Soil Impacts Groundwater impacts Vapor Intrusion

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Steven P. Sittler, P.G. Patriot Engineering and Environmental Inc. 6150 E. 75th Street, Indianapolis, IN 46250

(574) 876-9835 ssittler@patrioteng.com

Soil Impacts

Groundwater impacts

Vapor Intrusion

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Identify preferential pathways –may need to sample

Perform paired sub-slab (SS)/indoor air (IA) sampling (or soil gas sampling in certain situations)

Samples to be collected winter (heating) & summer (cooling) seasons – “worst case”

SS samples to be collected 3 per 5,000 ft2 plus 1 for each additional 2,000 ft2

IA samples – minimum of 3, more for larger buildings

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IDEM Definition: Pathway extends through both a soil or GW source area AND a building

Investigations typically involve soil gas sampling of backfill surrounding utility corridors

A recent study in Indiana found that while 88% of identified preferential pathways were complete, only 8% resulted in subsequent IA issues!

“The relationship between the presence of elevated PCE/TCE concentrations in utility corridor backfill leading to an indoor air problem may be overstated”

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Sub-Slab Indoor Air

Soil Gas

How long should the sampling period be?

When should I sample?

Where should I sample?

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8-Hour Samples for Commercial/Industrial Sites

24-Hour Samples for Residential Sites

What about background chemicals?

What if someone tampers with the sampling device?

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Figure from Blayne Hartman presentation – Battelle 2016

8-Hour or 24-Hour Sampling may not give you an accurate representation of exposure!!!

Summa canisters

Passive samplers

Continuous samplers

Educate yourself on the benefits and

limitations of sampling options

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Additional Sampling

Positive Pressure HVAC System

Vapor Mitigation System

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Passive or active systems

PASSIVE

Sealing Vapor barriers (pre- and post-

construction) Passive venting

ACTIVE

Sub-slab depressurization systems Building overpressurization (HVAC)

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So what does that involve?

“Routine long term operation, maintenance & monitoring (OMM) of the vapor mitigation system will be necessary for as long as it is used to interrupt the VI pathway” – IDEM Vapor Remedy & Implementation Guidance document – February 2014

You are here

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Schedule 1

1. Perform activities specified in Section 3.3, generally on an annual basis.

2. Annual sampling of lAduring the winter worst case season during the first, second, and fifth year, and every fifth year thereafter.

Schedule 2

l. Perform activities specified in Section 3.3, generally on an annual basis.

2. Annual sampling of IA during the winterworst case season during t.ie first, second, and fourth year, and every other year thereafter.

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VAPOR MITIGATION IS A TREATMENT, NOT A CURE!!

=“It’s a Vicious Circle”

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Fully quantitative

Low detection levels

Short analysis time

Multiple locations

Low operating costs

Very stable

Real-time data

Summary from Blayne Hartman presentation – Battelle 2016

Identify fluctuations in target constituent concentrations

Pinpoint sub-slab source areas

Avoid unnecessary VI mitigation

Save $$$

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HOW MUCH FARTHER IS IT?”

MUST know source areas and distribution of impacts

MUST understand site biogeochemical conditions

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Focused Soil Excavation

Remedial Injections

ISCO - In-Situ Chemical Oxidation (ISCO)

Injection of aggressive chemicals to promote

oxidation of contaminants

Rapid remediation

Limitation: contact-based approach – injection

materials must physically contact contaminants

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ENHANCED BIO

Adding oxygen (aerobic) or electron

donors/bacteria (anaerobic) to

accelerate degradation

Not diffusion limited because bacteria move with groundwater flow

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Off-Site plume impacting unknown portion of Site

VI mitigation system installed during construction

8 buildings – most with little or no indoor air issues

Sub-slab ports installed in all buildings – sampled with VI systems off

Results – only 1 of 8 buildings will need continued VI mitigation &

long-term sampling

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Would operate indefinitely without

remediation of backfill, soil, &

groundwater impacts

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ISCO injection in backfill immediately below slab in source area

ERD injection in groundwater in source area and vicinity

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30 Sites

30 of 30 (100%) rec’d NFA

Average time to closure: 3 years

Average cost to closure: $70,000

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Vapor intrusion is a (perhaps THE) primary driver of environmental projects today

Current commonly-accepted VI sampling methodologies may give false or misleading results

Vapor intrusion does not always require vapor mitigation

Vapor mitigation is a treatment not a cure – and long-term stewardship applies!

Focused remediation can eliminate long-term stewardship requirements (and save $$$$).

Closures CAN BE ACHIEVED!!!