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kTj KLEINFELDER 6. CONCLUSIONS AND RECOMMENDATIONS Kleinfelder conducted this limited soil sampling and analysis of selected areas of the proposed Glenbriar Estates School Site to evaluate the presence of certain suspect contaminants. A total of seven (7) soil samples were collected from five shallow hand augered soil borings and two five foot hand augered soil borings. Seven soil samples were subsequently chemically. The approved scope of work was modified in the field based on significant changes in site conditions since Sierra Environmental Consultants' April 11, 1997 Phase I Environmental Site Assessment report. Based on the results of this assessment, Kleinfelder has the following conclusions and recommendations: 1. Given the changed site conditions that had occurred the approved scope of work could not be conducted as proposed and was modified in the field. In the event that the client desires additional investigation at the site, Kleinfelder recommends that the Jefferson Unified School District requests that the property owner(s) cease the import of fill and any other changes that may be planned (e.g. excavation of a retention pond, etc.). 2. Halogenated Volatile Organics were not detected in any of the soil samples analyzed from the gravel pit area. Therefore, no further analyses for Halogenated Volatile Organics in the gravel pit area appears warranted. r 3. Unidentified Extractable Hydrocarbons (UEH) were detected in the sample obtained from a depth of 5 feet in boring B2 (gravel pit area) at a concentration of 1,030 mg/I.. The source or extent of UEH in that area is unknown. However, UEH was not detected in the soil sample obtained from boring B 1 (also in the gravel pit area) at a depth of 5 feet. Additional samples were not able to be obtained at other locations by hand auguring due to the extensive overburden of fill dirt which has been placed over the area. If additional sampling is required by either Jefferson Unified or PHS/EHD, hollow stem auger drilling would be necessary. 4. It is Kleinfelder's opinion that concentrations of metals detected in soil samples analyzed during this assessment at the proposed Glenbriar Estates School Site reflect background concentrations rather than contaminants. 5. In the eastern portion of the site 4,4'- DDE was detected in the soil samples obtained from a depth of /z foot bgs at concentrations ranging up to 122 µg/kg. The concentrations detected are up to an order of magnitude below the U.S. EPA Region IX Preliminary Remediation Goals (PRGs) for Residential Property dated August 1, 1996 of 1,300 µg/kg. The compound 4,4'-DDE is a persistent organochlorine pesticide related to, and sometimes a breakdown product of, DDT. The half life for DDE in soil may range up to approximately 30 years. Because of its affinity to soil particles, DDE, generally does not readily leach to significant depth. Because the above-noted findings, no further investigation or cleanup appears warranted as it relates to the DDE concentrations in the shallow orchard soils. ;I 20-4202-01.P02/2018R669 Page 1 I of 14 _ © 1998.Kleinfelder,Inc. October 28, 1998