Passive grab samplers – revolutionizing groundwater monitoring

21 March 2024


Groundwater monitoring has always been a critical component of environmental management. The use of Passive Grab Samplers has transformed the way environmental consultants can approach sampling tasks, so let’s take a deep dive into the mechanics of Passive Grab Samplers and the benefits they offer, compared to active groundwater sampling methods.

How do they work?

The process relies on natural groundwater flow to bring aquifer-quality water through the screen, where the passive sampler “grabs” the water from an interval without changing the velocity or direction of natural flow. The water and everything in it is sealed inside the device, isolating it from overlying water layers as the sampler is removed from the well.

Passive sampling collects a groundwater sample without pulling stagnant or aerated water in, therefore no purging and time-consuming monitoring of stabilization parameters is needed to obtain a representative sample.

Benefits over traditional methods:

  • Time and cost efficiency – Traditional methods, often labor-intensive and time-consuming, can escalate project costs. Passive Grab Samplers can collect samples in less than 10 minutes and cut total field time by more than half.
  • Sample integrity and reliability – Passive grab samplers offer enhanced sample integrity. They reduce the risk of cross-contamination and disturbance to the water’s chemistry, ensuring an accurate representation of in-situ conditions.
  • Ease of use and safety – Passive grab samplers require minimal training and no special tools. They are also small, easy to transport, and require no set-up time prior to sample collection.
  • Environmental impact – Passive grab samplers are less intrusive. Disturbance to the aquifer is minimal and they require no power source to function.  Storage, transportation, and disposal of hazardous or contaminated IDW is eliminated.

HydraSleeves – A leading example:

The HydraSleeve from Eon Products is a passive grab sampler that makes groundwater sampling a simple, three-step operation that is more efficient than traditional purge methods involving pumps or bailers.

The HydraSleeve is a collapsible, flexible tube of low – or high – density polyethylene (LDPE or HDPE) that is sealed at the bottom end and has a self-sealing reed valve at the open top end. It is installed into the water column within the screen interval of the well, causing very little displacement or disturbance. Hydrostatic pressure keeps the device closed until it is pulled upward through the water during retrieval. As the sampler is pulled upward, to collect the sample, the tube opens and sleeves around the stationary water collect a “core” of the water in the interval.  When the sampler is full the valve closes and seals, ensuring that only the specific target interval is sampled.

Get in touch with us today for a quote. Check out the HydraSleeve technology on our website.