SacPEMA November Meeting - Tuesday, November 19, 2019

Design Considerations for the Mitigation of Vapor Intrusion

Synopsis: As northern California real property continues to increase in value, land developers are increasingly turning to distressed properties to meet real estate demand. This is particularly true for affordable housing. Potentially toxic, volatile organic compounds can exist on these properties, increasing the risk of exposure to building occupants. Concurrently, California regulators are tightening the rules for characterizing and mitigating these impacts. The outcome is that more new land developments, and some existing ones, are incorporating vapor migration barriers and sub-slab depressurization systems (SSDSs). Proper design and construction of these features can increase the building owner’s confidence that occupants are protected and reduce the associated legal liability. SSDSs, in particular, can be ineffective when under-designed and cause harmful backdraft conditions when over-designed. Understanding and measuring SSDS performance is critical.

Andrew and Jon will explain how to make it simple. Designers also face the challenges of properly sizing wind turbines and radon fans that will act on SSDSs in a safe vacuum range. However, scant data are available on the performance of these turbines in the low pressure range of an SSDS, leaving many designers to make a best estimate instead of a confident calculation to achieve the desired sub-slab vacuum.

This presentation explains engineering design, construction, and quality control techniques the presenters have used to instill confidence in the installation of vapor intrusion mitigation systems. Empirical data and the observational method enable the sizing and specification of passive,
roof-top wind turbines and active radon fans. Design details allow building owners to monitor and control SSDS operation within a safe range of depressurization values and non-obtrusively monitor sub-slab vapors. Techniques include characterization of the pneumatic performance of SSDS systems and turbines within the appropriate range of air suction values. This presentation also provides
performance data for use by others on several active and passive turbines.

Jon Gamble has over 10 years of experience in environmental consulting. His experience includes soil, soil vapor and groundwater assessment and remediation projects for industrial, commercial and residential development sites. He supports industry with environmental characterization, remediation and/or mitigation of soils, soil vapor and groundwater, due diligence investigations for property transfers, and storm water pollution prevention plans (SWPPPs) for industrial, construction and municipality projects. He is a Registered Professional Geologist and a Qualified Storm Water Developer (QSD) and Qualified Industrial Storm Water Practitioner (QISP) in the State of California.

Andrew Campbell has held responsible charge of nationwide environmental remediation projects involving chlorinated solvents, fuels, and heavy metals for nearly 20 years. He specializes in
developing optimized remediation strategies and building consensus between clientele, regulatory agencies, and other stakeholders to return contaminated properties to productive use. Andrew’s approach typically involves the design of low-cost remediation and closure plans to mitigate risks associated with complete exposure pathways, and that has increasingly involved vapor intrusion.
His clientele have included private parties, major airlines, utilities, and state and federal government agencies. Andrew is a registered civil engineer in California and eight other states.


Date: Tuesday, November 19, 2019

Time: 11:30 a.m. to 1:00 p.m. (registration/networking from 11:30 a.m. to noon)

Where: Firehouse Restaurant, 1112 2nd Street, Sacramento, CA 95814


  • Sliced Grilled Steak Sandwich - garlic sauteed mushrooms, crispy onion rings, rosemary roll
  • Baby Gem and Blue Cheese Salad with Grilled Chicken - Point Reyes Bay blue cheese, pickled onion, baton croutons, crispy bacon
  • Wild Mushroom Pasta (vegetarian option) - cream, butter, truffle, asiago cheese


  • Members -
    $30.00 + $1.20 cc fee
  • Non-Members - $35.00
    + $1.30 cc fee
  • Walk-ins -

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The Professional Environmental Marketing Association (PEMA) is an organization comprised of local and regional chapters whose membership is involved in business development, sales, marketing, and other related professional activities in the environmental field. The Sacramento California Chapter of PEMA operates in the greater Sacramento metropolitan area which includes Sacramento, El Dorado, Placer, Yolo, and San Joaquin counties.Sacramento PEMA was founded as a marketing and networking organization in 1995 as an affiliate of the Northern California Chapter of PEMA. Networking encourages formation of business relationships, development of business and teaming opportunities, and exchange of ideas. Sacramento PEMA recently broadened its scope to provide technical and regulatory information of interest to its members.