The 3-Channel CMT® Multilevel Monitoring System is ideal for direct push installations, as it is only 1.1″ (28 mm) in diameter. Often with these installations, the annulus available is too small to accurately place sand and bentonite layers for isolating the monitoring zones. Therefore, bentonite cartridges (spring and pre-formed) have been developed to give reliable seals between zones. Accompanying sand cartridges are used to complete the installation. The cartridges are approximately 2.4″ (61 mm) in diameter, slide easily onto the CMT, and will fit inside larger direct push drill rods.
Choosing Cartridges
Clients source and choose sand for filling cartridges to suit their application and the information they are monitoring. Coarse sand will allow fine particles to reach the screened port, while fine sand will filter out smaller particles before reaching the port. The client also sources the bentonite pellets used in the spring cartridges. The bentonite pellets in the spring cartridges set more quickly than pre-formed bentonite cartridges – days versus weeks. As such, the spring cartridge is recommended as the primary seal. The choice between bentonite cartridges is also based on application and client preference.
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| Sand Cartridge Filled in the Field |
Pre-formed Bentonite Cartridge Ideal for Infilling | Spring Cartridges use Bentonite Pellets |
CMT Installation to Monitor Groundwater and Soil Gas Beneath a Building
Remember to consider CMT Multilevel Systems as a quick and cost effective way to delineate soil gas concentrations below buildings. Multilevel monitoring allows chemistry comparisons of near-slab, sub-slab, and groundwater data.
® CMT is a registered trademark of Solinst Canada Ltd.
