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Mr. Wayne Dietz July 14, 2008 2154 S . El Dorado Street Investors, a California Limited Partnership Page 4 of 8 custody procedures and delivered to SunStar Labs a state accredited laboratory in Tustin, California. Following the completion of groundwater sampling, temporary well casing were removed and the borings were backfilled to grade with tremie pipe and a grout mixture of neat cement with 5% bentonite. The sampling equipment used repeatedly at the site was decontaminated on-site between groundwater samples to minimize the likelihood of cross-contamination. Investigation derived waste (IDW) such as drill cuttings, groundwater sampling purge water and some miscellaneous sample equipment decontamination rinse water were containerized in four (4) DOT certified 55-gallon drums pending necessary profiling and disposal. ENVIRONMENTAL SCREEENING LEVELS ROKEN determined that Environmental Screening Levels (ESLs)4 developed by the California Regional Water Quality Control Board, San Francisco Bay Region are most appropriate for evaluation of groundwater conditions at the site. The ESLs are considered to be conservative. Under most circumstances, and within certain limitations, the presence of a chemical in soil, soil gas or groundwater at concentrations below the corresponding ESL can be assumed to not pose a significant, long-term (chronic) threat to human health and the environment. Additional evaluation is usually necessary at sites where a chemical is present at concentrations above the corresponding ESL. Active remediation may or may not be required depending on site-specific conditions and considerations. The development and presentation of ESLs are modeled after similar documents published by the Ontario Ministry of Environment and Energy (MOEE 1996), the Massachusetts Department of Environmental Protection (MADEP 1994) and the Netherlands (Vetger 1993). Screening levels for groundwater consider the following criteria: 1 ) Protection of human health • Current or potential drinking water resource • Emission of subsurface vapors to building interiors 2) Protection of aquatic habitats (discharges to surface water) 3) Protection against nuisance concerns (odors, etc.) and general resource degradation. Screening levels for groundwater and surface water are summarized in the F series of tables. For the purpose of developing Tier 1 screening levels, it is assumed that all groundwater could at some point in time potentially discharge to a body of surface water. Discharge could occur through natural processes (e.g. , natural discharge of groundwater to a stream, river, lake, wetland, bay, etc. via springs) or through human activities (e. g., pumping and discharge of groundwater at remediation or construction dewatering projects). Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater, California Regional Water Quality Control Board, San Francisco Bay Region, INTERIM FINAL—November 2007 (Revised May 2008).