Vapor Intrusion

EKI investigates, evaluates, and mitigates the potential for volatile organic compound (VOC) vapor intrusion (VI) from the subsurface to indoor air at existing or planned buildings. EKI assists owners, developers, and government clients in remediating the source of VI concerns, managing their VI risks, and successfully developing commercial, multi-family residential, and mixed-use properties where there are actual or potential VI concerns. EKI VI experts assist regulatory agencies in developing guidance for VI Assessment and Mitigation. EKI performed VI assessments for hundreds of properties and evaluated, designed, or implemented VI mitigation for numerous buildings totaling over four million square feet of building footprint. EKI assists with air permitting, oversight during construction of vapor mitigation systems, ongoing monitoring, third-party review of VI assessments and mitigation system designs prepared by other consultants, and external peer review of state and federal regulatory guidance. EKI advocates on behalf of our clients with regulatory agencies and assists with public participation processes involving parties potentially impacted by VI.

VI Assessment and Modeling

• Phase I and II site assessments to screen for potential VI risks;
• Soil vapor, sub-slab vapor, and indoor air sampling and analysis to assess site-specific conditions;
• Pathway assessment to identify and mitigate potential preferential VI pathways (e.g., sewer, utility conduits, floor cracks, and gaps);
• Building ventilation (HVAC) system evaluations and indoor air pressure monitoring to evaluate mitigation provided by existing HVAC system and potential modifications to mitigate VI risks.
• Site-specific VI transport modeling based on soil conditions, VOCs of concern, and existing or future building conditions.
• VOC mass flux analysis to assess upper limit VI risks or demonstrate that VI mitigation is not necessary.

VI Risk Management Evaluation

EKI skillfully develops, assimilates, and evaluates multiple lines of evidence to provide defensible risk evaluations to assist in risk management; to demonstrate VI is not a concern for existing or new buildings; to design a practical mitigation approach acceptable to regulatory agencies and the building owner/occupant(s); or to support an exit strategy for a VI mitigation system.

VI Mitigation System Design and Construction Observation

EKI develops and implements VI mitigation systems tailored to site conditions and the requirements and limitations of building construction and planned occupancy. EKI develops construction quality assurance (CQA) plans and performs construction observation in accordance with the CQA plan to confirm that the VI mitigation system is constructed as designed.

EKI’s experience includes the following types of VI mitigation systems:

• Passive sub-slab ventilation (SSV) systems for site conditions with low VI risks for VOCs;
• Active sub-slab depressurization (SSD) systems, which are the most effective systems to confidently mitigate VI risks;
• Contingent SSD systems, providing basic infrastructure that can be “activated” in the future if pre-occupancy sampling indicates VI is an actual concern; and
• Isolated SSD (ISSD) systems, a modification to active SSD with an extra liner to reduce flow rates and VOC emissions, to allow implementation with smaller fans and lower VOC emissions to eliminate air permitting requirements, and reduce long-term monitoring obligations and costs.