What this tool does
Turns measured casing geometry and water level into a transparent standing-volume calculation while keeping the field-plan multiplier explicit.
When to use it
Use only when the approved method calls for a purge target based on standing well volumes; low-flow methods may instead use drawdown and stabilization evidence.
Inputs and supported units
Each labelled field explains the quantity it expects. Unit-system changes convert existing numeric entries once and keep calculations on a single SI internal basis. Supported shared units include L/min and GPM, metres and feet, kPa and psi, millimetres and inches, kW and hp, and °C and °F as relevant.
Calculation or decision method
Well volume = π × (inside diameter ÷ 2)² × water column
Target = well volume × entered multiplier
How to interpret the result
Read the primary result with the supporting breakdown and warning. A plausible number is not evidence that every input, operating case or design constraint has been included.
Worked example
A 50 mm ID well, 12 m deep with water at 4 m contains about 15.7 L. At an entered 3× target and 1 L/min, the result is about 47.1 L, 47.1 minutes and three 20 L usable containers.
Assumptions
Well construction, water levels, equipment dimensions, flow and field readings are site-specific measurements entered in consistent units. All comparison criteria are supplied by the user from the governing plan or authority.
Limitations
These tools calculate geometry, displacement and numeric variation only. They do not select a sampling method, prove sample representativeness, establish laboratory requirements or authorize collection or disposal.
Sources
- U.S. EPA — Groundwater Sampling Operating Procedure (EQASOP-GW4)
- U.S. EPA — Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures
- U.S. Geological Survey — Purge Analyzer Tool (PAT)