Slurry

Slurry is formed when pressurized water breaks apart soil particles and mixes with them to create a pumpable liquid. The consistency varies from thin, watery fluid in sandy soils to thick, heavy mud in clay soils. The vacuum system must generate enough suction to lift this slurry through the dig tube, up through the boom, and into the debris tank.

The water-to-soil ratio in the slurry affects both the efficiency of the excavation and the capacity of the debris tank. Experienced operators use just enough water to loosen the soil without creating an excessively wet slurry, maximizing the amount of soil that can be held in the tank before dumping is required. Overuse of water fills the tank faster and increases disposal costs.

Slurry disposal regulations vary by jurisdiction. Most areas require disposal at an approved dumping facility, which may be a wastewater treatment plant, a licensed disposal site, or a dewatering facility. Some jurisdictions allow dewatered spoils to be spread on agricultural land or used as fill material after testing confirms the absence of contaminants.