The quality and availability of groundwater in Alaska is a common concern for businesses, residents and government agencies. Groundwater sampling is used to determine the conditions of a well’s aquifer and check for contaminants. The objectives of a groundwater sampling program include determining the direction of groundwater flow, water levels, and the distribution of contamination, if any exists.

The method used is normally dependent on the specific site being surveyed, with a variety of pumps, bailers and other materials used. The following three methods are the most commonly used for groundwater sampling.

Low-Stress Purge & Sample

As the most common methodology used for sampling, the low-stress approach to groundwater sampling purges water using bailers or high-speed pumps. After removing three to five casing volumes, geo scientists will then collect their sample.

Dedicated pumping systems are preferred when using this method, as there should be no prior disturbance in the water column before pumping. The process is time-intensive and best carried out by trained technicians.

Fixed-Volume Purge & Sample

Ideal for routine monitoring programs and inducing inflow from a large-volume aquifer, fixed-volume purging pumps three or more times the volume of water in the well lining through a monitoring borehole.

Typical equipment used during this methodology include inertial pumps, suction pumps and submersible pumps. While this groundwater sampling method tends to be more time- and labor-intensive, it is best suited for non-specialists.

Zero-Purge & Passive Sampling Methods

Not every groundwater sampling method requires purging. Zero-purge uses devices such as hydrasleeves and equilibrators to collect samples at discreet depths. This method creates minimal disturbance and is great for sampling from short-screened monitoring wells. As a simple process, it is closest in similarity to low-flow testing methods.

For more information on groundwater sampling methods, contact the experts at GeoTek Alaska in Anchorage. Recognized as one of the state’s leaders in geophysical services, this company specializes in acquiring subsurface data that is used for environmental and geotechnical purposes. To learn more about the services they offer, including groundwater sampling, auger drilling and well monitoring, visit their website or call them today at (907) 569-5900.