|
10.1 Earthwork
10.1.1 Surface Preparation
10.1.2 Anchorage System
10.2 Geomembrane Placement
10.2.1 Field Panel Identification
10.2.2 Field Panel Placement
10.2.2.1 Location
10.2.2.2 Compensation for Material Expansion and
Contraction, OR
10.2.2.2 Intimate Subgrade Contact
10.2.2.3 Installation Schedule
10.2.2.4 Weather Conditions
10.2.2.5 Method of Placement
10.2.2.6 Damage
10.3 Field Seaming
10.3.1 Seam Layout
10.3.2 Seaming Equipment and Products
10.3.2.1 Fusion Seaming
10.3.2.2 Extrusion Seaming
10.3.3 Seam Preparation
10.3.4 Weather Conditions for Seaming
10.3.5 Overlapping and Temporary Bonding
10.3.6 Trial Seams
10.3.7 General Seaming Procedure
10.3.8 Nondestructive Seam Continuity Testing
10.3.8.1 Concept
10.3.8.2 Submittals
10.3.8.3 Vacuum Testing
10.3.8.4 Air Pressure Testing
10.3.8.5 Spark Testing
10.3.8.6 Visual Examination
10.3.9 Destructive Testing
10.3.9.1 Concept
10.3.9.2 Location and Frequency
10.3.9.3 Sampling Procedure
10.3.9.4 Size of Samples
10.3.9.5 Field Testing
10.3.9.6 Construction Quality Assurance Laboratory
Testing
10.3.9.7 Installer's Laboratory
Testing
10.3.9.8 Destructive Sample Pass/Fail
Criteria
10.3.9.9 Procedures if Destructive
Sample Fails
10.4 Defects and Repairs
10.4.1 Identification
10.4.2 Evaluation
10.4.3 Repair Procedures
10.4.4 Verification of Repairs
10.4.5 Large Wrinkles
10.4.6 Bridging of Geomembrane
10.4.7 Geomembrane Anchoring
10.5 Backfilling of Anchor Trench
10.6 Appurtenances
10. GEOMEMBRANE INSTALLATION
10.1 Earthwork
10.1.1 Surface Preparation
The Earthwork Contractor will be responsible for preparing the supporting
soil according to the project specifications. The CQA Consultant
will verify that:
- a qualified Land Surveyor has established all lines and grades,
and they are approved by the Project Manager;
- the supporting soil meets the density specification;
- the surface to be lined has been finished so as to be free of irregularities,
protrusions, loose soil, dessication cracks and abrupt changes in
grade;
- the 50 mm surface layer of the supporting soil does
not contain stones or other objects which may be damaging to the
geomembrane;
and
- there are no areas excessively softened by high water content.
The Installer will certify in writing that
the surface on which the geomembrane will be installed within the
next 24 hr is acceptable. The
certificate of acceptance will be given by the Installer to the Project
Manager prior to commencement of geomembrane installation in the
area under consideration. The CQA Consultant will be given a copy
of this certificate by the Project Manager. The CQA Consultant will
also acknowledge approval of the subgrade.
After the supporting soil has been accepted
by the Installer, it will be the Installer's responsibility to
indicate to the Project
Manager any change in the supporting soil condition that may require
repair work. If the CQA Consultant concurs with the Installer, then
the Project Manager will ensure that the supporting soil is repaired.
10.1.2 Anchorage Trenches
Anchor trenches will be excavated by the
Earthwork Contractor (unless otherwise specified) to the lines
and dimensions shown on the design
drawings, prior to geomembrane placement. The CQA Consultant will
verify that anchor trenches have been constructed according to the
design drawings.
The edge of the trench, over which the geomembrane enters the trench,
will be rounded to avoid sharp bends in the geomembrane. There shall
be no sharp protrusions on the inside wall of the trench. No loose
soil will be allowed to underlie the geomembrane in the trenches.
Water shall not be allowed to stand, or soften
the soil, in the anchor trench. Responsibility for dewatering
of the anchor trench shall be as agreed upon in the contract or
at the Preconstruction
Meeting.
Backfilling of anchor trenches will be conducted in accordance with
Section 10.5.
10.2 Geomembrane Placement
Before any geomembrane is deployed the documents listed in Appendix
B must be received from the Installer and be reviewed and approved
by the CQA Consultant and Project Manager.
10.2.1 Field Panel Identification
A field panel is a single piece of geomembrane (other than a patch
or cap strip) which is seamed in the field: i.e. a roll or a portion
of roll cut in the field.
It will be the responsibility of the CQA
Site Superintendent to ensure that each field panel is given an "identification code" (number
or letter-number) consistent with the layout plan. This identification
code will be agreed upon by the Project Manager, Installer, and CQA
Consultant. This field panel identification code should be as simple
and logical as possible. It will be the responsibility of the Installer
to ensure that each field panel placed is also marked with the original
roll number. The identification code and roll number will be marked
at a location agreed upon by the Project Manager, Installer, and
CQA Consultant.
Typically, panels will be numbered in the
order in which they are placed. The CQA Site Superintendent will
establish a table or chart
showing correspondence between roll numbers and field panel identification
codes. The field panel identification code will be used for all
CQA records.
10.2.2 Field Panel Placement
No geosynthetics shall be deployed, joined,
or tested unless a representative of the CQA Consultant is present
to monitor such activities.
10.2.2.1 Location
The CQA Consultant will verify that field panels and seam orientations
are approximately as indicated in the Engineer's or Installer's
approved layout plan, or as modified.
10.2.2.2 Compensation for Material Expansion and Contraction
Unless provided by the designer, as it should be, the Installer
will be responsible for determining the required amount of compensation
that must be installed in the geomembrane to ensure that it will
not be unduly tensioned due to temperature variations in service. Such
calculations shall be shown to the CQA Consultant and Project Manager. The
Installer will be responsible for ensuring that sufficient HDPE
geomembrane is installed to compensate for contraction of the material
during anticipated lower temperatures and to prevent expansion
and excessive wrinkling at possible higher covering temperatures.
The methods of installing compensation will be discussed with,
and approved by, the Project Manager and the CQA Consultant. The
geomembrane must not be tensioned and must be fully supported by
the subgrade when it is covered by soil or liquid ballast.
10.2.2.2 Intimate Subgrade Contact
Only that amount of geomembrane will be
deployed in one day that can be covered by other required geosynthetics
and the required
thickness of cover soil. The cover soil will initially be placed
as ballast around the periphery of that section of geomembrane.
The CQA Consultant will monitor the placement of geomembrane and
soil to confirm that the geomembrane is essentially in complete
contact with the subgrade at the end of the working day, and is
restrained in this position, without excessive tension, by the
peripheral soil.
The CQA Consultant will monitor the spreading of cover soil at
the start of the first shift of the next day to confirm that no
standing or folded wrinkles in the geomembrane are covered by soil.
The geomembrane must be in intimate contact with the subgrade.
At all times the exposed edges of geosynthetics will be kept clean
and protected from damage.
10.2.2.3 Installation Schedule
Field panels will be placed one at a time,
and each field panel will be seamed immediately after its placement
(in order to minimize
the number of unseamed field panels exposed to wind). It is beneficial
to "shingle" overlaps in the downslope direction to facilitate
drainage in the event of precipitation, shingling should also be
done in the downstream direction to minimize resistance to flow.
It is also beneficial to proceed downslope
and in the direction of (with) prevailing winds. Scheduling decisions must be made
during installation, in accordance with varying environmental conditions. In
any event, the Installer will be fully responsible for the decisions
made regarding placement procedures.
The CQA Consultant will evaluate every change in the schedule
proposed by the Installer and advise the Project Manager on the
acceptability of that change. The CQA Consultant will verify that
the condition of the supporting soil is still satisfactory for
installation of geomembrane.
The CQA Consultant will record the identification code, roll number,
location, weather conditions, and date of installation of each
field panel.
10.2.2.4 Weather Conditions
Geomembrane placement will not proceed
at geomembrane temperatures below -20°C unless approved by the project engineer. Geomembrane
seaming will not proceed at geomembrane temperatures between 0°C
and -20°C or above 75°C unless approved by the Project
Manager. Approval will not be unreasonably withheld provided the
Installer can demonstrate the ability to produce satisfactory seams.
The frequency of trial seams, or seam destructive test sampling,
(Section 10.3.6) may be increased at extreme geomembrane temperatures
(<5°C, >75°C). Geomembrane placement will not be
done during any precipitation, in an area of ponded water, or during
excessive winds except as approved in an Action Decision Meeting.
NOTE: The only temperature of significance
is the actual geomembrane temperature, not the ambient temperature. When
exposed to sunlight the geomembrane temperature will be significantly
higher than ambient.
The CQA Consultant will verify that the
above conditions are observed. Additionally, the CQA Consultant will verify that the
supporting soil has not been damaged by weather conditions. The
CQA Site Superintendent will inform the Project Manager if the
above requirements are not observed.
10.2.2.5 Geomembrane Placement
The CQA Consultant will verify that:
- equipment used does not damage the geomembrane as a result of
handling, trafficking, excessive heat, leakage of hydrocarbons,
or by other means;
- any All-Terrain Vehicles (ATVs) used to deploy geosynthetics
exert ground pressures less than 55 kPa (8 psi);
- ATVs are not operated: 1) at excessive
speeds, 2) in tight turning circles, 3) under extreme breaking
and accelerating conditions,
4) with dirty tires, and 5) over wrinkles, that might damage the
geomembrane;
- the prepared surface underlying the geomembrane has not deteriorated
since previous acceptance, and is still acceptable immediately
prior to geomembrane placement;
- any geosynthetic elements immediately underlying the geomembrane
are clean and free of debris;
- personnel working on the geomembrane do not smoke, do not wear
hard-soled shoes, and do not engage in activities which could damage
the geomembrane;
- frequently used pathways up and down geomembrane on slopes are
protected by a roll of geotextile;
- the methods used to unroll the panels do not cause excessive
scratches or crimps in the geomembrane and do not damage the supporting
soil;
- the method used to place the panels minimizes wrinkles (especially
differential wrinkles between adjacent panels);
- geomembrane is not allowed to unroll freely down a slope;
- geomembrane is not placed under tension, unless approved by the
Project Manager;
- adequate temporary loading and/or anchoring (e.g., sand bags,
tires), that does not damage the geomembrane, has been placed to
prevent uplift by wind;
- direct contact of equipment with the geomembrane shall not be
allowed, except as previously described for ATVs used to deploy
geosynthetics. The geomembrane shall be protected by geotextiles,
extra geomembrane, soil layers, or suitable materials, in areas
where equipment may be used or traffic may be expected;
- only hook bladed utility knives are used to cut through the geomembrane;
- appropriate care is to be taken to prevent shock and explosions
caused by static electricity discharges;
- all handholds cut for moving panels and damage caused by clamps
are repaired; and
- panels are not moved such that subgrade
soil can peel the underside seam flap.
The CQA Site Superintendent will inform the Project Manager if
the above requirements are not observed.
10.2.2.6 Temporary Ballasting
Temporary ballasting around the edges of
the installed liner shall be done with sandbags or equivalent
non-damaging ballast material
(e.g. tires without reinforcing wires exposed). Sandbags shall
be handleable by one person and shall be spaced to provide adequate
uplift protection against typical winds that might reasonably be
expected to occur prior to the addition of adjacent panels or prior
to permanent ballasting.
10.2.2.7 Damage
The CQA Consultant will visually examine
each panel, after placement and prior to seaming, for damage. The CQA Site Superintendent
will advise the Project Manager which panels, or portions of panels,
should be rejected or repaired. Damaged panels or portions of
damaged panels, which have been rejected will be marked, and their
removal from the work area recorded by the CQA Consultant. Repairs
will be made according to procedures described in Section 10.4.
At a minimum, the CQA Consultant will ensure that:
- each panel is placed in such a manner that it has not been, or
is unlikely to be, damaged; and
- any tears, punctures, holes, thin spots, and damaging inclusions,
gouges, and protuberances etc., are marked for repair, or the panel
is rejected.
10.3 Field Seaming
10.3.1 Seam Layout
Prior to the commencement of installation
activities the Installer will provide the Project Manager and the
CQA Consultant with a proposed
panel layout drawing. The CQA Consultant will review the panel layout
drawing and verify that it is consistent with the accepted state-of-practice
and this CQA Plan. No panels may be seamed in the field without
the Project Manager's approval. In addition, panels that significantly
change the layout drawing, (e.g. that change the orientation of seams)
shall not be installed without the Project Manager's prior approval. It
is, however, recognized that such a drawing is only a guide and will,
in practice, require modification.
In general, seams should be oriented parallel
to the line of maximum slope, i.e., oriented up and down, not across,
the slope. In corners
and other geometrically complex locations, the number of seams should
be minimized. No base seam or tee seam will be less than 2 m from
the toe of slopes, or areas of potential stress concentrations, unless
otherwise authorized by the Project Manager.
If roll end seams are unavoidable on slopes, the upslope panel shall
overlap the downslope panel and adjacent panel cross-seams shall
be staggered by at least 2 m.
A seam numbering system compatible with the
panel numbering system will be agreed upon at the Resolution or
Preconstruction Meeting.
10.3.2 Seaming Equipment and Products
Approved methods for field seaming are thermal
fusion (hot wedge, hot air, or combination) seaming and extrusion
seaming. Proposed
alternate methods will be documented and submitted to the Project
Manager and CQA Consultant for approval. Only apparatus that has
been specifically approved by make and model will be used. The Installer
will use appropriate measuring equipment to ensure that required
temperatures are being achieved.
The Project Manager will submit all documentation to the CQA Consultant
for his concurrence.
10.3.2.1 Fusion Seaming
Fusion seaming must be done with automated
self-propelled machines. The
fusion seaming machines will be equipped with gauges giving hot
wedge temperatures. Temperature, speed, and nip roll pressure
settings will be verified by the Installer prior to each seaming
period. Nip roll and wedge geometries shall be such as to minimize
residual stresses at the edge of the seam, i.e. to minimize reduction
in stress cracking resistance of the geomembrane.
The CQA Consultant will log ambient conditions,
geomembrane temperatures, seaming
apparatus temperatures and speeds, equipment serial number, and
operator initials.
The CQA Consultant will also verify that:
- the Installer maintains on-site the number of operable seaming
machines decided at the Resolution Meeting;
- equipment used for seaming does not damage the geomembrane;
- for tee seam intersections, all edge flaps are cut back to the
edge of the outer-most peel-tested track of the seam prior to seaming;
- electric generators and fuel containers are placed on a smooth
protective layer such that no damage occurs to the geomembrane;
- a smooth insulating plate or fabric is placed beneath the hot
seaming apparatus after usage;
- the geomembrane is protected from damage in heavily-trafficked
areas; and
- build-up of moisture between the sheets
is prevented. To accomplish
this a movable protective layer may be used directly below each
overlap of geomembrane that is to be seamed.
10.3.2.2 Extrusion Seaming
Extrusion-seaming apparatus will be equipped with gauges giving
the relevant temperatures of the apparatus such as the temperatures
of the extrudate, nozzle, and preheat air.
The Installer will provide documentation
(including QC certificates) regarding the welding rod or resin
pellets to the Project Manager
and the CQA Consultant, that show that the resin is the same HDPE
resin as the geomembrane itself. Other seaming resins must be
approved by the Project Manager and the CQA Consultant.
The CQA Consultant will log apparatus temperatures, extrudate
temperatures, ambient conditions, and geomembrane temperatures
at appropriate intervals.
The CQA Consultant will verify that:
- the Installer maintains on-site the number of operable seaming
machines decided at the Resolution Meeting;
- equipment used for seaming will not damage the geomembrane;
- the extruder is purged prior to seaming until all heat-degraded
extrudate has been removed from the barrel;
- feed resin is maintained clean and dry;
- the electric generator and fuel containers are placed on a smooth
intermediate layer such that no damage occurs to the geomembrane;
- a smooth insulating plate or fabric is placed beneath the hot
seaming apparatus after usage; and
- the geomembrane is protected from damage in heavily trafficked
areas.
10.3.3 Seam Preparation
The CQA Consultant will verify that:
- prior to seaming, the seam area is clean and free of moisture,
dust, dirt, debris of any kind, foreign material, and any mechanical
damage;
- if seam overlap grinding is required, the
process is completed according to the Manufacturer's instructions
but within 30 minutes of the seaming operation, and in a way that
does not damage the geomembrane;
- the abrading does not remove more than 10 percent of the thickness
of the geomembrane, and the resulting abrasion marks are covered
by the finished extrusion bead;
- any visible abrasion marks, after seaming, are essentially perpendicular
to the direction of the seam;
- the abrading does not introduce damaging gouges in the geomembrane;
and
- seams/panels are aligned with a minimum
of wrinkles and "fishmouths".
10.3.4 Weather Conditions for Seaming
The following protocols will be observed during seaming:
- Unless authorized in writing by the Project
Manager, no seaming will be attempted at geomembrane temperatures
below -0°C or above
75°C;
- Below a geomembrane temperature of 5°C,
the need for pre-heating and additional testing should be discussed
with the Project Manager
and CQA Consultant;
- In all cases, the geomembrane in the seaming area will be dry and
protected from wind and airborne particulates; and
- Geomembrane temperatures will be measured with a surface temperature
thermocouple or a calibrated infrared pyrometer.
If the Installer wishes to use methods which
may allow seaming at geomembrane temperatures below 0°C or above 75°C, the Installer
will demonstrate (by testing trial seams) that such methods produce
seams which are entirely equivalent to seams produced at geomembrane
temperatures above 0°C and below 75°C, and that the overall
quality of the seam and durability of the geomembrane are not adversely
affected. In addition, the Installer will prepare written certification
that states that the seaming procedure does not cause any physical
or mechanical modification to the geomembrane that will generate
any short or long-term damage to the geomembrane liner.
The CQA Consultant will verify that these
requirements are observed and will advise the Project Manager if
potential problems are perceived. The
Project Manager will then decide if the seaming will be stopped or
postponed. Such decisions may be the subject of an Action Decision
Meeting.
10.3.5 Overlapping and Temporary Bonding
The CQA Consultant will verify that:
- the panels of geomembrane have an overlap
of approximately 100 mm, sufficient to allow peel tests to be performed
on the inner
track of the seam;
- there is a free flap at the edge of the
top geomembrane a minimum
of approximately 10 mm wide, to allow a peel test to be performed
on the outer track of the seam;
- no solvent or adhesive is used unless the product is approved in
writing by the Project Manager (samples must be submitted to the
Owner for testing and evaluation);
- any procedure used to temporarily bond adjacent
panels together does not damage the geomembrane. In particular, the temperature
of hot air at the nozzle of any spot seaming apparatus will be controlled
such that the geomembrane is not damaged. "Damage" includes
a loss in durability; and
- temporary bonds do not interfere with the ability to perform shear
and peel tests on the actual production seam.
The CQA Consultant will log all relevant temperatures and conditions,
and will log and report any non-compliance to the Project Manager.
If protective layers of geomembrane are placed
on the barrier layer geomembrane for any purpose (e.g. puncture
protection in drainage
trenches), they shall not be tack or spot welded to the barrier layer. They
shall be fully welded, except a small pressure relief segment, along
the complete periphery of the protective layer or they shall not
be welded at all.
10.3.6 Trial Seams
Trial seams will be made by each machine/operator
combination on strips of HDPE geomembrane to verify that seaming can be successfully
performed. Such trial seams will be made at the beginning of each
seaming period (i.e., at the beginning and middle of each working
shift), but at least once every four hours, for each seaming apparatus/operator
combination used in the seaming period. In addition, a new trial
seam will be conducted when a welding apparatus has been restarted
after being switched off. A trial seam will also be made in the
event that the geomembrane temperature changes more than 25°C
since the last passing trial seam. Trial seams will be made under
the same conditions as production seams will be made. When geomembrane
temperatures are below 5°C or higher than 75°C more frequent
trial seams may be required. In general, trial seams will be conducted
as follows:
The trial seam sample will be at least 1.5
m long by 0.3 m wide with the seam centered lengthwise. Seam overlap will be as indicated
in Section 10.3.5. The CQA Consultant will observe all trial seam
procedures.
Four specimens, each 25 mm wide and a minimum
of 150 mm long, will be cut from the center section of the trial
seam sample by the Installer. Two
specimens will be tested in shear and two in peel using a calibrated
field tensiometer. They should meet project specifications. If
any specimen fails, the entire operation will be repeated. If the
second trial seam fails, the seaming apparatus and seamer will not
be approved for production seaming until the deficiencies are corrected
and two consecutive successful trial seams are achieved. The remainder
of the successful trial seam sample will be assigned a number and
marked accordingly by the CQA Consultant, who will also log the date,
time, geomembrane temperature, number of seaming unit, settings,
name of seamer, and pass or fail description.
The remainder of the sample will be cut into two pieces, one each
to be retained by the Owner, and Installer.
A trial seam shall also be prepared by each seaming machine/operator
at the completion of seaming each day to determine whether changes
in seam quality might have occurred during the last part of the seaming
period.
10.3.7 General Seaming Procedure
Unless otherwise specified, the general seaming procedure used by
the Installer will be as follows:
- For fusion seaming, a movable protective
layer of plastic may be placed directly below each overlap of geomembrane
that is to be seamed. This
is to help prevent any moisture build-up between the sheets to be
seamed;
- If required, a firm substrate may be provided by using a flat board,
or other similar hard surface placed directly under the seam overlap;
- Fishmouths or wrinkles at the seam overlaps
will be cut along the peak of the wrinkle in order to achieve a
flat overlap. The cut
fishmouths or wrinkles will be seamed and any portion where the overlap
is inadequate will then be patched with an oval or round patch of
the same geomembrane material extending a minimum of 150 mm beyond
the cut in all directions. The end of the cut should be rounded;
- If seaming operations are carried out at night, adequate illumination
will be provided;
- Seaming will extend to the outside edge of panels placed in the
anchor trench.
Each seam will be labelled with the seaming machine number, the
operator's initials, machine temperature and speed settings, date,
time, and direction seamed. The CQA Consultant will monitor the above
seaming procedures, and will inform the Project Manager of any unsatisfactory
deviations from standard practice.
10.3.8 Nondestructive Seam Continuity
Testing
10.3.8.1 Concept
The Installer will nondestructively test
all field seams over their full length using a vacuum test unit,
air pressure test (for
double fusion seams only), spark test, or other approved method. Vacuum
testing, air pressure testing, and spark testing are described
in Sections 10.3.8.3, 10.3.8.4, and 10.3.8.5 respectively). The
purpose of nondestructive testing is to check the continuity of
seams. It does not provide any information on seam strength. Continuity
testing will be carried out as the seaming work progresses, not
at the completion of all field seaming. Nondestructive testing
will not be permitted unless there is, in the opinion of the CQA
Consultant, adequate illumination.
The CQA Consultant will:
- observe all nondestructive testing;
- record location, date, test unit number, operator, and outcome
of all testing; and
- log and inform the Installer and Project Manager of any required
repairs.
- The Installer will complete any required repairs in accordance
with Section 10.4.
The CQA Consultant will:
- observe the repair and re-testing of the repair;
- mark on the geomembrane that the repair
has been successfully made and tested; and
- document the results.
The following procedures will apply to segments of seams that
cannot be nondestructively tested:
- All such seam segments will be cap-stripped with the same type
of geomembrane material, or
- All such seam segments will be very carefully prepared and welded
by the master seamer under the observation of the consultant.
- If the seam is accessible to testing equipment
prior to final installation (e.g. after prefabrication), the
seam will be nondestructively
tested prior to final installation.
- The seaming and cap-stripping operations must be observed for
proper procedures by the CQA Consultant and Installer's QC representative.
The installer will write the details of
each seam nondestructive test on the geomembrane. For air pressure tests this will include
the initials of the tester, the date, start time and pressure,
end time and pressure, and pass or fail result. For vacuum testing
this will include the initials of the tester, the date, and pass
or fail result. For spark testing this will include the initials
of the tester, the date, voltage setting, and pass or fail result. When
a test fails, the number of the appropriate repair will also be
recorded on the geomembrane.
10.3.8.2 Submittals
Prior to any nondestructive testing, the Installer shall submit
to the Owner and CQA Consultant calibration certificates for all
pressure gages to be used during vacuum and air pressure testing,
or shall otherwise demonstrate that all gages are in satisfactory
working condition.
10.3.8.3 Vacuum Box Testing
The equipment will be comprised of the following:
- a vacuum box assembly consisting of a rigid housing, a transparent
viewing window, a soft neoprene gasket attached to the bottom,
port hole, valve assembly, and a vacuum gauge;
- a vacuum tank and pump assembly equipped with a pressure controller
and pipe connections;
- a pressure/vacuum hose with fittings and connections;
- a soapy solution that does not cause environmental stress cracking
in the geomembrane, and
- a soap solution applicator.
The following procedure will be followed:
- for fusion seams (not normally tested with a vacuum box), cut
off the free flap with an approved cutter (so that the lower geomembrane
is not damaged) prior to testing the seam;
- energize the vacuum pump and reduce the tank pressure to approximately
5 kPa gauge;
- with a soapy solution, wet a strip of geomembrane which is wider
and longer than the vacuum box;
- place the box over the wetted area;
- close the pressure relief valve and open the vacuum valve;
- ensure that a leak-tight seal is created;
- examine the geomembrane seam through the viewing
window for the presence of soap bubbles (large bubbles, or fine
froth) for
a period of not less than 5 seconds;
- if no bubbles or foam appear after 5 seconds,
close the vacuum valve and open the pressure relief valve. Move
the box over to the adjoining section of seam, with some overlap,
and repeat the
process;
- all areas where soap bubbles appear will be marked and repaired
in accordance with Section 10.4.3; and
- excess soap solution shall be cleaned or rinsed off the geomembrane
and seam.
10.3.8.4 Air Pressure Testing
The following procedures are applicable
to those seaming processes which produce a double track seam
with a central channel. The equipment
will be comprised of the following:
- an air pump equipped with a pressure gauge capable of generating
and sustaining a pressure between 160 and 280 kPa mounted on a
cushion to protect the geomembrane;
- a pressure hose with fittings and connections;
- a sharp hollow needle, or other approved pressure-feed device
attached to a pressure gage; and
- clamps or other devices to seal the ends of the seam to be tested.
- The following procedures will be followed:
- seal both ends of the seam to be tested;
- insert the pressure-feed device into the channel of the seam;
- energize the air pump to a pressure between 165 and 275 kPa (depending
on geomembrane thickness) as indicated in Table 2, close the valve,
and allow the temperature of the air in the channel, and thus the
pressure, to stabilize for about 2 minutes;
TABLE 2. AIR CHANNEL TEST PRESSURES FOR HDPE GEOMEMBRANES
- verify that the stabilized pressure is
within the required range and note the pressure loss after a
further 5 minutes. If loss
of pressure exceeds the amount indicated in Table 3, or if the
pressure does not stabilize, locate the faulty area and repair
it in accordance with Section 10.4.3;
TABLE 3. ALLOWABLE PRESSURE LOSS IN AIR CHANNEL
TEST
- verify that the full length of the seam
section has been tested by observing the air pressure gauge for
a decrease in pressure
when the seal at the end of the channel away from the air pump
is removed. If there is a blockage in the channel, the entire
seam must be capped, with cap seams being nondestructively tested,
or the location of the blockage must be found and the untested
part of the seam must be properly tested; and
- remove the needle or other approved pressure-feed device and
seal the hole.
Note that a decrease in the geomembrane temperature (e.g. due
to clouds) will also cause a reduction in air channel pressure.
10.3.8.5 Spark Testing
Spark Testing performed according to ASTM
D6365 is frequently used on short, detail (sump, penetration)
extrusion welds that
cannot be tested by vacuum box testing. Occasionally it is used
on long extrusion seams as the primary nondestructive test method. The
same general test method can also be applied to the geomembrane
panels themselves when they are manufactured with an electrically
conductive bottom surface layer.
For seams, a copper wire or tape is placed
within the geomembrane overlap, just to the inside of the center
of the extruded bead. The
wire is exposed at one end of the seam or it is buried in the conductive
subgrade.
Prior to testing, a trial calibration seam must be made to confirm
the minimum voltage required to discharge across a hole in the
seam between the search electrode and the copper wire.
The test procedure is as follows:
- Connect the negative (ground) electrode of the testing equipment
to the end of the copper wire, or to a grounding rod if the copper
wire is buried in the subgrade;
- Connect the positive electrode to the wire brush or other type
of search electrode;
- Clean all debris and moisture from the seam area;
- Apply a potential difference of between
20 and 55 kVDC, as determined in the calibration test, between
the electrodes. ASTM D6365 recommends
the following equation to determine the required potential difference:
| V= _______ |
where: ________
|
| |
________ :
|
- Sweep the wire brush electrode over the surface of the seam,
maintaining contact with the extruded bead and the top of the lower
geomembrane at the edge of the bead;
- Monitor for audible and/or visible spark
discharges that are indicative of a defect. Mark defects for
repair.Care must be taken when spark testing almost completed
landfill caps - a spark can
cause a small landfill gas explosion. Spark testing must not be
performed when the liner is wet.
10.3.8.6 Visual Examination
Air pressure, vacuum box, and spark testing
methods apply only to seams. Installer and CQA personnel shall
continuously visually examine the geomembrane panels for the
presence of other penetrating
and nonpenetrating defects and shall continuously feel for protuberances
when walking on the geomembrane.
Visual examination should take advantage of low angles of sunlight
and early morning condensation on the geomembrane.
10.3.9 Destructive Testing
10.3.9.1 Concept
Destructive seam tests will be performed
at selected locations. The
purpose of these tests is to evaluate seam bond strength and the
effects of seaming on the adjacent geomembrane. Seam strength
testing will be done as the seaming work progresses, not at the
completion of seaming.
10.3.9.2 Location and Frequency
The CQA Site Superintendent will select
locations where seam samples will be cut out for laboratory testing. Those
locations will be established as follows:
- A minimum frequency of one sample for every 150 m of seam made
by each extrusion machine/operator combination and each fusion
machine each day - unless a different frequency is stated in the
project specifications.
- Conditions under which testing frequency
may be increased or decreased as the project progresses will
be agreed upon by the Installer,
Project Manager, and CQA Manager at the Resolution or Preconstruction
Meeting.
- Test locations will be determined during
seaming at the CQA Site Superintendent's discretion. Selection
of such locations may be prompted by suspicion of overheating,
contamination, offset seams,
or any other evidence of imperfect seaming;
- If trial seams are not made at the end of the day one sample
for destructive testing shall be removed from the last seam made
by each seaming machine at the end of each working day.
The Installer will not be informed in advance of the locations
where the seam samples will be taken.
Test frequencies may be increased or decreased at the CQA Site
Superintendent's discretion depending on the consistency of the
test results.
10.3.9.3 Sampling Procedure
Samples will be cut by the Installer as
the seaming progresses in order to have laboratory test results
before the geomembrane
is covered by another material.
The CQA Consultant will:
- observe sample cutting;
- assign a number to each sample, and mark it accordingly; and
- record the sample location on the layout drawing.
All holes in the geomembrane resulting
from destructive sample removal will be immediately repaired in accordance with
repair procedures described in Section 10.4.3. The continuity
of the new
seams in the repaired area will be tested according to Section
10.3.8.
10.3.9.4 Size of Samples
At a given sampling location, two types of samples will be taken
by the Installer.
First, two pairs of specimens for field
peel and shear testing will be taken. Each of these specimens
will be 25 mm wide by at least 150 mm long, with the seam centered
across the width.
The distance between these two pairs of
specimens will be 1.1 m. If both pairs of specimens pass the field tests described in
Section 10.3.9.5, a sample for laboratory testing will be taken.
The sample for laboratory testing will be located between the two
pairs of specimens taken for field testing. Unless determined
otherwise at the Preconstruction Meeting, or in the Project Specifications,
the destructive sample will be 0.3 m wide by 1.1 m long with the
seam centered lengthwise.
The sample will be cut into three parts and distributed as follows:
- one portion, measuring 0.3 m x 0.3 m, to the Installer for QC
laboratory testing;
- one portion, measuring 0.3 m x 0.3 m, to the Owner for archive
storage; and
- one portion, measuring 0.3 m x 0.5 m, to the CQA Consultant for
CQA Laboratory testing.
10.3.9.5 Field Testing
The four 25 mm wide specimens mentioned
in Section 10.3.9.4 will be tested in the field, by calibrated
gaged tensiometer, one of
each pair in peel and one in shear. If any field test specimen
fails to pass the criteria of Table 4 and the project specifications,
then the procedures outlined in Section 10.3.9.9 will be followed.
The CQA Consultant will witness all field
tests and mark all samples and portions with their unique sample
number. The CQA Consultant
will also log the date and time of sampling, and test pass or fail
description.
If the two pairs of specimens meet the
project specifications, the sample qualifies for testing in the
laboratory; if they fail,
the seam should be repaired in accordance with section 10.4.3.
10.3.9.6 Construction Quality Assurance Laboratory Testing
Destructive test samples will be packaged
and shipped to the CQA laboratory by the CQA Consultant, in a
manner which will not damage
the test sample. The Project Manager will verify that packaging
and shipping conditions are acceptable. The Project Manager will
be responsible for storing the archive samples. This procedure
will be fully outlined at the Resolution Meeting. Test samples
will be tested by the CQA Laboratory.
Testing will follow ASTM D4437 as modified
in NSF 54 Appendix A (1993), but with no requirement for sample
conditioning time. The
minimum acceptable values to be obtained in these tests are those
indicated in the specifications or as shown in Table 4. Five specimens
will be tested in peel and five in shear. Specimens will be selected
alternately by test from the samples (e.g., peel, shear, peel,
shear, etc.).
The CQA Laboratory will provide test results
no more than 6 hours after they receive the samples. The CQA
Site Superintendent will review laboratory test results as soon
as they become available,
and make appropriate recommendations to the Project Manager.
10.3.9.7 Installer's Laboratory Testing
The Installer's laboratory test results will be available to the
Project Manager and the CQA Consultant for review.
10.3.9.8 Destructive Sample Pass/Fail Criteria
The criteria shown in Table 4, or the requirements of the project
specifications (whichever are the more comprehensive) must be met
for the acceptance of peel and shear test specimens:
TABLE 4. SEAM SPECIMEN TEST (ASTM D4437) SPECIFICATIONS
* The yield strength specified by the Manufacturer,
which is usually the population average value less 2 standard
deviations.
The peel criteria apply to both tracks of double track seams. Nine
out of the ten specimens in a seam destructive sample must meet
the criteria above for acceptance of the complete destructive sample.
The CQA Consultant will ensure that the CQA Laboratory retains
all sample and specimen remnants, clearly labelled, for at least
30 days after the last specimen for the project has been tested.
10.3.9.9 Procedures if Destructive Sample Fails
The following procedures will apply whenever
a sample fails a destructive test, whether that test is conducted
by the CQA Laboratory,
the Installer's laboratory, or on the field tensiometer.
The Installer has two options:
- Reconstruct the seam between the nearest passing destructive
test locations on each side of the failed sample; or
- Trace the seaming path to an intermediate
location (3 m minimum from the failed test location in each direction)
and take a small
sample for an additional field test at each location. If these
additional samples pass tensiometer testing, then full destructive
test samples should be taken. If these laboratory destructive
test samples pass the tests, then the seam should be reconstructed
between these locations by capping. If either sample fails, then
the process is repeated to establish the zone in which the seam
should be reconstructed.
If a fusion-type seam fails destructive
testing and the Installer chooses to repair the seam, the only
acceptable repair method is
as described in Section 10.4.3. Applying topping (bead of extrudate)
is not an approved method of capping any seam unless it can be
shown that this procedure will not reduce the stress rupture resistance
of the seam below 75% of that of the parent geomembrane.
Only seams bounded by two locations from which samples passing
laboratory destructive tests have been taken will be considered
acceptable. An additional destructive test sample will be taken
from repair seams when the length of a reconstructed seam exceeds
50 m. This sample must pass destructive testing or the procedure
outlined in this section must be repeated. The CQA Co |
