LAUSR

Abstract Monitoring wells (MWs) are key components of all engineering geology projects, for groundwater seepage, effective stresses and monitoring. To assess the local hydraulic conductivity, a solid object or a water volume is used to change suddenly the hydraulic head in the MW to start a variable-head (VH) or slug test. Proper interpretation of water level recovery data yields the hydraulic conductivity value KVH for the test. When groundwater is sampled at a constant flow rate for 15- to 40-min, this is said to produce a constant-head (CH) test that provides a KCH value. Subsequent recovery data in the MW are then used as if they were from those of a VH test, even though the initial change was not sudden. Recovery data may on the other hand yield strange plots. This paper proves first that VH theory is valid for recovery data when the MW is correctly designed and installed. Recovery data of seven such tests are then examined as if they were VH tests. This provides proof that correctly designed and installed MWs yield very close values for KCH and KVH, with the later displaying straight velocity plots including a CH point. On the other hand, poorly designed and installed MWs yield inconsistent values for KCH and KVH and velocity data of the later yield curved or scattered plots when they should be linear. This hence provides to geological engineers a simple method for quality control of MW installation.