This document discusses conducting a vapor encroachment condition (VEC) investigation for a Phase I environmental site assessment using the newly revised ASTM E2600 standard. It provides an overview of vapor intrusion vs. vapor encroachment and why vapor migration should be considered in Phase I assessments. It then details how to conduct a Tier 1 VEC screen, including defining the area of concern, identifying known contamination sources, and making a VEC and VEC-to-REC determination using professional judgment. The document emphasizes using the screening to identify whether a vapor-related recognized environmental condition exists requiring further investigation.

1. CONDUCTING THE VEC
INVESTIGATION FOR A PHASE I
USING THE NEWLY REVISED
ASTM E2600 STANDARD
By: Anthony J. Buonicore, P.E., BCEE, QEP
CEO, The Buonicore Group
Chairman, ASTM Vapor Intrusion Task Group

2. OVERVIEW
▸Background
▹Vapor intrusion vs. vapor encroachment
▹Why the concern?
▹Phase I and Vapor Migration
▸Conducting a VEC Screen
▸Making VEC-to-REC Determinations
▸Conclusions

3. WHAT IS VAPOR INTRUSION?

4. WHAT IS VAPOR ENCROACHMENT?
▸ Vapors released into the vadose zone of the TP from on-
site and/or off-site contamination
▸ Off-site vapors must migrate across the boundary of the
TP and “encroach upon” the vadose zone
▸ An example off-site source may be a nearby dry cleaner
or gas station
▸ Vapor encroachment does not necessarily result in a
vapor intrusion condition
▸ For a vapor intrusion condition to exist, vapors must not
only be “encroaching” on the TP, but be able to migrate
into structures on the TP and cause an indoor air quality
problem

5. WHY SHOULD PROSPECTIVE PROPERTY
OWNERS BE CONCERNED?
▸ Avoid potential future vapor migration/intrusion
investigation costs after a property is acquired
▸ Eliminate concern about “closed” sites being re-opened
(e.g., NY, MA, ME, CA, etc.)
▸ Eliminate anything that can potentially justify a tenant
breaking a lease
▸ Avoid potential property stigma
▸ Avoid potential future liability, including toxic tort
litigation, arising from tenant suits or other third party
suits

6. ASTM E 1527 PHASE I STANDARD
▸ ASTM E1527-13 clarified that vapor migration is to be
considered in Phase I investigations no differently than
contaminated groundwater migration
▸ CERCLA/AAI do not differentiate by form (e.g., solid, liquid,
vapor) of the release to the environment
▹ EPA in its December 30, 2013 AAI Amendment to the Rule
re-confirmed that the 2005 AAI Rule includes consideration
of vapor migration
▸ Migrate/migration defined in E1527 to include vapor in the
subsurface
▸ ASTM E2600 is a referenced document in E1527

7. CONDUCTING A TIER 1
VEC SCREEN

8. “Presence or likely presence of COC vapors in the
subsurface of the TP caused by the release of vapors
from contaminated soil or groundwater either on or near
the TP”
VAPOR ENCROACHMENT CONDITION (VEC)
▸ Vapors must penetrate (“encroach upon”) TP
boundary
▸ Vapors from on-site contamination have already
penetrated TP subsurface (vadose zone)

9. CRITICAL DISTANCE
▸ Represents lineal distance COC vapors volatilized
from contaminated groundwater or contaminated
soil might migrate in the vadose zone
▸ The distance is measured between the nearest
edge of the contaminated plume (soil or
groundwater) and the nearest TP boundary
▸ 100’ for COC Sources and Petroleum Hydrocarbon
LNAPL sources
▸ 30’ for dissolved Petroleum Hydrocarbon sources

10. AREA OF CONCERN (AOC)
▸ Consists of the target property and the
surrounding area, within which, if sources of
volatile contamination are present, such
contamination may produce vapors that can
encroach upon the TP
▸ Measured from TP boundary to known or
suspect contaminated property that is the
source of volatile vapors (e.g., nearby dry
cleaner)
▸ Default AOC vs. Adjusted AOC

11. DEFAULT AOC
▸ 1/3rd mile (1,760 ft.) for known or suspect
contaminated sites with COCs (volatile/semi-volatile
hazardous substances)
▸ 1/10th mile (528 ft.) for known or suspect
contaminated sites with Petroleum Hydrocarbon
COCs
▸ Measured from TP boundary to known or suspect
contaminated property

12. DETERMINING THE DEFAULT AOC
TP
Contaminated
Plume
Length (?)
Vapor Migration Zone (100 ft)
Groundwater flow
direction
Up-Gradient Source of Contamination

13. DETERMINING THE DEFAULT AOC

14. DETERMINING THE DEFAULT AOC

15. ADJUSTED AOC
▸Default AOC may be adjusted based upon
the EP’s professional judgment and
experience with respect to local area
conditions.

16. COMMON WAYS TO ADJUST THE AOC
▸Use knowledge of groundwater flow direction
▸Use local knowledge of subsurface characteristics such
as:
▹ the presence of relatively impermeable soil or soil
layers, such as wet, fine-grained or highly organic soils
– clay, silty-clay soils that retard vapor migration
▹ the presence of a perched water table (clean water
above contaminated groundwater) – can reduce VI
potential
▹ a very deep water table – can reduce groundwater
contamination potential and therefore vapor
migration
▹ fractured bedrock can increase VI potential

17. COMMON WAYS TO ADJUST THE AOC
▸Use knowledge of surface natural features such as:
▹major water tributaries (rivers, etc.) that can intercept
migrating vapors
▹wetlands that can impede vapor migration
▸Use knowledge of man-made features such as:
▹utility corridors under major roadways that can intercept
migrating vapors and lead them away from TP (or toward TP)
▹nearby buildings with characteristics that can impede vapor
flow such as a building with well-ventilated multi-story
underground parking below the building

18. COMMON WAYS TO ADJUST THE AOC
▸Use knowledge of the type target property or planned
development, and the local environment
▹on a relative basis, vapor migration represents a greater
concern for residential property (e.g., multifamily) than for
industrial, office, hotel and retail property
▹may want to be especially conservative in establishing
the AOC for residential property

19. EXAMPLE:
ADJUSTING THE AOC WHEN
GROUNDWATER FLOW DIRECTION
IS KNOWN OR CAN BE INFERRED

20. ADJUSTING THE AOC WHEN GROUNDWATER FLOW
DIRECTION IS KNOWN OR CAN BE INFERRED

21. ADJUSTING THE AOC WHEN GROUNDWATER FLOW
DIRECTION IS KNOWN OR CAN BE INFERRED

22. ADJUSTING THE AOC WHEN GROUNDWATER FLOW
DIRECTION IS KNOWN OR CAN BE INFERRED

23. ADJUSTING THE AOC WHEN GROUNDWATER FLOW
DIRECTION IS KNOWN OR CAN BE INFERRED
Up-gradient
▸1,760 ft. (1/3rd
mile) for COC
sources
▸528 ft. (1/10th mile)
for Petroleum
Hydrocarbon
Sources
Down-gradient
▸100’ COC
Sources/Petroleum
Hydrocarbon LNAPL
sources
▸30’ Dissolved
Petroleum
Hydrocarbon
Sources
Cross-gradient
▸100’ COC
Sources/Petroleum
Hydrocarbon LNAPL
sources plus Plume
Width Consideration
▸30’ Dissolved
Petroleum
Hydrocarbon Sources
plus Plume Width
Consideration

24. ACCOUNTING FOR PLUME WIDTH FOR A CROSS-
GRADIENT SOURCE UNDER A CONSERVATIVE
SCENARIO WITH NO ACTUAL PLUME DATA*
▸ Assume worst case location for cross-gradient COC source, i.e., point
of maximum plume width
▸ Assume plume width (Pw) can be estimated as 1/3rd of the 90th
percentile plume length (Pl90)(supported by Domenico’s and Gelhar’s
et. al. work; Newell et. Station LUST data; actual dry cleaner plume
data and actual SHWS plume data)
* Buonicore, A.J., “Methodologyfor Identifying the Area of Concern Around aProperty Potentially
Impacted by Vapor Migration from Nearby Contaminated Sources,” Paper #2011-A-301, Proc. AWMA
104th Annual Conference, Orlando, FL, June 20-24, 2011

25. ADJUSTED AOC FOR TIER 1 SCREENING
OF KNOWN OR SUSPECT COC SOURCES
Source Location
Up-gradient
Down-gradient
Cross-gradient
E 2600-15
1,760’
1,760’
1,760’
E 2600-15 w/ Suggested
Methodology
1,760’
100’
365’

26. ADJUSTED AOC FOR TIER 1 SCREENING
OF KNOWN OR SUSPECT PHC SOURCES
Source Location
Up-gradient
Down-gradient
Cross-gradient
E 2600-15
528’
528’
528’
E 2600-15 w/ Suggested
Methodology
528’
100’ (LNAPL)
30’ (Dissolved)
165’ (LNAPL)
95’ (Dissolved)

27. TIER 1 SCREENING FOR VECs
▸ Tier 1 designed as a screening tool to preferentially be
used in conjunction with a Phase I – relies on all the
information already collected in Phase I investigation
▸ Tier 1 involves three steps:
1. Starting with the Default AOC, determine if AOC can be
adjusted
2. Identify known or suspected sources (e.g., dry cleaner) of
volatile vapors (“chemicals of concern” or “COCs”) within
established AOC

28. Identify Known or Suspected Sources of COC
Contamination: Phase I Government Records
▸ Check the following databases for known or suspected
sources of COC contamination (TP and Established AOC)
▸ NPL
▸ CERCLIS
▸ CORRACTS
▸ Non-CORRACTS TSD
▸ State Hazardous Waste Sites
▸ Voluntary Cleanup Sites
▸ Brownfield Sites
▸ Landfills
▸ LUST

29. PHASE I GOVERNMENT RECORDS cont’d
▸ Check the following TP records for
potential COC releases or COC
contamination (on TP)
▸ Hazardous waste generation/storage
▸ Registered above- and below-ground storage
tanks
▸ Reported spills
▸ Mitigated on-site contamination managed by
Institutional/Engineering Controls (AULs)

30. IDENTIFY KNOWN OR SUSPECTED SOURCES OF
COC CONTAMINATION: HISTORICAL RESEARCH
▸ Check for high liability former property
uses on TP or in the established AOC
with known or suspected COC
contamination (such as dry cleaners, gas
stations, manufactured gas plant sites,
industrial sites, etc.)

31. MOST PREVALENT SOURCES OF CONCERN
▸ Present and former gas station sites
▸ Present and former dry cleaner sites
▸ Present and former industrial sites,
particularly those using chlorinated
solvents for degreasing and parts cleaning
▸ Former manufactured gas plant sites
▸ Former hazardous waste disposal sites
▸ Present and former garbage landfills

32. TIER 1 SCREENING FOR VECs cont’d
3) Make a VEC determination:
- VEC exists, or
- VEC does not exist
▸ When used in conjunction with a Phase I, if a VEC exists, EP
to determine if VEC represents a REC
▸ If a VEC exists, user may also ask EP what further
investigation, if any, is warranted (such as proceeding to
E2600-15 Tier 2 in order to obtain greater certainty about
the VEC)
▸ If VEC does not exist, the investigation is ended (VI
assumed to be a moot issue)

33. SUGGESTED APPROACH TO
VEC SCREENING IN A PHASE I ESA

34. CONDUCTING A TIER 1 VEC SCREEN
(ASSUMING NO PREFERENTIAL PATHWAYS)
1. Identify AOC and minimize to the maximum extent
possible based on experience
a. Start out with 1/3rd mile – 1/10th mile – Default
AOC
b. Reduce Default AOC when GW flow direction
known or can be inferred (Adjusted AOC)

35. ▸ Use professional judgment to reduce the AOC further
▸ Hydraulic barriers (rivers, wetlands)
▸ Sub-surface man-made physical barriers (preventing
vapors from reaching TP)
▸ Utility lines in main roads (intercept vapors)
▸ Low permeability soil in the sub-surface (impede
vapor movement)
▸ Confining layers in the subsurface (low permeability
soil layer, fresh water lens – impede vapor movement)
CONDUCTING A TIER 1 VEC SCREEN
(ASSUMING NO PREFERENTIAL PATHWAYS)

36. CONDUCTING A TIER 1 VEC SCREEN
2. Are there any known or suspect COC contaminated
sites in the established AOC?
a. Government records
b. Historical research
c. Other (?)
3. Evaluate any COC site(s) remaining in the
established AOC
a. Remediation status?
b. Did remediation consider vapor pathway?
c. Review AULs – contamination left on-site?
d. Other (?)

37. CONDUCTING A TIER 1 VEC SCREEN
4. Identify VEC status
a. Exists
b. Does not exist
5. If VEC does not exist, vapor migration evaluation
completed

38. 6. If VEC exists, determine if VEC is a REC
a. Rely on ASTM “De minimis” Criteria
b. Rely on State VI Guidance Criteria
c. Other (e.g., Federal VI Guidance, etc.)
7. If VEC is a REC, Tier 2 in E2600 offers a suggested
scope-of-work for follow-up vapor investigation in a
Phase II
CONDUCTING A TIER 1 VEC SCREEN

39. PROFESSIONAL JUDGMENT FOR
VEC-REC DETERMINATIONS

40. VEC-REC DETERMINATION: MAJOR CONSIDERATIONS
▸ State VI Guidance
▸ Typically identifies a distance between the nearest edge of
the contaminated groundwater plume and the nearest
structure on the property – where VI may be a concern
▸ If distance not specified in State VI guidance, it is typical to
rely on EPA VI Guidance (June 2015, p. 67, 100 ft.) or the
ITRC Guidance (Jan. 2007, p.16, 100 ft.) or other (refer to
E2600-15, Appendix 5)
▸ E1527 de minimus criteria (conditions that do not present
material risk of harm to public health and the environment,
and would not be subject to enforcement action by regulatory
agency are not RECs)

41. ▸ NJDEP VI Guidance – distance horizontally or vertically
between the nearest edge of the contaminated
groundwater plume and the nearest structure on the TP,
equal to:
▸ 100’ for COC or LNAPL PHC-COC
▸ 30’ for Dissolved PHC-COC
FOR EXAMPLE…

42. FOR EXAMPLE…
▸ PADEP VI Guidance – distance horizontally or vertically
between the nearest edge of the contaminated soil or
groundwater plume and the nearest structure on the TP:
- Contaminated GW: 100’ horizontally
30’ uncontaminated sand
vertically above GW
15’ uncontaminated other soil
vertically above GW
- Contaminated Soil: 100’ horizontally
10’ uncontaminated sand/soil
vertically between contaminated
soil and building

43. REC EVALUATION
▸ VEC may exist using E2600-15 Tier 1 criteria because
of groundwater contamination on or near the target
property (TP), but a REC may not exist (under the
ASTM de minimus condition clause) because the
distance between the structure and the nearest edge of
the contaminated plume may be greater than the
distance specified in VI guidance document

44. KEY DISTANCES…
▸ Building location on property (proximity to contaminated
plume with volatile vapors)
▸ Distance from nearest building edge facing contamination source to
property line
▸ Distance from property line to volatile vapor contamination source
▸ No building on property, e.g., raw land or property not yet
developed
▸ Distance from property line to volatile vapor contamination source

45. Assume State VI Guidance has actionable distance at 100’
Distance Downgradient Dry Cleaner’s Nearest Plume
Edge to TP Boundary: 75’
Does VEC exist (use ASTM 100’ Criteria)? Yes
Distance TP Boundary to Nearest Bldg: 80’
Distance Nearest Plume Edge to Nearest Bldg: 155’
Does a REC exist (use State VI 100’ criteria)? No
EXAMPLE

46. JUST A NOTE…
IL EPA added Indoor Inhalation Exposure Route to
Tiered Approach to Corrective Action Objectives (TACO)
in 2013:
▸ TACO focuses on an existing subsurface source of volatile
chemicals on the property that have potential to migrate from
soil and groundwater to indoor air (inhalation pathway)
▸ No “actionable/nonactionable” distance criteria specified
▸ Tier 1 evaluation in TACO begins with “contaminants detected
at the site” – TACO effectively comes into play AFTER Phase I/Phase
II which identify that contaminants exist on the property

47. ▸ What is the contaminant concentration?
For example, VEC may exist because of groundwater
contamination on the TP or near the TP, but a REC may not
exist (under the ASTM de minimus condition clause)
because the contaminant concentration is below the risk
screening level (RSL) in the State VI Guidance
OTHER CONSIDERATIONS

48. ▸ What is the depth to contaminated groundwater?
For example, VEC may exist because of groundwater
contamination on the TP or near the TP, but a REC may
not exist (under the ASTM de minimus condition
clause) because the depth to contaminated
groundwater at the property may be greater than the
applicable critical distance (100’ or 30’) or distances in
the State VI Guidance.
OTHER CONSIDERATIONS

49. WHY IT MAKES SENSE TO USE E2600 TIER 1 AS THE PREFERRED
METHODOLOGY TO EVALUATE VAPOR MIGRATION IN A PHASE I…
▸ E2600 methodology has been standardized through the
ASTM consensus process
▸ Methodology was developed by industry experts
▸ E2600 distances can be used without documentation (other
than referencing the E2600 standard)
▸ If an EP decides to use another methodology, E1527
requires sufficient documentation be included in the Phase
I to permit reconstruction by a third party
▸ E2600 allows for professional judgment and experience (to
adjust the AOC)
▸ Relying on E2600 reduces EP liability

50. THE BOTTOM LINE…
▸ Vapor migration evaluation is a required part of a Phase I
investigation (no different than evaluation of contaminated
groundwater migration)
▸ The only question for the EP is how to evaluate vapor
migration
▸ E 2600-15 Tier 1 provides an industry consensus screening
methodology
▸ EP can accept a Default AOC or modify the AOC (Adjusted AOC)
consistent with professional judgment and experience
▸ Tier 1 is a cost effective screening methodology for use in a
Phase I investigation

51. QUESTIONS?