Vapor Intrusion Evaluation

Hicksville, New York

Roux Associates was retained to complete a complex soil vapor intrusion study for an existing occupied commercial building. Previous operators of the property had obtained and disclosed inappropriate soil gas data to state agencies and a building evacuation order was pending for the 18 tenants within the building. Roux Associates developed a expedited soil vapor survey to identify vapor concentrations in and under the building slab using the current New York State Department of Health (NYSDOH) Draft Guidance for Evaluating Soil Vapor Intrusion in the State of New York. Tasks included:

• Pre-sampling inspection, location stakeout and utility clearance activities
• collection and analysis of sub-slab vapor samples
• Collection and analysis of ambient indoor and outdoor background air samples
• Report preparation

Holes were drilled through the floor slab and temporary probes constructed of Teflon-lined tubing were inserted into the sub-slab material. All sub-slab vapor samples were analyzed for volatile organic compounds (VOCs). Indoor and outdoor air samples were collected concurrently with the sub-slab sampling. The samples were collected at a height that is representative of the typical breathing zone. Appropriate Quality Assurance/Quality Control (QA/QC) was followed for sample collection and laboratory analysis.

The results of the study were used to generate a formal risk assessment report that resulted in suspension on the building evacuation order. Roux Associates was able to negotiate a formal written response from the state agencies stating no increased risk was present within the building due to vapor issues. Roux Associates then developed a complete vapor intrusion mitigation plan. The design of the plan included a sub-slab depressurization system, which would not disturb existing tenants within the building.