Vapor Intrusion Challenges for Urban Infill Projects Presented by Jeff Tyburski, PG, RSM Mid-Atlantic Associates, Inc. MAAONLINE.COM
Urban Infill Sites Urban setting Real/perceived presence of contamination Multiple on/off-site sources Planned redevelopment for higher use Primary focus on VI Risk pathway and risk mitigation Typically addressed under the NCDENR Brownfields Program
Presentation Outline When is VI mitigation warranted? Data needs Integrating a Vapor Intrusion Mitigation System (VIMS) into the site redevelopment process Installation oversight Pre and Post-occupancy testing Q&A
When Is VI Mitigation Warranted? Hard to prove mitigation is not required due to uncertainties Data collection Data trends over time How site is redeveloped will effect the VI pathway Uncertainties make it difficult to risk away the VI pathway Combined with liability concerns this often leads to VI mitigation
So How Much Data Is Needed? Complete VI exposure pathway? Evaluate existing sampling data Exceed screening levels? Data gap analysis Need for additional assessment? Soil groundwater Soil gas Indoor air Look before you leap
Understanding The Project Proposed reuse of site Redevelopment design considerations Brownfields regulatory requirements/approach Owner, lender, general contractor and team risk tolerance Third party liability concerns Other environmental data requirements/needs A lot of variables to consider Team approach Internal External A lot of chefs in the kitchen
Understanding The Project Design approaches Source removal Planned uses/land planning Placement of buildings Utilities and infrastructure Foundation systems Get the design team involved early This is the hard stuff! Vapor Block Plus 20 VIMS System
Understanding The Project Conceptual Site Model
Understanding The Project Building Overlay
Understanding The Project Team Input
Understanding The Project Data Collection EMP Development
What Is The Best VIMS Solution? Basis of Design Reviewed assessment data Team decision conduct VI mitigation VI barrier, active sub-slab depressurization Educate team members Team input Brownfields Program input A sound VIMS design is a marriage of technical and site redevelopment design criteria and regulatory approval Cannot design a cost-effective VIMS system in a vacuum
VIMS Tool Box Geo-Seal Multi-layered membrane system Good puncture resistance Designed vent mat system Robust system Top GeolSeal Installation, Contemporary Art Museum, Raleigh, NC Left GeoSeal installation, Valentine Commons, Raleigh NC
VIMS Tool Box Vapor Block Plus 20 20 mil EVOH geomembrane (polyethylene) Good puncture resistance Similar to typical moisture barrier 10 x 150 rolls Vapor Block Plus 20 installation, Winston Salem, NC
VIMS Tool Box Cupolex Ventilated sub-slab Interlocking domes Depressurize entire footprint of install Passive or active Much smaller fan/energy requirement Cupolex installation, day care facility
VIMS Design Solution
VIMS Design Team Input Tie-in to foundation and basement walls Horizontal vent pipe run locations for uniform negative pressure Vertical vent riser locations Utility penetrations Structural, MEP conflicts Fresh air intakes in relation to vent riser exhausts Pilot testing and blower selection Installation oversight QA/QC O&M/Facility management criteria Regulatory approval process Municipal/permitting approval process
VIMS Installation Oversight Installation QA/QC Worker training Damage prevention Address issues before going vertical System only as good as installation Micro pile installation and vertical construction, Valentine Commons Raleigh, NC
VIMS Testing - Does It Work? Multiple lines of evidence Acknowledges uncertainty More data from different sources Focus on pressure differentials Sub-slab COC concentrations Site-specific attenuation factors using radon Site-specific screening levels Indoor air sampling and new building materials don t mix well Most common indoor contaminant at a student housing center? Vertical riser testing Valentine Commons, Raleigh NC
Summary Often easier to mitigate than to build a case not to mitigate Team approach Can t assess/design in a vacuum Your VIMS is an integral part of your EMP Create less reliance on the VIMS by developing an effective EMP Your VIMS system is only as good as its installation Utilize multiple lines of evidence for pre and postoccupancy testing
MAAONLINE.COM Mid-Atlantic Associates, Inc. 409 Rogers View Court Raleigh, NC 27610 (919) 250-9918 Facsimile (919) 250-9950 jtyburski@maaonline.com