ASTM D5881-95(2005)

The assumptions of the physical system are given as follows:

The aquifer is of uniform thickness, with impermeable upper and lower confining boundaries.

The aquifer is of constant homogeneous porosity and matrix compressibility and constant homogeneous and isotropic hydraulic conductivity.

The origin of the cylindrical coordinate system is taken to be on the well-bore axis at the top of the aquifer.

The aquifer is fully screened.

The well is 100 % efficient, that is, the skin factor, f, and dimensionless skin factor, σ, are zero.

The assumptions made in defining the momentum balance are as follows:

The average water velocity in the well is approximately constant over the well-bore section.

Frictional head losses from flow in the well are negligible.

Flow through the well screen is uniformly distributed over the entire aquifer thickness.

Change in momentum from the water velocity changing from radial flow through the screen to vertical flow in the well are negligible.

1.1 This test method covers determination of transmissivity from the measurement of water-level response to a sudden change of water level in a well-aquifer system characterized as being critically damped or in the transition range from underdamped to overdamped. Underdamped response is characterized by oscillatory changes in water level; overdamped response is characterized by return of the water level to the initial static level in an approximately exponential manner. Overdamped response is covered in Guide D4043; underdamped response is covered in D5785, D4043.

1.2 The analytical procedure in this test method is used in conjunction with Guide D4043 and the field procedure in Test Method D4044 for collection of test data.

1.3 Limitations—Slug tests are considered to provide an estimate of the transmissivity of an aquifer near the well screen. The method is applicable for systems in which the damping parameter, ζ, is within the range from 0.2 through 5.0. The assumptions of the method prescribe a fully penetrating well (a well open through the full thickness of the aquifer) in a confined, nonleaky aquifer.

1.4 The values stated in SI units are to be regarded as standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.