Sampling of Ground Water Monitoring Wells - Part 1
Sampling methods that don't disrupt the aquifer matrix or sand pack need to be used.
Ground water quality typically is determined by analyzing samples acquired from cased monitoring wells. Traditionally, three to five casing volumes of water are purged from each well prior to sample acquisition, typically at high pump rates or with a bailer. This is intended to remove stagnant casing water from the borehole, replacing it with water from the aquifer. Samples then are obtained in much the same manner, i.e. by bailing or high-speed pumping. This approach to purging and sampling may seem reasonable, but numerous problems can occur that affect both sample quality and data interpretation.