Ecological & Human Health Risk Assessment

Project Name: Ella Elementary School, Marysville, California Services: Preliminary Environmental Assessment including Screening Level Risk Assessment Client: Marysville Joint Unified School District

Padre completed a Preliminary Environmental Assessment (PEA) for the Ella Elementary School site located at 4850 Olivehurst Avenue in Marysville, Yuba County, California. The Ella Elementary School was constructed in 1939 and currently consisted of 41,575 square feet (ft²) of building footprint, and a student capacity of 600 students. Three leaking underground storage tank (LUST) sites with reported soil and groundwater impacts are located northeast and adjacent to the Project Site. Based on the results of the soil gas and groundwater screening level evaluation conducted for the Project Site, the cumulative risk from soil vapor is estimated to be 4.9 x 10-7. Additionally, the cumulative hazard is estimated to be 0.004, and does not provide a significant health hazard (>1). Therefore, the Project Site has not been significantly impacted by the proximity of the three LUST sites. Chlordane and dieldrin were initially identified at concentrations up to 4,000 and 6,700 µg/kg, respectively in soil samples collected around the existing school restroom facility. After performing a housekeeping activity at the restroom structure and collecting confirmation soil samples, chlordane was not detected at or above its reporting limit, and dieldrin was detected at a maximum concentration of 130 micrograms per kilogram (µg/kg). Using the highest site concentration for dieldrin, the cumulative risk index for the Project Site was calculated to be 3.76. According to the Excel Calculator, a risk index greater than 1.0 indicates that further evaluation and/or remediation may be necessary. However, to provide a more representative evaluation of the cumulative risk for the Project Site from the presence of dieldrin, the risk index was also estimated using the 95% upper confidence limit (UCL) for dieldrin (23 µg/kg). Using the 95% UCL, the cumulative risk index for the Project Site was re-calculated to be 0.67. The results of the PEA screening level risk assessment and housekeeping activities do not indicate that the Project Site has been significantly impacted by past and current uses of the Project Site. Currently, there appears to be no significant impacts from the presence of three, adjacent LUST sites. Therefore, based on current site conditions, Padre recommends the issuance of a “No Further Action” designation from the DTSC regarding the Project Site.