vapor intrusion risk pathway regulatory updates & practical field lessons
DESCRIPTION
Technical FieldTRANSCRIPT
Vapor Intrusion Risk Pathway:
Regulatory Updates &
Practical Field Lessons
BlayneHartman Ph.D.
858-204-6170
February 2012
CA-CUPA
EPA Guidance Updates (Release Date: 6/2014)
• EPA (OSWER & Superfund) - Anticipated
– Preference for sub-slab & indoor air
– 7 to 30 day indoor air sampling period
– Fixed Att factor of 0.03 for SG & 0.001 for GW
– Sub-slab Att factor 0.03
– Modeling no longer an exit
http://www.epa.gov/oswer/vaporintrusion
No Public Comment on Draft!!
EPA Guidance Updates (Release Date: 6/2014)
• EPA-OUST: Guidance for HCs
– Exclusion criteria? Yes
– Testing/Adoption of Biovapor model? In theory
– Frequently Asked Questions - done
– Summary of State Guidances - done
http://www.epa.gov/oust/cat/pvi/index.htm
No Public Comment on Draft!!
New TCE Standard
(As of October 2011)
• Residential (1e-6)
– Indoor Air cancer: 0.43 ug/m3 (down from 1.2 ug/m3)
– Indoor Air non-cancer: 2.1 ug/m3
– Groundwater: 1.1 ug/L
• Commercial/Industrial (1e-6)
– Indoor Air: 3.0 ug/m3 (down from 6.1 ug/m3)
– Indoor Air non-cancer: 8.8 ug/m3
– Groundwater: 7.4 ug/L
EPA R9 & DTSC Have Adopted
OEHHA Has Not Adopted C/I
New PCE Standard
(As of March 2012)
• Residential (1e-6)
– Indoor Air cancer: 9.4 ug/m3 (up from 0.41 ~22x !!)
– Indoor Air non-cancer: ~47 ug/m3
• Industrial (1e-6)
– Indoor Air: ~47 ug/m3 (up 22x)
– Indoor Air non-cancer: 8.8 ug/m3
EPA R9 Has Adopted
DTSC & OEHHA Have Not Adopted Either!
ITRC PVI GUIDANCE (Due out early 2014)
1. Introduction
2. Types of PVI Sites
3. Conceptual Site Model
4. Basic Investigative Framework for PVI Sites
5. Site Screening and Prioritization
6. Investigative Toolbox
CA Agencies
• CA-DTSC
– New VI Guidance (10/2011) & Soil Gas Advisory (4/2012)
– Recently adopted RAGS Part F
• EPA Region 9
– Adopted Region 3 Screening Levels for TCE & PCE
• SF-RWQCB
– ESLs updated January 2013
• OEHHA
– Still using out-dated CHHSLs (pre RAGS Part F)
• SWQCB
– Low Threat Closure Policy – Summer 2012
DTSC VI Guidance Changes
• Preference for Sub-slab Samples for Cl-VOCs
• Collect Exterior SG Samples At Source
• Repeated Sampling of Soil Gas
• Raising Sub-slab AF to 0.05 (5x stricter)
• Can now measure permeability, diffusivity and radon for attenuation factor
• Changes in Toxicity of Some Compounds
Defers to LUFT Manual for Petroleum HCs (p.38)
Soil Gas Allowed Levels
PCE in Soil Gas, Residential Receptor
RBSL (ug/m3)
DTSC Sub-slab 8.2
EPA Sub-slab (new) 300
CHHSL 180
DTSC – 5’ soil gas 205
EPA R9 – 5’ soil gas now 4,700
EPA R9 – 5’ soil gas new 300
DTSC Soil Gas Advisory Changes
• Sampling
– Purge volumes: include dry bentonite
– Equilibration times: 2 hours for tubes, ? for probes
– Leak check specifications: report at VOC RL
• Analysis
– Methods 8021, 8260, TO-14, TO-15, TO-17 ok
– Naphthalene preferred by TO-17
– Syringes & tedlar bags ok to use (in lieu of canisters)
Low Threat Closure Policy VI Scenarios
LNAPL: 30’ Dissolved: 5’ or 10’
Dissolved with O2 12
Low-Threat Closure Policy
• If 30’ of Biozone, NAPL screens out
– Vertically & horizontally
• If 10’ of Biozone, benzene up to 1000 ug/L
• If 5’ of Biozone, benzene up to 100 ug/L
Bioattenuation zone: TPH-soil < 100 mg/kg
Site Screens Out from VI Pathway if:
Note: O2 not Required
Low-Threat Closure Policy
The Power of Oxygen
• Separation distance drops from 10’ to 5’ for
benzene up to 1000 ug/L
• Soil gas SLs increase by 1000x!
TPH-soil required for all scenarios but O2 not
If oxygen in soil gas >4%:
Allowable Benzene in GW 1e-6 risk, Residential Scenario
• DTSC VI Guidance:
0.084 ug/m3 / 0.002 = 0.42 ug/L / 0.2 = 0.21 ug/L
• New EPA OSWER Guidance:
0.31 ug/m3/0.001 = 0.31 ug/L/0.2 = 1.5 ug/L
~3000 times lower than EPA-OUST Value!!
~5000x lower than Low Threat Value of 1000 ug/L ____________________________________________________
Soil Gas Allowed Levels
Benzene in Soil Gas, Residential Receptor, 1-6 Risk
RBSL (ug/m3)
DTSC Sub-slab 1.6
CHHSL 37
DTSC – Step 5 42
CA Low-Risk Policy: O2<4% 85
CA Low-Risk Policy: O2>4% 85,000
Ambient levels: 1 to 10 ug/m3
Low-Threat Policy:
A VI Pathway Game Changer
• Active Service Stations Excluded
• Sampling
– Soil phase TPH needed from two depths
– O2 in soil gas
• Soil Gas Analysis
– Needed at all?
– Benzene, ethylbenzene & naphthalene only
– No longer worry about TPH??
VI Assessments Much Simpler & Less Expensive
Methods to Assess VI
• Indoor Air Sampling
• Groundwater Sampling
• Soil Phase Sampling
• Predictive Modeling
• Measure Flux Directly
• Soil Gas Sampling
• Supplemental Tools/Data
Ingredients for Effective
VI Assessments
• Investigatory Approach
• Determine Correct Screening Levels
• Sample & Analyze Properly
• Know & Use Supplemental Tools
• Demonstrating Bioattenuation
The Most Important Ingredient
• Experience:
– Consultant
– Collector – done soil gas before?
– Lab – certified for methods?
– Regulator
– Public
– YOU!
What level person is going in the field?
Most Common VI Bloopers
• Unit Confusion
– Assuming ug/L equivalent to ppbv
– Assuming ug/m3 equivalent to ppbv
• Screening Levels
– Comparing to generic screening levels
– Not calculating correct levels
• Sampling & Analysis Errors
– Program design: soil gas? GW? SS? IA?
– Using wrong hardware
– Using wrong analysis
O2=7.5%
Probe Considerations
• Tubing Type – Rigid wall tubing ok (nylon, teflon, SS)
– Flexible tubing not (tygon, hardware store)
• Probe Tip – Beware metal tips (may have cutting oils)
• Materials Used to Bury Probes – Sand, cement
• Equipment Blanks – Need to collect blank through collection system
Some Lessons Learned
•Do not mark sample locations with spray paint: toluene
•Watch what you use to seal holes
Loaded with TCE
Loaded with TBA
Deconning or Contaminating?
Better Be Sure to Triple Wash!
Benzene =1530 ug/m3
Soil Gas Sampling Issues • Sample Size
– Greater the volume, greater the uncertainty
– Smaller volumes faster & easier to collect
• Containers – Canisters: More blank potential. Higher cost
– Tedlars: Good for ~2 days. Easier to collect
• Flow Rate & Purge Volume – Really not imp. But most agencies < 200 ml/min
• Tracer/Leak Compound
– Crucial for sub-slab & larger sample volumes
– Gases (He, SF6, Propane) & Liquids (IPA)
Leak Testing
Gases
Tent Shroud
Liquids
Vacuum Test
Canisters vs Tubes
SVOC Sampling
Typical
Simpler
Beware of the Hardware
TO-17 for Soil Gas Samples
Advantages:
• Fast & Easy to Sample. No pumps, swageloks, chokes
• Disposable - No Chance of Carry-over/False Positives
• Easy/cheaper to Handle & Ship
• 2 Tubes per Sample Ensures Meeting RSLs
Why use one of these?
On-site TO-14 (8021)
• Small Footprint GC (Flies free on SW)
• Fast Start-up (~45 min)
• 5 minute run time for TCE & PCE
• Can get to <1 ug/m3 for TCE, CCl4, PCE
• But Also Can Measure High (>10,000 ug/m3)
• Cost ~ 1/4 of TO-15 ($50/sample)
• Can Go Into Automated Monitoring Mode
On-site GC: TO-14 Modified (ECD)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
7/26/2011 9/14/2011 11/3/2011 12/23/2011 2/11/2012 4/1/2012
Vap
or
Co
nce
ntr
atio
n (
ug/
m3
)
Date & Time
PCE Field GC Indoor Air Data - 422
1st 422 Basement 422
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
11/28/11 0:00 12/8/11 0:00 12/18/11 0:00 12/28/11 0:00 1/7/12 0:00 1/17/12 0:00 1/27/12 0:00 2/6/12 0:00
Vap
or
Co
nce
ntr
atio
n (
ug/
m3
)
Date & Time
PCE Field GC Subsurface Air Data
SSP-2 WP-3 SGP9-6 SGP8-9 SGP2-9 SSP-4 A on A off B on
B/C off D on D off E on E off F on F off G on G off
0
50
100
150
200
250
300
11/23/2011 12/3/2011 12/13/2011 12/23/2011 1/2/2012 1/12/2012 1/22/2012 2/1/2012 2/11/2012 2/21/2012
Vap
or
Co
nce
ntr
atio
n (
ug/
m3
)
Date & Time
PCE & CHCl3 - SGP9-6
PCE CHCl3
Probe A3 (TCE - Normalized)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
13:5
0:09
10:5
0:26
7:50
:44
4:51
:04
1:51
:43
22:5
3:46
5:43
:29
2:43
:47
23:4
4:04
20:4
4:22
17:4
4:39
14:4
4:57
11:4
5:15
8:45
:32
16:0
2:01
13:0
2:18
10:0
2:36
7:02
:55
4:03
:12
1:43
:56
22:4
4:15
7:06
:41
4:06
:59
1:07
:19
22:0
7:58
19:1
1:25
Time (3/16/07 to 4/10/07)
Nor
mal
ized
Con
cent
ratio
n
Probe A3-3' (Port 9)
Probe A3-8' (Port 10)
Probe A3-17' (Port 5)
Soil Gas Temporal Study
Previews of the VI Future
• VI Likely to be a Concern at Your Sites
• Variable Regulatory Guidance Makes
Assessment Tricky & Slow
• New EPA OSWER Guidance to be Stricter
• ASTM Standard Increase # of Sites
• Hydrocarbons to be Less of a Concern
Forthcoming VI Events
• AEHS Conf – San Diego: March 18, 2013
– CALUFT & Low Threat Policy Workshop (Mon)
– EPA OSWER & OUST all Day Workshop (Tues)
– Petroleum VI Workshop (Tues night)
– All Day Session/Presentations on VI
