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D4050-20 – Standard Test Method Technical Guide
ASTM D4050-20 establishes the standard field procedure for performing withdrawal and injection well testing to determine the hydraulic properties of aquifer systems. This method specifically addresses the operational steps required to conduct a valid field test, from selecting well locations to controlling pumping rates and accurately measuring water level responses.
📐 Scope, Limitations, and Units
The scope of D4050-20 covers the controlled field testing of wells to generate data suitable for analyzing the hydraulic properties of aquifers and adjacent confining beds. This test method is explicitly designed to be used in conjunction with analytical procedures, such as Test Methods D4105/D4105M or D4106. The specific analytical approach is selected based on the guidance provided in ASTM Guide D4043, which helps match field conditions to appropriate analysis models.
It is critical to understand the limitations of this methodology. The accuracy and validity of the determined hydraulic properties are directly linked to how well the existing field situation corresponds to the simplifying assumptions inherent in the selected analytical model. Furthermore, the standard specifies that values stated in SI units are regarded as the standard for reporting. All observed and calculated values must conform to the guidelines for significant digits and rounding established in Practice D6026. The procedures used to specify how data are collected, recorded, or calculated are regarded as the industry standard.
| 🟦 Key Parameter | 🎯 Description and Requirement |
|---|---|
| Test Type | Withdrawal (pumping) or injection well testing. |
| Target Data | Hydraulic properties of aquifers and adjacent confining beds. |
| Primary Controls | Rate of discharge or injection must be measured and controlled. |
| Measurements | Water levels in the pumped well and observation wells. |
| Reporting Units | SI units are standard; other units are not non-conformance. |
⚙️ Field Procedure and Data Collection
The core operational requirements of D4050-20 focus on the rigorous execution of the field test. This includes careful selection of well locations to ensure that the testing captures representative data for the aquifer system. Controlling the change rate of discharge or injection is essential for meeting the boundary conditions required by the subsequent analytical methods. Measurements of water levels must be made with appropriate precision to detect the aquifer response to the imposed stress. Users of this standard are responsible for establishing appropriate safety, health, and environmental practices prior to testing.
This test method offers a set of instructions for performing these operations. It is intended to be used by professionals familiar with aquifer testing principles. The document cannot replace education or experience and must be used in conjunction with professional judgement.
⚠️ Critical Consideration: The limitations of this test method are primarily related to the correspondence between the field situation and the simplifying assumptions of analytical methods such as D4105/D4105M or D4106. Professional judgement is required to assess the validity of these assumptions.
| 📏 Referenced Standard | 📐 Role in D4050-20 Analysis |
|---|---|
| D4043 | Guide for selection of the appropriate aquifer test method. |
| D4105/D4105M | Analytical procedure for evaluating withdrawal well test data. |
| D4106 | Analytical procedure for evaluating injection well test data. |
| D6026 | Prescribes guidelines for significant digits and rounding. |
| D653 | Provides standard terminology for soil, rock, and contained fluids. |
📊 Required Analytical Integration and Compliance
D4050-20 does not stand alone; it is the field component of a comprehensive testing program. The data generated by this procedure is designed specifically for input into analytical test methods like D4105/D4105M or D4106. The selection of the analytical method is guided by the user’s objectives and site characteristics as outlined in Guide D4043.
Compliance with this standard requires strict adherence to reporting guidelines. Significant digits must be