United States

Department of

Agriculture

Forest Service

Technology &

Development

Program

2300 Recreation

August 2000

0023-2838-MTDC

In cooperation

with

United States

Department of

Transportation

Federal

Highway

Administration

Geosynthetics

for Trails in

Wet Areas

2000 Edition

Geosynthetics

for Trails in

Wet Areas

2000 Edition UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION
The Forest Service, United States Department of Agriculture (USDA), has developed this

information for the guidance of its employees, its contractors, and its cooperating Federal

and State agencies, and is not responsible for the interpretation or use of this information

by anyone except its own employees. The use of trade, firm, or corporation names in this

document is for the information and convenience of the reader, and does not constitute an

endorsement by the Department of any product or service to the exclusion of others that may

be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and

activities on the basis of race, color, national origin, sex, religion, age, disability, political

beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all

programs.) Persons with disabilities who require alternative means for communication of

program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET

Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write

USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence

Avenue, SW, Washington, D.C. 20250-9410 or call (202) 720-5964 (voice and TDD). USDA

is an equal opportunity provider and employer.

Steve Monlux

Geotechnical Engineer, Northern Region

Brian Vachowski

Project Leader

Technology and Development Program

Missoula, Montana

0E02A40—Geosynthetics for Trails in Wet Areas

August 2000

Geosynthetics

for Trails in

Wet Areas

2000 Edition
ii

Introduction _____________________________________ 1

Section 1: Geosynthetics—General Information ________ 2

Geotextiles ________________________________________________ 2

Geonets __________________________________________________ 2

Sheet Drains ______________________________________________ 3

Geogrids _________________________________________________ 3

Geocells __________________________________________________ 3

Proprietary Products_________________________________________ 4

Section 2: Basic Geosynthetic Design and Utilization

Concepts for Trail Construction in Wet Areas __________ 5

Section 3: Specific Design Applications _______________ 6

Geotextile or Geonet ________________________________________ 6

Geotextile With Encapsulated Free-Draining Rock __________________ 7

Geotextile With Poles or Logs _________________________________ 8

Geogrid With Geotextile or Geonet ______________________________ 8

Sheet Drains Under Tread Fill _________________________________ 9

Sheet Drains or Geonets Used as Drainage Cutoff Walls ____________ 10

Geocell With Geotextile and Permeable Tread Material _____________ 10

TrailMaster With Geotextile __________________________________ 11

Section 4: Geosynthetic Product Information__________ 13

General Notes ____________________________________________ 13

Geotextiles _______________________________________________ 13

Geonet (Geonet Composites) _________________________________ 14

Sheet Drains _____________________________________________ 14

Geogrids ________________________________________________ 15

Geocells _________________________________________________ 15

Proprietary Materials _______________________________________ 16

Section 5: Identification of Unsuitable Tread Fill

Material ________________________________________ 17

Method A—Field Comparison ________________________________ 17

Method B—Laboratory Test __________________________________ 17

Method C—Geotextile Field Test ______________________________ 17

Additional Information ____________________________ 18

Contents

SSteve Monlux is the principal author of this report. Brian Vachowski

assisted in review coordination and preparation for publication. Others

throughout the Forest Service assisted by reviewing the drafts.

Acknowledgments


1



Introduction TTrails in soft, water-saturated soils present

special challenges to trail managers.

Muddy trails are anathema to livestock and

hikers, which tend to skirt the edges of mud

holes. This increases the area of damage to

sensitive soils. Incorrectly constructed trails in

wet areas lead to soil compaction, sedimentation, multiple trails, and unhappy trail users.

Traditional trail construction methods for wet

areas include turnpike or puncheon. These have

worked well where rock or wood materials are

readily available. However, geosynthetics can

increase the effectiveness of construction

methods and offer additional alternatives.

Geosynthetics are synthetic materials (usually

made from hydrocarbons) that are used with

soil or rock in many types of construction. Their

use has grown significantly in road construction

over the past 20 years, and in trail construction

for the past 10 years.

Guidelines on how to use geosynthetics in trail

construction have not been readily available to

trail managers. The information presented here

applies some roads technology to trail design

and construction in five categories: ❖ General information on geosynthetic products. ❖ Basic geosynthetic design and utilization

concepts.

❖ Specific design diagrams for trail construction

over wet saturated soils.

❖ A list of product manufacturers, price ranges,

and physical properties.

❖ Identification of unsuitable tread fill materials.
2

 Section 1: Geosynthetics—General Information

GGeosynthetics perform three major functions: separation, reinforcement, and drainage. Geosynthetic

materials include geotextiles (construction fabrics),

geonets, sheet drains, geogrids, and geocells. All these

materials become a permanent part of the trail, but must be

covered with soil or rock to prevent early deterioration by

ultraviolet light. TrailMaster, a proprietary product, is also

discussed. TrailMaster can be used as trail tread, and is

placed directly over wet areas. Since all these products are

synthetic, their use in wilderness should be reviewed and

approved prior to use.

Geotextiles

Geotextiles (Figure 1) are the most widely used geosynthetic.

Geotextiles are often called construction fabrics. They are

constructed from long lasting synthetic fibers that are bonded

to form a fabric held together by weaving, heat bonding, or

other means. They are primarily used for separation and

reinforcement over wet unstable soils. They have the ability

to support loads through tensile strength and can allow water,

but not soil, to seep through. They can also be used in drainage applications where water flow is much greater than

normally exists in wet areas. The physical requirements

listed for all geotextiles in Section 4 are stringent enough

so the products will also work for properly designed highflow drainage applications. These representative products

are low cost, readily available, and easy to use. There are

many other products on the market.

Geonets

Geonets or geonet composites (Figure 2) have a thin polyethylene drainage core that is covered on both sides with

geotextile. They are used for all three functions—separation, reinforcement, and drainage. Since geonets have a

core plus two layers of geotextile, they provide more reinforcement than a single layer of geotextile.

Figure 2—The net-like core of geonet allows sideways drainage that

is normally adequate for the amount of seepage found under trails in

wet areas.

Figure 1—Geotextiles. Felt-like products are easier to work with than

heat bonded, slit film, or woven products that have a slick surface

texture. They are easier to cut and their flexibility makes them easier

to place on curved trail sections.
3



Sheet Drains

Sheet drains (Figure 3) are another form of composite made

with a drainage core and one or two layers of geotextile. The

core is usually made of a polyethylene sheet that is formed

into an egg-crate shape. The core provides an impermeable

barrier unless perforated by the manufacturer. Perforated

cores are always covered with geotextile on both sides to

prevent soil clogging the drainage passages. Geotextile is

bonded to one or both sides of the core to provide filtration

and separation. When used under the trail tread material,

sheet drains provide separation, reinforcement, and

drainage. Since they have greater bending strength than

geotextiles or geonets, less tread fill is often needed. They

can also be used vertically in covered trenches beside the

trail to drain off subsurface water. Figure 4—Geogrids are normally placed on top of a layer of geotextile

to obtain separation from saturated soils in wet areas.

Figure 3—Sheet drains have a large cross-section that provides

significant drainage capacity. If placed under the trail tread, orient

the sheet drain with the geotextile side on the bottom and the plastic

core on top. This orientation reduces the amount of fill needed.

Figure 5—Geocell usually has geotextile under it to provide separation

from wet saturated soils.

Geogrids

Geogrids (Figure 4) are made from polyethylene sheeting

that is formed into very open grid-like configurations. Geogrids are good for reinforcement because they have high

tensile strengths, and coarse aggregate can interlock into

the grid structure.

Section 1: Geosynthetics—General Information

Geocells

Geocells (Figure 5) are usually made from polyethylene

strips from 50 to 200 millimeters (2 to 8 inches) high that are

bonded at intermediate points to form a honeycomb structure.

The product is shipped in a collapsed and compact form.

During installation, the material is pulled open and the honeycomb structure is staked to the ground surface. Each of the

cells is filled with select backfill and compacted. Compacting

trail tread material within the cell increases the bending

strength of the layer, which reduces settlement into soft

saturated soils. Geocells are good for reinforcement and

reduce the amount of fill material required.
4



Figure 6—TrailMaster is a very stiff material, but it can be rolled up

for relatively easy transport.

Section 1: Geosynthetics—General Information

Proprietary Products

TrailMaster (Figure 6) is made from 3-millimeter (1⁄8-inch)

thick polypropylene that has 13-millimeter (1⁄2-inch) diameter

extruded holes about 32 millimeters (11⁄4 inches) on center.

The extrusions extend 16 millimeters (1

⁄8 inch) below the top

of the sheet. This product was originally marketed under

the Gripmaster name and weighs about 2.8 kilograms per

square meter (0.57 pounds per square foot). Bending strength

is high enough to distribute loads from pack animals over

a large enough area so that the material essentially floats

on top of saturated soils. TrailMaster is excellent for reinforcement because no fill material is required.
5



Section 2: Basic Geosynthetic Design and Utilization

Concepts for Trail Construction in Wet Areas

GGeosynthetics provide a stable trail surface in wet areas.

Unstable trail surfaces are usually caused by saturation

from subsurface moisture and precipitation. Geosynthetics assist in obtaining stable surfaces by providing:

❖ Separation—Geotextiles, geonets, and sheet drains keep

saturated, weak native soils from contaminating stronger,

load-bearing trail surface materials. They allow water, but

not soil, to pass through.

❖ Drainage—Geotextiles, geonets, and sheet drains improve

subsurface drainage to avoid saturation and weakening of

the trail tread.

❖ Reinforcement and Load Distribution—All geosynthetics discussed in this paper provide some degree of tread

reinforcement and load distribution. This decreases the

amount of imported fill material required. TrailMaster provides

enough load distribution so it can be placed directly on the

saturated soil and also serves as the trail tread with no

additional fill needed.

Geosynthetics are relatively simple to use. Products that

meet the physical requirements discussed in Section 4 are

tough enough to be placed over small stumps that stick up

from the ground surface after brushing. Cutting stumps and

brush to within a few inches from the ground is usually all

that is necessary. Where joints occur in geotextiles, geonets,

or geogrids, the overlap should normally be at least 300

millimeters (12 inches). Pins or clips are used at joints for

the other products. All geosynthetics must be stored in shipping wrappers until installation since they will gradually

deteriorate when exposed to ultraviolet light.

Selecting good tread fill material is very important. Organic,

silt, or clay soils should not be used as tread fill since they

become muddy during wet weather. Use firm mineral soil,

coarse-grained soils, granular material, or small well-graded

angular rock instead. Soil from wet areas is normally not

suitable for use as tread fill. Unsuitable organic soils are

easily identified by a dark color and musty odor when damp.

Many soils containing clays and silts are just as unstable,

but identification is more difficult. Avoiding unsuitable tread fill

is very important because poor materials will fail when wet

and costs for excavation and haul are high. Poor materials

can be identified in the field by several methods discussed

in Section 5.

How much acceptable tread fill material you need over the

geosynthetic selected depends on several site-specific

factors:

In addition to the nine applications illustrated in Section 3,

other combinations are possible and perhaps preferable,

depending on mud hole conditions and natural building materials available. Once you understand the design/utilization

concepts and product capabilities, try different applications.

Mineral soil with little

rock, less than 20-

percent silt or clay

Horse or motorcycle

Predominantly high

Continuously wet

areas over 2 feet

deep

Single layer of

geotextile (Figure 1)

Less than annual

Trail fill quality

Trail tread surface

Tread surface

moisture content

during traffic

Amount of foundation settlement

Geosynthetic

alternative selected

Trail surface crown

maintenance

Granular, freedraining materials

Foot traffic

Predominantly low

Intermittent soft,

wet areas under

2 feet deep

Geotextile with logs

(Figure 9)

Geocell, (Figure 13)

Annual

FACTORS AFFECTING

TREAD THICKNESS

NEEDED

MAXIMUM

THICKNESS

MINIMUM

THICKNESS
6

 Section 3: Specific Design Applications

MMost all of the techniques shown can be integrated into

standard trail turnpike construction specifications. To

simplify the illustrations, not all the components of a

complete turnpike (ditches, curb rocks, or logs, etc.) are

shown. For many trail locations through flat muddy sites,

the traditional trail side ditch and long outlet ditch will not be

necessary. Curb logs or rocks are still needed to confine

tread fill except where tread fill materials are quite granular.

Shoulders must be maintained to keep geosynthetics covered

to protect them from ultraviolet light and traffic abrasion. The

figures are simplified cutaway cross-sectional views of the

trail. They normally look much better on paper than they do

during construction.

Geosynthetics are usually placed directly on the natural

ground without prior excavation. Many of the illustrations

show the various applications with a sag in the native soil

surface along the center of the trail alignment. This sag is

caused by adding the weight of the tread fill. The actual

amount of settlement is very site specific and depends on

soil type, level of saturation, and weight of tread fill used.

Less tread fill can be used over geosynthetic products that

are rigid or have high bending strengths because the weight

of fill is distributed over a larger area. Settlements are decreased when less fill is needed to obtain a stable tread

surface. For example, much more tread fill is required for

a single layer of geotextile (Figure 7), than for geocell with

geotextile (Figure 13). In this example, the cost of importing

tread fill must be compared to the increased cost of the

geocell.

All alternatives that use tread fill should have a crowned or

outsloped surface to help shed water quickly and improve

stability and control erosion and sediment. Additional tread

fill may be necessary to rebuild the crown after initial settlement. More imported fill will be necessary to maintain the

crown if tread wear is high. Alternatives are compared in

Table 1.

Geotextile or Geonet

Single-layer geotextile or geonet (Figure 7) separates fill

material from saturated soils and distributes fill weight so

less settling takes place. Since geonets cost more, use them

only where drainage and subsurface moisture conditions are

worst. Avoid using organic, silt, or clay soils for trail tread

material because little subsurface drainage will occur and

the trail tread will become muddy in wet weather. Rocky soils

or crushed aggregate should be used as a tread material

if possible. These materials retain much of their strength

Table 1—Comparisons of geosynthetic alternatives.

Evaluation Criteria of

Construction Objectives

Geosynthetic Application

Figure

71

Geotex

B

D

D

D

A

A

0.68

0.57

0.14

0.25

Figure

72

Geonet

B

D

D

C

B

C

4.05

3.42

0.89

1.64

Figure

83

A

A

B

A

C

A

1.36

1.14

0.28

0.50

Figure

94

A

A

A

B

C

B

2.04

1.71

0.42

0.75

Figure

105

Geotex

B

B

B

C

C

C

4.13

3.47

0.32

0.60

Figure

106

Geonet

B

A

A

C

C

C

7.50

6.32

1.07

1.98

Figure

117

B

B

B

B

B

C

7.50

6.26

2.3

4.25

Figure

128

NA.

NA.

C

D

D

C

7.50

6.26

2.3

4.25

Figure

139

Geocell

A

A

B

B

C

D

10.08

8.45

1.9

3.45

Figure

1410

C

B

A

A

A

D

16.68

14.07

3.0

5.40

Separation (keep tread fill separate from poor

soils)

Reinforcement (turnpike over deep layer of

very weak soil)

Reduce quantity of imported fill material

Eliminate trail side ditching

Ease of product placement

Low-cost geosynthetic

Cost for geosynthetics per square meter . . . .

 per square yard . . . . .

Weight of geosynthetics:

 kilogram per square meter . . . .

 pound per square yard . . . . . . .

Alternative Rating Code: A = Best alternative; B = Better than most; C = Not as good as most; D = Least effective; NA. = Not applicable

1 Single layer of geotextile.

2 Single layer of geonet.

3 Geotextile with encapsulated free-draining rock.

Rock can be large, single-size cobbles, down to

relatively clean sands.

8 Sheet drains or geonets for drainage cutoff wall.

Extensive ditching required.

9 Geocell with geotextile and permeable tread.

Granular fill material required; costs and weights

are based on 100-mm-deep cells.

10TrailMaster with geotextile. Curb logs are required.

4 Geotextile with poles, logs. Must have small trees

onsite.

5 Geogrid with geotextile.

6 Geogrid with geonet.

7 Sheet drains under tread fill.
7



when saturated. Excess surface moisture can drain off

through these permeable materials if the trail is located on

a grade or side slope.

Geotextile With Encapsulated FreeDraining Rock

(Sausage Technique, Figure 8). The geotextile provides

separation from the saturated soil, and the rock provides

drainage for excess water. Twenty-five-millimeter (1-inch)

Figure 8—Encapsulation or “sausage” technique where native rock is used for drainage.

Figure 7—Typical placement of geotextile or geonet through flat, boggy areas. Side or lead-off ditches may not be needed.

Geotextile Tread fill material

or geonet

Free-draining rock

Geotextile (300 millimeters

(12 inch) overlap at center)

Tread fill

material

Section 3: Specific Design Applications

flexible plastic pipe outlets for subsurface water may be

desirable where trails are constructed on very flat terrain to

avoid the “bath tub” effect. If the trail has grade or is built

on a sideslope, other drainage options exist. The rock may

be single-size material from pea gravel size to cobbles (75

to 300 millimeters or 3 to 12 inches), or it may be a mixture

of rock materials that does not contain silt or clay. The freedraining rock can be placed to a thickness equal to the maximum size rock if only drainage is desired. If reinforcement

is also needed, at least 75 millimeters (3 inches) of rock is

recommended. The geotextile is wrapped over the rock layer

with a 300-millimeter (12-inch) overlap to ensure encapsulation, since settlement of saturated soil can pull the overlap

joint apart.
8



Geotextile With Poles or Logs

Figure 9 provides a system that requires less imported fill

and resists being pushed down into soft saturated soils. No

subsurface drainage is provided with this design, although

longitudinal drainage may occur along the poles if the trail

is on a grade. Another approach is to place interior logs

perpendicular to the trail after cutting them to lengths equal

to the trail width. This method does not utilize log bending

strengths as effectively and is more labor intensive. An outlet pipe or daylight section would provide drainage where

trails are on a grade or side slope.

Settling of saturated soil is minimal; the turnpike structure

is light weight since it is primarily wood; the bending strength

of wood distributes dead load (tread fill) and live loads (traffic);

and wrapping trees together with geotextile distributes concentrated live loads.

This alternative is attractive for areas that have wood and

not much rock for obtaining drainage. If the trail alignment

is very swampy, this alternative has strong advantages because the flotation and bending strength of wood is utilized.

Keeping wood continually wet or dry is necessary to control

rotting. Otherwise the life of the structure will be cut to less

➛ ➛

Layer of geotextile

to keep wood wet

Geotextile

Poles, logs, or saplings

Note 300 millimeter (12-inch) minimum overlap.

Figure 9—Poles or logs wrapped with geotextile.

Fill material (100 millimeters

(4 inches) minimum thickness)

Section 3: Specific Design Applications

than half. A layer of geotextile placed down the centerline

over the logs will help keep the wood saturated and also

keep individual logs from coming up through the trail tread

surface.

Geogrid With Geotextile or Geonet

Figure 10 shows geogrid placed on top of the geotextile or

geonet adds bending strength to the system and decreases

settling. This reduces the amount of fill material required.

Very little drainage is required with this design, unless geonets are used or the tread material is permeable (rocky soils

or crushed aggregate). The geogrid should be pulled taut

to remove wrinkles before staking. The stakes and poles

provide some pretension of the grid, to better utilize its

strength. The geotextile or geonet provides separation from

the saturated soil and keeps the drainage paths along the

bottom of the fill material from clogging. See Section 913

of the Standard Specifications for Construction of Trails for

additional information.
9



Figure 10—Geogrid with geotextile or geonet.

Pole rests against stakes.

Geogrid

Fill material, permeable soil, or aggregate preferred

Sheet Drains Under Tread Fill

Sheet drains under tread fill (Figure 11) provide separation

from saturated soils and distribute the trail tread weight to

limit settling. Install the product with the plastic core side

facing up and the fabric side facing down. This orientation

takes advantage of the plastic core compressive strength

Figure 11—Sheet drain under fill material.

Sheet drain

Geotextile or geonet

Stakes (600 millimeters (24 inches)

or longer) driven through geogrid

Geotextile

Any type fill material (100 millimeters

or 4 inches minimum thickness)

Section 3: Specific Design Applications

and the fabric’s tensile strength, which will reduce the

amount of settling and also the amount of tread fill required.

Twenty-five-millimeter (1-inch) diameter flexible plastic pipe

can be used as a drainage outlet to take full advantage of

the drainage capability of the sheet drain. If the trail is on a

grade or side slope, an outlet pipe or daylight section could

provide drainage.
10



Sheet Drains or Geonets Used as

Drainage Cutoff Walls

If the trail section is on a sideslope where subsurface water

saturates the uphill side of the trail, a cutoff wall can be

constructed to intercept surface and subsurface moisture

(Figure 12) and help drain and stabilize the trail section. This

application is especially beneficial where cutslope sloughing

continually closes ditches. The sheet drain or geonet should

be installed within 1 meter (3 feet) of the trail’s edge. The

proper depth of the collection pipe and location of the sheet

drain can be determined by probing the saturated soil with

a short length of Number 4 reinforcing steel. Collector and

outlet pipes can be made from flexible plastic pipe. Keeping

the top edge of the drain above the ground will capture surface runoff moving downslope. Cover the exposed material

with large rocks to protect it from deterioration from ultraviolet

light. The collector pipe can be drained into an outlet pipe

or with a sheet drain or geonet panel under the trail section.

This application requires ditching for proper interception and

drainage of water. Ditching is normally more extensive on

flatter terrain.

Figure 12—Sheet drain or geonet used to intercept seepage.

SURFACE

NATURAL

Seepage

Large

rocks

Timber

Outlet pipe or

sheet drain

Fill material

Collector

pipe

Sheet drain or geonet.

Geotextile side faces

uphill to intercept

seepage.

Section 3: Specific Design Applications

Geocell With Geotextile and Permeable

Tread Material

The geocell provides confinement chambers that distribute

the trail tread loads over a wider area and reduce settling

(Figure 13). This works best in sandy soils, rocky soils,

crushed aggregate, or free-draining rock. The net effect is to

increase the load-bearing capacity of the tread and prevent

feet and hooves from punching down into the trail. The geotextile provides separation between saturated soil and the

tread fill. Somewhat less tread fill is required because settling

is reduced. There is no subsurface drainage if the trail is on

flat ground. If the trail has a grade or is built on a sideslope,

drainage will occur through the permeable tread fill. Organic,

silt, and clay soils are not desirable fill for geocells because

these soils will likely remain saturated and unstable, and

thus not strong enough to carry the loads placed on the

trail. Geocell itself does not increase the load-bearing

strength of clay or silt.
11



TrailMaster With Geotextile

TrailMaster with geotextile (Figure 14) is made from 3-millimeter (1

⁄8-inch) thick polypropylene with 16-millimeter (5⁄8-inch)

diameter extruded holes about 32 millimeters (11⁄4 inches) on

center. This material is quite rigid, although it can be rolled

up for easier transport. It is widely used in horse stalls to

keep hooves dry.

It can be used without fill material since it has significant

bending and tensile strength and is durable enough to resist

abrasion from pack animals and even motorcycles. Since

the material is used as the trail surface and grasses can

grow through, it also resists erosion better than tread fill

materials. The geotextile allows water, but not soil, to be

pumped through the TrailMaster. The water collected on the

surface can be removed by an outlet ditch at the lowest point

on flat trail sections, or by using rolling dips or outsloping

on other trails. Since the surfacing will deflect under the

Figure 13—Geocell with geotextile and permeable tread material.

Geocell (100-millimeter (4-inch) deep cell

recommended).

Permeable tread material

Section 3: Specific Design Applications

weight of stock, rebar with hooks on the upper ends must be

used to anchor the geotextile and TrailMaster to the ground.

Rebar staples are normally needed for transverse joints.

The poles provide a curb to keep traffic on the surface and

also help anchoring. Settling should be minimal since the

weight of TrailMaster is only 2.8 kilograms per square meter

(0.57 pounds per square foot). The high price of this product

may be offset by not having to import fill for a turnpike

section. It can be cut with a hand saw. Turns in the trail are

normally cut on angles, which makes constructing winding

trail alignments more difficult.

Before placing a large order, it’s a good idea to obtain a

sample for examination. This is a manufactured material

and does not blend well with natural forest environments.

Since installation is relatively quick, it may be especially

useful as a temporary surface until a more aesthetically

pleasing alternative is constructed.
12



Curb log

No. 4 rebar staples

for transverse joints.

Figure 14—TrailMaster with geotextile.

TrailMasterTM (no fill material required).

No. 4 rebar, minimum length of 600

millimeters (24 inches), spaced 1 meter

(3 feet) on center. Geotextile

Section 3: Specific Design Applications
13

 Section 4: Geosynthetic Product Information

General Notes

TThe listed manufacturers and products were obtained

from the Geotechnical Fabrics Report, 1995 Specifier’s Guide. The products listed meet the physical properties shown for each type of geosynthetic. These physical

properties were selected to meet typical muddy trail construction conditions. These properties are on the “low end”

of those available since trails applications are much less

demanding than geosynthetic applications in road construction where heavy machinery and large angular boulders

require heavier products. These products are lighter, easier

to work with, and also cost less.

Phone numbers and web sites have been updated using

the Geotechnical Fabrics Report, 2000 Specifier's Guide.

However, we have not updated the product numbers, prices,

and specifications. Geosynthetic products that have entered

the market since 1995 are not described here. For a copy

of the newest Specifier's Guide, contact the Industrial Fabric

Association International (page 18).

The products listed are ones that are readily available. Many

other products from these and other manufacturers may be

appropriate. There are literally hundreds of products available

from manufacturers and even home improvement centers.

Most manufacturers and Geotechnical/Materials Engineers

can assist in selecting products if you provide details on soil

and moisture conditions and expected loads (light loads

for trails).

Price ranges shown are approximate and vary throughout

the country due to shipping costs. Call the listed phone

numbers for current prices delivered to your area, or for the

local sales representative. For comparison, price ranges

shown are in dollars per square meter for all products. Price

ranges in parenthesis are in dollars per square yard. Manufacturers may provide prices by the square meter, square

yard, square foot, or for full roll quantities. Unit costs decrease

as the amount ordered increases. Prices shown are based

on the minimum one roll quantity, FOB the manufacturing

location.

All geosynthetic products can be either field cut or precut

by the manufacturer to meet your width requirements and

weight handling capability.

Geotextiles

Manufacturers:

COMPANY PRODUCT

AMOCO Fabrics & Fibers 4545

Phone: 800–445–7732

TC Mirafi 140N

Phone: 888–795–0808

Web site: http://www.tcmirafi.com

Linq Industries 1300EX

Phone: 800–543–9966

Web site: http://www.linqind.com

Price Range: $0.63 to $0.72 per square meter ($0.53 to

$0.60 per square yard)

Typical Product Unit Weight: 0.13 kilogram per square

meter (0.25 pound per square yard)

Critical Physical Properties for Trail Construction:

• Material structure: Nonwoven.

• Polymer composition: Polypropylene.

• Apparent opening by ASTM D 4751-87: Less than

0.297 millimeters (greater than No. 50 mesh).

• Permittivity by ASTM D4491-92: Greater than 4060

liters per minute per square meter (Greater than 100

gallons per minute per square foot).

• Puncture strength by ASTM D48833-88: Greater than

0.245 kilonewtons (greater than 55 pounds).

• Mullen burst by ASTM D 3786-87: Greater than 1275

kilopascals (more than 185 pounds per square inch).

• Trapezoid tear strength by ASTM D4533-91: Greater

than 0.18 kilonewtons (more than 40 pounds).

• Grab tensile at 50 percent elongation by ASTM

D4632-91: Greater than 0.40 kilonewtons (Greater than

90 pounds).

• Ultraviolet degradation: Greater than 70 at 150 hours.

Notes: The products listed are nonwoven, felt-like materials

that are easier to work with than heat bonded or slit film

products that have a slick surface texture. Physical property

requirements are minimum average roll values where applicable. Compare desired widths with standard roll widths

and consult with manufacturers for field or factory cutting.

Costs are based on one roll quantities which normally cover

400 to 500 square meters (475 to 600 square yards).
14



Geonet (Geonet Composites)

Manufacturers:

COMPANY PRODUCT

Tenax TNT 204042

Phone: 800–356–8495

Web site: http://www.tenax.com

Tensar Corp. DC4205

Phone: 800–836–7271

Web site: http://www.tensarcorp.com

Price Range: $3.50 to $4.60 per square meter ($2.97 to

$3.87 per square yard)

Typical Product Unit Weight: 0.89 kilograms per square

meter (1.64 pounds per square yard)

Critical Physical Properties for Trail Construction:

• Polymer composition of core (net or mesh): Medium

or high-density polyethylene.

• Geotextile: Must be attached to both sides of the Core,

and meet or exceed the requirements of AASHTO M 288

Subsurface Drainage Class B with permeability greater

than 0.0001 centimeters per second, and an apparent

opening size less than 0.297 millimeters (greater than

the No. 50 U.S. Standard Sieve).

• Core thickness: Greater than 5 millimeters by ASTM

D5199.

• Compressive strength of core: Greater than 500 kilopascals by ASTM D1621.

• Transmissivity with gradient at 0.1, pressure at 10

kilo-pascals: Greater than 0.0009 meters2 per second

(greater than 4 gallons per minute per foot).

Notes: Discuss the roll width and length requirements for

your project with manufacturers.

Sheet Drains

Manufacturers:

COMPANY PRODUCT

TC Mirafi Miradrain 6000

Phone: 800–445–7732

Web site: http://www.tcmirafi.com

Contech C-Drain 15K

Phone: 800–338–1122

Web site: http://www.contech-cpi.com

Presto Amerdrain 500

Phone: 800–548–3424

Web site: http://www.prestogeo.com

Price Range: $6.50 to $8.50 per square meter ($5.40 to

$7.11 per square yard).

Typical Product Unit Weight: 2.3 kilogram per square

meter (4.25 pounds per square yard).

Critical Physical Properties for Trail Construction:

• Structure: Single- or double-dimpled core.

• Core polymer composition: Polystyrene or polypropylene.

• Attached geotextile: Nonwoven on one side if core

solid, on both sides if core perforated. Geotextile must

meet or exceed the requirements of AASHTO M 288

Subsurface Drainage Class B with permeability greater

than 0.0001 centimeters per second, and an apparent

opening size less than 0.297 millimeters (greater than

the No. 50 U.S. Standard Sieve).

• Core thickness by ASTM D5199: Greater than 10 millimeters (greater than 0.40 inches).

• Core compressive strength at yield by ASTM D1621:

Greater than 650 kilopascals (greater than 95 pounds

per square inch).

Notes: Compare desired width with standard sheet width

and consult with manufacturers for field or factory cutting.

Various core thicknesses are available. For example, Presto

makes a product called Akwadrain that has a 25-millimeter

core thickness, with fabric on both sides. It has significantly

greater bending strength which helps limit the amount of

settling in soft soils, and reduces the amount of fill material

required.

Section 4: Geosynthetic Product Information
15



Geogrids

Manufacturers:

COMPANY PRODUCT

Contech BX1100

Phone: 800–338–1122;

Web site: http://www.contech-cpi.com

or

Tensar Corp. BX1100

Phone: 800–836–7271

Web site: http://www.tensarcorp.com

Carthage Mills FX-3000

Phone: 800–543–4430

Web site: http://www.carthagemills.com

TenaxMS300

Phone: 800–356–8495

Web site: http://www.tenax.com

Huesker Fortrac 35/20-20

Phone: 800–942–9418

Web site: http://www.huesker.com

TC Mirafi Miragrid 5T

Phone: 800–445-7732

Web site: http://www.tcmirafi.com

Price Range: $2.15 to $4.75 per square meter ($1.80 to

$4.00 per square yard). Low-cost products are made from

polypropylene, higher cost products are made from

coated polyester. Both product types are adequate for

trails.

Typical Product Unit Weight: 1.75 kilograms per square

meter (0.34 pounds per square yard).

Critical Physical Properties for Trail Applications:

• Polymer type: Polypropylene or polyester with acrylic or

PVC coating.

• Mass per unit area by ASTM D5261-92: 175 grams per

square meter (greater than 5.5 ounces per square yard).

• Maximum aperture size: Machine direction (MD): 25

centimeters (1 inch). Cross direction (XD): 33

centimeters (1.3 inches).

• Wide-width strip tensile strength at 5-percent strain by

ASTM D4595-86: Machine direction (MD): 8 kilonewtons

per meter (550 pounds per foot). Cross direction (XD):

6 kilonewtons per meter (410 pounds per foot).

Notes: Specify desired product widths and lengths for the

project application.

Geocells

Manufacturers:

 Expanded Dimensional Properties

Individual Cell Whole Sheet

COMPANY PRODUCT Depth x Length Length x Width

Presto Geoweb 100 x 200 mm 6.10 x 2.44 m

Phone: 800–548–3424 (4 x 8 in) (20 x 8 ft)

Web site: http://www.prestogeo.com

AGH Envirogrid Same Same

Phone: 800–434–4743

Web site: http://www.aghindustries.com

WEBTEC

Phone: 800–438–0027 TerraCell Same Same

Web site: http://www.webtechgeos.com

Price Range: $7.50 to $11.30 per square meter ($6.30 to

$9.45 per square yard.

Typical Product Unit Weight: 1.55 kilograms per square

meter (2.9 pounds per square yard).

Similar Physical Properties for Listed Products:

• Composition: Polyethylene or high-density polyethylene

• Geocell weight expanded: Greater than 1.4 kilograms

per square meter (greater than 45 ounces per square

yard).

• Minimum cell seam peel strength by U.S. Army Corps

of Engineers Technical Report G:-86-19 Appendix A:

800 newtons (180 pounds).

• Expanded dimensional properties: As specified by the

designer—see dimensions listed for the products shown

above.

Notes: Specify desired product widths for the project application. The 100-millimeter (4-inch) cell depth should be

adequate for trails—depths from 50 to 200 millimeters (2 to 8

inches) are available. Consult manufacturers for availability

of different section widths and alteration of standard section

widths to fit your project needs.

Section 4: Geosynthetic Product Information
16



Proprietary Materials

Manufacturers:

COMPANY PRODUCT APPROXIMATE COST

GroundMaster TrailMaster $16 per sq m

Phone: 800–968–2930 ($13.50 per sq yd)

Physical Property Description: This is a proprietary product, and no standards for testing and acceptance are available. When specifying or ordering, describe the product as

follows:

TrailMaster—

• Polypropylene sheet thickness: Greater than 3 millimeters (1

⁄8 inch).

• Extruded hole diameter (nominal): 16 millimeters

(

5

⁄8 inch).

• Percent open area (nominal): 12 percent.

• Space between extruded holes (nominal): 32 millimeters

(11⁄4 inches).

• Minimum product weight: 2.8 kilograms per square

meter (5.13 pounds per square yard).

Notes: Consult the manufacturer for appropriate widths

and lengths of product desired prior to placing order.

Section 4: Geosynthetic Product Information
17



Section 5: Identification of Unsuitable Tread Fill Material

SSoils from wet areas are normally not suitable for use as

 tread fill because they are too moisture sensitive and

lose strength easily when they become wet. Avoiding

unsuitable tread fill is very important since poor materials

will fail when wet, and costs for excavating and hauling are

high. Poor materials can be identified by several methods:

Organic Soils: Identified by musty odor when damp, and

dark in color.

Other Unsuitable Tread Fill Materials: Stability of tread

fill material is primarily influenced by the amount of silt or

clay present. If the percentage exceeds 20 percent, the

materials will likely become very unstable when wet.

Rough evaluations for suitability can be done by the

following methods:

Method A—Field Comparison

Make comparisons between existing trail tread materials

with borrow sources. Compare the proportions of gravel,

sand, and fines. Individual “fine-size” material particles are

actually not visible to the naked eye and are classified as

silt or clay. If the proportions of gravel, sand, and fines are

similar, you can expect the borrow materials to perform as

well as the existing trail tread materials. If less fines exist

in the borrow source, you can expect better performance.

Method B—Laboratory Test

Take a 5-kilogram (10-pound) sample of the proposed tread

fill material to a materials testing laboratory, and have them

perform a washed sieve analysis test to determine the percentage of minus No. 200 material. Since the minus No. 200

represents the amount of silt or clay, if the amount exceeds

20 percent, the material is not suitable. Typical cost for this

test is between $35 and $50.

Method C—Geotextile Field Test

Build a short section of a small-scale trail over a wet area

with a 2-meter (6-foot) square piece of geotextile and the

proposed tread fill material. The depth of tread fill should

be at least 150 millimeters (6 inches), and should be saturated with water after placement to assimilate moisture

contents that one would expect under the worst conditions.

Evaluate the stability of the tread material by repeated load

testing with your foot.
18



Additional Information

Industrial Fabric Association International (IFAI)

The Geotechnical Fabrics Report, Specifier’s Guide, is published annually by IFAI. To purchase a copy of the latest

Specifier’s Guide, to subscribe to Geotechnical Fabrics

Report, or learn about other publications, check out IFAI’s

web site at: http://www.ifai.com. Here are some other ways

to contact IFAI.

IFAI Resource Center

1801 County Road BW

Roseville, MN 55113–4061

Phone: 800–207–0729 or 651–222–2508

Fax: 651–631–9334

Federal Highway Administration

The Federal Highway Administration’s Recreational Trails

Program provides funds to the States to develop and maintain recreational trails and trail-related facilities for motorized

and nonmotorized recreational trail uses. For additional

information, see FHWA’s Recreational Trails Program web

site at: http://www.fhwa.dot.gov/environment/rectrail.htm.
19



To order a copy of this document, you can use the

order form on the FHWA’s Recreational Trails Program

web site at: http://www.fhwa.dot.gov/environment/

trailpub.htm. Fill out the order form and fax it to the

distributor listed on the order form. If you do not have

Internet access, you can send a fax request to 202–366–

3409, or request a copy by mail from:

USDOT, Federal Highway Administration

Office of Human Environment, Room 3301

400 7th Street SW

Washington DC 20590

Electronic copies of MTDC’s documents are

available on the Internet at:

http://www.fs.fed.us/eng/t-d.php?link=pubs

Monlux, Steve; Vachowski, Brian, 2000. Geosynthetics for

trails in wet areas: 2000 edition. Tech. Rep. 0023-2838-

MTDC. Missoula, MT: U.S. Department of Agriculture, Forest

Service, Missoula Technology and Development Center.

18 p.

Geosynthetics are synthetic materials that are used with soil

or rock in many types of construction. They perform three

major functions: separation, reinforcement, and drainage.

Produced by:

USDA FS, Missoula Technology & Development Center

5785 Hwy. 10 West

Missoula, MT 59808–9361

Phone: 406–329–3978

Fax: 406–329–3719

E-mail: wo_mtdc_pubs@fs.fed.us

For further technical information, contact Brian

Vachowski at MTDC.

Phone: 406–329–3935

Fax: 406–329–3719

E-mail: bvachowski@fs.fed.us

Library Card

This report describes several types of geosynthetics; explains

basic geosynthetic design and utilizaiton concepts for trail

construction in wet areas; and provides geosynthetic product

information. Detailed product specifications and procurement

sources are listed.

Keywords: geocells, geogrids, geonets, geosynthetics,

geotextiles, sheet drains, trail construction, trail turnpikes
20



This document was produced in

cooperation with the Recreational

Trails Program of the Federal

Highway Administration, U.S.

Department of Transportation.

This document is disseminated under the sponsorship

of the U.S. Department of Transportation in the interest

of information exchange. The United States Government assumes no liability for its contents or use thereof.

The contents of this report reflect the views of the

contractor, who is responsible for the accuracy of the

data presented herein. The contents do not necessarily

reflect the official policy of the Department of Transportation.

This report does not constitute a standard, specification,

or regulation. The United States Government does not

endorse products or manufacturers. Trade or manufacturer’s names appear herein only because they are

considered essential to the object of this document.

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION