Idaho Well Data field records · 2026 survey

Guide to Interpreting a Well Driller's Log

To read a well driller's log effectively, focus on key sections such as well depth, static water level, yield, and geological formations encountered during drilling. Understanding these elements will help you assess the viability and sustainability of a water source on your property.

Key Components of a Well Driller's Log

1. Well Depth

The total depth of the well is crucial as it indicates how far the driller had to go to reach a reliable water source. In Idaho, well depths can vary significantly depending on the geological formations and the location. Generally, deeper wells may provide more sustainable water sources, but they can also be more expensive to drill and maintain.

2. Static Water Level

The static water level measures the distance from the ground surface to the water in the well when the pump is not operating. This level can fluctuate with seasonal changes and usage. A lower static water level might indicate a more reliable water source, but it is essential to monitor changes over time to ensure continued water availability.

3. Yield

Yield, often measured in gallons per minute (GPM), indicates the rate at which water can be pumped from the well. A higher yield is generally better, especially for larger households or agricultural needs. However, it's important to balance yield with the recharge rate to avoid over-extraction.

4. Geological Formations

Understanding the geological layers encountered during drilling can provide insights into the quality and sustainability of the water source. The log will list various soil and rock types, such as sand, gravel, clay, or bedrock, and their respective depths. Certain formations, like sand and gravel, are typically more favorable for water flow than clay or solid rock.

Interpreting Additional Information

Drilling Method and Equipment

The log may note the drilling method used, such as rotary or cable tool drilling, which can affect the well's efficiency and cost. Knowing the equipment can also help in future maintenance or repairs.

Well Casing and Screen

The type and depth of casing installed are critical for preventing contaminants from entering the well. A properly installed screen at the bottom of the well helps filter out sediments while allowing water to flow freely.

Water Quality Tests

Some logs include results from initial water quality tests, providing a baseline for contaminants like nitrates or bacteria. Regular testing is recommended to ensure safe drinking water.

Cost Considerations

Drilling costs can vary based on depth, geological conditions, and the drilling company. It's wise to obtain multiple estimates and consider both upfront and long-term maintenance costs when planning for a well.

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