Humidity Cell Tests — MEND, Sobek (EPA), and ASTM D5744 Methods
These tests are used to evaluate the long-term weathering characteristics of mine waste materials disposed under subaerial conditions. Tests are run in strict adherence to standard procedures. Possible analyses of leachates include: pH, Eh, electrical conductivity, TDS, hardness, sulphate, anions (nitrate, nitrite, chloride, fluoride, phosphate, ortho-phosphate, TKN, ammonia), alkalinity, acidity, Hg by CVAF, and dissolved metal scans by ICP-ES or ICP-MS.
Leach Columns (Lysimeters)
While similar to humidity cell-based analyses, these tests simulate site waste disposal conditions more closely. Water is typically added in a trickle leach fashion, but periodic flushings are possible to better simulate field conditions. Analyses that can be conducted on leachate water are the same as those for humidity cell tests.
Subaqueous Disposal Columns
These tests simulate underwater disposal of tails or wasterock and the impacts of such disposal on the water system. Acrylic or clear PVC column type cells are used. These have a series of ports, which enable sampling of surface water and pore water within the waste material. These tests can be operated under anoxic conditions using nitrogen or argon to displace oxygen. An in-line sampling port can be installed for in-situ analysis of selected parameters such as pH, Eh and dissolved oxygen. Analyses conducted on the water samples are the same as those for leach column tests, with the addition of dissolved oxygen analysis.
Other Non-Standard Tests
Maxxam has the ability to construct and operate customized test systems for the purpose of ARD and/or metal leaching prediction. This allows for investigation of scaled-up tests or custom environmental conditions to simulate field conditions. Larger scale versions of the humidity cell and static water leach tests are offered. These provide a larger volume of leach water, which may be required for atypical water analyses such as radionuclides investigation, confirmation of novel control or prevention measures. Also, customized sequential leach tests are offered.