One of the most important design considerations is the dispersal of the substrate in the subsurface.  more...

One of the most important design considerations is the dispersal of the substrate in the subsurface. If you cannot obtain and maintain control of the system (aquifer), you cannot consistently manage the microbial processes reponsible for reductive dechlorination. This is directly related to the selection of a substrate delivery method. In most cases, there are three methods of delivering a substrate: injection through existing wells or injection galleries, injection through direct push equipment, and direct mixing with soil. The physical properties of the substrate can also directly affect the delivery method. less...

One popular substrate delivery method is injection through permanent wells. Permanent wells have the more...

One popular substrate delivery method is injection through permanent wells. Permanent wells have the advantage of being readily available for additional applications. The disadvantages of permanent wells is their capital cost, limited coverage, their susceptibility to damage, and their limited use with solid or very viscous substrates. Since most plumes require multiple injections, permanent wells have become popular. This limits the number of times that a drilling crew must be mobilized and provides some level of flexibility with regards to reinjection timing. Permanent wells are best suited to long-term systems such as recirculation systems or barriers and are less suited to very large plumes where control of the aquifer is impractical. Highly viscous substrates can significantly complicate injection through permanent wells and the injection of solid substrates may not be possible. Also, the capital costs of permanent wells may not be financially justifiable on sites that do not have groundwater recirculation or control systems and require only one or two injection events. less...

Direct push injection of substrates allows the practitioner to optimize injection point  more...

Direct push injection of substrates allows the practitioner to optimize injection point placement but the direct push process is limited to the depth capability of the available equipment. Generally speaking, light to moderate weight direct push equipment is limited to less than about 75’ below ground surface in most situations. Deeper injections have been accomplished but these are not the norm. The advantages of direct push injection are the short site time and cost. Generally, direct push points can be completed in an hour or so each, thereby increasing the amount of plume that can be covered in a given time period. Direct push injection can also be very valuable at sites requiring fracturing of the soils. With solid substrates like ChitoRem® this can be done by suspending the substrate in a slurry of guar and water. The resulting mixture can be injected with standard direct push tools or with specialized hydraulic fracturing equipment for deep applications. less...

Substrates can also be mixed with the soils at the bottom  more...

Substrates can also be mixed with the soils at the bottom of an excavation or at the surface. This is usually done with solid substrates but can also be done with liquid substrates. The technique is limited in that it can only impact the soil and groundwater in the immediate vicinity of the substrate, and any water flowing through the substrate but this is the most inexpensive application method. Generally, the substrate is spread across the surface and then “raked’ into the top few inches of exposed soil. The ”raking” can be done with the teeth of a bucket on an excavator or even by hand. In theory, any water that flows through the treated area picks up carbon and moves that carbon into the same groundwater zones responsible for contaminant travel. This technique can be an excellent addition to injections.

JRW provides information regarding our products as a service to our clients. JRW is not a consultant and does not provide professional services. Every site is unique and care must be exercised by the practitioner to fully understand their own circumstances. less...