Tile Drain Base-flow Phosphorus Removal Using St. George Black

Maddie SanAngelo, Nisha Nadkarni, Andres Torizzo, Watershed Consulting Associates, (2025). Tile Drain Base-flow Phosphorus Removal Using St. George Black. Technical Report # 109, Grand Isle, VT. Lake Champlain Basin Program.

Tile drain effluent is a fairly new research topic, but potentially significant source of phosphorus (P) loading into Lake Champlain. End-of-tile treatments require specific approaches based on the changing flow conditions in a particular setting. The Vermont Tile Drain Advisory Group deemed “treatment technologies” as an effective tile drain intervention in combination with broader education and management strategies. While it is understood that particulate P export is highest during high tile flows, P export in baseflow conditions is equally important to consider for treatment.

Watershed Consulting, with support from Friends of Northern Lake Champlain and the University of Vermont College of Agriculture and UVM Extension conducted a three-year long experiment (August 2018-November 2021) evaluating the performance of an adsorptive filter material as a tile drain treatment technology. The primary objective of this study was to evaluate the efficacy of a locally sourced shale material, St. George Black (SGB), as an adsorptive phosphorus filter exclusively in low-flow conditions on tiled agricultural fields. The study took place in St. Albans, VT on private agricultural land with permission from the landowner. The treatment site was located on tile-drained fields in the Jewett Brook-St. Albans Bay watershed.