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SynC · Historical revision

Geosynthetics and Geotextiles

Revision4
EditedOct 8, 2026
StatusSuperseded
Contents

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Historical revision. This is editorial revision 4, kept so citations to it stay resolvable. It is not the current text of this standard — see the current revision.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Remade from scratch to the authoring rules: organized by function (separation, stabilization, filtration, drainage, reinforcement, paving interlayer, clay liner), with strength and opening size taken from the AASHTO M 288 class or the soil instead of one fixed value

1 Scope

NOTE This standard governs the selection, furnishing, conformance, and placement of geosynthetic materials used in civil site construction to separate, stabilize, filter, drain, reinforce, interlay, or contain, from the accepted surface the geosynthetic is placed on to the first lift of cover placed over it. (1.1)
NOTE The products covered are listed below. (1.2)
  • Woven and nonwoven geotextiles of polypropylene or polyester
  • Extruded, welded, and coated geogrids of polypropylene, polyester, or polyethylene
  • Drainage geocomposites of a geonet or cuspated polymer core with a bonded geotextile filter on one or both faces
  • Paving fabrics, paving grids, and grid-fabric composite interlayers for asphalt courses
  • Geosynthetic clay liners of sodium bentonite carried between geotextiles or on a geomembrane backing
NOTE A geosynthetic is specified by the function it performs, and the function, not the product name, fixes the properties that matter: the same nonwoven geotextile is judged by its survivability class when it separates, by its opening size and permittivity when it filters, and by its asphalt retention and melting point when it lies under an overlay. A property required for one function is irrelevant to another, and a product that satisfies the wrong column of a property table is non-conforming even where it is a better product. (1.3)
NOTE Most of the geosynthetics on a site belong to another system: the filter around a subdrain, the composite on a foundation wall, the geogrid in a retaining wall, the geotextile wrapping a stormwater chamber bed. Those systems decide where their geosynthetic goes, which configuration it takes, and how it connects, and their standards govern that work. This standard is written to be called by those standards for the product's properties and conformance, and it governs the whole of the work where the geosynthetic is placed for its own function on the subgrade, in a fill, under a pavement, or as a liner. (1.4)
NOTE The following are outside this standard and are governed elsewhere. (1.5)
  • Silt fence, fiber rolls, rolled erosion control products, and turf reinforcement mats, under Erosion And Sediment ControlErosion and Sediment ControlResolves to the current adopted revision.sync/erosion-and-sediment-control
  • The geogrid reinforcement, connection strength, layout, and facing of segmental and mechanically stabilized earth walls, and the filter fabric in the drainage zone behind a retaining wall, under Retaining WallsSite Retaining WallsResolves to the current adopted revision.sync/retaining-walls
  • The trench-wrap filter geotextile, the pipe sock, and the geocomposite panel of a pipe-and-aggregate subdrain, together with its apparent opening size selection against the native soil, under SubdrainageSubdrainageResolves to the current adopted revision.sync/subdrainage
  • The envelope geotextile and the prefabricated wall drainage composite of a building perimeter footing drain, under Foundation DrainageFoundation DrainageResolves to the current adopted revision.sync/foundation-drainage
  • The bentonite geotextile composite membrane applied to a below-grade wall or slab for waterproofing, under Below Grade WaterproofingBelow-Grade WaterproofingResolves to the current adopted revision.sync/below-grade-waterproofing
  • Whether a stormwater facility receives a barrier against infiltration, the extent of that barrier, the wrap around its chamber and aggregate beds, and any geomembrane, under Stormwater Management SystemsStormwater Management and Detention SystemsResolves to the current adopted revision.sync/stormwater-management-systems; the reservoir separation fabric and the impermeable membrane of a permeable pavement, under Permeable PavingPermeable PavingResolves to the current adopted revision.sync/permeable-paving
  • The aggregate base course, and the decision whether a separation geotextile is placed beneath it, under Aggregate Base CourseAggregate Base CourseResolves to the current adopted revision.sync/aggregate-base-course
  • Subgrade preparation, proof rolling, undercut, fill, compaction, and the decision to stabilize a rejected subgrade, under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork
  • The asphalt course placed over an interlayer, its minimum thickness and placement temperature, and the tack coat between asphalt lifts, under Asphalt PavingAsphalt PavingResolves to the current adopted revision.sync/asphalt-paving
  • Under-slab vapor retarders, under Vapor Barriers Under SlabUnder-Slab Vapor BarriersResolves to the current adopted revision.sync/vapor-barriers-under-slab
  • Aggregate piers, deep mixing, and jet grouting, under Ground ImprovementGround Improvement (Aggregate Piers and Soil Mixing)Resolves to the current adopted revision.sync/ground-improvement
  • The composite liner, leachate collection layer, and geomembrane of a regulated landfill, waste-disposal cell, or hazardous-waste containment, which no standard in this library covers
1.6 Where a stormwater facility is lined with a geosynthetic clay liner, the liner requirement and its limits are set under Stormwater Management SystemsStormwater Management and Detention SystemsResolves to the current adopted revision.sync/stormwater-management-systems and the geosynthetic clay liner shall conform to this standard.
1.7 Where another sitework standard calls for a geotextile, geogrid, or geocomposite by reference to this standard, the product shall conform to the property and conformance requirements of this standard for its function, and that standard's placement, overlap, and connection requirements shall govern where they are stated.
1.8 Where this standard and the geotechnical investigation report or the pavement design differ on a subgrade strength, a required property, or a layout, the geotechnical report or the design shall govern unless the Engineer of Record directs otherwise in writing.
1.9 The Contractor shall coordinate work under this standard with EarthworkEarthworkResolves to the current adopted revision.sync/earthwork for acceptance of the subgrade before placement and for the stabilization of a rejected subgrade; with Aggregate Base CourseAggregate Base CourseResolves to the current adopted revision.sync/aggregate-base-course for the first lift of base over a separation or stabilization geosynthetic; with Asphalt PavingAsphalt PavingResolves to the current adopted revision.sync/asphalt-paving for the overlay placed on an interlayer; and with SubdrainageSubdrainageResolves to the current adopted revision.sync/subdrainage, Foundation DrainageFoundation DrainageResolves to the current adopted revision.sync/foundation-drainage, and Stormwater Management SystemsStormwater Management and Detention SystemsResolves to the current adopted revision.sync/stormwater-management-systems where a geocomposite or liner furnished under this standard connects to a drain, a collector, or an outlet those standards govern.

2 Referenced Standards

2.1 Materials, testing, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
AASHTO M 288 Geosynthetic Specification for Highway Applications
ASTM D276 Identification of Fibers in Textiles
ASTM D4354 Sampling of Geosynthetics and Rolled Erosion Control Products for Testing
ASTM D4355 Deterioration of Geotextiles by Exposure to Light, Moisture and Heat in a Xenon Arc Type Apparatus
ASTM D4491 Water Permeability of Geotextiles by Permittivity
ASTM D4533 Trapezoid Tearing Strength of Geotextiles
ASTM D4632 Grab Breaking Load and Elongation of Geotextiles
ASTM D4716 Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant Head
ASTM D4751 Determining Apparent Opening Size of a Geotextile
ASTM D4759 Determining the Specification Conformance of Geosynthetics
ASTM D4833 Index Puncture Resistance of Geomembranes and Related Products
ASTM D4873 Identification, Storage, and Handling of Geosynthetic Rolls and Samples
ASTM D4884 Strength of Sewn or Bonded Seams of Geotextiles
ASTM D5101 Measuring the Filtration Compatibility of Soil-Geotextile Systems
ASTM D5261 Measuring Mass per Unit Area of Geotextiles
ASTM D5321 Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear
ASTM D5887 Measurement of Index Flux Through Saturated Geosynthetic Clay Liner Specimens Using a Flexible Wall Permeameter
ASTM D5888 Storage and Handling of Geosynthetic Clay Liners
ASTM D5890 Swell Index of Clay Mineral Component of Geosynthetic Clay Liners
ASTM D5891 Fluid Loss of Clay Component of Geosynthetic Clay Liners
ASTM D5993 Measuring Mass per Unit of Geosynthetic Clay Liners
ASTM D6140 Determining Asphalt Retention of Paving Fabrics Used in Asphalt Paving for Full-Width Applications
ASTM D6241 Static Puncture Strength of Geotextiles and Geotextile-Related Products Using a 50-mm Probe
ASTM D6243 Determining the Internal and Interface Shear Strength of Geosynthetic Clay Liner by the Direct Shear Method
ASTM D6495 Acceptance Testing Requirements for Geosynthetic Clay Liners
ASTM D6496 Determining Average Bonding Peel Strength Between Top and Bottom Layers of Needle-Punched Geosynthetic Clay Liners
ASTM D6637 Determining Tensile Properties of Geogrids by the Single or Multi-Rib Tensile Method
ASTM D6766 Evaluation of Hydraulic Properties of Geosynthetic Clay Liners Permeated with Potentially Incompatible Aqueous Solutions
ASTM D7005 Determining the Bond Strength (Ply Adhesion) of Geocomposites
ASTM D7406 Time-Dependent (Creep) Deformation Under Constant Pressure for Geosynthetic Materials
ASTM D7737 Individual Geogrid Junction Strength
GRI GCL3 Test Methods, Required Properties, and Testing Frequencies of Geosynthetic Clay Liners
FHWA-NHI-07-092 Geosynthetic Design and Construction Guidelines

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for the Engineer of Record's review before any geosynthetic is delivered to the site:
  • Product data for each geosynthetic, identifying the manufacturer, the product designation, the polymer, the construction, and the function and AASHTO M 288 class it is furnished to satisfy
  • Manufacturer's certified test report for each roll lot, reporting the measured value and the test method for every property this standard requires for the product's function
  • For each geotextile, the grab tensile strength and elongation per ASTM D4632, the trapezoid tear strength per ASTM D4533, the static puncture strength per ASTM D6241, the apparent opening size per ASTM D4751, the permittivity per ASTM D4491, the mass per unit area per ASTM D5261, and the retained strength after exposure per ASTM D4355
  • For each geogrid, the tensile strength per ASTM D6637 in the machine and cross-machine directions at ultimate and at 2 percent and 5 percent strain, the junction strength per ASTM D7737, and the aperture dimensions
  • For each drainage geocomposite, the in-plane flow rate per ASTM D4716 at the normal stress and hydraulic gradient of the installation, the ply adhesion per ASTM D7005, the compressive creep report per ASTM D7406 where required, and the properties of the bonded filter geotextile
  • For each paving fabric, the asphalt retention per ASTM D6140 and the melting point per ASTM D276; for each paving grid, the tensile strength per ASTM D6637
  • For each geosynthetic clay liner, the bentonite mass per unit area per ASTM D5993, the swell index per ASTM D5890, the fluid loss per ASTM D5891, the peel strength per ASTM D6496, and the hydraulic conductivity or index flux per the test basis in the datasheet
  • The interface shear strength per ASTM D5321, or per ASTM D6243 for a geosynthetic clay liner, where the geosynthetic lies on a slope steeper than 4 horizontal to 1 vertical or within a reinforced fill
  • The manufacturer's written installation instructions, including overlap widths, seaming methods, anchoring, repair procedures, the permitted exposure period, and, for a paving fabric, the sealant type and application rate
  • A panel layout and seaming plan where seams are sewn, where panels are oriented to a drainage flow, or where a geosynthetic clay liner is placed
Action Submittals Requiredcheckbox
☑ Product data by function and AASHTO M 288 class
☑ Certified test report per roll lot
☐ Geotextile property test results
☐ Geogrid property test results
☐ Drainage geocomposite property test results
☐ Paving fabric and paving grid property test results
☐ Geosynthetic clay liner property test results
☐ Interface shear strength report
☑ Manufacturer's installation instructions
☐ Panel layout and seaming plan
3.1.2 No geosynthetic shall be placed until the product data and the certified test report for its roll lot have been reviewed and returned.
3.1.3 Review of a submittal does not relieve the Contractor of responsibility for furnishing a product that conforms to the Contract Documents.

3.2 Informational Submittals

3.2.1 The Contractor shall submit the following for record:
  • A roll identification log correlating each delivered roll number to its lot and to the certified test report for that lot
  • The subgrade acceptance record for each area, showing the date of acceptance under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork and the date the geosynthetic was placed
  • A placement record for each area, recording the product, the roll numbers placed, the overlap or seam type used, the date covered, and the weather
  • A field repair log recording the location, the cause, and the method of each repair
  • Independent conformance test results where independent sampling is selected in the datasheet
  • For a geosynthetic clay liner, a record of the panel layout as placed, the overlap widths, the supplemental bentonite placed, and the date and thickness of the first cover
Informational Submittals Requiredcheckbox
☑ Roll identification log
☐ Subgrade acceptance record
☐ Placement record
☑ Field repair log
☐ Independent conformance test results
☐ Geosynthetic clay liner placement record

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 Each geosynthetic shall be the product of a manufacturer that operates a documented manufacturing quality control program and tests each roll lot for the properties it certifies.
4.1.2 A drainage geocomposite and a geosynthetic clay liner shall each be furnished as a single manufacturer's assembled product, with the bonded geotextile and the core, or the bentonite and its carrier geotextiles, covered by one certified test report.

4.2 Certified Test Reports and Conformance

4.2.1 The certified test report for each roll lot shall report measured values obtained by the test method cited for each property, and shall not substitute a catalog value or a statement of compliance for a measured value.
4.2.2 Reported strength, puncture, tear, and hydraulic values shall be minimum average roll values unless the report identifies a value as a typical or a maximum value.
4.2.3 Conformance of a reported or an independently measured value to a specified minimum or maximum shall be judged in accordance with ASTM D4759.
4.2.4 Roll-to-lot traceability shall be maintained from delivery to placement through the roll identification log, and a roll whose lot cannot be identified shall not be placed.
NOTE A certified test report is a claim about a lot, and the roll log is what ties the roll on the subgrade to that claim; without the log, a passing report proves nothing about the roll in the ground. (4.2.5)

4.3 Pre-Installation Conference

4.3.1 A pre-installation conference shall be held at the site before the first geosynthetic is placed.
4.3.2 The conference shall be attended by the Engineer of Record or the Owner's Representative, the geotechnical engineer where one is retained, the General Contractor, the earthwork subcontractor, the installer, and, where an interlayer is placed, the paving subcontractor.
4.3.3 The conference shall cover subgrade acceptance and its documentation, the function and class of each product and the area it serves, overlap and seaming, anchoring, the first lift of cover and the equipment that places it, the exposure limit, repair procedures, and, for a geosynthetic clay liner, hydration protection and the sequence of cover.
4.3.4 Minutes shall be recorded by the General Contractor and distributed to all attendees within 5 working days.

5 Service Conditions

5.1 Ultraviolet Exposure

NOTE Polypropylene and polyester lose tensile strength under ultraviolet light, and the loss is invisible on inspection: a geotextile left on the subgrade through a summer month looks the same as the day it was unrolled and tears under the first lift of stone. The retained-strength test exposes the product to a xenon arc for a fixed period and reports the strength that survives, which is a measure of the product's stabilization package rather than a prediction of its life in the ground. (5.1.1)
5.1.2 Every geotextile shall retain, after exposure in accordance with ASTM D4355 for 500 hours, not less than the percentage of its grab tensile strength indicated in the datasheet.
Geotextile Retained Grab Strength After 500 h Ultraviolet Exposure (ASTM D4355)radio
● 50 percent
○ 70 percent
NOTE A 50 percent retention after 500 hours is the AASHTO M 288 requirement for every function and is what the standard product lines carry; a 70 percent retention is a stabilized product that costs more and is selected where the geosynthetic will stand exposed for longer than the placement sequence of ordinary earthwork allows, as on a staged fill or a slope face that waits for its cover. (5.1.3)
5.1.4 A geogrid shall be stabilized against ultraviolet degradation with carbon black or an equivalent stabilizer and shall retain not less than 70 percent of its tensile strength after exposure in accordance with ASTM D4355 for 500 hours.

5.2 Soil and Groundwater Chemistry

NOTE Polyester hydrolyzes in strongly alkaline and strongly acidic pore water, and the loss is a loss of molecular weight rather than of a surface, so it is not stopped by a coating; polypropylene and polyethylene are inert across the pH range found in natural soils and in lime- or cement-treated subgrades. The hazard to polyester is a treated subgrade, a concrete-contact zone, or an industrial fill, not an ordinary clay. (5.2.1)
5.2.2 A polyester geotextile or geogrid shall not be placed in contact with soil, fill, or groundwater whose pH is below 3 or above 9, or against a lime- or cement-treated layer, unless the manufacturer certifies the product's chemical durability for that condition in writing.
5.2.3 Where the geotechnical investigation report identifies a pH, a sulfate, a hydrocarbon, or another chemical condition in the soil or the groundwater, the Contractor shall furnish a polymer the manufacturer certifies as durable for that condition for the design service life.

6 Function and Product Selection

NOTE The functions a geosynthetic performs on the site are listed below; a product can serve more than one at the same location, and the properties required are the union of the properties for each function it serves. (6.1)
  • Separation: keeps a coarse aggregate layer and a fine-grained subgrade from mixing, so the aggregate is not contaminated from below and pumped into the subgrade under traffic
  • Subgrade stabilization: separation plus a measured improvement in the load response of a soft subgrade, so that a working platform or a base can be built and compacted on it
  • Filtration: retains the protected soil while passing water across the plane of the geotextile, where the geotextile stands alone as the filter or forms the filter face of a geocomposite
  • Subsurface drainage: conveys water within the plane of a geocomposite core to a collector or an outlet
  • Base reinforcement: a geogrid that confines an aggregate base or a working platform through interlock, reducing the thickness the base needs or extending the life of the section
  • Asphalt interlayer: a paving fabric, paving grid, or grid-fabric composite placed in a sealant beneath an asphalt course to retard reflective cracking and, for a fabric, to resist moisture
  • Bentonite containment: a geosynthetic clay liner forming a low-permeability barrier beneath a pond, a secondary containment, or a cap
6.2 The geosynthetic functions required on the project shall be as indicated in the datasheet.
Geosynthetic Functions Requiredcheckbox
☐ Separation
☐ Subgrade stabilization
☐ Filtration
☐ Subsurface drainage
☐ Base reinforcement
☐ Asphalt interlayer
☐ Bentonite containment
6.3 Each geosynthetic shall be furnished for the function it is placed to perform, with the product type and the properties required by the article of this standard for that function.
6.4 A geosynthetic shall not be substituted for a product of a different construction, polymer, or class without the Engineer of Record's written acceptance.
6.5 The polymer of each geotextile shall be as indicated in the datasheet.
Geotextile Polymerradio
● Polypropylene
○ Polyester
NOTE Polypropylene is the polymer of nearly every separation, stabilization, filtration, and paving geotextile sold, because it is inert in soil and cheap; polyester carries a higher modulus and creeps less under sustained load, which matters only where the geotextile is a tensile reinforcement, and it carries the pH limit stated under Service Conditions. (6.6)

7 Separation Geotextile

NOTE A separation geotextile is placed between a fine-grained subgrade and the aggregate placed on it: beneath an aggregate base, beneath crushed stone in an undercut or a trench bottom, beneath a working platform, and beneath a stone drainage layer that is not part of a subdrain. It carries no design load; it survives placement and then keeps two materials apart for the life of the section. (7.1)
NOTE Whether a separation geotextile is placed beneath an aggregate base is decided under Aggregate Base CourseAggregate Base CourseResolves to the current adopted revision.sync/aggregate-base-course, and whether one is placed beneath the crushed stone of a stabilized subgrade or a trench bottom is decided under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork; this article governs the geotextile those decisions call for. (7.2)

7.3 Separation Geotextile Type

7.3.1 The separation geotextile type shall be as indicated in the datasheet.
Separation Geotextile Typeradio
○ Woven slit-film polypropylene
○ Woven monofilament
○ Nonwoven needle-punched
○ Nonwoven heat-bonded
NOTE A woven slit-film geotextile carries the highest strength per dollar and the lowest permittivity, and is the common choice where the geotextile only has to separate and the subgrade drains through the base rather than through the fabric; a woven monofilament passes more water than a slit-film at similar strength and costs more; a nonwoven needle-punched geotextile elongates before it tears, conforms to a rough subgrade, and passes water freely, so it tolerates a rocky or rutted surface and serves where the layer must also filter; a nonwoven heat-bonded geotextile is thin and stiff with a low permittivity, placed where a thin, puncture-resistant separator is wanted on a smooth subgrade. (7.3.2)

7.4 Separation Survivability Class

NOTE AASHTO M 288 sets geotextile strength requirements by survivability class, which measures the severity of placement, not the load in service: the angularity and size of the aggregate dropped on the geotextile, the roughness of the subgrade, the thickness of the first lift, and the weight of the equipment that places it. Within a class the required strengths differ by the elongation of the product, so a woven and a nonwoven of the same class carry different minimums. (7.4.1)
7.4.2 The AASHTO M 288 survivability class of the separation geotextile shall be as indicated in the datasheet.
Separation Geotextile Survivability Class (AASHTO M 288)select
Class 1
Class 2
Class 3
NOTE Class 2 is the AASHTO M 288 default for separation and covers an aggregate base placed in ordinary lifts by ordinary equipment on a prepared subgrade; Class 1 is selected where angular stone larger than about 2 in. is dropped on the geotextile, where the subgrade is rocky, rutted, or uncleared, or where tracked equipment runs on a thin first lift; Class 3 is a lighter product accepted where the subgrade is smooth and fine-grained, the first lift is placed by light equipment, and the Engineer of Record accepts the reduction in writing. (7.4.3)
7.4.4 The grab tensile strength, grab elongation, trapezoid tear strength, and static puncture strength of the separation geotextile shall be not less than the AASHTO M 288 values for the survivability class in the datasheet and the elongation class of the product furnished.
7.4.5 The apparent opening size, the permittivity, and the retained strength after ultraviolet exposure of the separation geotextile shall satisfy the AASHTO M 288 requirements for the separation function.
7.4.6 Where the separation geotextile is placed on a subgrade whose strength is below the range AASHTO M 288 assigns to separation, the geotextile shall be furnished under the Subgrade Stabilization article instead.

8 Subgrade Stabilization

NOTE Stabilization is called for where the subgrade is too soft to carry construction traffic or to let the first lift of base be compacted, and the geosynthetic does two things: it separates, and it spreads the wheel load over a wider area of the subgrade so that a thinner stone layer carries the traffic. A geotextile does this by tension in its plane as the subgrade deflects; a geogrid does it by interlocking the stone in its apertures so the stone acts as a stiffer plate. The weaker the subgrade, the more the interlock matters and the less a fabric alone achieves. (8.1)
NOTE Whether a rejected subgrade is stabilized with a geosynthetic, and the depth and extent of the stone over it, is decided under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork at each occurrence; this article governs the geosynthetic that decision calls for. (8.2)

8.3 Stabilization Geosynthetic Selection

8.3.1 The stabilization geosynthetic shall be as indicated in the datasheet.
Stabilization Geosyntheticradio
○ Woven geotextile
○ Nonwoven geotextile
○ Geogrid
○ Geogrid over a separation geotextile
○ Geogrid-geotextile composite
NOTE A woven stabilization geotextile develops tension at small strain and is the common choice where the subgrade CBR is in the range of about 1 to 3 and the stone is placed in a single lift; a nonwoven stabilization geotextile strains more before it carries load but survives a rough surface and passes water, so it serves where the subgrade is wet and drains upward through the stone; a geogrid alone confines the stone and is selected where the subgrade is firm enough not to pump fines through the apertures; a geogrid over a separation geotextile adds the separation the grid lacks and is the usual answer where the CBR is below about 1 and the subgrade is fine-grained; a geogrid-geotextile composite does the same in one factory-bonded product at a higher material cost and a faster placement. (8.3.2)
8.3.3 The stabilization geosynthetic shall be selected for the subgrade strength reported in the geotechnical investigation report at the location of the work, and where the Contractor and the Engineer of Record disagree whether the reported strength applies at a location, the geotechnical engineer shall make the initial determination.

8.4 Stabilization Geotextile Survivability Class

8.4.1 The AASHTO M 288 survivability class of a stabilization geotextile shall be as indicated in the datasheet.
Stabilization Geotextile Survivability Class (AASHTO M 288)select
Class 1
Class 2
Class 3
NOTE AASHTO M 288 assigns Class 1 to stabilization, because a stabilization geotextile is by definition placed on a soft, often wet and rutted subgrade and loaded by the stone that bridges it, which is the severe placement condition; Class 2 is accepted where the subgrade is soft but smooth and the first lift is placed by light equipment, and Class 3 has no stabilization application except where the Engineer of Record accepts it for a thin working platform on a clean, fine-grained surface. (8.4.2)
8.4.3 The strength and hydraulic properties of a stabilization geotextile shall be not less than the AASHTO M 288 values for the stabilization function, the survivability class in the datasheet, and the elongation class of the product furnished.
8.4.4 A geogrid used for stabilization shall conform to the Base Reinforcement Geogrid article.
8.4.5 A geosynthetic shall not be placed to stabilize a subgrade that has not been proof-rolled and dispositioned under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork; a stabilization geosynthetic supplements a subgrade that has been prepared and does not replace its preparation.

9 Filtration Geotextile

NOTE A filtration geotextile holds the protected soil in place while water crosses its plane into a coarser layer: beneath a stone drainage blanket, beneath riprap and rock protection on a slope or at an outfall, around a stone-filled interceptor that is not a piped subdrain, and as the filter face bonded to a drainage geocomposite. The filter at a piped subdrain, at a footing drain, behind a retaining wall, and around a stormwater chamber bed is governed by the standard for that system, which selects the opening size against its own soil. (9.1)
NOTE A filter works only within a band: an opening too large lets the protected soil pipe through and the layer behind it fills with fines, and an opening too small blinds with those same fines on the soil side and stops passing water. Both failures are slow, both are invisible from the surface, and both are decided at the time the opening size is picked against the gradation of the soil, which is why the opening size and the permittivity are derived from the soil and not chosen from a catalog. (9.2)

9.3 Filtration Geotextile Type

9.3.1 The filtration geotextile type shall be as indicated in the datasheet.
Filtration Geotextile Typeradio
● Nonwoven needle-punched
○ Woven monofilament
NOTE A nonwoven needle-punched geotextile has a three-dimensional pore structure that retains soil through its thickness and holds its permittivity as fines collect, and it is the product nearly every filtration application uses; a woven monofilament has a regular, measurable opening and a high percent open area, and is selected where a uniform coarse sand or a gap-graded soil calls for a filter whose opening can be matched to the soil exactly, or where the filter lies under riprap and must resist abrasion. (9.3.2)
9.3.3 A woven slit-film geotextile shall not be furnished for the filtration function.

9.4 Filtration Opening Size and Permittivity

9.4.1 The maximum apparent opening size of the filtration geotextile, determined in accordance with ASTM D4751, shall be as indicated in the datasheet.
Filtration Geotextile Maximum Apparent Opening Size (ASTM D4751)range
mm
0.150.180.210.250.30.430.60.85
Derived — the percent of the protected soil passing the No. 200 sieve reported in the geotechnical investigation report, per the AASHTO M 288 subsurface drainage requirements (by default)
9.4.2 The minimum permittivity of the filtration geotextile, determined in accordance with ASTM D4491, shall be as indicated in the datasheet.
Filtration Geotextile Minimum Permittivity (ASTM D4491)range
1/s
0.050.10.20.50.711.52
Derived — the percent of the protected soil passing the No. 200 sieve reported in the geotechnical investigation report, per the AASHTO M 288 subsurface drainage requirements (by default)
NOTE AASHTO M 288 steps the maximum opening size down and the minimum permittivity down as the fines content of the protected soil rises, so the pair is read from the same soil fraction and moves together; an engineer who sets one by a filter design for a gap-graded, dispersive, or internally unstable soil sets the other from the same design rather than leaving it at the M 288 value. (9.4.3)
9.4.4 The strength properties of the filtration geotextile shall be not less than the AASHTO M 288 Class 2 values for the elongation class of the product furnished, unless the Engineer of Record designates a different class in writing for the placement condition.
9.4.5 Whether a soil-geotextile filtration compatibility evaluation in accordance with ASTM D5101 is required for the protected soil shall be as indicated in the datasheet.
Soil-Geotextile Filtration Compatibility Evaluation (ASTM D5101)radio
○ Required
○ Not required
NOTE A gradient ratio test runs the actual soil against the actual geotextile under a head and reports whether the system clogs or pipes; opening size and permittivity alone do not predict the behavior of a dispersive clay, a silt that migrates, or a gap-graded sand with a missing fraction, so the evaluation is required where the geotechnical report describes such a soil and is omitted where it describes a well-graded soil with a stable fine fraction. (9.4.6)
9.4.7 Where the evaluation is required and the measured gradient ratio exceeds 3, the Contractor shall submit a different geotextile for the Engineer of Record's review before any filtration geotextile is placed.

10 Drainage Geocomposite

NOTE A drainage geocomposite replaces a thickness of drainage aggregate with a polymer core that carries water in its plane and a geotextile bonded to the core that keeps the soil out of it. It is placed where there is no room for stone, where stone would have to be hauled to a place a roll can be carried, or where a thin drainage plane is wanted beneath a slab or a liner, on a slope face, or as a capillary break between a subgrade and the layer above it. (10.1)
NOTE The wall drainage composite on a foundation wall and the geocomposite panel of a subdrain are selected, configured, and connected under Foundation DrainageFoundation DrainageResolves to the current adopted revision.sync/foundation-drainage and SubdrainageSubdrainageResolves to the current adopted revision.sync/subdrainage; this article governs the geocomposite itself and the geocomposite placed for its own function beneath a slab, a liner, a fill, or a slope face. (10.2)

10.3 Core and Filter Construction

10.3.1 The drainage geocomposite core type shall be as indicated in the datasheet.
Drainage Geocomposite Core Typeradio
○ Biplanar geonet
○ Triplanar geonet
○ Cuspated or dimpled sheet
NOTE A biplanar geonet is two sets of crossed polyethylene strands with a modest flow channel and a high crush resistance, and it is the economical core where the normal stress is high and the required flow is moderate; a triplanar geonet adds a set of straight central ribs that keep a larger channel open under load, carrying several times the flow of a biplanar at the same thickness and a higher price; a cuspated or dimpled sheet holds the largest open channel at low normal stress and is the core of most wall and sheet drains, and it loses channel height first when it is loaded beyond its rated stress. (10.3.2)
10.3.3 The faces of the core carrying a bonded filter geotextile shall be as indicated in the datasheet.
Drainage Geocomposite Filter Geotextile Facesradio
○ One face
○ Both faces
NOTE A single-faced geocomposite lies with its bare core against a structure, a liner, or a concrete surface, where nothing can enter the core from that side; a double-faced geocomposite is buried in soil or between two soil layers, where either face admits fines without a filter. (10.3.4)
10.3.5 The filter geotextile bonded to the core shall conform to the Filtration Geotextile article for the soil it faces.
10.3.6 The bond strength between the filter geotextile and the core, determined in accordance with ASTM D7005, shall be not less than the manufacturer's published minimum for the product, and the filter shall not delaminate from the core during handling or placement.

10.4 In-Plane Flow Capacity

10.4.1 The minimum in-plane flow rate per unit width of the drainage geocomposite, determined in accordance with ASTM D4716, shall be as indicated in the datasheet.
Drainage Geocomposite Minimum In-Plane Flow Rate (ASTM D4716)range
gpm/ft
0.512510152550100
Per drawings — the subsurface drainage design (deferred by default)
10.4.2 The in-plane flow rate shall be reported at the normal stress the geocomposite carries at the deepest point of its installation, at the hydraulic gradient of the installation, and with the boundary materials the geocomposite lies between in service.
NOTE A flow rate reported between rigid plates at a low normal stress overstates what the same core delivers under 20 ft of fill between two soils, because the geotextile intrudes into the channel under load and the core compresses; the only flow rate that means anything to the design is the one measured under the stress and against the boundaries the product will see. (10.4.3)
10.4.4 Whether compressive creep testing in accordance with ASTM D7406 is required for the geocomposite core shall be as indicated in the datasheet.
Drainage Geocomposite Compressive Creep Testing (ASTM D7406)radio
○ Required
○ Not required
NOTE A short-term flow test does not show the channel height a core keeps after years under a sustained load; creep testing is required where the geocomposite carries a deep fill, a liner cover, or a structure for the life of the installation, and omitted where it drains a shallow slab base or a slope face under a thin cover. (10.4.5)
10.4.6 The drainage geocomposite shall discharge to a collector pipe, a drainage aggregate, or an outlet through the manufacturer's transition fitting or the detail shown on the subsurface drainage details, and shall not be terminated against soil.
10.4.7 Where the geocomposite discharges to a subdrain, a footing drain, or a stormwater facility, the connection shall be made as that system's standard requires.

11 Base Reinforcement Geogrid

NOTE A geogrid reinforces an aggregate base or a working platform by interlock: the stone penetrates the apertures and is held by the ribs, so the layer resists lateral spreading under a wheel and acts as a stiffer plate than the same stone unreinforced. What the design relies on is therefore the stiffness of the grid at small strain, the stability of its apertures, and the strength of its junctions, not the ultimate strength of the ribs, and two grids with the same ultimate strength and different aperture geometry perform differently under the same wheel. (11.1)
NOTE The geogrid in a segmental or mechanically stabilized earth retaining wall is a different product serving a different function, with a long-term design strength, a connection strength, and a layout the wall design fixes; it is governed by Retaining WallsSite Retaining WallsResolves to the current adopted revision.sync/retaining-walls. (11.2)

11.3 Geogrid Type

11.3.1 The geogrid type shall be as indicated in the datasheet.
Geogrid Typeradio
○ Extruded biaxial, punched and drawn
○ Extruded multiaxial, triangular aperture
○ Coated woven or knitted polyester
○ Welded strip
NOTE An extruded biaxial geogrid is a punched and drawn polypropylene sheet with square or rectangular apertures and stiff integral junctions, carrying its stiffness in two directions; an extruded multiaxial geogrid distributes its stiffness through 360 degrees around a triangular aperture, which matches the radial loading under a wheel and is the basis of the proprietary design methods its manufacturers publish; a coated woven or knitted polyester geogrid carries a high tensile strength at low cost in its yarn directions, with junctions that rely on the coating, and serves where the function is tensile reinforcement of a fill more than confinement of a base; a welded strip geogrid of polyester or polypropylene strips has strong junctions and flat ribs and is selected where a high strength per unit weight is wanted in a reinforced fill. (11.3.2)
11.3.3 The geogrid shall be a single integrally formed, welded, or coated structure with uniform apertures, and the strength of its junctions, determined in accordance with ASTM D7737, shall be not less than the manufacturer's published minimum for the product.
11.3.4 The aperture dimensions of a base reinforcement geogrid shall lie within the manufacturer's published range of compatible aggregate sizes for the nominal maximum size of the aggregate placed on it.

11.4 Geogrid Strength

11.4.1 The minimum ultimate tensile strength of the geogrid, determined in accordance with ASTM D6637 in each principal direction, shall be as indicated in the datasheet.
Geogrid Minimum Ultimate Tensile Strength, Each Principal Direction (ASTM D6637)range
lb/ft
50010000
Per drawings — the pavement design in the geotechnical investigation report (deferred by default)
11.4.2 Where the pavement design states the geogrid by its tensile strength at 2 percent or 5 percent strain, by an aperture stability modulus, or by a product-specific design method, the geogrid furnished shall meet that stated basis in addition to the ultimate strength in the datasheet.
11.4.3 The geogrid shall be furnished with its machine direction oriented as the design shows, and a geogrid whose two principal directions differ in strength shall not be rotated in the field.

11.5 Reinforced Fill and Working Platforms

11.5.1 Where a geogrid or a high-strength geotextile is placed as tensile reinforcement in an embankment, a reinforced slope, or a working platform over soft ground, its long-term design strength, its layers, and its layout shall be as indicated on the geotechnical design for the reinforced fill.
11.5.2 Reinforcement in a fill shall be placed with its strong direction perpendicular to the slope face or across the span it reinforces, pulled taut, and anchored before the fill above it is placed.
NOTE A reinforcement layer that lies slack or folded carries no load until the fill above it has moved far enough to straighten it, which is the movement the reinforcement exists to prevent. (11.5.3)

12 Asphalt Interlayer

NOTE An interlayer is placed beneath an asphalt course to change how the course behaves over the cracks, joints, and movement in the layer under it. A paving fabric saturated with asphalt sealant forms a membrane that keeps surface water out of the base and a soft layer that dissipates the strain over a crack before it reaches the new surface; a paving grid holds the overlay together in tension across a crack; a composite does both. None of them bridges a failed base, and an interlayer placed over a pavement that moves vertically under load delays the reflection of that movement by a season rather than preventing it. (12.1)
NOTE The surface the interlayer is placed on, the sealant tack between asphalt lifts, and the asphalt course placed over the interlayer, with its thickness, placement temperature, and the same-day coverage of the interlayer, are governed by Asphalt PavingAsphalt PavingResolves to the current adopted revision.sync/asphalt-paving; this article governs the interlayer product, its sealant, and its placement. (12.2)

12.3 Interlayer Type

12.3.1 The asphalt interlayer type shall be as indicated in the datasheet.
Asphalt Interlayer Typeradio
● Paving fabric
○ Paving grid
○ Grid-fabric composite
NOTE A paving fabric is the interlayer of nearly every parking lot and site overlay, because it is the only one that forms a moisture barrier and it costs the least to furnish and place; a paving grid adds tensile capacity across a crack and is selected over a jointed concrete pavement or a pavement with wide thermal cracks where a fabric alone has been seen to reflect the crack, and it carries no moisture barrier; a grid-fabric composite pairs the two in one product for a pavement that needs both, at the highest material cost and with a sealant rate set by the fabric component. (12.3.2)

12.4 Paving Fabric

12.4.1 The paving fabric shall be a nonwoven polypropylene geotextile with a mass per unit area, determined in accordance with ASTM D5261, not less than the value indicated in the datasheet.
Paving Fabric Minimum Mass per Unit Area (ASTM D5261)range
oz/yd²
3.54.14.568
12.4.2 The paving fabric shall have an asphalt retention, determined in accordance with ASTM D6140, of not less than 0.20 gal/yd², and a melting point, determined in accordance with ASTM D276, of not less than 300°F.
NOTE The 4.1 oz/yd² fabric is the AASHTO M 288 paving fabric and the product the whole market is built around; a heavier fabric holds more sealant and lies on a rough milled surface without bridging, and is selected over a badly cracked or milled surface at a proportionally higher sealant rate. (12.4.3)
12.4.4 The grab tensile strength and elongation of the paving fabric shall satisfy the AASHTO M 288 requirements for a paving fabric.

12.5 Interlayer Sealant

12.5.1 The sealant that saturates and bonds the interlayer shall be as indicated in the datasheet.
Interlayer Sealant Materialradio
● Paving-grade asphalt cement
○ Asphalt emulsion
NOTE Hot paving-grade asphalt cement saturates the fabric on contact and bonds the overlay the same day, which is why every fabric manufacturer publishes it as the sealant and most specify it alone; an emulsion is accepted by some manufacturers for some fabrics where hot asphalt cannot be delivered, and it must break and cure to leave the residual asphalt the fabric needs before the fabric is placed into it, which adds a weather-dependent wait and leaves the fabric floating if the fabric is placed early. (12.5.2)
12.5.3 Where an asphalt emulsion is indicated in the datasheet, it shall be a grade the fabric manufacturer accepts in writing for the fabric furnished, and the fabric shall not be placed until the emulsion has broken and cured to the manufacturer's stated condition.
12.5.4 The sealant shall be applied at the residual rate indicated in the datasheet.
Interlayer Sealant Residual Application Raterange
gal/yd²
0.150.4
Derived — the asphalt retention of the fabric furnished per ASTM D6140, plus the amount needed to bond the fabric to the existing surface for its condition, per the fabric manufacturer's published rate (by default)
NOTE The sealant rate is the single most common cause of an interlayer failure: too little leaves the fabric dry and the overlay debonds, too much floats the fabric and the overlay shoves and bleeds. The fabric's retention sets the floor, and the surface sets the rest: a smooth, dense surface takes the retention plus a small margin, a milled or absorbent surface takes more, and the manufacturer publishes the adjustment for each. (12.5.5)
12.5.6 The Contractor shall not reduce the sealant application rate to control tracking by hauling vehicles.
12.5.7 The sealant for a paving grid without a fabric component shall be applied at the rate the grid manufacturer publishes for the grid furnished and the surface it is placed on.

12.6 Paving Grid

12.6.1 The fiber of a paving grid shall be as indicated in the datasheet.
Paving Grid Fiberradio
○ Glass fiber
○ Polyester
NOTE A glass-fiber grid has a high modulus and does not creep, so it carries load at the small strains a crack opening produces, and it is brittle under construction traffic before the overlay covers it; a polyester grid tolerates the paver and the trucks and recovers from a fold, and it strains further before it carries the same load, which suits a flexible pavement with thermal movement more than a jointed concrete pavement with a fixed crack pattern. (12.6.2)
12.6.3 The minimum tensile strength of the paving grid, determined in accordance with ASTM D6637 in each principal direction, shall be as indicated in the datasheet.
Paving Grid Minimum Tensile Strength, Each Principal Direction (ASTM D6637)range
lb/ft
200015000
Per drawings — the overlay design (deferred by default)
12.6.4 A paving grid shall be furnished with the fabric backing, self-adhesive coating, or asphalt-compatible coating the manufacturer requires to bond it to the sealant and hold it under the paver, and a grid shall not be placed bare where the manufacturer's instructions require a backing.

13 Geosynthetic Clay Liner

NOTE A geosynthetic clay liner is a layer of sodium bentonite held between two geotextiles or on a geomembrane backing, which swells on hydration under confinement into a barrier with a hydraulic conductivity in the range of a compacted clay liner several feet thick. It is placed beneath ponds, basins, and secondary containments, and over caps, within the civil sitework scope; the composite liner of a regulated waste cell is outside this standard. (13.1)
NOTE The bentonite does its work only when it hydrates under a confining load: a liner that wets before it is covered swells unconfined, loses bentonite at its overlaps, and does not recover the conductivity it was tested for. Every placement rule in this article follows from that one fact. (13.2)

13.3 Liner Construction

13.3.1 The geosynthetic clay liner type shall be as indicated in the datasheet.
Geosynthetic Clay Liner Typeradio
● Needle-punched, geotextile-encapsulated
○ Stitch-bonded, geotextile-encapsulated
○ Geomembrane-laminated
NOTE A needle-punched liner carries fibers through the bentonite from one carrier geotextile to the other, giving it an internal shear strength that holds on a slope and a peel strength that keeps the bentonite in place during handling, and it is the product nearly every site liner uses; a stitch-bonded liner holds its layers with rows of stitching, with a lower internal shear strength between the rows, and is placed on flat grades; a geomembrane-laminated liner adds a thin polyethylene film to one face, which blocks the liquid from reaching the bentonite at a puncture in the film and lowers the system's conductivity, at a higher cost and with the interface shear of the film to account for on a slope. (13.3.2)
13.3.3 The bentonite in the liner shall be as indicated in the datasheet.
Geosynthetic Clay Liner Bentoniteradio
● Natural sodium bentonite
○ Polymer-amended sodium bentonite
NOTE Natural sodium bentonite reaches its design conductivity with fresh water and loses it when the permeant carries calcium, salts, or a low pH, which collapse the swelled clay; a polymer-amended bentonite holds its conductivity against those permeants and is selected where the liquid is a brine, a leachate, a de-icing runoff, or a process water, which is also the condition under which the conductivity is tested with the site liquid rather than with water. (13.3.4)
13.3.5 The bentonite shall have a swell index, determined in accordance with ASTM D5890, of not less than 24 mL per 2 g, and a fluid loss, determined in accordance with ASTM D5891, of not more than 18 mL.
13.3.6 The minimum bentonite mass per unit area, determined in accordance with ASTM D5993 at the moisture content GRI GCL3 states, shall be as indicated in the datasheet.
Geosynthetic Clay Liner Minimum Bentonite Mass per Unit Area (ASTM D5993)range
lb/ft²
0.61.5
Default: 0.75 lb/ft²
13.3.7 The peel strength of a needle-punched liner, determined in accordance with ASTM D6496, shall be not less than the GRI GCL3 minimum for the product.

13.4 Hydraulic Conductivity

13.4.1 The maximum hydraulic conductivity of the geosynthetic clay liner shall be as indicated in the datasheet, determined on the test basis indicated in the datasheet.
Geosynthetic Clay Liner Maximum Hydraulic Conductivityrange
×10⁻⁹ cm/s
12510
Geosynthetic Clay Liner Hydraulic Conductivity Test Basisradio
● ASTM D5887 with water
○ ASTM D6766 with the site permeant
NOTE The index flux test with water is what every manufacturer certifies on every lot and what the GRI GCL3 value is written against; the test with the site permeant is run on the project's liquid and is selected where the geotechnical report, the process, or the runoff identifies a liquid that attacks sodium bentonite, in which case the water value says nothing about the liner in service. (13.4.2)
13.4.3 Where the test basis is ASTM D6766, the permeant shall be a sample of the liquid the liner will contain, or a laboratory solution matching its chemistry, identified in the submittal.

13.5 Confinement and Cover

13.5.1 The geosynthetic clay liner shall be covered with the cover soil or the layer the drawings show above it to a minimum thickness, measured perpendicular to the liner, as indicated in the datasheet.
Geosynthetic Clay Liner Minimum Cover Thicknessrange
in
12182436
NOTE Twelve inches of cover is the confinement the manufacturers' conductivity testing assumes and the minimum every manufacturer publishes; a deeper cover is placed where the liner lies under a pond that is drawn down, where equipment runs on the cover, or where frost or roots would reach a thinner cover. (13.5.2)
13.5.3 Cover soil shall be free of stones larger than 1 in. and of sharp material within the 6 in. in contact with the liner, unless a cushion geotextile is placed between the liner and the cover.
13.5.4 Where the subgrade beneath the liner lies below Seasonal High Groundwater ElevationSeasonal High Groundwater ElevationParameterEach project supplies its own value.seasonal-high-groundwater-elevation, the liner shall be placed on a subgrade that has been drained or dewatered and shall be covered to the full cover thickness before groundwater is allowed to rise against it.
13.5.5 Where the liner lies on a slope steeper than 4 horizontal to 1 vertical, the internal and interface shear strengths determined in accordance with ASTM D6243 shall be not less than the values the design states, and the liner shall be anchored at the crest in the trench shown on the liner anchor trench detail.

14 Conformance Testing

NOTE Acceptance of each geosynthetic rests on the manufacturer's certified test report for its roll lot, and independent sampling is added where the geosynthetic is the barrier or the reinforcement the design depends on, where a public agency's quality program requires it, or where a lot's report is in question. (14.1)
14.2 The conformance testing basis shall be as indicated in the datasheet.
Conformance Testing Basisradio
● Manufacturer's certified test report per lot
○ Certified test report plus independent conformance sampling
14.3 Where independent conformance sampling is indicated, samples shall be taken from delivered rolls in accordance with ASTM D4354 in the presence of the Engineer of Record's representative, at not less than one sample per the quantity of each product indicated in the datasheet, and shall be tested by a laboratory accredited for the test methods cited.
Independent Conformance Sampling Frequency, Area of Product per Samplerange
yd²
5000100002500050000100000
NOTE A sampling frequency is a judgment about the cost of a bad lot: a liner or a reinforcement whose failure is buried for the life of the project is sampled at the tight end, a separation geotextile under a parking lot at the loose end, and a product whose certified reports have never failed earns the loosest interval the Engineer of Record accepts. (14.4)
14.5 A geosynthetic clay liner shall be accepted in accordance with ASTM D6495 in addition to the sampling indicated in the datasheet.
14.6 Where an independently tested sample fails a specified value under ASTM D4759, the lot it represents shall be rejected unless the manufacturer's retest of two further samples from the same lot, witnessed by the Engineer of Record's representative, passes, and the cost of the retest and of any replacement shall be borne by the Contractor.
14.7 Where seams are sewn, the seam strength determined in accordance with ASTM D4884 on a sample seam made with the field equipment, thread, and stitch shall be not less than 90 percent of the grab tensile strength required of the geotextile, before any production seam is sewn.

15 Installation

15.1 Subgrade Acceptance

15.1.1 No geosynthetic shall be placed on a subgrade that has not been proof-rolled, dispositioned, and accepted under EarthworkEarthworkResolves to the current adopted revision.sync/earthwork, except that a stabilization geosynthetic shall be placed on the rejected area the earthwork disposition directs it to.
15.1.2 The surface receiving a geosynthetic shall be free of standing water, sharp protrusions, loose rock larger than the first-lift aggregate, vegetation, frozen lumps, and debris, and shall be graded so that the geosynthetic lies in continuous contact with it.
NOTE A geosynthetic placed over a rut, a hump, or a protrusion is tented across the gap and carries the first lift as a bridge rather than on the subgrade, and it tears or pulls out of its overlap at the first wheel load; the class of the product does not correct a surface it does not touch. (15.1.3)
15.1.4 Where the Contractor and the Engineer of Record disagree whether a surface is acceptable to receive a geosynthetic, the geotechnical engineer, or the Engineer of Record where none is retained, shall make the initial determination.

15.2 Placement and Anchoring

15.2.1 Each geosynthetic shall be unrolled in the direction of placement of the cover, laid without wrinkles, folds, or tension, and in continuous contact with the surface beneath it.
15.2.2 Each geosynthetic shall be anchored against displacement by wind and by the placement of cover with pins, staples, sandbags, or a continuous edge of cover material, placed as the roll advances.
15.2.3 At a curve, a corner, or a change in grade, the geosynthetic shall be cut and overlapped or folded so that the specified overlap is maintained and no gap opens at the inside of the curve.
15.2.4 At a pipe, a structure, or another penetration, the geosynthetic shall be cut to fit around the penetration and the cut shall be covered with a patch of the same product extending not less than the specified overlap beyond the cut in every direction.
15.2.5 A geotextile, geogrid, or geocomposite shall not be dragged across the subgrade, and a roll shall not be lifted by a sling that crushes it or by its wrapping.

15.3 Overlaps and Seams

15.3.1 The seam type for geotextiles and geogrids placed for separation, stabilization, filtration, or reinforcement shall be as indicated in the datasheet.
Geotextile and Geogrid Seam Typeradio
● Overlapped
○ Sewn
NOTE An overlap transfers no tension and keeps the separation continuous only while the two edges stay together, which they do on a firm subgrade and stop doing on a soft one as the subgrade deflects under each wheel; a sewn seam carries tension across the joint and is used where the subgrade is too soft for any overlap to hold, where the geotextile is a reinforcement, or where the quantity of fabric the overlaps consume costs more than the sewing. (15.3.2)
15.3.3 Where panels are overlapped, the minimum overlap shall be as indicated in the datasheet.
Minimum Panel Overlap, Separation, Stabilization, and Reinforcement Layersrange
in
1218243648
Derived — the subgrade CBR reported in the geotechnical investigation report, per the AASHTO M 288 overlap requirements (by default)
NOTE AASHTO M 288 widens the overlap as the subgrade softens and replaces the overlap with a sewn seam below a CBR of about 0.5, because the deflection of the subgrade under a wheel is what pulls an overlap apart; an engineer who derives the overlap from the geotechnical report at each area, rather than from the softest area on the site, uses the fabric the project needs and no more. (15.3.4)
15.3.5 Overlaps shall be shingled in the direction the cover is spread, with the leading edge of the following panel beneath the trailing edge of the panel already covered.
15.3.6 Where a geotextile overlap must hold against a lateral drainage flow, the upstream panel shall lie over the downstream panel.
15.3.7 Geogrid panels shall be overlapped not less than the value in the datasheet or tied at the manufacturer's published spacing with the manufacturer's connectors, and a geogrid overlap on a soft subgrade shall be tied.
15.3.8 Where seams are sewn, the seam shall be a double-thread chain stitch or a lock stitch in a polymer thread the geotextile manufacturer accepts, of the stitch type and seam configuration qualified under the Conformance Testing article, and the seam shall face upward where the cover is placed.
15.3.9 An overlap or a seam shall not be located beneath a wheel path concentrated by a haul route, and the Contractor shall offset panel ends in adjacent rolls so that no four corners meet.

15.4 Cover and Construction Traffic

15.4.1 The first lift of cover over a separation, stabilization, or reinforcement geosynthetic shall be placed by dumping on previously placed cover and spreading forward onto the geosynthetic, and shall not be dumped directly onto the uncovered geosynthetic.
15.4.2 No construction equipment shall operate directly on a geotextile, geogrid, or geocomposite, and the minimum compacted cover between any equipment and the geosynthetic shall be as indicated in the datasheet.
Minimum Cover Over Geosynthetic Before Construction Trafficrange
in
68121824
NOTE Six inches of cover protects a Class 2 geotextile on a firm subgrade from a loaded dump truck; a soft subgrade needs more, because the wheel load that deflects the subgrade stretches the geosynthetic as it deflects, and a tracked dozer turning on a thin lift scrubs the geosynthetic through the stone. The thickness is set for the subgrade and the equipment the Contractor proposes, and the geotechnical report and the manufacturer's instructions are where that answer is found. (15.4.3)
15.4.4 Equipment shall not turn sharply or brake hard on the first lift over a geosynthetic, and a tracked vehicle shall not pivot on it.
15.4.5 A geogrid shall be pulled taut and staked so that it lies flat and without slack before the cover is placed, and a lift placed over a slack geogrid shall be removed and the geogrid re-tensioned at the Contractor's cost.
15.4.6 Compaction of the first lift over a stabilization geosynthetic shall be by static rolling until the lift is thick enough that vibration does not disturb the subgrade.

15.5 Exposure Limit and Repair

15.5.1 Each geosynthetic shall be covered within the period after its wrapping is removed indicated in the datasheet, unless the manufacturer certifies a longer exposure for the product furnished in writing.
Maximum Exposure of Geosynthetic Before Coveringrange
days
371430
NOTE Fourteen days is the AASHTO M 288 limit and is what the standard 50 percent retention product is tested to survive; a 70 percent retention product is specified where the sequence will leave the geosynthetic uncovered longer, and a shorter limit is written where a thin heat-bonded fabric or a paving fabric is placed in high summer. (15.5.2)
15.5.3 A geosynthetic that has been exposed beyond the limit in the datasheet shall be removed and replaced at the Contractor's cost, unless the Engineer of Record accepts, in writing, an independent retest of a sample cut from the exposed material showing that it still meets its specified strengths.
15.5.4 A geosynthetic that is torn, punctured, cut, or contaminated with soil, sealant, or chemicals during placement shall be repaired by a patch of the same product extending not less than the specified overlap beyond the damage in every direction, or the damaged panel shall be removed and replaced, at the Contractor's cost.
15.5.5 A patch on a geogrid shall extend not less than 3 ft beyond the damage in every direction and shall be tied to the geogrid on all sides.
15.5.6 A geosynthetic that has been repaired more than twice within one roll width shall be replaced over the full width of the roll between the two nearest undamaged seams.
15.5.7 The Contractor shall record each repair in the field repair log before the repair is covered.

15.6 Interlayer Placement

15.6.1 A paving fabric shall be placed into the sealant while the sealant is hot, within the sealant manufacturer's placement window, with the fabric side the manufacturer designates against the sealant, and shall be broomed or rolled into the sealant so that it lies flat and saturated without wrinkles or air pockets.
15.6.2 Adjacent interlayer panels shall be overlapped not less than 2 in. and not more than 4 in. along the longitudinal joint and not less than 4 in. and not more than 6 in. at the transverse joint, with the overlap sealed with the sealant and the transverse overlap shingled in the direction of paving.
15.6.3 A wrinkle in a placed interlayer that folds over on itself shall be slit, laid flat, and sealed before the overlay is placed, and a wrinkle that cannot be laid flat shall be cut out and patched.
15.6.4 The interlayer shall not be placed when the pavement surface is wet, when the surface temperature is below 50°F, or when rain is forecast before the overlay is placed over it.
15.6.5 Traffic on a placed interlayer shall be limited to the vehicles delivering the overlay, which shall not turn, stop, or start sharply on it, and sand shall be spread on the interlayer where the sealant bleeds through and picks up on tires.
15.6.6 An interlayer that has been rained on, that has lost its bond to the sealant, or that has been damaged by traffic before the overlay covers it shall be removed and replaced at the Contractor's cost.

15.7 Geosynthetic Clay Liner Placement

15.7.1 The subgrade beneath a geosynthetic clay liner shall be smooth-rolled, free of stones larger than 1 in., free of desiccation cracks wider than 1/4 in., and free of standing water, and shall be accepted by the Engineer of Record's representative in writing before any liner is placed.
15.7.2 The liner shall be unrolled directly from the roll into position without dragging, placed with the face the manufacturer designates toward the liquid, and not placed in rain, in standing water, or when precipitation is forecast before the day's placement will be covered.
15.7.3 Adjacent liner panels shall be overlapped not less than the value indicated in the datasheet along their longitudinal edges and not less than 24 in. at the panel ends, with the overlaps shingled downslope and oriented so that no overlap faces the direction of flow.
Geosynthetic Clay Liner Minimum Longitudinal Overlaprange
in
69121824
NOTE Six inches is the narrowest overlap any manufacturer publishes and is used on a flat, firm, well-prepared subgrade with a self-sealing edge; a wider overlap is placed on a slope, over a subgrade expected to settle, or where the installer's control of the lap width is in question, because a lap that opens is the only place the barrier can be lost. (15.7.4)
15.7.5 Where the liner is not a product with a factory bentonite-impregnated overlap zone, granular sodium bentonite shall be placed continuously in the overlap zone at the manufacturer's published rate before the overlying panel is laid.
15.7.6 A damaged liner panel shall be repaired with a patch of the same product extending not less than 12 in. beyond the damage in every direction, with granular bentonite placed in the lap zone, or the panel shall be replaced.
15.7.7 Each day's placed liner shall be covered to the minimum thickness in the datasheet, or protected with a cover the manufacturer accepts against hydration, before the end of that working day.
15.7.8 A liner that has hydrated before it was confined, that shows bentonite loss at an overlap, or that has been displaced by wind or water shall be removed and replaced at the Contractor's cost.
15.7.9 Cover over the liner shall be placed from the toe of a slope upward and from previously placed cover forward, and no equipment shall operate on the liner or on less than the minimum cover thickness in the datasheet.

16 Delivery, Storage, and Handling

16.1 Each roll shall be delivered in the manufacturer's original wrapping, labeled in accordance with ASTM D4873 with the manufacturer, the product designation, the lot number, the roll number, and the roll dimensions.
16.2 Rolls shall be stored off the ground on a level, drained surface, protected from ultraviolet light, precipitation, mud, chemicals, fire, and temperatures outside the manufacturer's storage range, and the wrapping shall stay on each roll until the roll is placed.
NOTE The wrapping is the roll's ultraviolet protection, and a roll that has lost it in the yard has used up part of its exposure limit before it reaches the subgrade. (16.3)
16.4 Rolls shall be lifted with a core bar or a spreader bar and shall not be dropped, dragged, or lifted by a chain or cable around the roll.
16.5 A geosynthetic clay liner shall be stored and handled in accordance with ASTM D5888, kept dry under an impermeable cover, and stored no more than the number of rolls high the manufacturer publishes.
16.6 A roll whose wrapping has been breached and whose geosynthetic shows discoloration, brittleness, or, for a geosynthetic clay liner, swelling or bentonite loss, shall be rejected.

17 Warranty

17.1 The manufacturer shall warrant each geosynthetic against defects in materials and manufacture for the period indicated in the datasheet, measured from the date of delivery to the site.
Manufacturer's Material Warranty Periodrange
yr
12510
NOTE A 1-year material warranty is what most geosynthetic manufacturers offer on the standard lines without a request; a longer term is available from the larger manufacturers on liners, geogrids, and paving fabrics, usually at the cost of a registered installation or an approved installer, and it buys the Owner a replacement of a defective lot found after the Contractor's correction period has run, which is when a buried geosynthetic's defects first show. (17.2)
17.3 The Contractor shall warrant the installed geosynthetic against defects in placement, overlap, seaming, and cover for the correction period of the Contract Documents, and a repair made under that warranty shall be warranted for a fresh full term from the date the repair is completed or for the remainder of the original term, whichever ends later.
17.4 The Contractor shall bear the cost of removing and replacing the cover, base, pavement, or liner cover above a geosynthetic repaired under warranty and of restoring the surface to the condition recorded before the work was covered.
17.5 The material warranty shall not be voided by a placement condition the manufacturer's installation instructions permit, and the manufacturer shall state in writing before delivery any site condition under which the warranty would not apply.

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