ARCHIVED REPORTS_2019 SOIL MGMT PLAN (JULY-REVISED)

Home Browse Search

Brusca File No. 137-002 BruscaAssociates.com ● P.O. Box 332, Roseville, CA 95661 ● Phone (916) 677-1470 Page 8 March 9, 2018 Murphy Parkway Property Excavation and Materials Management Plan Agency (Regional Screening Levels [USEPA-RSLs]) and the California Department of Toxic Substances Control [DTSC-SLs]).3 4 Exceptions to this screening protocol for the site are outlined below: • Arsenic: It is widely considered impractical to evaluate arsenic by comparison to the referenced screening levels since background concentrations of arsenic in native soils often exceed the screening levels by two to three orders of magnitude. More commonly, arsenic concentrations are compared to background/naturally-occurring soil arsenic concentrations for screening purposes. AGE summarized soils metals data from the site area as a part of the site investigation and characterization work (see referenced Site Assessment Summary Report). Based on data presented in the Site Assessment Summary Report, background arsenic soil concentrations occur within a range of non-detect to 8.6 milligrams per kilogram (mg/kg); such a range is not uncommon for alluvial deposits within the Central Valley. Per California Department of Toxic Substances Control guidance for the development of arsenic cleanup goals, the upper limit of the data set (8.6 mg/kg) is selected as the arsenic screening level for evaluation of the stockpiled wastes for reuse at the site.5 It is noted that the soil sample containing 8.6 mg/kg arsenic at the site was collected from Test Pit T129, situated on the subject parcel over 800 feet southeasterly of the areas historically subject to waste handling, and, as such, is appropriate for background arsenic determination. • Petroleum Hydrocarbons: The listed USEPA-RSL values for total petroleum hydrocarbons are defined by carbon ranges (fractions) that are not typically reported via the EPA Method 8015B test method. As such, for reuse purposes any detected petroleum hydrocarbon concentrations will be compared to San Francisco Bay Regional Water Quality Control Board (SFBRWQCB) Environmental Screening Levels (ESLs) for commercial/industrial shallow soil exposure.6 In the event that soil sample data from any of the stockpiled waste materials exhibit laboratory data exceeding hazardous waste criteria or the screening levels cited above, additional sampling of the relevant 250 cubic yard section(s) of stockpiled waste materials may ensue to further define the portion(s) of the stockpile exhibiting these characteristics. Any stockpiled waste materials that are identified to contain the tested analytes at concentrations exceeding the described hazardous waste criteria or the referenced screening levels will be subject to the offsite disposal procedures described below in Section 6.7. The results of the DI- WET metals analyses will be compared to California drinking water Maximum Contaminant Levels (MCLs). In the event that any exceedances of the MCLs are indicated by the laboratory results, modelling or other methodology will be utilized to evaluate whether any reused waste materials could result in groundwater impact. Removed/stockpiled waste materials that are demonstrated to not pose an unacceptable risk to groundwater quality and meet the screening criteria described herein will be deemed acceptable for onsite reuse in engineered fills. 3 USEPA; “Regional Screening Levels, TR=1E-06, HQ=1”; November 2017 4 DTSC: “DTSC-Modified Screening Levels (DTSC-SLs); January 2018. 5 Department of Toxic Substances Control; “Arsenic Strategies, Determination of Arsenic Remediation, Development of Arsenic Cleanup Goals”; January 16, 2009. 6 San Francisco Bay Regional Water Quality Control Board; “Environmental Screening Levels”; February 2016.