Why is Evergreen’s site-specific Lead standard (2240 ppm) so much higher than the state standard (1000 ppm)?

The PADEP’s Non-Residential Medium Specific Concentration (MSC) was derived using the Society for Environmental Geochemistry and Health (SEGH) model (Wixson, 1991). Since that time, the PADEP has endorsed the use of alternative uptake biokinetic models for the evaluation of lead toxicity including the Bower model (Bowers et al., 1994) for non-residential site uses. The USEPA adapted the Bowers et al. model to develop the Adult Lead Model (ALM). The ALM is a widely.accepted approach to risk characterization for non-residential exposure scenarios and recommended by the USEPA (EPA, 2001). Evergreen used the EPA’s default assumptions for assessing non-residential risks from lead exposure in the ALM model to develop the site specific standard for lead.