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D4750-87 – Standard Test Method Technical Guide
📖 Scope and Significance
This test method, designated D 4750 – 87 (Reapproved 2001), provides standard procedures for measuring the level of liquid in a borehole or monitoring well (observation well) and specifically determining the stabilized liquid level. The method applies to boreholes (cased or uncased) and wells that are vertical or sufficiently vertical so a flexible measuring device can be lowered into the hole.
In geotechnical, hydrologic, and waste-management investigations, establishing the presence of groundwater and precise liquid depths is frequently required. This standard ensures consistent, repeatable field measurements for these critical assessments.
⚠️ Critical Limitation: Borehole liquid-level measurements obtained using this test method do not necessarily correspond to the actual ground-water level in the vicinity of the borehole unless sufficient time has been allowed for the level to reach hydraulic equilibrium (Section 1.3). This test method is