progress and status report - pvi database€¦ · benze 1.e+01 n ‐10 0 1020 304050 60 distance...
TRANSCRIPT
PVI work Group Webinar - July 12, 2011
Progress and S tatus Report – PVI Progress Database
and Status Report PVI
I an H I Hers, GoG ld A i tlder Associates Robert Truesdale, RTI International
Prepared under subcontract to Skeo Solutions for U.S. EPA Office of Undergg round Storagg e Tanks
OBJECTIVES AND PURPOSE
Assemble database of petroleum release sites where pathway has been evaluated via soil gas and groundwater measurements.
Consolidate & independently check database efforts to date naA l yze ad t ase t o t ed t ermi ne wh d d h tA l d t t t d t i hen and under wha t
conditions there is potential for a complete PVI pathway (does not necessarily indicate unacceptable risk)
Develop data sets that could be used for model comparisons (e.g., BioVapor)
eveD op anl suppord me ot th d id t ti h t D l d t th ds and criteria that can be use db d to exclude (and include) petroleum releases sites from further PVI investigation and concern.
May 24, 2012 2
CONTEXT AND PROCESS
Robin’s fall 2010 (updates in 2011) database starting point (great body of starting work)point (great body of work)
Additional data from ME, MN, IL Independent checks conducted process to Independent checks conducted – process to
ensure completeness and “data of known qualityquality”
Add data and conduct additional analysis Review/add other work (e g Chevron database Review/add other work (e.g., Chevron database
of sites presented at AEHS conference San Diegg o March 2011,, upp dated Battelle 2011) )
May 24, 2012 3
ADDED SITE DATA ELEMENTS
Concentration data BTEX hexane heptane naphthalene concentrations in BTEX, hexane, heptane, naphthalene concentrations in
groundwater & soil vapor (limited number of sites) Aliphatic/Aromatic fractions, MTBE (ME sites only)p , ( y) TPH concentrations in soil Methane concentrations Field headspace PID concentrations
Analytical methods TPH il d d t (MADEP VPH APHTPH soil vapor and groundwater (MADEP VPH, APH
for ME sites) Fixed gases (field and Fixed lab)gases (field and lab)
May 24, 2012 4
ADDED SITE DATA ELEMENTS (cont.)
City Generic soil typyp e (( for site)),, US SCS soil classification,
simplified classification (fine, coarse, very coarse) ,
Contamination type (gasoline, diesel, BTX) Facility type (UST, terminal, refinery, petrochemical) Surface cover at soil vapor probe (building, pavement,
ground)ground) Distance from soil vapor probe to groundwater well Buildin g g pp ropp erties: use,, foundation typyp e,, size Flags to link soil vapor probes, wells, and buildings For some sites only limited data available or entered
May 24, 2012 5
SITES IN CURRENT DATABASE
Arizona: 1 (in-progress, not yet added to database) California: 7 California: 7 Maine: 10 (3 in progress) Minnesota: 22 (limited data for some sites) New Jersey: 3 Ohio: 4 ou S t aroh C l na: 1i S th C li 1 Utah: 4 Unknown US: 1 Unknown US: 1 Canada: 2 Australia: 1
May 24, 2012 6
ADDITIONAL SITES
Maine – groundwater, soil, soil gas, soil data for 13 UST sites Provided by Peter Eremita (ME DEP) Sites in Augusta, Berwick, Gorham, Leeds, Lewiston, Livermore
Falls, Milo, North Windham, Portland (2), Saco, Sanford, S. Portland Comprehensive data: O2, CO2p , CH4, PID;2, 2, 4, ; MADEP VPH and APH DEP’s EGAD database provides multiple, consistent formats Great documentation, with maps, aerial photos, boring logs, etc.
(over 100 files)(over 100 files) Return visits, two SG levels, at several sites
Minnesota – 22 sites; additional information requested D ta on possibl e i l Dat ibl inclusi it es ( H tf (e.g., Hartford ion sit d Illi i (l fi )Illinois (large refinery),
Chevron Ohio) not yet obtained
May 24, 2012 7
DATA ANALYSIS
Screening to separate NAPL vs. dissolved sites Benzene soil vapor concentration vs. vertical distance Benzene soil vapor concentration vs. vertical distance
above contamination source and conditional probability analysis
EE sttii matte thithi ckk ness cll ean soil il ff or bbenzene tto attttenuatte below threshold (Robin Davis analysis)
Oxygen vs hydrocarbon relationships Oxygen vs. hydrocarbon relationships Methane versus vertical distance relationships Preliminary analysis aliphatic/aromatic fraction data
May 24, 2012 8
SCREENING OVERVIEW
Hypothesis is behavior is different for LNAPL vs. dissolved pphase
Develop exclusion depth methods for both LNAPL vs. dissolved phase sites (they will likely be different)
AA nall yze dd attabb ase tto separatte ddii ssoll vedd vs. NAPLNAPL sitites using number of criteria; take into account whether there is NAPL or contamination above water table
Develop criteria for identifying NAPL vs. dissolved phase sites – this does not necessarily need to be the same as criteria used to screen sitescriteria used to screen sites
Develop inclusion criteria for special cases (just for NAPL sites?) )
May 24, 2012 9
NAPL vs. DISSOLVED SCREENING INDICATORS - SUMMARY
Primary Direct indicators of NAPL (sheen , p( , p roduct in well, dye
tests, visual evidence) , y
Report or author indicates vapor probe is in contamination or NAPL contamination source zoneor NAPL source zone
Inferred from proximity probe to facility (UST nest, dispensers ) (p ) within 20 feet)( )
Groundwater concentration indicators Secondary Soil concentration indicators Headspace concentrations
May 24, 2012 10
NAPL vs. DISSOLVED SCREENING INDICATORS (cont.)
Groundwater concentration indicators1
Groundwater benzene > 5 mg/L Groundwater TPH > 30 mg/L
Soil concentration indicators Soil benzene > 1 0 mg/kg2 Soil benzene > 10 mg/kg2
Soil TPH > 300-500 mg/kg Field headspace vapor concentration > 1,000 ppm In almost all cases, soil concentration indicators didn’t affect
screening (i.e., there were other factors that indicated NAPL) 1 For limited number of sites (Santa Clara and Jackson’s) where there is long dissolved
plume (several hundred feet ) and where no evidence for LNAPL (and also unlikely for LNAPL body to migrate this far), the above criteria was overridden (i.e., site was designated dissolved)
2. Based on Csat calculation and foc = 0.006
May 24, 2012 11
BENZENE SOLUBILITY CONSIDERATIONS
From pure-phase solubility, the calculated benzene concentration for a mole fraction of 0.01 would be 18mg/L concentration for a mole fraction of 0.01 would be 18
But given that mole fraction tends to be less than 0.01, weathering will occur, and non-equilibrium conditions expected, benzene groundwater at many sites with residual NAPL will be closer to 1 mg/L (g (CAL LUFTmanual)
May 24, 2012 12
NAPL vs. DISSOLVED SCREENING INDICATORS (cont.)
Possible Additional Line of Evidence Soil gas composition i e aliphatic aliphatic vs vs. aromatic Soil gas composition, i.e., aromatic
concentrations Dissolved would be expp ected to have higg her aromatic
to aliphatic ratio due to faster degradation of aliphatics, consequently the ratio in soil vapor may also be loweralso be lower.
Only limited data available to test this hypothesis (mainly ME sites)
May be a future line of evidence
May 24, 2012 13
DEPTH TO TOP OF CONTAMINATION
Soil gas probes NAPL
Top of LNAPL smear/soil contamination zone estimated from logs, PID results, historical maximum water table height
DISSOLVED Water table measured
approximately same time as soil gas
May 24, 2012 14
CLEAN SOIL THICKNESS CALCULATION FOR BENZENE ATTENUATION
For locations where the measured soil gas benzene concentration is less than < 100 ug/m 3 a clean soil concentration is less than < 100 ug/m3 , a clean soil thickness was calculated except when vertical distance between probes is greater than 10 ft. (in sufficient resolution to enable thickness to be calculated))
Distance to first probe with Cvapor < 100 ug/m3
(Method 1)(Method 1) Lower depth = Depth to top of contamination Upppp er depp th = Depp th to soil vapp or pp robe with
benzene concentration <= 100 ug/m3
May 24, 2012 15
CLEAN SOIL THICKNESS CALCULATION FOR BENZENE ATTENUATION
Interpolated Distance (Method 2) Where benzene Where benzene attenuates to low concentrationsattenuates to low concentrations
(less than 40 ug/m3), upper depth is interpolated (half-way) between depths to probes with benzene concentrations <= 40 ug/m3 and > 100 ug/m3 , subject to minimum thickness of 0.5 ft.
For locations where the measured soil gas benzene For locations where the measured soil gas benzene concentration does not attenuate to less than < 100
3
a miug/m
i ,
n mum thick ness ( greater than) i s calcul t d la clean soil thickness can not be calculated, but
i i thi k ( t th ) i l lated equal to distance between shallowest probe and top of contamination
May 24, 2012 16
PAULSBORO, NJ (Roggemans, 2002)
Building
Area 1AMethod 1: 19’-8 = 11’Method 2: 19 – (12+8)/2 = 9’
Site D19’-8 = >11’
0
Feet Below Grade Area 2
(Site D)
Area 1A
Method 2: 19 (12+8)/2 9
0
5519.6 % 19.1 %
24’
10340,000
38,000
Sand Soil
240,000
5 5
390,000
3.5 %
1.0 %
19.2 %
6.0 %
19.5 %
11.0 %
8’
12’19’
Benzene in GW 9,600 ug/L to
LNAPL
20
160,000500,000 630,0001.0 %6.0 % 6.1 %
16’
BENZENE – DISSOLVED SITES
1.E+04
3)
Benzene vs. Distance 32 sites 223 data points < DL replaced
1.E+02
1.E+03
Conc. (ug/m3
> DL
< DL
< DL replaced with DL
95th percentile = 85 ug/m3
1.E+01
zene Vazpor C
g
10000
100000
c (ug/L)
Dissolved Sites
1.E‐01
1.E+00
Benz
100
1000
undw
ater Con
c‐10 0 10 20 30 40Distance between soil vapor probe and contamination (ft.)
1
10
100
Benzen
e Grou
May 24, 2012 18
1
0% 20% 40% 60% 80% 100%
BENZENE – NAPL SITES - ALL
1.E+07
1.E+08
3)
Benzene vs. Distance 44 sites 545 data points
1.E+04
1.E+05
1.E+06
r Conc. (ug/m3
> DL
< DL
< DL replaced with DL
NAPL Sites
1.E+01
1.E+02
1.E+03
nzene Vazpor
10000
100000
onc ((ug
/L)
NAPL Sites
1.E‐01
1.E+00
‐10 0 10 20 30 40 50 60
Ben
Di b il b d i i (f )100
1000
ound
water Co
Distance between soil vapor probe and contamination (ft.)
1
10
Benzen
e Gro
May 24, 2012 190% 20% 40% 60% 80% 100%
BENZENE – NAPL SITES
1 E+07Benzene vs. Distance
1 E+08Benzene vs. Distance
UST, Refinery, Terminal UST Only
1.E+05
1.E+06
1.E+07
. (ug/m
3)
> DL
< DL1 E+05
1.E+06
1.E+07
1.E+08
. (ug/m
3)
> DL
< DL
1.E+02
1.E+03
1.E+04
ne Vazpor Conc.
1.E+02
1.E+03
1.E+04
1.E+05
ne Vazpor Conc.
1.E‐01
1.E+00
1.E+01
Benzen
1.E‐01
1.E+00
1.E+01
Benzen
‐10 0 10 20 30 40 50 60Distance between soil vapor probe and contamination (ft.)
‐10 0 10 20 30 40 50 60Distance between soil vapor probe and contamination (ft.)
May 24, 2012 20
CONDITIONAL PROBABILITIES
Evaluate probability for benzene vapor concentration to exceed threshold for for varying distances aboveexceed threshold varying distances above contamination
Add additional constraint related to source contamination or groundwater concentrations (simplest dissolved vs. NAPL)
P(Cv <=100 ug/m3/z > d, Cg (z=0) < Ccriteria)
Where z = distance to soil gg as pp robe,, d = sepp aration distance, in this case Ccriteria is NAPL vs. dissolved
May 24, 2012 21
BENZENE - CONDITIONAL PROBABILITIES
80
100
ug/m
3
Dissolved Sites
80
100
g/m
3 )
NAPL Sites
40
60
80
Cv <= 10
0 u
40
60
80
Cv <= 10
0 ug
0
20
Prob
ability
0
20
40
Prob
ability C
0 2 4 6Distance above Contamination (ft)
0 10 20
P
Distance above Contamination (ft)30
Possible benzene exclusion distances Dissolved sites ~ 5 ft. NAPL sites ~ 15-20 ft. (consistent with analysis by Matt Lahvis,
May 24, 2012 22
ShellShell, TTomom PearginPeargin, Chevron)Chevron)
4
30 NAPL Sites ‐Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (actual value ‐Method 1)
NAPL Sites ‐ Thickness Clean Soil Unattenuated benzene > 100 ug/m3
NAPL Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (interpolated value ‐Method 2)
Dissolved Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (actual value ‐Method 1)
Dissolved Sites ‐ Thickness Clean Soil Unattenuated benzene > 100 ug/m3
Dissolved Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (interpolated value ‐Method 2)
Dissolved Sites NAPL Sites 18
162525
14
12
1010
8
6
4Thiickness Clea
n Soil (ft)
Thhickness Cleann Soil (ft)
20
15
10
5 2
000 1 2 3 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 5 0 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 6 0 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 7 0 7 1 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 8 9 9 0 9 1 9 2 9 3 9 4 9 5 9 6 9 7 9 8 9 9 0 0 1 0 1 0 2 1 0 3 1 0 4 0 5
95th percentile Method 1 = 20 ft. 95th percentile Method 1 = 10 ft., Method 2 = 5.5 ft.
0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 5 0 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 6 0 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 7 0 7 1 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0 8 1 8 2 8 3 8 4 8 5 8 6 8 7
THICKNESS CLEAN SOIL BENZENE ATTENUATION < 100 ug/m3 (all data)
May 24, 2012 23
THICKNESS CLEAN SOIL BENZENE ATTENUATION < 100 ug/m3
25
30
n) (ft)
NAPL Sites ‐Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (actual value ‐ Method 1)
NAPL Sites ‐ Thickness Clean Soil Unattenuated benzene > 100 ug/m3
NAPL Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (interpolated value ‐Method 2)
Dissolved Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (actual value ‐ Method 1)
Dissolved Sites ‐ Thickness Clean Soil Unattenuated benzene > 100 ug/m3
20
contam
ination Dissolved Sites Thickness Clean Soil Unattenuated benzene > 100 ug/m3
Dissolved Sites ‐ Thickness Clean Soil Attenuate Benzene < 100 ug/m3 (interpolated value ‐Method 2)
Red – NAPL Green - Dissolved
Square – Actual to Solid symbol – No
15
il (fro
m top of
Triangle – Interpolated to < 100 ug/m3 (Method 2)
< 100 ug/m3 (Method 1)Solid symbol No attenuation to < 100 ug/m3
10
ess "Clean"
Soi
0
5
Thick
n
May 24, 2012 24
0
1 10 100 1000 10000 100000
Benzene Groundwater Concentration (ug/L)
Oxygen vs. Distance Oxygen vs. Distance 25 30
20 25
Oxygen Coo
nc. (%)
15
10
Oxygen Coo
nc. (%)
20
1515
10
5 5
0 0
‐10 0 10 20 30 40 ‐10 10 30 50 70
Distance between soil vapor probe & contamination (ft.) Distance between soil vapor probe & contamination (ft.)
Dissolved Sites NAPL Sites
OXYGEN
O2 trends follow expected behavior for dissolved & NAPL sites Dissolved sites: O2 > 1 % and typically > 5% NAPL NAPL sites: sites: OO2 depleted until until distance distance > 11 ft. 2 depleted 11 ft.
May 24, 2012 25
OXYGENDensity
Dissolved Sites NAPL Sites
1 E+07
1.E+08
1.E+09
)
O2 vs. TPH
1.E+07
1.E+08
)
O2 vs. TPH
LowerHigher
(Probability)
• leakage?• long screens
Lower
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
Vapor COnc. (ug/m
3
1.E+03
1.E+04
1.E+05
1.E+06
Vapor COnc. (ug/m
3 • long screens• in bio layer?
Lower
1.E+00
1.E+01
1.E+02
0 5 10 15 20 25 30
TPH V
O2 Conc. (%)
1.E+00
1.E+01
1.E+02
0 5 10 15 20 25
TPH V
O2 Conc. (%)
HigherLower
Higher
O ll f i l ( )
1 E+05
1.E+06
1.E+07
1.E+08
(ug/m3)
O2 vs. Benzene( )
1.E+03
1.E+04
(ug/m3)
O2 vs. Benzene Higher
Lower
Overall fairly poor
correlation
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
enzene
Vapor Con
c. (
1 E+00
1.E+01
1.E+02
enzene
Vapor Con
c. (
Lower HigherMay 24, 2012 26
1.E‐01
1.E+00
0 5 10 15 20 25 30
Be
Oxygen Conc. (%)
1.E‐01
1.E+00
0 5 10 15 20 25
Be
Oxygen Conc. (%)
Higher
METHANE
Dissolved Sites NAPL Sites
80Methane vs. Distance
100Methane vs. Distance
50
60
70
ne (%
)
60
70
80
90
ne (%
)
10
20
30
40
Methan
10
20
30
40
50
Metha
n
0
10
0 10 20 30 40Distance above Contamination (ft)
0
10
0 10 20 30 40 50 60Distance above Contamination (ft)
CH4 trends follow expected behavior for dissolved & NAPL sites CH4 > 5%: Alameda, Huntingdon, Cumberland Portland ME 1939 CH4 = 1 to 5%: Coachella
May 24, 2012 27
4
HEXANE
Dissolved Sites NAPL Sites
1.E+04Hexane vs. Distance
1.E+06Hexane vs. Distance
1.E+03
Conc. (u
g/m3)
1.E+04
1.E+05
Conc. (u
g/m3)
1.E+01
1.E+02
Hexan
e Vazpor C
1.E+01
1.E+02
1.E+03
Hexan
e Vazpor C
1.E+00
‐10 0 10 20 30
H
Distance between soil vapor probe and contamination (ft.)
1.E+00
‐10 0 10 20 30
HDistance between soil vapor probe and contamination (ft.)
Initial analysis suggests approximately similar trends to benzene Appears hexane would likely not be a risk driver, assuming hexane
RfC of 200 ug/m3 and approximately 100-fold dilutionMay 24, 2012 28
S
Lewiston, Maine EASTWEST 7-Eleven, 345 Main Street , EAST
Dec. 21, 2010 data (Maine DEP, March 2011)
7-Eleven Store
< 2 < 2 7850 < 20
< 2 14 2600 < 30
78000 < 580
0
Feet Below Grade
Residence 480/<2
SSV-02SSV-01
SV-105, adjacent to bldg north side & MW-3A
<2 0.032/0.048
0 26/0 6917.5/18.3
<2 0.028/0.18318.2/18.3 0 71/0 92
78000 580
10 <2
Residence
SV-107
480/<2
14.4/19 <2
0.035/35.4
0.026 19 2
Basement 11/163.115 2/17 4
3200/1300
0.26/0.69 0.71/0.92
20
<2
<2 SV 107
0.027 19.5
18.3 0.183
19.2
SSV-03
MW-3A
2600 15.2/17.4
Contaminated Soil
110000/-3097/-14.8/- Contaminated soil
d t i d Dissolved, ug/L: Benzene 8,790 TPH 27,200
MW-101
KEY Indoor air sample
Dissolved, ug/L: Benzene 14,400 TPH 91,700
78000 zone determined from PID (819 ppm @5’)
Feet horizontal
0 25
SV-107 Single- or Multi-Depth vapor sample
MTBE O2 % TPH-gro, mg/m3
1.24 17.4 11 1500 Benzene, ug/m3
SSV-03 Sub-Slab vapor sample
DISCUSSION
Developing exclusion and inclusion criteria – what is needed to developp and technicallyy defend? Initial criteria: Minimum X ft. clean soil between lowest part of building
and shallowest impacted site Dissolved contamination, as evidenced by:
No LNAPL in wells GW GW benzene benzene < X mg/L GW mg/L TPH < < X , GW TPH Y mg/L< Y mg/L Continuous soil cores over interval of interest indicating:
Absence of NAPL (sheens, staining, strong odours) Testing at 6 inch intervals; Headspace PID < X ppm, TPH
soil < Y ppm (no rapid change in PID concentrations), or Oxygen < X %
May 24, 2012 30
DISCUSSION
Implementation – How will exclusion criteria be adopted and impp lemented byy states in the field? Whatmeasurements will be needed? What are next steps at “included” sites?
‘Closing’ c urrent effort and maintaining database into the ‘Closing’ c rrent effort and maintaining database into the future.
Possible data gapg p s and additional analysisy Aliphatic and aromatic fractions (ME data) Ethanol sites and methane Comparisons to model predictions Inclusion sites
May 24, 2012 31
AK GUIDANCE
Sheens (*NAPL should be expected to be present as residual residual phase phase aat t any any locations locations with historic with NAPLhistoric occurrence); headspace vapors (PID head space
NAPL
readings of thousands of parts per million (ppm) at recent recent gasoline gasoline spill sites hundreds of ppm at recent spill sites, hundreds of ppm at recent diesel spill sites and old gasoline spill sites, and tens of ppm at old diesel spill sites are likely to indicate the presence of NAPL according to: http://www.dec.state.ak.us/spar/csp/guidance/hrc/HR C%20User%20Manual.pdf)?C%20User%20Manual.pdf )?
May 24, 2012 32
CA GUIDANCE
LUFT site is assumed to present no unacceptable risk from vapp or intrusion if the followingg site conditions are met:
1) For soil sources and low strength groundwater sources: 5 feet or more of clean soil between the bottom of the building and the shallowest impacted soil or impactedbuilding and the
‐
shallowest impacted soil or impacted groundwater.
2 ) ) For high‐strength groundwater sources: 10 feet or more of
g g g clean soil between the bottom of the building and the
shallowest impacted soil or impacted groundwater. 3) For measurable f ree prod ct on the ater table 30 feet 3) For meas rable free produ ct on the water table: 30 feet
or more of clean soil between the bottom of the building and the water table.
May 24, 2012 33
CA GUIDANCE (cont.)
A “low strength groundwater source” is defined as didi ssol
‐lvedd ‐phase bh
‐
b enzene groundwatd t er concentratit ons t < i <1,000 μg/L & dissolved phase TPH concentrations < 10,000 μg/L. A “high strength groundwater source” is defined as dissolved benzene concentrations >1,000 μg/L & dissolved‐phase TPH concentrations > 10,000 μμg/Lg/L.
In the unsaturated zone, clean soil is defined as TPH concentrations < 100 mg/kg PID readings < 10 ppm, or O2 >4%.
May 24, 2012 34
NJDEP Vapor Intrusion Guidance
30-foot distance criterion (both horizontal and vertical), for petroleum related ground water contamination based, in part, on 2004 PA VIG; 100-feet for petroleum LNAPL.
Allows assessment of biodegradation for petroleum hydrocarbons and depth to ground water. based based on subsurface O2 on subsurface O2 and depth to ground water.
Soil gas sampling (e.g., vertical profiling of volatiles, O2 and CO2) “usually more relevant” than ground water sampling for evaluating VI when GWSL are exceededVI when GWSL are exceeded.
Use of additional10x ground water to indoor air AF for PHCs assumes a minimum of 4% oxygen exists in the soil
Recommends collection of sub-slab soil gas samples in lieu of indoor air samples for PHCs.
May 24, 2012 35