Dye Trace Study of a New Septic System in Door County, Wisconsin

A professionally designed, installed and inspected conforming waste water treatment system and a conforming water supply well were installed at a new restaurant in rural Door County, Wisconsin. In the two weeks following the opening of the restaurant, over 250 people became ill with viral gastroenteritis. Testing of the new, conforming well at the restaurant found contamination with a viral agent causing the illnesses. Stool samples of ill individuals had positive test results for norovirus, campylobacter and salmonella. Following the installation of a multi-stage water treatment system on the well, the restaurant re-opened and no further illness has occurred. The raw water from the well continues to show evidence of human waste contamination. A dual dye trace was conducted to identify possible rapid connections between the waste water treatment system and the water supply well. Dye injected in the dosing chamber that feeds the system drain field began to appear in the water supply well after fifteen days. The appearance of this dye is a measure of the flow through time from the dosing chamber to the water supply well. A second dye injected into a toilet in one of the restaurant's restrooms began to appear in the water supply well after six days. The rapid appearance of this latter dye indicates a leak in the plumbing system before the effluent reaches the dosing chamber. Both dyes reached off site private wells about one-half mile down gradient in about three months and document a natural gradient groundwater flow velocity of about three kilometers per year. These results in a new conforming rural waste water disposal system call into question the efficacy of the current construction standards, guidelines and siting practices for large on-site waste water disposal treatment systems in karst.