Monitoring Well Construction

Monitoring Station Construction

A typical groundwater monitoring station consists of one monitoring well screened in each major aquifer present in that area. In the Piedmont and Mountains, a typical well nest will have one monitoring well completed in the fractured bedrock aquifer and one well completed in the saprolite aquifer.

Coastal Plain hydrogeology is much more complex, as there are numerous aquifers arranged in a layer-cake fashion in many parts of the Coastal Plain. A typical Coastal Plain well nest may consist of two wells to more than 10, depending on which aquifers are present in that area. For a list of Coastal Plain aquifers and the distribution of DWR's monitoring wells by aquifer, click here.

Monitoring Well Construction

When drilling a water supply well, the driller's goal is to install a well that will yield the most high quality water possible. As such, drillers will often install well screens and/or filter packs in numerous aquifers until the desired yield is reached.

When installing monitoring wells, however, the exact opposite is often true. Monitoring wells are most useful when they are screened or open in one specific aquifer or one zone within a certain aquifer. This ensures that the data that is collected from that well is representative of only that aquifer or zone. By constructing numerous monitoring wells screened in only one aquifer each, scientists can study the interconnections (or lack thereof) between the different aquifers. This information is critical for studies assessing recharge and yield of various aquifers.

Please click each link below for descriptions and diagrams of typical construction for saprolite, bedrock, and Coastal Plain monitoring wells.

Saprolite

Bedrock

Coastal Plain

Well Installation Methods

DWR uses three major types of drilling methods when installing its monitoring wells. Each is described below. Click on the headings for photos and descriptions of equipment used in each method.

Hollow-Stem Auger

Air Rotary

Mud Rotary

Common Installation Problems

Over the years, DWR has experienced several problems regarding the proper installation of monitoring wells. These problems are listed here so that others who may install similar monitoring wells may avoid them.

Excessive Gravel Pack

Loss of Mud Circulation in Highly Transmissive Zones

Finding "True" Bedrock