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D5473 – Standard Test Method Technical Guide
📐 Overview and Scope
This practice covers an analytical solution for determining the horizontal and vertical hydraulic conductivity of a nonleaky confined aquifer. It analyzes water level responses to discharges from partially penetrating control wells, using data from Test Method D4050. The practice is subject to limitations related to field conditions versus simplifying assumptions, such as aquifer homogeneity and constant pumping rate.
Units are provided in SI and inch-pound systems, each to be used independently. All observed and calculated values must conform to significant digit guidelines established in Practice D6026. This standard does not address safety concerns; users must establish appropriate practices.
⚙️ Test Procedure and Analysis
The procedure involves conducting an aquifer test with a partially penetrating control well. Drawdown data from observation wells is analyzed using the analytical solution to estimate horizontal and vertical hydraulic conductivities. The test must be performed according to Test Method D4050, ensuring proper well construction, screen placement, and data collection over time.
Key assumptions include a homogeneous, isotropic, nonleaky confined aquifer of infinite extent and a constant discharge rate. Partial penetration effects require the control well screen length to be less than the aquifer thickness. The solution accounts for both radial and vertical flow components.
📊 Key Parameters and Data Requirements
Essential parameters include well penetration ratio, discharge rate, drawdown, and time-drawdown data. The following table summarizes units and accuracy guidelines per the standard.
| 🟦 Parameter | 📏 SI Unit | 📐 Inch-Pound Unit | 🎯 Accuracy Standard |
|---|---|---|---|
| Horizontal Hydraulic Conductivity | m/s | ft/day | Conform to D6026 |
| Vertical Hydraulic Conductivity | m/s | ft/day | Conform to D6026 |
| Discharge Rate | m³/s | ft³/s | Field measurement per D4050 |
| Drawdown | m | ft | Precision per D4050 |
| Aquifer Thickness | m | ft | Measured with care |
💡 Important: Partial penetration is critical for vertical hydraulic conductivity. Ensure the control well screen length is less than the full aquifer thickness to capture vertical flow effects.
⚠️ Caution: This practice assumes nonleaky confined conditions. Deviations from these assumptions, such as leakage or anisotropy, may invalidate results. Professional judgment is essential.
❓ Frequently Asked Questions
🔍 What is the primary purpose of D5473?
To determine horizontal and vertical hydraulic conductivity in nonleaky confined aquifers by analyzing drawdown from partially penetrating control wells.
💡 Which test method provides the required data?
Test Method D4050 for field procedures in aquifer tests, including pumping rate and water level measurements.
⚡ How should units be reported?
Values must be reported in either SI or inch-pound units independently; mixing systems may cause nonconformance. Significant digits follow Practice D6026.
📌 What are the main limitations?
The assumptions of homogeneous, isotropic, nonleaky confined aquifer with constant pumping rate; field conditions must closely match these for valid results.