Patrick Sutton
    E2600 VES - Critical Distances for Vapor Migration
    Topic posted April 29, 2011 by Patrick SuttonSuper Contributor , last edited January 19, 2012
    1009 Views, 8 Comments
    E2600 VES - Critical Distances for Vapor Migration

    E2600-10 VES guidance recommends using a critical distance of 30 feet and 100 feet for petroleum and chlorinated vapor migrations, respectively, from the edge of groundwater or soil plumes.  Does anyone know where and how these numbers were established?

    I think I found the 100 foot reference in a USEPA/OSWER 2002 document called "Draft Guidance for Evaluating Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils."  This document says the the 100-foot vapor migration distance, irrespective of petroleum versus chlorinated plumes, is a conservative distance based on empirical data from Coloroda sites where vapor intrusion pathways have been evaluated.  I'm guessing chlorinated plumes were the driving factor for establishing that 100-foot distance, but the document doesn't appear to elaborate.

    My next question is if there is a published report for the Colorado study referenced in the 2002 USEPA document?

    I have no idea where the 30 foot distance came from for petroleum plumes, any ideas?

    And does anyone use local vapor migration studies instead of the E2600 guidance?



    • Paul Chasco

      Tony Bounicore did a talk on this issue at the 2011 Due Dilligence at Dawn.

      The short version is the distances are based on the 90% length of plumes. 

      90% of petroleum plumes are 390 feet or less and vapors can travel in a sand/gravel soil up to 100 feet.  390+100=480 feet.  1/10 mile is 528 feet.

      90% of non-petroleum plumes are 1590 feet in length or less.  1590+100=1690.  1/3 mile is 1760 feet.

      The critical distances come from instances when only the dissolved phase of contaminants exist.

    • Patrick Sutton

      Thanks Paul,

      I think they actually took the median length for non-petroleum plumes and the 90% length for petroleum plumes.  The median length of non-petroleum plumes in the SF Bay Area is also about 1600 feet, but the 90% plume length is about 1.2 miles. 

      The question I'm really inerested in is how the 30' and 100 ' vapor migration distances were determined?  Is there a report reference or was this just an internal study performed by the ASTM committee that has not been published?   


    • abuonicore


      The critical distances in the E 2600 standard were based upon Task Group member experience in the field working on many of the major vapor intrusion sites in the U.S. and their published works. In addition, the Task Group was able to rely on the experience of a number of participating organizations, inlcuding EPA, the American Petroleum Institute and the Halogenated Solvents Institute. EPA, for example, had used the 100 ft distance for non-petroleum hydrocarbons, e.g., chlorinated solvents, in its draft 2002 vapor intrusion guidance. I would also refer you to Phil Lowell's and Bart Eklund's publication, VOC Emission Fluxes as a Function of Lateral Distance from the Source, in AIChE's Environmental Progress, Vol. 23, No.1, published in April 2004; Robin Davis's publication, Vapor Attenuation in the Subsurface from Petroleum Hydrocarbon Sources, in LustLine Bulletin  52, May 2006; Tom Hugh's recent excellent summary, Evaluation of Vapor Attenuation at Petroleum Hydrocarbon Sites: Considerations for Site Screening and Investigation, published in the International Journal of Soil and Sediment Contamination, Vol. 19, No. 10, July/August 2010; the extensive modeling work by Lilian Abreu and Paul Johnson, including their 2005 publication in Environmental Science and Technology (Vol. 39, No. 12), Effect of Vapor Source - Building Separation and Building Construction on Soil Vapor Intrusion as Studies with a Three Dimensional Numerical Model; and much more.

      The area of concern in E 2600 was established based upon 90th percentile plume lengths from statistical evaluation of thousands of both chlorinated plumes and petroleum plumes across the country. Additional information may be found in "A Smaller Intrusion: Reducing the AOC on the ASTM Vapor Intrusion Standard," published in the May 2009 issue of Pollution Engineering.



    • Patrick Sutton

      Tony, thanks for all the references, this is just what I was looking for.

    • Bill Wagner

      IDEM's new Remediation Closure Guide reported that "Data indicate that 95% of BTEX groundwater plumes will terminate within 750 feet of their origin, regardless of the physical properties of the subsurface or the nature of the release." (Mace et al., Extent, Mass, and Duration of Hydrocarbon Plumes from Leaking Petroleum Storage Tank Sites in Texas (1997); Newell et al., A Hydrogeologic Database for Groundwater Modeling (1990); Rice et al., California Leaking Underground Fuel Tank (LUFT) Historical Case Analysis (1995); Widenmeier et al., Natural Attenuation of Fuel Hydrocarbons and Chlorinated Solvents in the Subsurface (1999).  Additionally, "Regardless of the size of a petroleum (BTEX) release or hydrogeological conditions, benzene will stabilize to 10 ppb within 750 of the release point.”  (Newell and Connor, 1998).  "Conversely, groundwater plumes of persistent chemicals (e.g., tetrachloroethene) can extend for long distances - sometimes more than a mile." 

      I’ve also heard that U.S. EPA is considering whether to extend the 100 foot distance to 300 feet for VOC plumes.  Anyone know the status of this?

      • jessedphillips

        Does the 750 foot designation assume that the source has been removed? 

        Regardless of the physical properties of the subsurface or the nature of the release?  What about 5 feet of free product at the origin in karst topography where there are direct conduits? 

    • Bill Wagner

      Sorry Jessie, I just repoted what IDEM stated.  I agree that karst topography has its challenges. 

      Mace assumes the release is continuous and presumably not yet removed.  See p. 4


    • Patrick Sutton

      Anthony, how come the ASTM task group didn't make their evaluation of 90% plumes lengths for petroleum and non-petroleum groundwater plumes available?  I'm asking because I'm particularly curious how the 90% chlorinated groundwater plume length of 1,590 feet was evaluated? 

      I'd be even more curious to see the results of a study that looks at the 90% plume length from dry cleaning facilities versus other facilities.  If there is a significant difference, that would be really useful to know when assessing potential plume migration.  I've read two other studies (one based on empirical data in the SF Bay Area and one from nationally collected data) that found 90% chlorinated groundwater plume lengths of 6,300 feet and 2,600 feet, respectively.  The range of 90% plume lengths appears to be significant.  It would be helpful to have more information from ASTM regarding their study so that we can make a better determination of appropriate search distances when conducting due diligence.