Filling ENVIROTUBES with fine grain materials for constructing spoil areas on a dredge job
When filling with fine grain materials, all of the ports should be closed to allow the water to exit through the fabric. A polymer has to be used to get a good dewatering function. The ENVIROTUBE must be filled or pumped several times; even then some final settling must be allowed for.
If the fine grain material is allowed to get very dry, cracking will occur. In dewatering, cracking is desirable; it helps with the drying. The tube can be covered to prevent re-saturation with rainwater, etc.
If the ENVIROTUBE is subjected to pounding surf or severe wake, precautions must be taken to prevent the fill material from being pounded out through the fabric. This can be done by lining the tube with nonwoven fabric. The anchor tubes on the scour aprons are always lined with a nonwoven fabric.
How It Works
Dewatering with Envirotubes technology is a three-step process:
Step 1: Filling -- Sludge (dredged material) is pumped into the Envirotube container. Environmentally-safe polymers are added to the sludge, which makes the solids bind together and water separate. The Envirotube's fabric confines the fine grains of the material.
Step 2: Dewatering -- Clear effluent water simply drains from the Envirotube through the small pores in the specially engineered textile. This results in effective dewatering and efficient volume reduction of the contained materials. And this volume reduction allows for the repeated filling of the Envirotube™. Over 99% of solids are captured, and clear filtrate can be collected and recirculated through the system. The decanted water is often of a quality that can be reused/returned for processing or returned to native waterways without additional treatment.
Step 3: Consolidation -- After the final cycle of filling and dewatering, the solids remain in the bag and continue to densify due to desiccation as residual water vapor escapes through the fabric. Volume reduction can be as high as 90 percent. When full, the Envirotube™ and contents can be deposited at a landfill, remain on-site, or the solids can be removed and land-applied when appropriate.
Laydown Recommendations - Dewatering
Consult your Envirotubes Technical Representative for specific recommendations on polymers for your application.