10047 Atherton_C Units 75-80 Addendum 20150217

 
Correspondence:
Amec Foster Wheeler Environment & Infrastructure, Inc.
1308 Patton Avenue
Asheville, North Carolina 28806
Tel [phone]
NC Engineering License No. F-1253

February 17, 2015

Ms. Carolyn Minnich, Brownfields Project Manager
North Carolina Department of Environment and Natural Resources
Division of Waste Management
Brownfields Program
1646 Mail Service Center
Raleigh, North Carolina 27699-1646

Subject: Addendum to Vapor Mitigation System Construction Package
Atherton Mill Property – Corridor 100 North of Unit 80
2000 South Boulevard
Charlotte, Mecklenburg County, North Carolina
Brownfields Project Number: 10047-06-60
Amec Foster Wheeler Project: 6228-12-0051

Dear Ms. Minnich:

On behalf of Atherton Mill (E&A), LLC (Owner), Amec Foster Wheeler is pleased to provide this
Addendum to the Vapor Mitigation System Construction Package for Units 75 and 80, dated
February 9, 2015, for the Atherton Mill property in Charlotte, North Carolina. This addendum
includes vapor mitigation system information for Corridor 100 which is located adjacent to
the north of Unit 80. This addendum provides information on the installation of a Geo-Seal
vapor mitigation system in Corridor 100, similar to the system proposed for Units 75 and 80.

Figure 1: Location of Corridor 100

Concurrent with the removal and disposal of the existing wood block flooring and concrete slab
within Units 75 and 80, the wood block flooring and concrete slab in Corridor 100 will be
Addendum to Vapor Mitigation Construction Package February 17, 2015
Atherton Mill – Corridor 100 North of Unit 80
Amec Foster Wheeler Project: 6228-12-0051

2 

removed. After flooring and slab removal, the subgrade will be leveled to design elevation and
an approximate four-inch thick layer of wash stone will be placed in the area.

A Land Science Technologies™ Geo-Seal Vapor Intrusion Barrier® and Vapor-Vent™ vapor
collection system will be installed by a Geo-Seal certified contractor on top of and within the
wash stone layer. Above the Geo-Seal vapor mitigation system a new four-inch thick
concrete floor slab will be constructed, and in accordance with Charlotte-Mecklenburg Historic
Landmarks Commission requirements, new replacement wood block flooring will be installed in
the corridor. A cross-section detail of the wall between Unit 80 and Corridor 100, showing the
proposed systems on both sides of the wall and the replacement wood block flooring in the
corridor, is provided below.

Figure 2: Detail through wall between Unit 80 (Tenant Space) and Corridor 100

Addendum to Vapor Mitigation Construction Package February 17, 2015
Atherton Mill – Corridor 100 North of Unit 80
Amec Foster Wheeler Project: 6228-12-0051

3 

A cross-section detail of the wall between Corridor 100 and Unit 85 is provided below.

Figure 3: Detail through wall between Corridor 100 and Unit 85 (Tenant Space)

Termination details and procedures for installation of the Geo-Seal vapor mitigation system in
Corridor 100 will be as described and shown in the Vapor Mitigation System Construction
Package for Units 75 and 80.

A Vapor-Vent™ collection system will be installed in Corridor 100, and will connect to a riser pipe
that will be extended through the roof of the structure. At this time, installation of in-line fans is
not proposed; however, the discharge vent ends will be equipped with an AV-3-PVC Aura
ventilator cap that will draw a vacuum on the system when the wind blows (similar to Unit 75
and 80 discharge vent ends). The discharge vent will be located at the high point of the roof, on
the opposite side of the masonry parapet wall from the Unit 75 and 80 discharge vents. A layout
of the vapor vent collection system for Corridor 100 is provided on the next page.

Addendum to Vapor Mitigation Construction Package February 17, 2015
Atherton Mill – Corridor 100 North of Unit 80
Amec Foster Wheeler Project: 6228-12-0051

4 

Figure 4: Vapor-Vent™ Layout in Corridor 100

Amec Foster Wheeler will perform oversight of the system installation, as well as perform
quality assurance testing of the system in accordance with the manufacturer’s requirements.