09066_Sonoco Vapor Workplan Response 20070529

North Carolina Department of Environment and Natural Resources
Dexter R. Matthews, Director Division of Waste Management Michael F. Easley, Governor William G. Ross Jr., Secretary

1646 Mail Service Center, Raleigh, North Carolina 27699-1646
Phone [phone] \ FAX [phone] \ Internet http://wastenotnc.org
An Equal Opportunity / Affirmative Action Employer – Printed on Dual Purpose Recycled Paper
May 29, 2007
Sent Via E-mail and USPS

Mr. Carleton Riser
Hawkins Street Holdings, LLC
Care of Morgan Group
5606 south Rice Avenue
Houston, TX 77081

Subject: Vapor Intrusion Mitigation Plan
Sonoco Flexible Packaging Facility
2203 Hawkins Street
Charlotte, Mecklenburg County
Brownfields Project Number 09066-05-60

Dear Mr. Riser:

On April 25, 2007, the North Carolina Department of Environment and Natural
Resources (DENR) received the Risk Evaluation of Potential Indoor Air Exposure and Vapor
Intrusion Mitigation Plan dated March 30, 2007 prepared by MACTEC on behalf of Hawkins
Street Holdings, LLC for the above referenced property. The plan was submitted in accordance
with Notice of Brownfields Property Land Use Restriction Number 4. Upon review of the
material submitted, DENR finds the risk evaluation complete and agrees a passive vapor
mitigation plan is acceptable. However MACTEC recommends a passive barrier, this is
unacceptable for of the following reasons:

• Does not complete the elimination of vapors, therefore occupants may accidentally
penetrate the barrier as part of general building maintenance. Inadvertently creating a
pathway.
• Polyvinyl chloride membranes (even thick ones 10-20 mil) are likely to be damaged
during construction, particularly if place below concrete slabs, which is called for in the
submitted plan.
• No contingency was included in the plan to enhance the passive barrier if not adequate
after installation
• No testing procedure for efficacy of the passive barrier after the slab is in place such as
soil gas sampling or indoor air sampling once buildings are constructed, as well as
periodic groundwater monitoring.

Mr. Riser
May 29, 2007
Page 2 of 2

DENR recommends a passive venting system in combination with a passive barrier for because
of the following:

• Works well for new construction, which we have at this site.
• Passive barrier prevents the soil-gases from entering the building and the passive vents
allow the gases to be removed.
• System often applied when vapor intrusion is possible, but not occurred which is likely
based on the risk evaluation prepared by MACTEC.
• Relatively low costs of installing a passive venting system versus the cost of additional
sampling and long-term monitoring.
• Can be modified to active system if necessary

Construction details and requirements should be followed from the United States Environmental
Protection Agency Building Radon Out, A step by Step Guide on how to build radon resistance
homes dated April 2001.

If you have questions about this correspondence or require additional information, please feel
free to contact me by phone at 704/661-0330, or by e-mail at [e-mail].

Sincerely,

Carolyn Minnich
Carolyn Minnich
Brownfields Project Manager
Division of Waste Management

cc: Project File

ec: Bruce Nicholson, DENR
Robert Foster, MACTEC