THE FOLLOWING PRE-FILED TESTIMONY ATTACHMENT WILL BE

Glenn Tofani, Geokinetics Inc.

---

77 Bunsen

Irvine, CA 92618

Tel 949.502.5353, Fax 949.502.5354

E-Mail: geokinetics@appliedgeokinetics.com

February 23, 2009

SUBJECT: COMMENTS IN RESPONSE TO PROPOSED AMENDMENTS TO

SECTION 742 OF THE STATE OF ILLINOIS’ TIERED APPROACH TO

CORRECTIVE OBJECTIVES (TACO) DOCUMENT, DATED 5-23-08

The purpose of this letter is to address proposed amendments to Section 742 of the State

of Illinois’ Tiered Approach to Corrective Objectives (TACO) Document, dated May 23,

2008. Specifically, this letter addresses Section 742.1210c of that document, which

recognizes building control technologies for the purpose of determining remediation

objectives that exceed residential remediation objectives. Under the sub-membrane

depressurization (SMD) systems section, a “cross-laminated polyethylene membrane liner

at least 0.15 mm (or 6 mil)” would be recognized as an adequate vapor barrier. This letter

addresses our concerns with respect to the use of this type and thickness of material for

vapor mitigation purposes.

GeoKinetics has extensive experience in the investigation and mitigation of subsurface

methane gas and organic vapors – both naturally occurring (as is typically the case for

methane) or associated with releases of gasoline, chlorinated solvents and other

hydrocarbon compounds. GeoKinetics has performed subsurface methane and/or soil

vapor investigations and interior air quality monitoring at many thousands of residential

and/or commercial properties. These investigations have involved both existing and

planned structures. Where regulated levels of methane or Volatile Organic Compounds

(VOC’s) have been identified, GeoKinetics has implemented appropriate mitigation

measures under regulatory oversight. These mitigation measures have included the

installation of sub-slab vapor barriers, the installation of passive and active subsurface

ventilation systems, and others. The undersigned have prepared plans and specifications

for methane and/or vapor mitigation systems for more than 10,000 buildings in the United

States over the last three decades. These buildings have included single family

residences, multi-family residences, school facilities, hospitals, apartment buildings, retail

centers, shopping malls, and commercial / industrial buildings. GeoKinetics has provided a

full range of services with respect to methane and VOC barriers – including permitting,

installation, and post-installation monitoring. GeoKinetics has developed smoke testing

procedures to confirm the integrity of membrane installations and manufactures the

equipment necessary for this type of testing. Smoke testing can help insure that tears,

perforations, pin-holes, and improperly sealed seams or penetrations are not present in the

membrane at the completion of the installation.

Electronic Filing - Received, Clerk's Office, February 24, 2009

---

Comments in Response to Proposed Amendments to Section 742 of

February 23, 2009

page 2

In addition to the design of methane and organic vapor barrier systems, GeoKinetics has

been extensively involved in the testing of these barriers for performance, reliability and

chemical compatibility. Along these lines, GeoKinetics has performed diffusion testing,

permeability testing, and strength testing for a number of membrane materials and

products. Many of the diffusion tests have extended for periods in excess of six months in

order to more thoroughly evaluate the long term performance and chemical compatibility of

the membranes. We have also performed post-construction monitoring and testing of sub-

slab membrane installations. This work has included the collection of air samples above

the membrane and below the floor slab, as well as on the interior of the protected building,

to monitor for contaminants. It has also included the coring of floor slabs at more than

1,000 buildings to collect membrane samples for inspection and testing. Many of the

membrane samples that were retrieved had been in place for ten years or more.

Several things have become apparent based upon our experience as set forth above. First

of all, no membrane is completely effective in so far as blocking the passage of

contaminants. All membranes “leak” to some degree. Secondly, there is significant

variability in the effectiveness of different types of vapor barrier materials – in other words,

some membranes leak much more than others. For example, the rate at which organic

vapors can pass through a 6-mil low density polyethylene membrane can be orders of

magnitude greater than for a more conventional 60-mil high density polyethylene

membrane. Third, damage in the form of penetrations and tears, along with improperly

sealed seams, can cause order of magnitude increases in the rate of vapor transmission

across a membrane. Relatively thin 6 to 10-mil membranes are much more prone to

construction damage than the standard 60-mil membranes that are typically used for VOC

vapor mitigation. Of the thousand+ structures with 6 and 10-mil vapor barriers that we

have performed post-construction testing on to date, we have yet to find a single

installation that did not have an unacceptably high rate of membrane holes / open

penetrations for a VOC barrier application. This is in contrast to standard 60-mil

membranes where holes / open penetrations are rare.

Based upon our experience and observations, we do not believe the use of a 6-mil cross

laminated polyethylene vapor barrier would be effective or appropriate for many

installations. As outlined above, there is a much greater potential for elevated rates of

vapor migration across such a membrane for many reasons. Our experience indicates a

typical 6-mil installation is not nearly as effective or reliable as a standard 60-mil barrier.

This is not to say there are no suitable applications for 6-mil vapor barriers. There are

many appropriate applications that need to be evaluated and identified on a site by site

basis. However the adoption of a standard that would allow for the universal use of a 6-mil

vapor barrier would be problematic and would likely result in excessive VOC vapor

transmission, along with potential exposure issues, and/or excessive water vapor

transmission and associated property damage in many instances.

Electronic Filing - Received, Clerk's Office, February 24, 2009

---

Electronic Filing - Received, Clerk's Office, February 24, 2009