chapter  2
26 Pages

Design and Field Observation

WithWilliam C. Walton

The purpose of pumping test design is to ensure that a proposed test site and associated equipment will yield acceptable results, and to minimize uncertainties in data collection and analysis. Criteria used in site evaluation are (Stallman, 1971, pp. 6–8):

The production well should be equipped with reliable power, pump, and discharge-control equipment.

The water discharged should be conducted away from the production well to minimize or eliminate recirculation.

The wellhead and discharge lines should be accessible for installing, regulating, and monitoring equipment.

It should be possible to measure water levels in the production well before, during, and after pumping.

The diameter, depth, and position of all intervals open to the aquifer system should be known, as should total depth.

All production wells within the pumping test area of influence should be capable of being controlled, and their discharges should be known.

Fluctuations in nearby surface water stages should be monitored.

Existing production and observation wells should be utilized whenever possible.

Response of observation wells to changing water level stages should be tested by injecting a known volume of water into each well and measuring the subsequent decline of water levels. The initial rise of water levels 10should usually be dissipated within a few minutes if the observation well is to accurately reflect changes of head in the aquifer system during the test.

Radial distance and direction from the production well to each observation well and from any interfering production wells should be determined.

Radial distance and direction from any known boundaries to each observation well should be determined.

Depth to, thickness of, and areal and vertical limits of the aquifer system should be determined.

Nearby aquifer system discontinuities should be mapped.

The order of magnitude of pertinent aquifer system hydraulic characteristics should be estimated.