ASTM D4106-20 PDF Download

ASTM D4106-20 is a standard practice that provides an analytical procedure for determining the transmissivity and storage coefficient of nonleaky confined aquifers using the Theis Nonequilibrium Method. The standard specifies a set of assumptions that should be followed during the analysis process. These assumptions include the constant discharge rate of the well, the well being fully penetrable and of infinitesimal diameter, and the aquifer being homogeneous, isotropic, and receiving insignificant water contribution from confining beds. It is also assumed that the discharge from the well is solely derived from aquifer storage.

The standard also discusses the application of the Theis Method to unconfined aquifers. It states that while the assumptions are applicable to confined conditions, the Theis solution may be applied to unconfined aquifers if the drawdown is small compared to the saturated thickness of the aquifer, or if the drawdown is corrected for the reduction in thickness of the aquifer and the effects of delayed gravity yield are negligible.

The document highlights the significance of the personnel's competence, as well as the suitability of equipment and facilities used, in producing reliable results. It emphasizes that compliance with the standard does not guarantee reliable results on its own and that various factors should be considered.