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MONITORING WELLS-A Technical Definition and Description-

By William Novak

A monitor ing wel l is a pipe bored into a groundwater source that col lects water for test ingpurposes.Many t imes, there are contaminates such as fuel or f ine part ic les that should not be mixed withthe populat ions dr inking or hygiene related water. I t is important to col lect samples from thegroundwater source to determine the how the chemicals are ef fect ing the aquifer.

Source: http://www.wm.com/wm/environmental/...

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Monitoring Well Components

Sampling

Cap

The covering of the well. This cap keeps any of the moisture build up inside the casing from

mixing with the wells contents.

Bottom

CapA cap that keeps the collected water from leaking out the bottom of the tube.

The

Casingand Post

This refers to the wells protection. Often times, the well can be hidden with foliage or

snowfall and the pole and casing can be used to locate and also protect the well from

vehicles and other mishaps. The casing will most likely be locked to prevent tampering.

Weep

HoleThis hole is used to remove any excess moisture build up inside the well.

Slotted

CasingMaterial that keeps unwanted substances from entering the inner tube.

GravelThe gravel is used to enhance the flow of water. Water easily moves into the monitoring wel

where it will be stored and sampled.

Three Basic Types of Monitoring Wells

Individual

Wells

Consists of an individual casing in the borehole. Installed in unique locations separate

from one another. Most common type. See Figure 2 below.

Nested

Wells

Consists of two or more casings in one borehole. The depth at which each of the casing

strings goes down varies so that water can be obtained from different water zones. See

Figure 2 below.

Clustered

Wells

Consists of individual monitoring wells that are grouped closely together. The purpose is

similar to that of the nested monitoring wells. The depth of each borehole will vary with

each of the wells to get data on different water zones. See Figure 2 below.

Source: http://www.dpla.water.ca.gov/...

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Drilling

Well

Placement

The photo above shows the excess dirt and rock being removed from the borehole

that will allow the workers to install the monitoring well assembly.

In order for a monitoring well to work, the well must be bored to a correct depth.

Unfortunately, aquifers are located at various depths in the ground. The drillingprocess requires a little trial and error. Once found, the aquifer will allow the well to

collect the water needed for sampling purposes.

Source: http://www.maf.govt.nz/sff/about-projects/...

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The Process

How the

Well

Collects

Water

Now that the monitoring well is installed into an aquifer, it is important to understand

how it will collect water. As shown in the figure above, water collects in an

underground location from the slow infiltration of rainwater and other forms of

precipitation. As the precipitation saturates in the ground, it will eventually collect and

form pockets below the water table. The porosity of the ground will affect the rate at

which the saturation zone replenishes. Human factors, such as roads and parking lots,

are less porous, which negatively affect the rate of saturation zone replenishment.

Highly concentrated water in the saturation zone becomes an aquifer. Water will flow

through the ground and collect in this porous zone. The bottom of the well is also

porous, allowing the water in the aquifer to slowly build up in the well. Now that water

is collecting in the well, it can be sampled. I will discuss the sampling process in the

next paper of this Monitoring Well Series.

Source: http://ga.water.usgs.gov/edu/watercyclegwstorage.html