DEQ presentation flags common vapor intrusion pitfalls that delay occupancy

Jordan, a groundwater professional presenting to Brownfields stakeholders, summarized common construction and sampling problems that delay occupancy of redevelopment projects and offered practical steps to reduce delays.

‘‘We really need a final installation report with pre-occupancy sampling in accordance with the VI matrix before we can give a green light to occupancy,’’ Jordan said, stressing that installation documentation and pre-occupancy field data are necessary for DEQ to clear sites for occupancy.

Jordan listed several recurring issues: fans not installed or installed backwards; missing vertical risers or incomplete routing that create preferential pathways; improper building materials used to seal seams (for example, roofing tar is not a substitute for rated vapor-barrier tapes); and omitted or insufficient photos and labels in install reports. She warned that incomplete reports often require returning to the field to collect photos or re-sample, which pushes back occupancy dates.

On sampling practice, Jordan recommended recording four pressure readings for summa canisters (what the sample left the lab with, what it arrived to the field with, what it left the field with, and what the lab received back) and noted that if pressure reads zero at any point a resample is likely. She also flagged indoor-air confounding factors, such as off-gassing from new furniture, that can distort TCE and other vapor results.

Jordan discussed design considerations for long sub-slab runs (moisture entrapment that affects remote pressure monitoring), the need to account for pour-back areas in operation-and-maintenance plans and the suggestion to complete final-grade sampling after mass grading and curb/gutter work.

She encouraged communication among contractors, engineers and DEQ reviewers (calendar invites to inspectors were singled out as useful), and recommended engineer-sealed vent modifications for significant changes to VIMS plans.