ASTM D4105/D4105M-20 PDF Download

The ASTM D4105/D4105M-20 standard is titled "Standard Practice for (Analytical Procedure) for Determining Transmissivity and Storage Coefficient of Nonleaky Confined Aquifers by the Modified Theis Nonequilibrium Method".

The standard describes an analytical procedure for determining the transmissivity and storage coefficient of a nonleaky confined aquifer. This procedure specifically applies to situations where there is radial flow to a fully penetrating well with constant flux. It is based on the Theis nonequilibrium method, which is explained in detail in Practice D4106.

The practice outlined in this standard is meant to be used in conjunction with the field procedure provided in Test Method D4050. However, it has some limitations that should be considered. These limitations are primarily related to how well the field situation corresponds to the simplifying assumptions made in the practice. Additionally, the application of this practice is valid only for values of u (as defined in Eq 2 in section 8.6) less than 0.01.

All observed and calculated values obtained using this practice should adhere to the guidelines for significant digits and rounding established in Practice D6026. The procedures used in this standard are considered the industry standard for data collection, recording, and calculation. However, it is important to note that the standard does not consider variations in materials, specific purposes for obtaining the data, or the user's objectives. Adjustments to the number of significant digits reported may be necessary to align with these considerations.

It is important to recognize that this standard is not intended to replace the professional judgment and experience of individuals performing the procedure. It should be used in conjunction with professional judgment, and not all aspects of the practice may be applicable in every circumstance. The standard emphasizes that it does not represent or replace the standard of care for professional services, and it should be applied with consideration for the unique aspects of each project.