When sampling for VOCs, an important goal is to minimize the disturbance of groundwater in order to reduce off-gassing of VOCs.<\/p>\n

Low flow sampling is a widely accepted sampling protocol, especially when VOCs are involved. Low flow sampling involves extracting groundwater at rates comparable to ambient groundwater flow. Drawdown, mixing, and turbulence are minimized, allowing a sample that is representative of actual in-situ conditions.<\/p>\n

Next, the required sampling depths had to be taken into account. The four monitoring wells being sampled have static water level at 37.5 meters below ground surface. Samples are required from 42, 46, and 48 meters below the surface.<\/p>\n

This ruled out the use of low flow sampling options, such as a peristaltic pump, which is designed for shallow groundwater sampling scenarios.<\/p>\n

3. Water Temperature Stability<\/h2>\n

The concentration of PCE in groundwater is highly sensitive to variations in temperature. Therefore, this excluded the use of samplers that use submersible motors.<\/p>\n

The use of down-well motors could potentially raise the temperature of the groundwater, causing the concentration of PCE to change and become unrepresentative of the actual conditions.<\/p>\n