Do you have a Well Log?

Posted: January 25, 2016

One of the most useful - and often missing – records a private well owner can have is the well completion report. This is the report that documents the construction of the well and the geology that will determine so much of the water quality.

An accurate, complete log of the water well is a written record about the well that describes the types of rock penetrated, observations of the well while it was being constructed, and method of construction as well as construction practices as grouting and material used in the casing. This will be available long after the owner and driller forget and carry this information through successive well owners. This information is part of the well completion report that should be given to the well owner upon completion of well construction.

This is an important document that should be kept with all testing and repair records. The folder should, ideally, be passed along when the property is sold, but seldom is.

This report contains information on the finished depth of the well, the total number of feet of casing that was used, the length and diameter of the screen, if present, and should describe the different rocks that were drilled through in as much detail as possible. The well log also should record the depth, thickness, and yield of water-bearing zones. Well logs contain useful information on determining the local depth to bedrock and depth to water.

The Pennsylvania Geological Survey has a simple guide for logging wells available on-line. This is a useful, concise guide for drillers that includes a field guide for selecting color, grain size, and other characteristics that the driller can use in rock descriptions. This is good information to know for homeowners preparing to drill a new well.

If there is a zone producing poor quality water it may be cased off. To make this a viable option, it is important to know the depths and yields of water-bearing zones, so that the well will continue to produce sufficient water. In other cases, this won’t work and a new well may be needed.

All wells can develop problems over time. A good well log can provide important information to help understand and correct the problems. Some problems that can arise are:

  • Cloudy water/caving. The log may show soft shale or other rock that disintegrated.
  • Hard water. The log may show limestone.
  • Sulfur. The log may show black shale.
  • Iron/manganese. The log may show rock that produces iron/manganese.
  • Voids: The log may show caves or old coal mines.

Penn State has a fact sheet on "Water Well Maintenance and Rehabilitation” with additional information for well owners experiencing problems.

Well owners that don’t have a copy of the well completion report can try to obtain a copy by contacting the well driller (if known) or logging in to the Pennsylvania Groundwater Information System (PaGWIS).

Licensed well drillers are required to file well completion reports with the state. Since June 1, 2009, drillers have been required to file reports online through WebDriller. Prior to that date, paper reports were accepted. These reports are being added as funding and personnel permit. Not all records have been added to the PaGWIS system, however, roughly half of the 1 million wells in Pennsylvania can be found in the database.

Finally, what happens to wells that are no longer in use? By law, unused wells should be decommissioned to prevent danger to animals or children becoming trapped and to protect the aquifer from contamination, potentially affecting the new well and others drawing on the same aquifer. This process involves removing all equipment from the well and properly sealing the well.

So, check your records for a copy of your well completion report.

Diane Oleson
Extension Educator – Natural Resources
Renewable Natural Resources Team
Penn State Extension
York County