10036_South End Transit_Vapor Mitigation System_12-02-2011-OCR

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SECTION XXXX
VAPOR MITIGATION SYSTEM

PART 1 - GENERAL
1.1 DESCRIPTION
A. This section contains requirements for the installation of a vapor
mitigation system.
B. The purpose of the vapor mitigation system is to prevent potential
intrusion of petroleum and chlorinated vapors from impacted soil and
groundwater into the buildings.
1.2 DEFINITIONS
A. CAULKS AND SEALANTS - those materials which will significantly reduce
the flow of gases through small openings in the building shell.
B. CONDITIONED SPACE - all spaces which are provided with heated and/or
cooled air or which are maintained at temperatures over 50 deg. F during
the heating season, including adjacent connected spaces separated by an
un-insulated component (e.g. basements, utility rooms, garages,
corridors).
C. CONTRACTOR - a building trades professional licensed by the state.
D. DEPRESSURIZATION - a condition that exists when the measured air
pressure is lower than the reference air pressure.
E. ELASTOMERIC - that property of macromolecular material of returning
rapidly to approximately the initial dimensions and shape, after
substantial deformation by a weak stress and release of stress.
F. Mil - 1mil=1/1000 of a meter
G. MITIGATION - The act of making less severe, reducing or relieving.
H. OUTSIDE AIR - air taken from the outdoors and, therefore, not previously
circulated through the system.
I. SOIL DEPRESSURIZATION SYSTEM - a system designed to withdraw air below
the slab through means of a vent pipe and fan arrangement or venting
turbine.
J. SOIL GAS - gas which is always present underground, in the small spaces
between particles of the soil or in crevices in rock. Major natural
constituents of soil gas include nitrogen, water vapor, carbon dioxide,
and (near the surface) oxygen. Contaminants which may be present in the
soil gas include volatile petroleum constituents such as benzene toluene
ethylbenzene and xylenes (BTEX) and chlorinated solvents such as 1,2-
dichloroethene.
K. VAPOR BARRIER – High density polyethylene (HDPE) flexible sheet
material; or other system of materials placed between the soil and the
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building for the purpose of reducing the flow of soil gas into the
building.
L. VENTILATION - the process of supplying or removing air, by natural or
mechanical means, to or from any space. Such air may or may not have
been conditioned.
1.3 SCOPE OF WORK
A. Subgrade soil shall be excavated to a minimum depth of 4-inches below
the bottom of the ground floor slab and any shallow foundation
components and 12-inch along the vapor laterals. It should be noted that
if impacted soil is encountered during excavation activities of the
vapor mitigation piping, footers, grade beams, and installation of
utilities a qualified hazardous materials specialty contractor will be
required to handle the impacted soil as described in the site soil
management plan.
B. Install a minimum 4-inch thick granular blanket beneath the entire
building slab. The granular blanket may be constructed of coarse sand,
pea gravel, or other self-compacting material having an in-place
hydraulic conductivity of greater than 1 x 10-3 cm/sec.
C. The base of the excavation shall be sloped in accordance with the
grading plan to prevent ponding of water in the subgrade. Therefore, the
thickness of the gravel blanket will vary between 4-inches and 18+
inches.
D. Install vapor recovery piping within the granular blanket. The vapor
recovery piping shall be constructed of 4-inch diameter Schedule 40 PVC
flush threaded well screen. The well screen will be machine slotted with
at least a 0.040 inch slot size, and covered with a geotextile sock.
Vapor recovery piping shall be installed horizontally beneath the
building slab at intervals of no less than one (1) vapor lateral (along
the centerline) per building slab (SEE FIGURE 1). However, in buildings
requiring a split foundation a vapor lateral will be installed along the
centerline of each building slab (SEE FIGURE 2).
E. The vapor recovery piping shall be connected to a common riser, which
shall be run inside each building within a utility corridor. The vapor
recovery riser shall terminate in a vent, which shall extend a minimum
of 2-feet above the top of the building and shall be capped with a
turbine. The vent stack should be installed to meet all of the following
requirements:
(1) be ten feet or more from any window, door, or other opening (e.g.,
operable skylight, or air intake) into conditioned spaces of the
structure,
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(2) be ten feet or more from any opening into an adjacent building.
The total required distance (ten feet) from the point of discharge to
openings in the structure shall be measured either directly between the
two points or be the sum of measurements made around intervening
obstacles. If the point of discharge is at or below any window, door, or
other opening into conditioned spaces of the structure the total
required distance (ten feet) shall be measured horizontally between the
two points.
F. The passive vapor recovery system should be installed to allow easy
conversion to an active recovery system, if this ever should become
necessary. Conversion of the system to active would require the
installation of a vacuum blower or fan on the vent stack.
G. A vapor barrier, consisting of minimum 10 mil, reinforced HDPE plastic
sheeting shall be installed immediately above the granular blanket and
below the concrete slab. The vapor barrier should extend beneath the
entire building slab.
H. All utility penetrations through the vapor barrier shall be sealed to
the extent possible. Overlapping joints in the vapor barrier shall be
sealed with a butyl rubber, or equivalent sealant.
PART 2 - PRODUCTS
2.1 PERMEABLE BACKFILL MATERIAL
A. Permeable backfill shall consist of self-compacting import soil having a
compacted permeability of no less than 1 x 10-3 cm/sec. Acceptable
materials are:
1. Pea gravel.
2. 57 stone.
2.2 VAPOR BARRIER
A. Vapor barrier membrane material shall consist of minimum 10 mil,
reinforced high density polyethylene (HDPE) sheeting.
B. Acceptable materials are Florprufe™ 120 Vapor Barrier, manufactured by
Grace Construction Products or engineer-approved equivalent.
C. Vapor barrier materials must provide excellent environmental stress
crack resistance, impact strength and high tensile strength including
additives to retard polymer oxidation and UV degradation.
2.3 VAPOR PIPING
A. Horizontal (i.e., slotted) vapor piping shall consist of 4-inch
diameter, Schedule 40 flush-threaded PVC, factory-slotted well screen
(0.040 inch slot size).
B. Horizontal vapor piping shall be wrapped in geotextile fabric (sock).
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C. Vertical (i.e., non-slotted) vapor piping shall be 4-inch diameter,
Schedule 40 PVC piping or piping approved by local building and/or fire
codes.
D. A 6-inch Schedule 80 PVC will be installed in the building footing to
allow the Vapor Lateral with the sample tubing to pass through the
building footing (See Figure 3).
2.4 SOIL VAPOR SAMPLING TUBE
A. Prior to wrapping the vapor laterals in the geotextile fabric a ¼-inch
inside diameter by 3/8-inch outside diameter Teflon sample tube is to be
installed along each of the vapor laterals.
B. One end of the Teflon tubing will be attached at the midpoint of the
lateral. The sampling tubing will be installed parallel to vapor lateral
and will be terminated approximately 1-foot above the finished grade at
the vapor lateral riser.
C. The Teflon tubing will be fastened to the vapor lateral using nylon
cable ties. The cable ties will be spaced approximately every 18-inches
along the vapor lateral (See Figure 3).
D. Once the sample tubing is installed and secured to the vapor lateral the
vapor lateral will be wrapped in the geotextile fabric (sock).
2.5 CAULKS, SEALANTS and TAPES
A. All caulks and sealants shall be resistant to petroleum and chlorinated
solvent vapors.
B. Acceptable caulks and sealants shall conform with ASTM C920-87 "Standard
Specifications for Elastomeric Joint Sealants" and ASTM C962-86
"Standard Guide for Use of Elastomeric Joint Sealants".
C. All sealant materials and methods of application shall be compatible
with the location, function and material of the surface or surfaces
being sealed.
D. Caulks and sealants shall be applied in accordance with manufacturer’s
directions.
E. Tapes used as a sealant shall be resistant to petroleum and chlorinated
solvent vapors and shall have a permeability of less than 10-6 cm/sec.
PART 3 - EXECUTION
3.1 EXCAVATION
A. Contractor shall excavate soils beneath each building slab to a minimum
depth of 4-inches below the bottom of the slab, and a minimum of 12-
inches in the trenches of the vapor laterals (See Figure 1 & 2)
3.2 INSTALLATION OF PERMEABLE BACKFILL
A. Permeable backfill material shall be installed beneath each building
slab to a minimum depth of 4-inches below the bottom of the slab, and a
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minimum of 12-inches in the trenches of the vapor laterals (See Figure 1
& 2).
B. The vapor barrier and vapor recovery piping shall be installed within
the backfill material as directed in Sections 3.3 and 3.4.
C. The backfill shall be placed in a controlled manner to avoid crushing of
the vapor recovery piping.
3.3 INSTALLATION OF VAPOR PIPING
A. The vent piping shall be installed within the permeable backfill at
approximately the center of the permeable layer (see Figure 1 and 2).
B. Temporarily cap the ends of the piping during installation to prevent
backfill material from entering the vapor recovery piping.
C. Slotted vent piping shall be installed horizontally throughout the foot-
print of the building area as shown on provided drawings. However, in
the event that grade beams or underground obstructions will present a
barrier to the lateral flow of air between horizontal piping sections,
spacing shall be decreased to allow at least 1 pipe per column line.
D. The lateral vapor piping shall have a minimum slope of 1/8 inch per foot
in order to drain any condensation back to soil beneath the soil gas
retarder. The system shall be designed and installed so that no portion
will allow the excess accumulation of condensation.
E. Vent pipes shall be terminated in locations that will minimize human
exposure to the exhaust air. Locations shall be above the eave of the
roof. To prevent exposure to vented soil vapor, the point of discharge
from vents shall meet all of the following requirements:
1. be ten feet or more from any window, door, or other opening (e.g.,
operable skylight, or air intake) into conditioned spaces of the
structure,
2. Be ten feet or more from any window, door, or other opening (e.g.,
operable skylight, or air intake) into conditioned spaces of the
structure, and (3) be ten feet or more from any opening into an
adjacent building. The total required distance (ten feet) from the
point of discharge to openings in the structure shall be measured
either directly between the two points or be the sum of measurements
made around intervening obstacles. If the point of discharge is at or
below any window, door, or other opening into conditioned spaces of
the structure the total required distance (ten feet) shall be
measured horizontally between the two points.
F. All exposed components of the soil depressurization system shall be
labeled "Soil Gas System" to prevent accidental damage or misuse. Labels
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shall be on a yellow band, two inches wide and spaced three feet apart
on all components.
G. All vent piping shall be located in compliance with existing and
applicable codes, with regards to clearances from mechanical equipment
and flues and notching of structural members. No vent shall penetrate a
fire wall or party wall.
H. Vent pipes shall be fastened to the structure of the building with
hangers, strapping, or other supports that will adequately secure the
vent material. Plumbing pipes, ducts, or mechanical equipment shall not
be used to support or secure a vent pipe.
I. Supports for vent pipes shall be installed at least every 6 feet on
horizontal runs. Vertical runs shall be secured either above or below
the points of penetration through floors, ceilings, and roofs, or at
least every 8 feet on runs that do not penetrate floors, ceilings, or
roofs or as local/state or federal codes require.
J. Vent pipes shall be installed in a configuration that ensures that any
rain water or condensation within the pipes drains downward into the
ground beneath the slab or soil-gas barrier.
K. The vent pipe shall be capped at the terminus with a minimum 4-inch
diameter, galvanized venting turbine, which is capable of operating in
low-wind conditions. The ventilator shall be a Model PT4A-4”
ventilator, manufactured by WSM Company, or equivalent.
L. Vent pipes shall not block access to any areas requiring maintenance or
inspection. Vents shall not be installed in front of or interfere with
any light, opening, door, window or equipment access area required by
code.
M. Cleaning solvents and adhesives used to join plastic pipes and fittings
shall be as recommended by manufacturer’s for use with the type of pipe
material used in the mitigation system.
3.4 INSTALLATION OF VAPOR BARRIER
A. The vapor barrier shall be installed to form a continuous sheet across
the entire building footprint.
B. All seams of the vapor barrier membrane shall be lapped at least 12
inches or as required by the manufacturer. Seams shall be sealed with
an approved sealant.
C. Where pipes, columns or other objects penetrate the vapor barrier, it
shall be cut and sealed to the pipe, column or penetration.
D. Punctures or tears in the vapor barrier membrane shall be repaired with
the same or compatible material.
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E. Seal vapor barrier membrane to foundation walls or grade beams at
building perimeter using approved sealant.
F. Avoid extended traffic over vapor barrier to prevent punctures or tears
in the vapor barrier membrane. Any punctures or tears will be repaired
as specified by the manufacturer’s guidelines.
3.5 SEALING OF SLAB PENETRATIONS
A. Small cracks and joints with widths less than 1/16 inch (0.0625") shall
be repaired by the application of an elastomeric material capable of
withstanding at least 25 percent extension and extending at least 4
inches beyond the length and width of the crack.
B. Large cracks and joints with widths larger than 1/16 inch (0.0625")
shall be enlarged to a recess with minimum dimensions of ¼ inch by ¼
inch (0.25" x 0.25") and sealed with an approved caulk or sealant
applied over a sealant backer in accordance with the manufacturer's
recommendations.
C. For utility penetrations, work spaces and large slab openings, such as
at a bath tub drain or a toilet flange, an acceptable method for sealing
the exposed soil shall include fully covering the exposed soil with a
solvent based plastic roof cement or other approved to a minimum depth
of 1 inch. Where voids between masonry foundation walls and the slab
edge are accessible, and are sealed in order to reduce vapor entry, non-
shrinking cementitious material may be used.
D. Any sump located in a conditioned portion of a building, or in an
enclosed space directly attached to a conditioned portion of a building,
shall be covered by a lid. An air tight seal shall be formed between the
sump and lid and at any wire or pipe penetrations.
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Description
FlorprufeTM 120 is a high performance
vapor barrier with Grace’s
Advanced Bond TechnologyTM that
forms a unique seal to the
underside of concrete floor slabs.
Comprising a highly durable
polyolefin sheet and a specially
developed, non-tacky adhesive
coating, Florprufe 120 seals to
liquid concrete to provide
integrally bonded vapor protection.
Florprufe exceeds ASTM E1745
Class A rating.
Advantages
•Forms a powerful integral seal to
the underside of concrete slabs
•Protects valuable floor finishes
such as wood, tiles, carpet and
resilient flooring from damage
by vapor transmission
•Direct contact with the slab
complies with the latest industry
recommendations
•Remains sealed to the slab even
in cases of ground settlement
•Ultra low vapor permeability
•Durable, chemical resistant
polyolefin sheet
•Lightweight, easy to apply, kick
out rolls
•Simple lap forming with
mechanical fixings or tape
Use
Florprufe 120 is engineered for
use below slabs on grade with
moisture-impermeable or
moisture-sensitive floor finishes
that require the highest level of
vapor protection.
Florprufe complies with the latest
recommendations of ACI
Committees 302 and 360, i.e. for
slabs with vapor sensitive
coverings, the location of the vapor
barrier should always be in direct
contact with the slab1.
The membrane is loose laid onto
the prepared sub-base, forming
overlaps that can be either
mechanically secured or taped.
The unique bond of Florprufe to
concrete provides continuity of vapor
protection at laps. Alternatively, if
a taped system is preferred,
self-adhered Preprufe®Tape can be
used to overband the laps.
Slab reinforcement and concrete
can be placed immediately. Once
the concrete is poured, an integral
bond develops between the
concrete and membrane.
FlorprufeTM 120
Integrally bonded vapor protection for slabs on grade
V apor Barrier Membranes
www.graceconstruction.com
PRODUCT DATA UPDATES TECH LETTERS DETAILS MSDS CONTACTS FAQS
1 ACI 302.1R-96 Addendum
Building wall
Exterior grade at
or below level of
subgrade – slope
away from structure
Footing
Moisture sensitive flooring
Concrete slab
Florprufe
5 in. x 8 in.
open drain rock
Compacted subgrade
Typical Assembly
Expansion board (optional)
Preprufe Tape
Bituthene Liquid
Membrane
Physical Properties: Exceeds ASTM E1745 Class A rating
Property Typical Value Test Method
Color White
Thickness (nominal) 0.5 mm (0.021 in.)ASTM D3767 – Method A
Water Vapor Permeance 0.03 perms ASTM E96 – Method B1
Tensile Strength 68 lbs/in.ASTM E1541
Elongation 300%ASTM D412
Puncture Resistance 3300 gms ASTM D17091
Peel Adhesion to Concrete >4 lbs/in.ASTM D903
1. Test methods that comprise ASTM E1745 standard for vapor retarders
Supply
Florprufe 120
Supplied in rolls 1.2 m x 35 m (4 ft x 115 ft)
Roll area 42 m
2 (460 ft2)
Roll weight 37 kg (81 lbs) approx.
Ancillary Products
Preprufe Tape is packaged in cartons containing 4 rolls that are 100 mm x 15 m (4 in. x 49 ft).
Bituthene Liquid Membrane is supplied in 5.7 L (1.5 gal) pails.
W. R. Grace & Co.-Conn.62 Whittemore Avenue Cambridge, MA 02140
Florprufe is a trademark and Preprufe is a registered trademark of W. R. Grace & Co.-Conn.
We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate and is offered for the users’ consideration, investigationand verification, but we do not warrant the results to be obtained. Please read all statements, recommendations or suggestions in conjunction with our conditions of sale,which apply to all goods supplied by us. No statement, recommendation or suggestion is intended for any use which would infringe any patent or copyright. W. R. Grace & Co.-Conn., 62 Whittemore Avenue, Cambridge, MA 02140. In Canada, Grace Canada, Inc., 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6.
These products may be covered by patents or patents pending. Copyright 2003. W. R. Grace & Co.-Conn. PF-001B Printed in USA 4/03 FA/GPS/2M
Visit our web site at www.graceconstruction.com printed on recycled paper
For Technical Assistance call toll free at 866-333-3SBM (3726).
Installation
Health & Safety
Refer to relevant Material Safety
Data Sheet. Complete rolls should
be handled by 2 persons.
Florprufe 120 can be applied at
temperatures of -4ºC (25ºF) or
above. Membrane installation is
unaffected by wet weather.
Installation and detailing of
Florprufe 120 are generally in
accordance with ASTM E1643-98.
Prepare substrate in accordance
with ACI 302.1R Section 4.1.
Install Florprufe 120 over the
leveled and compacted base. Place
the membrane with the smooth
side down and the plastic liner side
up facing towards the concrete
slab. Remove and discard plastic
liner. End laps should be staggered
to avoid a build up of layers.
Succeeding sheets should be
accurately positioned to overlap
the previous sheet 50 mm (2 in.)
along the marked lap line.
Laps
1. Mechanical fastening method –
To prevent the membrane from
moving and gaps opening, the laps
should be fastened together at 1.0 m
(39 in.) maximum centers. Fix
through the center of the lap area
using 12 mm (0.5 in.) long washer-
head, self-tapping, galvanized
screws (or similar) and allowing
the head of the screw to bed into
the adhesive compound to self-
seal. It is not necessary to fix the
membrane to the substrate, only
to itself. Ensure the membrane
lays flat and no openings occur.
(See Figure 1.) Additional
fastening may be required at
corners, details, etc. Continuity is
achieved once the slab is poured
and the bond to concrete develops.
OR
2. Taped lap method –
For additional security use Grace
Preprufe Tape to secure and seal
the overlaps. Overband the lap
with the 100 mm (4 in.) wide
Preprufe Tape, using the lap line
for alignment. Remove plastic
release liner to ensure bond to
concrete.
Penetrations
Mix and apply Bituthene Liquid
Membrane detailing compound to
seal around penetrations such as
drainage pipes, etc. (See Figure 2
and refer to the Bituthene Liquid
Membrane data sheet, BIT-230.)
Concrete Placement
Place concrete within 30 days. Inspect
membrane and repair any damage
with patches of Preprufe Tape. Ensure
all liner is removed from membrane
and tape before concreting.
Preprufe Tape
Bituthene Liquid
Membrane Florprufe
Figure 2
Figure 1