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D5092 – Standard Test Method Technical Guide
📚 Scope and Key Considerations
ASTM D5092/D5092M-16(2024) specifies a standard practice for designing and installing conventional groundwater monitoring wells with screened and filter-packed completions. It is applicable for formations ranging from unconsolidated sands and gravels to granular materials with grain-size distributions having up to 50 % passing a #200 sieve and as much as 20 % clay-sized material. Formations finer than this, such as silts and clays, can be monitored but may not yield sufficient water for sampling and require costly fine filter packs. This practice is not intended for fractured or karst rock conditions but may be used for other porous rock formations. The methodology assumes the program objectives include obtaining representative groundwater samples and data from a targeted zone defined by site characterization.
📐 Design Specifications and Materials
Sieve designations follow Specification E11 using the alternate system (e.g., #40, #200 sieves) with nominal opening sizes in inches and particle sizes in millimeters. Well screen slots are expressed in inches with metric equivalents provided in the terminology section (3.3.6). For coarse-grained aquifers, proper design combined with well development (D5521/D5521M), groundwater sampling (D4448), and well maintenance (D5978/D5978M) permits acquisition of samples free of artifactual turbidity and accurate hydraulic data. For fine-grained formations, it is generally necessary to use much finer pre-packed well screens (6.3.3.2) and/or employ sampling methods that minimize screen intake flow velocity.
| 🟦 Sieve Designation | 📏 Nominal Opening (in) | 📐 Particle Size (mm) |
|---|---|---|
| #40 | 0.0165 | 0.425 |
| #200 | 0.0029 | 0.075 |
⚙️ Installation and Development Procedures
This standard primarily applies to well design and installation methods used in drilled boreholes. In coarse-grained aquifers, following the prescribed procedures with proper development ensures representative samples and data. In fine-grained formations, using sampling methods that minimize screen intake flow velocity, such as low-flow purging (D6771) or passive sampling devices (D7929), can reduce the potential for sample bias associated with turbidity. All observed and calculated values should conform to the significant digits and rounding guidelines in Practice D6026.
💡 Tip: To improve sample quality in fine-grained formations, consider using low-flow purging or passive sampling techniques to minimize flow velocity and sediment disturbance.
⚠️ Warning: This practice is not applicable in fractured or karst rock conditions. Ensure site characterization confirms suitable geology for this standard.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D5092?
This practice covers design and installation of conventional groundwater monitoring wells in formations from unconsolidated aquifers to granular materials with up to 50% passing #200 sieve and 20% clay-sized material. It excludes fractured/karst rock.
💡 How does grain-size distribution impact well design?
Finer materials require finer filter packs and screens to achieve stable wells and representative samples. Coarse sands/gravels allow standard designs.
⚡ What methods address turbidity in fine formations?
Use finer pre-packed well screens and low-flow (D6771) or passive sampling (D7929) to minimize screen velocity and sample bias.
📌 What unit systems are permitted?
Both inch-pound and SI units are allowed. Sieve openings are in inches, particle sizes in mm. Values from each system are independent and should not be combined.