SITE INFORMATION AND CORRESPONDENCE

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Sent By: BASELINE; 510 420 1707; Nov-9-99 17:03; Page 7113 %malf %00� QUALITATIVE SUMMARY No potential terrestrial ecological habitat-,or individual species of plant,mammal,or other wildlife species were observed on the Weber Blnck Property during a site visit. The only potential habitat at the site therefore includes the Stockton Channel,an aquatic habitat, and the Center Street Bridge, which could be used by nesting swallows during the breeding season. The Stockton Channel is limited in terms of vegetation and tends to flush slowly, which affects the water quality. The Channel supports a variety of resident and non-resident game fish species. However, the Channel provides limited aquatic habitat for fish species and is unlikely to support sensitive fish species (Jones & Stokes, 1999). Any construction- or project-related impacts to ecological receptors(i.e.,fish and swallows)associated with the Weber Block redevelopment would be mitigated to reduce these to less than significant impacts. In addition,there are no potentially significant exposure pathways for contaminated soil or shallow groundwater at the site to impact the aquatic habitat under the proposed development.The site is and will largely remain capped and shallow groundwater flows generally away from the Channel,which is lined with seawalls. The seawalls will be repaired under the proposed site redevelopment to prevent shallow groundwater migration. Surface water drainage is and will continue to be directed to the City's storm water system. Based on the lack of habitat for ecological receptors at the site and no potentially significant exposure pathways,potential impacts to ecological receptors under current and proposed future site development activities from site contaminants are therefore assurned to be less than significant. UNCERTAINTY ANALYSIS The assumptions,procedures, and parameters used in the human health and ecological risk analysis are subject to various degrees of uncertainty. Uncertainty and conservatism may,in particular,be associated with field sampling, use of fate and transport models, representation of site conditions, and use of tonicity data. FIELD SAMPLING The sampling efforts implemented at the site were designed to identify areas that were suspected to have elevated chemical concentrations. This sampling bias may have resulted in a database that focuses on the worst-case areas of the site. Correspondingly, this focused approach results in overestimation of the actual risk/hazard associated with exposure to site contaminants for human health and ecological receptors. FATE AND TRANSPORT MODELS Use of fate and transportmodels results in highly conservative estimates of chemical transportto the surface from subsurface soil and groundwater sources. In turn,this results in an overestimation of human health risks. 97349etk.pea.wpd-1 ir+3rgu 29