ASTM D6028-17

5.1.1 The control well discharges at a constant rate, 5.1.2 The control well is of infinitesimal diameter and fully penetrates the aquifer.

5.1.3 The aquifer is homogeneous, isotropic, and areally extensive.

5.1.4 The aquifer remains saturated (that is, water level does not decline below the top of the aquifer).

5.1.5 The aquifer is overlain or underlain, or both, everywhere by confining beds individually having uniform hydraulic conductivities, specific storages, and thicknesses. The confining beds are bounded on the distal sides by one of the cases shown in Fig. 1.

5.1.6 Flow in the aquifer is two-dimensional and radial in the horizontal plane.

5.3.1 Paragraph 5.1.1 indicates that the discharge from the control well is at a constant rate. Paragraph 8.1 of Test Method D4050 discusses the variation from a strictly constant rate that is acceptable. A continuous trend in the change of the discharge rate could result in misinterpretation of the water-level change data unless taken into consideration.

5.3.2 The leaky confining bed problem considered by the modified Hantush method requires that the control well has an infinitesimal diameter and has no storage. Moench 5.3.3 The modified Hantush method assumes, for Cases 1 and 3 (see Fig. 1), that the heads in source layers on the distal side of confining beds remain constant. Neuman and Witherspoon (7) developed a solution for a case that could correspond to Hantush's Case 1 with K" = O  = S" except that they do not require the head in the unpumped aquifer to remain constant. For that case, they concluded that the drawdowns in the pumped aquifer would not be affected by the properties of the other, unpumped, aquifer when (Neuman and Witherspoon 5.3.4 Implicit in the assumptions are the conditions that the flow in the confining beds is essentially vertical and in the aquifer is essentially horizontal. Hantush's That form of relation between aquifer and confining bed properties may also be a useful guide for the case of two leaky confining beds.

1.4.1 The procedures used to specify how data are collected/recorded and calculated in the standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of these test methods to consider significant digits used in analysis methods for engineering data.