Accurately Locating High Capacity Wells Using GPS

Why does DNR require a latitude and longitude location?
Latitude and longitude location narrows a well’s location down to a point that is within a quarter of an acre. A PLSS quarter-quarter section location only narrows the well location down to a 40-acre parcel. With the Groundwater Quantity Legislation of 2003, we must evaluate the impact of any high capacity well within 1200 feet of a trout stream, exceptional resource waters, or outstanding resource waters. Additional accuracy is required for DNR to evaluate possible impacts.

Currently the Private Water Supply program requires the latitude and longitude on high capacity well applications and well construction reports for high capacity wells; however in the future lat-long locations will likely be required on all well construction reports, water system inspection forms, non-complying water system forms and well abandonment reports.

What format should I use to report GPS coordinates?
When you submit a high capacity well application, GPS locations should be in latitude and longitude in the format of degrees and decimal minutes with the minutes quantified to three digits to the right of the decimal point (Example: N 43° 04.517’ W 89° 22.825’). The datum should be set to WGS84. If the unit you use has several different WGS84 datum settings, you should use WGS84(G873). The major brands of new recreational GPS units are configured for this format and datum. You should not have to change any of the internal settings unless you buy a used unit. When a GPS unit is brand new, or has not used for several weeks, old data for satellite location may be stored in the memory, resulting in poor accuracy. So, turn on the unit where there is a clear view of the sky at least 20 to 30 minutes before use so it has time to receive revised satellite locations before using it for well location readings.

What if I use the DNRWebView website to obtain GPS coordinates?
The DNR’s WebViewer website shows coordinates in degrees, minutes and seconds. You will need to convert these coordinates into degrees and decimal minutes for our forms. You can use this Microsoft Excel spreadsheet to convert your coordinates.

What can I do to ensure the GPS data I send to the department does not contain major errors?

There are several things that you should do to ensure accurate GPS data:

• GPS units should be turned on and placed where there is a clear view of the sky at least 20 to 30 minutes before the unit is used. For example, turn it on and leave it on the dashboard on while you drive to the site. That way, the unit should have sufficient time to receive updated radio signals from the satellites.
• Hold the GPS unit over the well location for at least one minute without moving around to get an accurate reading.
• Double check your data after type it. It is easy to type in the wrong number or transpose digits.

Following these procedures, you should be able to report an accurate location every time.

Why is an accurate GPS location so important?
With the new criteria for evaluating high capacity well impacts, approvals will specify the required locations for proposed wells (with a plus or minus tolerance). After a well is constructed, use your GPS unit to determine the actual well location and write it on the well construction report. DNR’s data system will calculate whether the well was located within the tolerance specified in the high capacity approval. DNR inspectors may also check well locations with a GPS unit. It could be a significant problem for the driller or owner if a well is constructed closer to a groundwater protection area or public utility well than specified in the DNR approval.