Development of a Strip Mall With a Vapor Intrusion Threat

mall shoppingWhat is a Vapor Intrusion Threat?

A vapor intrusion threat refers to the potential for hazardous vapors, such as volatile organic compounds (VOCs), to enter indoor spaces from contaminated soil or groundwater beneath a building's foundation. The vapors can enter the building through cracks in the foundation or other openings, and can pose immediate or long-term health risks to occupants. Vapor intrusion threats are typically addressed through environmental site assessments and remediation efforts.

Developing Properties with a Vapor Intrusion Threat: San Francisco Bay Regional Water Quality Control Board's Updated Fact Sheet

In today's digital world, strip malls are out of favor and targets for development, redevelopment, or repurposing. Many of those strip malls are or were, the location of a dry cleaner, and some of those dry cleaners had a release of solvents such as tetrachloroethylene (PCE). If you are a developer or property owner of a strip mall with a dry cleaner, and are planning or implementing development, redevelopment, or repurposing, you will probably face PCE vapor intrusion issues.

In that regard, the San Francisco Bay Regional Water Quality Control Board (Board) recently updated (June 2022) their fact sheet regarding the development of properties with a vapor intrusion threat. Here are some highlights from the Board’s latest fact sheet.

Understanding Remediation and Vapor Intrusion Mitigation (VIM) for Contaminated Sites

Mitigation versus Remediation

The fact sheet makes clear that you must make efforts at cleanup (remediation) before vapor intrusion mitigation (VIM) is considered. Remediation refers to cleanup actions that reduce gross contaminant concentrations that potentially risk public health and/or the environment. Remediation is meant to continue “to the extent feasible”, which considers the benefit of continued remediation weighed against consequences and results. Remediation reduces contamination and potential risk, but does not necessarily achieve cleanup goals. In many cases, after remediation to the extent feasible, natural mechanisms such as biodegradation are relied upon to meet stringent cleanup goals. In the interim, VIM is applied. The Board notes that VIM is often necessary since achieving cleanup standards may take years. Also, the Board notes that VIM may be the only viable long-term solution where further cleanup may not actually reduce the amount of contamination and eliminate the vapor intrusion threat.

VIM Monitoring 

micromonmeter soil gasThe Board states that monitoring is necessary to verify that VIM measures are working to successfully control potential vapor intrusion exposure. The Board justifies this position by noting that VIM is not a fail-safe solution to controlling vapor intrusion.

VIM Oversight

The Board requests that they be informed “early” in the property development process concerning any vapor intrusion issues and the need for VIM. If the Board concurs that VIM is necessary, they ask that the following documents be prepared and submitted under the direction of an appropriately licensed professional for Board review:

  • VIM Funding Plan. To be submitted prior to construction.
  • VIM Design Plan (including VIM design, long-term monitoring plan, and contingency plan). To be submitted prior to construction.
  • VIM Operation, Maintenance, and Monitoring Plan. This is to be submitted after completion of VIM baseline and system testing and prior to building occupancy.
  • VIM Construction Completion Report. To be submitted prior to building occupancy.
  • Long-Term Monitoring Reports and Five-Year Review Reports. These reports are required as long as VIM monitoring is required.
  • VIM Incident Report. To be submitted 30 days after an incident and completion of contingency action to resolve the incident.
  • Active VIM Shutdown Work Plan or Passive VIM Decommissioning Work Plan. These plans are due when the Board agrees that suitable conditions are met.
  • Active VIM Shutdown Report or Passive VIM Decommissioning Report. These reports are due after shutdown or decommissioning is complete.

The Board states that it will coordinate with local agencies that have permitting authority over building, grading, and occupancy.

VIM Approval Timeframes 

The Board indicates that for planning purposes, assume that 60 days will be required to review the documents listed above. They mention that review times may be longer or shorter depending on workload and complexity, and that time frames should be explicitly discussed with the case manager.


Development at former or existing dry cleaner sites will make up a large portion of sites with vapor intrusion issues. With that in mind, we highlighted the Board’s recent fact sheet on development at sites with a potential for vapor intrusion. If you're up against vapor intrusion issues and red tape, we can help. Click the button below for a free consultation, or give us a call at (831) 475-8141.