This remediation technology, also known as environmental fracturing, involves creating or increasing fractures in bedrock or soil for the injection of amendments. It is used to enhance the efficacy of treatments such as in situ chemical oxidation (ISCO), in situ chemical reduction (ISCR), pump and treat (P&T), bioremediation, soil vapor extraction (SVE), and zero-valent iron (ZVI). Fracturing increases the bulk permeability of the subsurface by creating a network of pathways in the subsurface for the amendments to follow.
There are two commonly used methods of environmental fracturing and injection: pneumatic and hydraulic.
As their names imply, pneumatic emplacement uses a compressed gas source (typically nitrogen gas) to develop fractures, while hydraulic emplacement relies on water or liquid/solid slurry amendments to develop fractures.
Cascade offers pneumatic and hydraulic fracturing technology capable of emplacing the majority of remediation amendments available on the market today. Utilizing custom built fracture control modules, high-pressure inflatable packers, data acquisition systems, bulk mixing/injection platforms, and experience at hundreds of sites nationwide, Cascade has the equipment and experience to safely and successfully apply environmental fracturing technology.
Typically, lithology with hydraulic conductivities of less and 1 x 10-4 cm/sec requires creating or enhancing pathways for delivery of solid slurry amendments. Pneumatic fracturing involves specialized systems that can deliver high pressure nitrogen followed by injection of slurries up to 40% solid concentrations. Once injected, contaminants come in direct contact with these amendments, including secondary mechanisms like advection, dispersion, and diffusion. Generally, where target lithologies cannot be achieved by DPT, pneumatic fracturing is the recommended approach. For these applications, boreholes are created by sonic, auger, or air rotary drilling, and then target intervals are isolated with high pressure straddle packer systems.
A unique application of pneumatic fracturing is to enhance permeability for fine grained soils being remediated by soil vapor extraction (SVE). Depending on the lithology, a sand proppant may be injected to create a more persistent fracture.
Generally, where target lithologies can be achieved by DPT, hydraulic fracturing is the recommend approach. Typically, higher pressure and flow pumps are required versus injection following pneumatic fracturing.