www.geosyntec.com Implementation of a Strategic AApproachh ffor CCompllex VVapor Intrusion Assessment at a Large Military Facility David W. Himmelheber Emily H. Majcher, Paul Nicholson, Aron Krasnopoler, TToodddd MMccAAllaarryy, RRoobbeerrtt EEttttiinnggeerr ((GGeeoossyynntteecc CCoonnssuullttaannttss)) Jennifer Harris (General Physics Corporation) www.geosyntec.com JJoohhnn WWrroobbeell ((UUSS AArrmmyy,, UUSSAAGG AAbbeerrddeeeenn PPrroovviinngg GGrroouunndd)) Introduction to Vapor Intrusion What is Vapor Intrusion? • Vapor intrusion (VI) is the transport of gas-phase contaminants from the subsurface to indoor air • Typically originates from groundwater and/or soil contamination --- volatile organic compounds (VOCs) • Exposures of contaminants to building occupants are a major concern •• RReellaattiivveellyy nneeww rreegguullaattoorryy eemmpphhaassiiss oonn assessing VI risk ITRC Vapor Intrusion Team logo; http://www.itrcweb.org/teampublic_Vapor.asp www.geosyntec.com Site Background Aberdeen Proving Ground (APG) • Established in 1917 in northwestern region of Chesappeake Bayy • R&D, manufacture of military chemical agents • Portion of APG pplaced on NPL site in 1990 • Canal Creek Study Area (CCSA) • 700-acre pparcel • Chemical manufacturing 1918 – end of WWII • Current use is lab and pilot scale facilities • Over 20 years of soil and groundwater investigations www.geosyntec.com Site Background CCSA Groundwater Impacts (Courtesy of WESTON Solutions) www.geosyntec.com Site Background Key Project Challenges • Large number of buildings on Site (317) •• UUnniiqquuee ccoonnttaammiinnaannttss uunnccoommmmoonn ffoorr VVII aasssseessssmmeennttss • Co-mingled contaminant plumes • Complex hydrogeology below large site • WWoorrkkiinngg ccoonnssttrruuccttiivveellyy ttoo mmeeeett nneeeeddss ooff UUSS AArrmmyy Federal, and State regulators www.geosyntec.com P2 Site Background Proposed VI Assessment Strategies • Initially Proposed Strategy • Collect indoor air sampples from all buildinggs • Geosyntec • PPrrooppoosseedd pphhaasseedd aapppprrooaacchh ffoorr VVII eevvaalluuaattiioonn • Conceptual Site Model (CSM) development • DDaattaa ccoolllleeccttiioonn ttoo rreeffiinnee CCSSMM • Follow-up sampling for sub-set of buildings • Evaluate mitiggation needs and opptions www.geosyntec.com Slide 6 P2 Just a comment. I think we need to highlight that we took advantage of the amount of historical knowledge gained from previous investigations and used this information to develop a phased approach. There was a lot of good data, it just needed to be complied together and understood from a VI perspective. PNicholson, 9/22/2010 COPC Identification • Develop list of COPCs based on: • Calculated screening levels were developed based on risk to building occupants • DDettecttiion ffrequency anallysiis • COPC screeningg results • 15 of 90 contaminants retained for groundwater • 46 of 160 contaminants retained for soil • COPCs include VOCs, SVOCs, PCBs, chemical warfare material (CWM) degradation products, and mercury www.geosyntec.com Conceptual Site Model Development •• SSoouurrcceess ooff CCoonnttaammiinnaattiioonn • Primary – Locations of Former Activities •• SSeeccoonnddaarryy –– DDoowwnnggrraaddiieenntt CCoommiinngglleedd PPlluummeess • Pathways • Geology • Hydrogeology • Receptors (Building) Characteristics • Buildings (Use, Occupancy, Foundation, HVAC) www.geosyntec.com Conceptual Site Model Development Historical  analytical  Sample Locations data  BBuuiillddiinngg RRDDMMPSS3 CCSSMM GGIISS SSttrraattiiggrraapphhyy Inspections Interviews Building Locations Historical Activities www.geosyntec.com