Envirotubes are high strength fabric, tubular containers, designed to contain and dewater dredge spoils, industrial and municipal sludge, and other pump slurries products through environmental remediation projects.

Envirotubes are made of fabric designed specifically for the construction of this product. Combining the high strength necessary for the demanding structural strains, with the porous weave required for optimal dewatering capabilities. They are available in standard sizes of 15', 30', 45', and 60' circumference, in various lengths to accommodate the specific requirements of the project.

Although this is a relatively new method, many regulators and engineers are familiar with the procedure. In fact, in some areas, the use of Envirotubes can help in the permitting process.

Currently the most common reason Envirotubes are used is limited area near a project for containment and dewatering of material. Mechanical excavation for site preparation is minimal.

Hydraulic dredging would typically require the construction of a spoil area. The space to position such a spoil area is often very limited and sometimes totally unavailable. The use of Envirotubes opens a whole realm of possibilities. A marina can be dredged using the parking lot; a sludge lagoon can be cleaned by placing the Envirotubes on the levy dam; a suburban lake surrounded by homes can be cleaned using the commons ground. The use of Envirotubes in these applications is also much neater and safer than an open spoil area for use in parks or golf courses.

The other common factor in the decision to use Envirotubes has been cost savings. Despite the many logistical advantages of using Envirotubes, it is often the most cost effective way to do the project as well. This has been proven in many sludge applications that had previously been done by other methods; from projects where material had been hauled wet in tank trucks, to projects where presses and mechanical dewatering equipment was used.

From small ponds and municipal lagoons, to huge paper mill jobs with many hundreds of thousands of yards of material, the overall operations cost of the project was reduced by the use of Envirotubes.

• The dewatering system with no capital investment.
• The envirotube is a container made of high strength polypropylene geotextile. Its purpose is to contain pumped slurry and retain the solids while the water or fluid is released through the fabric.
• This is a function of time, gravity, and chemistry, not pressure.
• Envirotubes are a relatively new way to dewater dredged and other slurry when other methods are less practical or cost effective.
• Envirotubes take up less space than some dewatering methods, are less dangerous than some, less obtrusive than some and less costly than some, and easier to set up and transport than some.
• Envirotubes can be used to dewater most any slurry that contains solids.
• Envirotubes work in most any weather conditions.
• Envirotubes are available in a variety of sizes, and are inventoried in the common sizes used for dewatering for immediate delivery.
• Envirotube fabric is unaffected by ph and is impervious to most nonpetroleum materials and has even been used on some petroleum sludge successfully.
• Envirotubes are easy to install.
• Envirotubes eliminate many environmental problems on dredge and environmental cleanup jobs.
• Envirotubes can be used in process as well as for cleanups.
• Envirotubes can be left in place and/or used for erosion control.
• Envirotubes can be used to create islands with dredged materials.
• Envirotubes are often easier to permit than other methods.
• Envirotubes can reduce pumping distances.

The tubes are sized and measured by circumference and length. A tube cannot be measured by diameter because it never becomes round. Even when full, the cross section of the tube is elliptical.

The fabric the tubes are made from woven fabric that is in a 15 foot width. This makes 15 feet the common denominator for the circumference sizes. The tubes are 15', 30', 45' and sometimes 60' in circumference. Standard lengths are 50', 100', 150' and 200'. When the tube has been pumped, it can be measured by height and width. The maximum height that a tube can be pumped will vary some with the material that is being pumped into the tube, and the application. The height also determines the width.

Envirotubes are fabricated from 46T polypropylene high strength geotextile. The fabric has a 400 pound per inch strength lengthwise, and 600 pounds per inch crosswise. The weave of this fabric passes water easily, but retains solids well. The polypropylene fabric is very slippery and releases the filter cake well.

Dewatering in a tube is a factor of gravity, time, and chemistry that separates the water from the solids and allows the water to escape through the fabric. This is not a filter press function. The water must separate from the solids to escape through the fabric, and escapes through the top of the tube. A polymer is usually used to speed up the process, and to clear up the decant water. The dewatering process usually works best when more than one tube is used and the input flow is alternated between them, allowing still decant time.

A portable envirotube, placed into the back of a dump truck or roll off container, allows for even more convenient sludge removal.

How much material can be pumped into the tube with each pumping is determined by measuring the height of the tube. How many times the tube can be pumped is determined by measuring the stretch of the fabric. If the tube is not pumped over the safe height the tube may be pumped many times. The capacity of the tube can be determined by using the capacity chart and the hanging bag shrink test. This will give an estimate of how many feet of tube will be needed for a particular job. Sand, of course, does not shrink at all, whereas normal lake sediment will shrink about 50%, organic sludge will often shrink 75% to 90%. The best way to determine this is using the hanging bag, which comes with instructions how to run a test.

The side by side direction of the lay-down area should be level or nearly level. If there is a grade, the first tube must be laid at the lowest point. The subsequent tubes can then lean against the first tube to prevent rolling. The first tube will probably have to be restrained. The handles on the tubes will only hold the tube in place on the level surface, or hold the tube next to the previous tube for positioning while the filling process is started. The handles are designed to fail before the tube fabric fails. Sandbags can by placed under the low side of the tube to make up for a slight grade or dip. A plastic covered berm or concrete barriers for the tube to lean against make the best restraints. A dewatering tube will climb over too low a barrier like a slinky toy.

The tube does not easily roll lengthwise. The amount of lengthwise grade will however affect the capacity of the tube. A 1% grade will lose 1 foot of elevation per 100 feet on the high end. A 200 foot tube will lose 2 feet on the high end. This will average out to a 1 foot loss on the capacity chart. The height of the tube must be measured at the lowest ground elevation. The lay-down width dimension of the 45' circumference tube will be 21 feet wide when empty, and 18 or 19 feet when full.

A large volume of water will have to be dealt with; erosion is definitely a factor. Plastic should be used under the tube to prevent erosion on soft ground. The water exits the top of the tube, and cascades over the sides. Allow an exit path for the water (water will not flow out under or between the tubes).

*Above, safe efficient height for some materials

The above capacities are the actual displacement of the tube. The shrinkage factor will vary greatly from one material to another. Sand will not shrink from the insitu volume to be dredged. One CY of tube capacity will be needed for each CY of sand to be dredged. Organic or fine grain materials will shrink more than 50%. How much material can be put into a tube will depend on how many times the tube is pumped and how much time is allowed for dewatering. The dewatering time is affected by whether or not a polymer is used, although some materials will not dewater without a polymer being added. A shrink factor can be established with a shrink test using a hanging bag. The tube releases water faster if not pumped to full height; only pump the tube to full height on the last filling.