Site Mitigation & Restoration Program

We protect and maintain California’s land and places
by setting strict standards for land restoration and cleanup

Latest Brownfields News

California-based Attenuation Factor for Vapor Intrusion Sites

Many of us in the regulatory, development, and municipal communities have experienced the challenges of addressing volatile organic chemical contamination when we recycle contaminated land for housing and commercial uses. The potential risk posed by harmful vapors in breathing spaces, also known as vapor intrusion, is a challenge to redevelopment, particularly because it adds a high level of uncertainty to the decision making process. The Department of Toxic Substances Control is pleased to be able to share a preview of the process that has been used to derive a potential California-based attenuation factor for vapor intrusion calculations. The study, when complete, will provide the redevelopment sector with an additional tool to facilitate the land revitalization process. Although the study is under peer review and the report is not ready for release, DTSC is providing an overview of the data and process utilized for the calculations. Please e-mail for a copy of the presentation made at the California Land Recycling Conference 2020 – Communities Rising.


Among other types of properties, Site Mitigation and Restoration Program staff provides regulatory oversight for the evaluation and cleanup of brownfields. Brownfields are properties that are contaminated, or thought to be contaminated, and are underutilized due to perceived remediation cost and liability concerns. Many of these properties are in the urban core, near transit and often in underserved communities with housing and economic development needs. Cleaning up brownfield properties not only eliminates the threat to residents and neighborhoods from hazardous substances, it frees this abandoned or underutilized land for productive reuse. Redevelopment of brownfields also takes development pressures off previously undeveloped property, thereby preserving open space and agricultural land.

The State of California and DTSC realize the need for and importance of brownfield redevelopment. To support this priority, DTSC has created programs and administrative vehicles to formalize and streamline the engagement and oversight process. DTSC has several types of voluntary agreements that can be used to provide regulatory oversight for brownfields and other types of properties as well. Note that the decision-making process and environmental assessment and/or cleanup steps under voluntary agreements and for enforcement actions both follow all applicable regulatory requirements and demand the same rigor and scientific scrutiny to ensure the protection of human health and the environment. Both voluntary agreements and enforcement actions are subject to the same public participation process, and DTSC’s public participation process will vary based on the level of community interest in the project or property.

The oversight and engagement process is shown graphically in the flowchart below and accessed via the links in this Quick Reference Guide:

  1. Agreements
  2. Scoping Meetings
  3. Evaluation
  4. Remedy Selection
  5. Implementation
  6. Certification and Stewardship
DTSC’s Voluntary Agreements - Assessment & Cleanup Process Diagram

Download PDF version of this diagram.

This document is intended to be guidance only and it does not supersede or implement laws or regulations. The information in this advisory is intended solely as guidance and as educational reference material and should not be considered enforceable or regulatory in nature.