The Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) recently issued a technical standard guidance document identifying methods to verify depth to bedrock in agricultural fields subject to the state’s targeted performance standards for Silurian dolomite bedrock. The technical standard follows the adoption in 2018 of targeted agriculture performance standards that apply to areas of Wisconsin where Silurian bedrock is present with a depth to bedrock of 20 feet or less. The standard presents options including intrusive (probing and excavation) and geophysical methods (such as use of ground-penetrating radar) to verify bedrock depth for land applications of nutrients.

Agricultural land with a depth to Silurian dolomite less than 20 feet is defined as “Silurian Bedrock” under the agricultural performance standards of Wis. Admin. Code NR 151.015(17).  Fields that contain Silurian Bedrock are subject to specific performance standards set forth in Wis. Admin. Code § NR 151.075, such as not mechanically applying manure to such fields until infield bedrock verification has identified all areas where depth to bedrock is less than five feet. The area comprises portions of Brown, Calumet, Dodge, Door, Fond du Lac, Kenosha, Kewaunee, Manitowoc, Milwaukee, Outagamie, Ozaukee, Racine, Sheboygan, Walworth, Washington, and Waukesha counties.   

The recently released technical standard is the result of an inter-agency and stakeholder workgroup tasked with developing appropriate standards for depth-to-bedrock verification, and the resulting recommendations can be used by producers who must verify depth to bedrock in agricultural fields under NR 151. The technical document has not yet been promulgated as a rule, so its provisions are not enforceable. However, any farm that is required to undergo depth-to-bedrock verification based on local ordinance, WPDES permit or NR 151’s application, should consult the technical standard document for guidance on DATCP’s recommendations.