Why Use Multilevel Monitoring Wells?

Choosing the Right Monitoring Well

driller pouring bentonite in well on multilevel monitoring site

Source: https://health.hawaii.gov/heer/tgm/section-06/

Groundwater. We all recognize it as a necessity and the need to keep watch on its quality and quantity with time. However, how do we effectively monitor something that we can’t see? The short answer – choose the right monitoring wells!

As an environmental colleague working in the industry, your goal is our goal – to select a monitoring well that provides detailed information on hydraulic and transport properties and water chemistry from each geological stratigraphy so changes can be identified over time. You’re looking for cost-efficient, defensible data that’s easy to collect.

The Multiple Level Well (aka. Multilevel) – what is it?

As pictured, Multilevel monitoring wells use a number of individually isolated short screens to ‘capture’ water at each specific depth in a single borehole. Each well screen is isolated using sequences of clay seals or borehole Packers so that a representative water level and water sample can be collected from multiple depths in a single borehole.

Reasons for Using a Multiple Level Well.

Geology is not always ‘homogeneous’. Understanding the vertical differences in water levels and water chemistry across complex geology is key.

multilevel groundwater monitoring well examples

Well Cluster – Not Ideal

well clusters not ideal for groundwater monitoring

Arrows Indicate Groundwater Flow Direction

Installing well clusters can create ‘short-circuit’ pathways for water levels and chemistry across over-lapping sand packs.

long screened well installations not ideal

Long-screen wells can ‘over-estimate’ a contaminate thickness and ‘under-estimate’ the maximum concentration.

Nested Wells – Not Ideal

Void space between casing not sealed with grout

Nested wells can also present biased chemistry and water levels at poorly sealed zones.

Multiple Level Wells Provide High Resolution Data

Creating ‘transects’ across zones of interest provides depth discrete data that can be compared ‘seasonally’ through various geological strata.

multilevel monitoring wells provide three dimensional groundwater data

Image above showing Contaminant Plume Source and Groundwater Flow Direction. A Transect of Multilevel Systems Are Used to Monitor Detailed Contaminant Concentrations.