Background Standard for Known Upgradient Release

The staff at SRS developed a complex conceptual site model supported by a statistical analysis to demonstrate attainment of the background standard for a site in Pennsylvania under Act 2.  Methyl tert-butyl ether (MTBE) was demonstrated to be migrating from an upgradient UST source onto a site with a separate UST release.  The analysis utilized upper tolerance limits to show that the concentrations in the site background reference well were not exceeded in any point of compliance wells at the site.  This evaluation required a complex hydrogeologic model to demonstrate the extensive MTBE plume migration within a specific aquifer.