Soil Remediation for Agricultural Land Development

Soil remediation for developing California’s agricultural fields often requires a Removal Action Workplan (RAW) setting target concentrations so each chemical contaminant is reduced to an acceptable level for human health.

A multi-family residential development proposed on a former 15-acre Placer County orchard illustrates how an environmental impact report (EIR) can effectively address both the proposed project and RAW actions to streamline project implementation.

The site investigation and assessment reports identified approximately 7 acres, including two on-site drainage swales, as contaminated with lead; arsenic; the pesticides Endrin and DDT and DDTs breakdown products, DDE and DDD; and the insecticide Methoxychlor.

The RAW proposed excavating and removing approximately 11,600 cubic yards of soil at depths ranging from 12 to 18 inches.

As an effective way for the EIR to address both the RAW and the development, RAW implementation was included in the project description, and applicable components of RAW implementation are considered in the EIR’s impact analysis sections.

The EIR analysis of implementing the RAW for soil remediation considered:

  • Surface area of contaminated soils and anticipated depths of excavation
  • Site-specific clean-up goals identified in the RAW
  • Volume of soil that must be removed
  • Methods to control dust and soil from being released to the air or off-site properties during soil excavation and transport
  • How and where excavated soil will be disposed of
  • Amount of soil that will be imported to the site
  • Number of truck trips required to export and import soil
  • Driving route associated with soil export and import and traffic impacts from RAW-related truck traffic on that route
  • Noise, air quality, and climate change impacts from RAW-related truck traffic, equipment usage, and soil movement
  • Erosion control measures included in the RAW
  • Schedule for completing the RAW

The RAW also discussed alternative clean-up methods and the rationale for selecting the proposed method. This information is summarized in the EIR discussion of alternatives considered but rejected from further analysis.

It was important the EIR provide a clear description of the process to implement the RAW, obtain agreement from the California Department of Toxic Substances Control (DTSC) that the remediation goals have been met, and then proceed with project-related site grading.

The formal end to the RAW implementation process is DTSC’s issuance of a “No Further Action” letter. However, issuance of this letter may be delayed until laboratory testing results are received and a “Removal Action Completion Report” is prepared.

Waiting for lab test results before proceeding with site grading for project construction would leave disturbed areas of the project site exposed, increasing the potential for soil erosion and dust emissions. Instead, project EIR mitigation measures allow for project-related site grading to proceed upon issuance of a tentative “No Further Action” letter from DTSC and require certification from DTSC authorizing the project site for unrestricted land use prior to issuance of any building permits.

In this approach, the DTSC actions function as mitigation measure performance standards and timing triggers. This ensures ongoing project processing by the lead agency staff will mesh seamlessly with DTSC’s procedures and streamlines project implementation.