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