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API Case Examples of the Evaluation of the EI VaporPathway Guidance

American Petroleum Institute

Vic Kremesec, Ph. D.Senior Technology Consultant

January 17, 2002

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Purpose

> To Demonstrate the methodology and reasoning that APImembers will possibly use applying the Draft Guidance.

> To point out areas where we believe the Draft Guidance> Requires revision, e.g.,§ Table 2 and 3 screening criteria do not provide adequate

differentiation of sites; and§ Language that elicits a reasonable site specific analysis;

> Potential consequences of no revision, e.g.,§ Manpower and cost increases.

> To suggest revisions that would make the Screening Criteriain the Guidance able to identify sites those with biodegradablehydrocarbon vapor problems

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Presentation Overview

> Focus is on Petroleum Hydrocarbons• Chlorinated Compounds are not considered.

> Three Cases will be presented:> Case 1: Immediate Response Required; Long

Term Monitoring Discussed?> Case 2: Indoor/Outdoor Air Sampling; Applicable

Targets and Table 2 Criteria?> Case 3: Soil Gas Measurements; Applicability of

Models and Figure 2 (Table 3) Criteria?

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Case 1: Immediate Response Required

> Situation:> Likely source an underground line leak> Depth to Water (Product) is 2-3 ft> Soil: sand and fill> Unit Control Room with a subfloor above area of LNAPL

> EI Guidance Questions/Answers> Q1. Volatile Chemicals?

> Yes: gasoline constituents> Q2. Inhabited Building Nearby?

> Yes: Unit Control Room> Q3. Immediate Action Warranted?

> Yes: Odors, Fuel Seeping in sub-floor

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Actions - Case 1: Immediate Response Required

> Completed Pathway> Immediate Actions:

> Groundwater depressed with a wellpoint system> Sub-floor sealed to eliminate seeping of product> Building air flow pattern altered to sweep subfloor and vent

to outside stack> Building Ventilation upgraded – air is refinery ambient air.> Groundwater depression ceased

> Q7. Monitoring> Insure building ventilation is operating> Check potential seepage> Spot checks with benzene air monitoring meter

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Case 2: Indoor/Outdoor Air Measurements

> Situation (Work planned 1990, conducted 1991):> Historical leaks in tank farm 150 ft east of property

line> Pumping system near property line, 40 ft from

buildings has drawn product into the trough at afew points at the property line

> Offsite inhabited buildings> Soil: medium sand> No soil impacts above water table> Situation occurs along 4 city blocks

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Case 2 Site Map

Biovent System

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Case 2: Indoor/Outdoor Air Measurements, continued.

EI Guidance Questions/Answers> Q1. Volatile Chemicals?

> Yes: BTEX> Q2. Inhabited Building Nearby?

> Yes: Inhabited buildings 30 ft west> Q3. Immediate Action Warranted?

> No: No Odors, No wet basements, No short term safetyconcerns.

> Q4. Exceed Generic Tables?> Possibly?: GW below buildings < 5 ppb benzene (Detection

Limit); LNAPL within 40 ft. of a few buildings.> Potentially conflicting screening criteria

> Q5. Exceed scenario specific criteria?> Possibly?: sandy soil with DTW 5-15ft.

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Case 2: Indoor/Outdoor Air Measurements, continued.

> Result: Yes, for the sake of further discussion: butCriteria are Overly Conservative> Biodegradation ignored> Indoor Benzene Target Values too conservative> 100x factor too conservative based on experience

with such low groundwater and soil concentrations.> Proceed to Q6. Site Specific Assessment

• Chose Indoor Air Monitoring because a 1991project (soil gas understanding limited) and wantedto address homeowners directly

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Case 2: Indoor/Outdoor Air Measurements, continued.

> Air Sampling> Benzene was the targeted constituent.> Questionnaire and investigation to identify construction,

ventilation, and indoor sources> 353 sampling visits in 262 homes in winter and spring of

1991 by hygienists> Additional re-sampling in summer and fall and when

requested by occupant> Elevated concentrations generally easily associated with

indoor sources.> Mitigation of some indoor air sources (gas leaks, removal of

stored materials, etc).> Outdoor air samples collected at 5 locations over same

time periods.> Additional sampling conducted in homes along property line

about 4 yr later.

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Case 2: Indoor/Outdoor Air Measurements, continued.

> Results> Risks associated with indoor air were essentially the same

as risks associated with outdoor air.> Applicable target level was ambient air.> Pathway Incomplete.

> Q7. Monitoring> Tests conducted over the course of a year and then a

resampling several years later indicate no increased risk.> Situation has improved - Pumping and venting have

recovered most of the product.> Thus, continued monitoring has not been performed.

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Case 2: Indoor/Outdoor Air Measurements, continued.

> In-building testing was not simple:> Multiple samples taken over a year some of which exhibited

occasional high values often linked to indoor sources.> Evaluation required cooperation of resident and a skilled

hygienist.> Community interaction was handled well but could become quite

contentious.> Point is that screening criteria would not have eliminated this site.> The evaluation for Question 6 is likely quite complicated requiring

significant resources (both regulatory and industry) and will slow theEI process.

> Better screening criteria for petroleum hydrocarbons could avoidthis.

> Commitment needed to perform a reasonable site specific analysis

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Case 3: Soil Gas Profile Measurements

> Situation> Historical leaks in refinery migrated offsite> Offsite inhabited buildings> Fuel constituents in GW> DTW about 20 ft> Soil – wind-blown,silty-sand 5-8 ft; sand and

alluvial sand with gravel below that.

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Case 3 Site Map With Benzene GW (ppb) And Soil Gas Concentration

<40 ppbvBenzenein Vapor

<200

790 ppb<1

<1

0.5 ppb is the Groundwater , and 40 ppbv is Soil Gas Screening Criteria in Table 2

~400 ft

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Case 3: Soil Gas Profile Measurements, continued

EI Guidance Questions/Answers> Q1. Volatile Chemicals?

> Yes: BTEX> Q2. Inhabited Building Nearby?

> Yes:> Q3. Immediate Action Warranted?

> No: No Odors, No wet basements, No short term safetyconcerns

> Q4. Exceed Generic Tables?> Yes: GW below occupied buildings exceeds 0.5 ppb

benzene.> Q5. Exceed scenario specific criteria?

> Yes: sandy soil, DTW ~15-20ft, but Figure 2 (Table 3)correction only increases GW to ~ 5.6 ppb.

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Case 3: Soil Gas Profile Measurements, continued

> Result: Yes, but Criteria are Overly Conservative> Depth and Soil Type do not increase Attenuation

Factor sufficiently above 100x factor.> Biodegradation ignored.

> Proceed to Q6. Site Specific Assessment - Chose Soil Gas Sampling

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Case 3: Soil Gas Profiles indicate that Benzene Attenuates By a factor of1000, Xylene by a Factor of 100, and Trimethylbenzene by a factor of 10.

These Attenuation Factors would be Multiplied bya Building Attenuation Factor of 1000

Profiles Obtained Near 790 ppb GW well

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-14

-12

-10

-8

-6

-4

-2

0

0.0001 0.001 0.01 0.1 1

Normalized Soil Gas Concentration

1,2,4 TrimethylBenzene

Benzene

Xylenes

1,2,4 TMB Predicted

Benzene Predicted

Xylenes Predicted

Predicted Soil Gas Profile Includesthe Attenuation Rate in the Model

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Case 3: Soil Gas Profile - Results

> Profiles over 2 sampling events indicate an incompletepathway

> No further vapor monitoring performed

> This was not a simple field test and analysis:> Multiple samples were taken which exhibited occasional

variability approaching ~10x.> Evaluation required a skilled individual who could interpret

the variability, fit a model, and write the report.

> Point is that Question 6 could likely become quite complicatedrequiring significant resources (both regulatory and industry)and slow the EI process.

> Better screening criteria for petroleum hydrocarbons couldavoid this.

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Draft Guidance Screening Criteria for FuelHydrocarbons are Overly Conservative.

> Criteria in Table 2 were calculated:> With a conservative model, that does not include

biodegradation, and generally does not agree with fieldexperience.

> Using overly conservative target concentrations for indoorair

> Using conservative model parameters,> For fuel hydrocarbons sites, the criteria in Tables 2 & 3 will not

differentiate between sites making Q4 and Q5 generallyIrrelevant.

> Most sites will go from Q3 to Q6 almost immediately.> Guidance biased toward detailed site specific analysis

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Imposed Burdens of Conservative Screening Criteria

> Screening criteria will likely require additionalgroundwater and/or soil gas delineation

> 100 ft distance will increase number of inhabitedbuildings to be evaluated.

> Site specific analysis to determine attenuation factorwill put a significant burden on the resources ofindustry for assessment, analysis, and reporting; andregulatory bodies for review.

> Unnecessary site specific analysis will slow the EIprocess.

> Overemphasis on additional offsite analysis couldunnecessarily alarm neighboring communities.

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Revision Needed For Biodegradable Species

> Language eliciting a reasonable site specific analysis for theevaluation in Questions 4 through 6.

> We need screening criteria which can differentiate which sitesactually require more site specific analysis.

> Whether these are the criteria:> Proposed by Connor et. al. (2001), or> New ones calculated with realistic values and a quantitative

model.> WORK IS NEEDED

> Application of the 100 ft extended distance criteria needs to bebetter explained

> Guidance on potential conflicts between multiple screeningcriteria is needed.