19008 Residence Gateway Vapor Barrier Design 20150708

S&ME, Inc. / 9751 Southern Pine Blvd. / Charlotte, NC 28273 / p 704.523.4726 / f 704.525.3953 /
www.smeinc.com

July 8, 2015

Dominion Realty Partners
101 N. 5th Street, Suite B-1
Richmond, Virginia 23219

Attention: Mr. Michael M. Campbell via email: [e-mail]
Principal

Reference: Vapor Intrusion Barrier Design and Specifications
Proposed Residences at Gateway Village
West Trade Street & North Sycamore Street
Charlotte, Mecklenburg County, North Carolina
S&ME Project No. 4335-14-267, Phase 04
NCDENR Brownfields Project Number: 19008-15-060

Dear Mr. Campbell:

S&ME, Inc. (S&ME) is pleased to provide you with the attached Vapor Intrusion Barrier Design
for the above referenced site. The attached document and drawings were conducted in
accordance with S&ME’s proposal no. 43-1500426 dated, April 27, 2015 and authorized on April
28, 2015.

These documents were prepared to address the concerns as stated in a March 17, 2015, Draft
Decision Memorandum (Memorandum) by Ms. Carolyn Minnich of the North Carolina
Department of Environment and Natural Resources (NCDENR), Division of Waste Management,
Brownfields Section (Brownfields). Ms. Minnich stated in the Memorandum that due to site
groundwater concentrations exceeding the residential vapor intrusion screening level, either
assessment of soil vapors would be necessary in an attempt to possibly eliminate vapor risk, or a
vapor mitigation would be necessary for site redevelopment. After receipt and review of the
Memorandum, Dominion elected to proceed with vapor mitigation. The attached design is for the
mitigation of potential vapors during site construction.

S&ME appreciates the opportunity to provide this design for the Brownfields project. Please feel
free to contact us if you have any questions regarding the information contained in this document.

Sincerely,
S&ME, Inc.
Roger A. Smith, L.G. Thomas Raymond, P.E.
Senior Geologist/Project Manager Senior Environmental Engineer

Attachments: Vapor Intrusion Barrier Design
Cc: Ms. Carolyn Minnich, NCDENR Brownfields (via email)
Vapor Intrusion Barrier Design S&ME Project 4335-14-267
Gateway Apartments, West Trade St., Charlotte, NC July 2015
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VAPOR INTRUSION BARRIER DESIGN
Gateway Apartments
West Trade Street
Charlotte, North Carolina
S&ME Project 4335-14-267

1 GENERAL

The vapor intrusion barrier system is to be installed on the soil subgrade and over the
gravel base and under the concrete slab. The system consists of a gas-venting system
installed within the gravel base, a geotextile base layer, a spray applied vapor intrusion
membrane layer and geotextile protective layer.

1.1 Materials

A. GeoVent® Gas Venting System by Cetco® , or demonstrated equal, having
the following specifications:

Footnotes
1 – High Density Polyethylene

GAS-VENTING SYSTEM CORE PROPERTIES TEST METHOD RESULTS
Material N/A HDPE1
Comprehensive Strength ASTM D-1621 9,500 lbs / ft2
Thickness ASTM D-1777 1.0”
Flow Rate (Hydraulic gradient = 0.1) ASTM D-4716 30 gpm / ft of width

FABRIC PROPERTIES TEST METHOD RESULTS
Mass per Unit Area ASTM D-5261 4.0 oz. per yd2
Grab Tensile Strength ASTM D-4632 115 lbs.
Puncture Strength ASTM D-4833 65 lbs.
Apparent Opening Size (AOS) ASTM D-4751 70 US Sieve
Permeability ASTM D-4491 21 cm/sec
Fabric Flow Rate ASTM D-4491 170 gpm / ft2
UV Resistance ASTM D-4355 70%

DIMENSIONAL DATA
Standard Widths 12”
Roll Length 165 ft
Roll Weight 65 lbs

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B. BaseFabric ® base layer by Cetco® , or demonstrated equal, having the
following specifications:

C. Liquid Boot ® membrane layer by Cetco® , or demonstrated equal, having
the following specifications:

Fluid applied gas vapor intrusion barrier system – a single course, high build,
polymer modified, asphalt emulsion. Waterborne and spray applied at ambient
temperatures. A minimal thickness of 60 dry mils. Non-toxic and odorless.

BASE LAYER PROPERTIES TEST METHOD RESULTS
Grab Tensile Strength ASTM D-4632 240 lbs.
Elongation ASTM D-4632 60%
Trapezoid Tear ASTM D-4533 90 lbs.
Mullen Burst ASTM D-3786 2,100 psi
UV Stability ASTM D-4355 70%
AOS ASTM D-4751 140 US Sieve
Permittivity ASTM D-4491 1 second-1
Permeability Coefficient ASTM D-4491 0.1 cm/sec
Vertical Water Flow Rate ASTM D-4491 15 gpm/ft2
Puncture ASTM D-4833 70 lbs.

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D. UltraShield ® G-1000 protective layer by Cetco® ,or demonstrated equal,
having the following specifications:

Polypropylene, staple fiber, non-woven geotextile. Needle-punched fibers.

PROTECTIVE LAYER PROPERTIES TEST METHOD RESULTS
Tensile Bond Strength to Concrete ASTM C 297-94 7 psi
Mass/Unit Area ASTM D 5261 10 oz/yd2
Thickness ASTM D 5199 105 mils
Tensile Strength ASTM D 4632 270 lbs
Elongation ASTM D 4632 50%
Mullen Burst ASTM D 3786 520 psi
Puncture Strength ASTM D 4833 180 lbs.
Trapezoid Tear ASTM D 4533 105 lbs.
UV Resistance ASTM D 4355 70%
A.O.S ASTM D 4751 100 U.S. Sieve
Permittivity ASTM D 4491 1.2 sec-1
Permeability ASTM D 4491 0.30 cm/sec
Water Flow Rate ASTM D 4491 85 gal/min/ft2

1.2 Delivery Storage and Handling

Deliver materials to site in original unbroken packages bearing manufacturers
label showing brand, weight, volume, and batch number. Store materials at
site in strict compliance with manufacturer’s instructions. Do not allow
materials to freeze in containers.

1.3 Submittals

A. Submit product data for each type of vapor intrusion barrier, including
manufacturer’s printed instructions for evaluating and preparing the substrate,
technical data, and tested physical and performance properties.
B. Project Data - Submit shop drawings showing extent of vapor intrusion
barrier, including details for overlaps, flashing, penetrations, and other
termination conditions.
C. Samples – Submit representative samples of the following for approval:
1. Gas-venting core;
2. Gas-venting geotextile fabric;
3. Base layer;
4. Vapor barrier membrane layer;
5. Protective layer.
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D. Certified Installer Certificates – Submit certificates signed by manufacturer
certifying that installers comply with requirements under the “Quality
Assurance” article.

1.4 Project Conditions

A. Protect all adjacent areas not to receive vapor barrier. Where necessary, apply
masking to prevent staining of surfaces to remain exposed wherever
membrane abuts to other finish surfaces.
B. Perform work only when existing and forecasted weather conditions are
within manufacturer’s recommendations for material and product used.
C. Minimum clearance of required for application of product: 90° spray wand- 2
feet / Conventional spray wand- 4 feet.
D. Ambient temperature shall be within manufacturer’s specifications. If winter
conditions apply, we recommend the use space of heaters and
necessary cover (i.e. polyethylene sheeting) to bring the ambient temperature
to at least +45°F until the protection course and structural slab rebar or a
mudslab protection course has been placed.
E. All plumbing, electrical, mechanical and structural items to be under or
passing through the gas vapor barrier shall be positively secured in their
proper positions and appropriately protected prior to membrane application.
F. Gas vapor barrier shall be installed before placement of reinforcing steel.
When not possible, all exposed reinforcing steel shall be masked by
General Contractor prior to membrane application.
G. Expansion joints must be filled with a conventional waterproof expansion
joint material.
H. Surface preparation shall be per manufacturer’s specification.

2. EXECUTION

2.1 EXAMINATION
All surfaces to receive gas vapor barrier shall be inspected and approved by the applicator
at least one day prior to commencing work.

2.2 SURFACE PREPARATION
Provide 24 inch minimum clearance out from surfaces to receive the gas vapor barrier.
The application surface shall be prepared and provided to the applicator in accordance
with manufacturer’s specifications listed below:

A. Concrete/Shotcrete/Masonry
Concrete surfaces shall be light broom finish or smoother, free of any dirt,
debris, loose material, release agents or curing compounds. Fill all voids more
than 1/4 inch deep and 1/4 inch wide. Masonry joints, cold joints, and form
joints shall be struck smooth. All penetrations shall be prepared in accordance
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with manufacturer’s specifications. Provide a 3/4 inch minimum cant of
Liquid Boot®, or other suitable material as approved by manufacturer, at all
horizontal to vertical transitions and other inside corners of 120° or less.
Allow to cure overnight before the application of Liquid Boot®. All cracks or
cold joints greater than 1/16 inch must be completely grouted with non-shrink
grout as approved by engineer. Install hardcast reinforcing tape over all cold
joints, cracks and form tie holes (after holes and cracks are grouted).

B. Dirt & Gravel
The sub-grade shall be moisture conditioned and compacted to a minimum
relative compaction of 90 percent or as specified by the
civil/structural/geotechnical engineer. The finished surface shall be smooth,
uniform, and free of debris and standing water. Remove all stones or dirt clods
greater than 1/4 inch. (NOTE: Aggregate sub-bases shall be rolled flat, free
from any protruding sharp edges). Penetrations shall be prepared in
accordance with manufacturer’s specifications. All form stakes that penetrate
the membrane shall be of rebar which shall be bent over and left in the slab.
Trenches shall be cut oversize to accommodate gas vapor barrier membrane
and protection course with perpendicular to sloped sides and maximum
obtainable compaction. Adjoining grade shall be finish graded and compacted.
Excavated walls shall be vertical or sloped back, free of roots and protruding
rocks. Specific sub-grade preparation shall be designed by a qualified civil or
geotechnical engineer. If organic materials with potential for growth (i.e.:
seeds or grasses) exist within the sub-base, spray apply soil sterilant at the
sterilant manufacturer's recommended rate.

3. VAPOR INTRUSION BARRIER SYSTEM INSTALLATION

3.1 INSTALLATION ON CONCRETE/SHOTCRETE/MASONRY
(Follow the procedures below carefully)

A. Refer to section 3.3, "Sealing Around Penetrations", for procedures to seal the
vapor intrusion barrier around penetrations.

B. Provide a ¾” minimum bead of Liquid Boot® material, or other suitable
material as approved by engineer, at all horizontal to vertical transitions and
other inside corners of 120° or less. Allow to cure overnight before the
application of Liquid Boot membrane®.

C. Delineate a test area on site with a minimum dimension of 10 feet by 10 feet
(3m by 3m). Apply Liquid Boot® to a thickness of 60 mils and let it cure for 24
hours. Observe for blisters. If minor or no blistering occurs, proceed to the next
step. (See note regarding blisters). If significant blistering does occur, apply a
thin (10 mil) tack coat of Liquid Boot® “A” side without catalyst to the entire
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concrete surface and allow curing before proceeding. (See also information
regarding blister repair).

D. Spray-apply Liquid Boot® to a 60 mil minimum dry thickness. Increase
thickness to 100 dry mils if shotcrete is to be applied directly to membrane. If a
second coat is required, remove any standing water from the membrane before
proceeding with the second application.

E. Do not penetrate membrane. Keep membrane free of dirt and debris and traffic
until a protective cover is in place. It is the responsibility of the General
Contractor to insure that the membrane and the protection system are not
penetrated.

F. After membrane has cured and checked for proper thickness and flaws, install
protection material pursuant to manufacturer’s instructions.

NOTE: All testing or inspection to be performed prior to placing protection
course. NON-HORIZONTAL SURFACES: Spray on non-horizontal surfaces
should begin at the bottom and work towards the top. This method allows
the product to adhere to the surface before hitting catalyst runoff.

NOTE: Due to the nature of concrete as a substrate, it is normal for some
blistering to occur. This is caused by either concrete's tendency to off-gas or
water that is temporarily trapped between the concrete and the membrane. With
time and the applied pressure of backfill or over-slab, blisters will absorb into
the concrete without detriment to the membrane. A small number of blister
heads should be sampled and checked for proper membrane thickness. If the
samples have the minimum required membrane thickness, then the remaining
blisters should not be punctured or cut. If the samples have less than the
minimum required membrane thickness, then the area can either be re-sprayed
to obtain the proper thickness, or the blisters can be cut out and the area
resprayed or patched with Liquid Boot® Trowel Grade.

3.2 INSTALLATION ON DIRT SURFACES AND MUDSLABS

A. Roll out BaseFabric® T-60 geotextile on sub-grade with the heat-rolled side
facing up. Overlap seams a minimum of 6 inches. Lay geotextile tight at all
inside corners. Apply a thin 10 mil tack coat of Liquid Boot® “A” side without
catalyst within the seam overlap. Line trenches with geotextile extending at
least six inches (6") onto adjoining sub-grade if slab and footings are to be
sprayed separately.

B. Minimize the use of nails to secure the geotextile to the dirt subgrade. Remove
all nails before spraying membrane, if possible. Nails that cannot be removed
from the dirt subgrade are to be patched with geotextile or hardcast reinforcing
tape overlapping the nail head by a minimum of two inches (2"). Apply a thin
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tack coat of Liquid Boot® under the geotextile patch, when patching with
geotextile.

C. Refer to section 3.3, "Sealing Around Penetrations", for procedures to seal
around penetrations.

D. Spray-apply Liquid Boot® onto geotextile to a 60 mil minimum dry thickness.
Increase thickness to 100 dry mils if shotcrete is to be applied directly to
membrane. If a second coat is required, remove any standing water from the
membrane before proceeding with the second application.

E. Do not penetrate membrane. Keep membrane free of dirt, debris and traffic until
a protective cover is in place. It is the responsibility of the General Contractor to
insure that the membrane and the protection system are not penetrated.

F. After membrane has cured and checked for proper thickness and flaws, install
protection material pursuant to manufacturer’s instructions.

NOTE: All testing or inspection to be performed prior to placing protection course.

3.3 SEALING AROUND PENETRATIONS

3.3.1 OPTION 1

A. Clean all penetrations. All metal penetrations shall be sanded clean with emery
cloth.

B. Lay BaseFabric® layer on sub-grade with the heat-rolled side facing up,
overlapping seams a minimum of six inches (6"). Cut the geotextile around
penetrations so that it lays flat on the sub-grade. Lay BaseFabric® tight at all
inside corners. Apply a thin (10 mil) tack coat of Liquid Boot® “A” side
without catalyst within the seam overlap. BaseFabric® should extend up
penetration no more than 1”. Wrap penetration with polypropylene cable tie at a
point two inches (2") above the base of the penetration to hold the BaseFabric®
layer in place.

C. Spray apply Liquid Boot® to an 60 mils minimum dry thickness around the
penetration, completely encapsulating the collar assembly and to a height of one
and one half inches (1 1/2") minimum above the BaseFabric® as described in
3.3.1 B above. Spray-apply Liquid Boot® to surrounding areas as specified for
the particular application. (SEE MANUFACTURER’S STANDARD DETAIL)

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3.4 FIELD QUALITY CONTROL

Field Quality Control is a very important part of all Liquid Boot® applications.
Applicators should check their own work for coverage, thickness, and all
around good workmanship before calling for inspections. The membrane must
be cured at least overnight before inspecting for dry-thickness, holes, shadow
shrinkage, and any other membrane damage. If water testing is to be performed,
allow the membrane to cure at least 72 hours prior to the water test. When
thickness or integrity is in question the membrane should be tested in the proper
manner as described below.

3.4.1 ON CONCRETE/SHOTCRETE/MASONRY & OTHER HARD
SURFACES

A. Membrane shall be checked for proper thickness with a blunt-nose depth gauge,
taking one reading every 500 square feet. Record the readings. Mark the test
area for repair, if necessary.

B. If necessary, test areas shall be patched over with Liquid Boot® to a 60 mils
minimum dry thickness, extending a minimum of one inch (1") beyond the test
perimeter.

3.4.2 ON DIRT AND OTHER SOFT SUBSTRATES

A. Samples shall be cut from the membrane and geotextile sandwich to a
maximum area of 2 square inches. Measure the thickness with a mil reading
caliper, per 500 sq. feet. Deduct the plain geotextile thickness to determine the
thickness of Liquid Boot® membrane. Mark the test area for repair.

B. Voids left by sampling shall be patched with geotextile overlapping the void by
a minimum of two inches (2"). Apply a thin tack coat of Liquid Boot® under
the geotextile patch. Then spray or trowel-apply Liquid Boot® to a 60 mils
minimum dry thickness, extending at least three inches (3") beyond geotextile
patch.

3.4.3 SMOKE TESTING FOR HOLES

A smoke test shall be conducted by the contractor/applicator to detect any holes
or other breaches in the membrane. A smoke test involves pumping smoke
under the membrane for a specified period of time, under a specified pressure,
which varies from project to project.

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4. QUALITY ASSURANCE

A. Gas vapor barrier contractor/applicator shall be certified by the vapor barrier
manufacturer. A pre-installation conference shall be held prior to application
of gas vapor barrier to assure proper substrate and installation conditions, to
include contractor, applicator, architect/engineer, special vapor barrier
inspector and other trades influenced by vapor barrier installation.

B. Manufacturer Qualification: Obtain vapor intrusion barrier materials and
system components from a single manufacturer source.

C. Field Sample: Apply vapor intrusion barrier system field sample to
approximately 100 square feet of work site surface area to demonstrate
application, detailing, thickness, texture, and standard of workmanship.

1. Notify engineer one week in advance of the dates and times when field
sample will be prepared.
2. If engineer determines that field sample does not meet requirements,
reapply field sample until field sample is approved.
3. Retain and maintain approved field sample during construction in an
undisturbed condition as a standard for judging the completed vapor
intrusion barrier. An undamaged field sample may become part of the
completed work.

A. Coupon Sampling: Coupon sampling is the most accurate way to verify the
Liquid Boot® thickness. The following steps will be followed by the
engineer or designated representative:

1. Create a membrane testing log by obtaining a copy of the foundation
plan and then draw a 500 square foot grid over the foundation plan.
2. Note time, date, project name, inspector name, temperature and weather
conditions on testing log.
3. Number each quadrant and inspect sequentially.
4. When arriving at each quadrant quickly assess if there are any conditions
that might present any challenges in establishing a proper seal. Note
areas and discuss with applicator.
5. Conduct a visual inspection of the membrane. Look for areas where a
proper seal was not created, i.e. a fish-mouth at the termination and areas
where the membrane might be sprayed thin. Mark areas needed for
repair in the field with florescent paint or with chalk. Also make a note
on the testing log.
6. Calibrate mil reading caliper to account for the thickness of the
BaseFabric® layer. This is best done by obtaining a sample of the
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BaseFabric® layer and then zeroing out the caliper to the BaseFabric®
layer.
7. Collect a coupon sample in the area that is suspected to be sprayed thin.
Use a box cutter to cut a 3 square inch sample from the membrane.
Measure each side to confirm the specified minimum thickness has been
obtained. Number each sample and save in the job file. Mark the area for
repair in the field and on the site plan.
8. After sampling five quadrants it is at the discretion of the inspector to
continue collecting samples every 500 or 1,000 square feet.
9. Samples may be collected prior to the Liquid Boot® layer fully curing.
Observed shrinkage of the Liquid Boot® layer during the curing process
for horizontal surfaces is 10%. Assuming a 10% loss, a minimum of 66
mills thickness should be measured for a cured measurement of 60 mils.
Keep the coupon samples for the file.

B. Visual inspections prior to placement of concrete, but after the installation of
concrete reinforcing, is recommended to identify punctures that may have
occurred during the installation of rebar, post tension cables, etc. Punctures
in the Liquid Boot® system should be easy to indentify due to the color
contrasting layers of the system.

C. Smoke Testing: Smoke Testing shall be conducted by pumping non-toxic
smoke underneath the Liquid Boot® vapor barrier membrane and then
repairing the areas where smoke appears. This test is intended to visually
verify and confirm the proper installation of the Liquid Boot® system. The
smoke test will be performed by the applicator. Smoke testing should occur
after the Liquid Boot® layer has been installed and mil thickness verified and
before the UltraShield® G-1000 layer is installed. To conduct a smoke test
follow these steps:

1. One smoke test can cover between 2,000-3,000 square feet per test.
However, coverage will greatly depend on the sub grade under the
membrane. On sites where multiple smoke tests will be needed, use the first
two smoke tests to estimate the coverage area per test.
2. Visual verification of soundness of seams, terminations and penetrations
should be performed. Identify/correct any apparent deficiencies and/or
installation problems.
3. Note time, date, project name, inspector name, temperature and weather
conditions on testing log. In addition, record humidity, barometric pressure,
and wind speed/direction. Confirm wind speed is below 15 mph. Visual
identification of leaks becomes more difficult with increasing wind speed.
4. Cap other vapor-vents and outlets.
5. Activate the smoke generator/blower system and connect to sub-slab vent
riser.
6. To confirm the adequate flow of smoke under the membrane cut a 2” vent
in the membrane to facilitate the purging of air pockets under it. If working