Immediately call the DNR 24-hour, toll free hotline: 1-800-TIP-WDNR (1-800-943-0003) and request a conservation warden come to both document your call and sample the area suspicious for contamination - ditch, creek, wetland, etc. There are about 200 conservation and field wardens throughout the state. A good relationship with your local warden might make the difference between getting a quick response and getting his machine.
The current DNR Wastewater Specialist for our region is Eric Struck. Email him the information you left on the hotline with documented photos if you have them. Be sure to always follow up with written communication and keep that as a record of your paper trail.
Email address: Eric.Struck@wisconsin.gov Phone: 608-422-1512