX). The site characterization techniques commonly used by industry were originally developed to meet regulatory requirements for NAPL and BTEX. Over the past decade, however, there has been increased use of oxygenated compounds in gasoline, particularly methyl tertiary-butyl ether (MTBE). The chemical properties and subsurface behavior of oxygenated fuel additives are different from those of BTEX or other petroleum hydrocarbons, and so a reevaluation of traditional site characterization procedures is warranted. This technical bulletin uses the principles of risk-informed decision making to guide the evaluation of sites affected by MTBE or other oxygenates. It includes an introduction to the properties and uses of MTBE, provides guidance for conducting assessments at MTBE release sites, and reviews modern assessment tools and techniques for characterizing and monitoring MTBE in the subsurface. While the primary focus of this study is on MTBE, other fuel oxygenates are also addressed.
Risk-informed decision making is a management strategy that adds exposure and risk considerations to the traditional technical, social, and economic components of the corrective action process. The risk-informed approach presented in this bulletin uses site-specific risk factors to help determine the appropriate level of assessment at oxygenate release sites. It includes a review of the various risk factors associated with oxygenate sources, pathways, and receptors. Based on these factors, three levels of assessment are recognized. The standard level is appropriate for the greatest number of sites: it includes moderate sample spacing with some vertical characterization, as well as horizontal characterization. The limited level is appropriate at sites with fewer risk factors: it includes relatively large sample spacing with emphasis on horizontal characterization. The detailed level is warranted for sites with the most risk factors: it requires the highest level of effort for each characterization task, with relatively close sample spacing, and extensive vertical characterization of chemical concentrations and hydraulic properties. The appropriate level of assessment is initially determined based on receptor information, since receptor data are typically easier to obtain than source or pathway data.
As oxygenate usage has grown, however, so have concerns regarding the potential impacts of these compounds on groundwater quality. Traditionally, the greatest concerns associated with gasoline releases have been non-aqueous phase liquids (NAPL) and dissolved-phase benzene, toluene, ethylbenzene, and xylenes (BTEX). The assessment techniques commonly used by industry (API, 1996a) were originally developed to meet regulatory requirements for NAPL and BTEX characterization. However, many fuel oxygenates are more mobile and persistent in groundwater than BTEX or other petroleum hydrocarbons. These differences have important implications for subsurface assessment; for example, a small surface release of conventional fuel may have no apparent impact on shallow groundwater, while an equivalent release of oxygenated fuel may result in unacceptable concentrations of dissolved-phase MTBE. Furthermore, dissolved- phase MTBE plumes may be more difficult to detect and delineate than dissolved-phase BTEX plumes. In light of these differences, a reevaluation of traditional assessment procedures is warranted. This study uses the principles of risk-informed decision making to guide the evaluation of sites affected by MTBE or other ether oxygenates. The risk-informed decision making framework uses information about sources, pathways, and receptors to guide site management decisions to reduce or eliminate risks from exposures to chemicals released in the environment.