Hot Enough for Ya?

If Titus Seilheimer, Wisconsin Sea Grant’s fisheries outreach specialist, had to write one of those classic what-I-did-this-summer essays, his report would be rife with tales of portable hot water heaters and boat hulls.

Working in conjunction with the Fox River Navigation System Authority (FRNSA) and Lawrence University, Seilheimer spent several months last summer testing the effectiveness of hot water to heat boat compartments, which can be used as a treatment to kill aquatic invasive species lurking in the live wells and nooks and crannies of several common types of recreational boats. It was the culmination of a project begun several years ago by Phil Moy, Wisconsin Sea Grant’s then-director of outreach, and completed with Moy’s help.

Rapid Croche, one of the locks on the Fox River, has been closed to prevent the spread of sea lamprey, spiny water fleas and quagga mussels from Green Bay into the lower river. For several years, FRNSA has been interested in creating a contained transfer station in which the live wells of recreational boats could be decontaminated, allowing boaters to begin to pass upstream and downstream at the lock location again. Area communities are also interested in seeing a resolution, as the lock closure has cost them tourist dollars.

Seilheimer was charged with testing the capacity of hot water to treat boats of several hull types, including aluminum, fiberglass and wood–and then analyzing the results.

“The concern was not specifically the hulls, but the live wells and other compartments,” explained Seilheimer. “It was really about testing this hot water treatment at the boat scale. It was a learning experience about what worked, and what different factors came into play.”

In the lab, student researchers at Lawrence University working with Dr. Bart De Stasio have proven that a temperature of 110 degrees Fahrenheit for at least five minutes can kill lurking invasive species, such as adult zebra mussels, quagga mussels, and spiny water fleas.

But the lab isn’t the real world. As Seilheimer discovered, in the field, several factors complicated the process, including the availability of a consistent water pressure to the water heater.  At several points, Seilheimer had to fashion wind blocks to keep the gas fired water heater running.

“If the fire went out, we had to start the test over again,” he said.

He discovered that the size of the boat made a much bigger difference in the effectiveness of the heating than the type of hull, as did whether the boat was in the water or up on a trailer. But in most cases, pumping hot water at the prescribed water temperature effectively heated the live wells and other compartments.

“We ended up with a lot of data,” said Seilheimer.

Moving forward, Seilheimer said the biggest need for a potential future transfer station will be validation and careful record keeping—essentially, following the steps of a system similar to hazard analysis and critical control points (HACCP).

“You need to document that the boat came in and that you measured the full five-minute treatment process above 110° F.”

The fieldwork wrapped up in September, and Moy and Seilheimer submitted the report to FRNSA and the DNR in the fall.

“They felt better about how the system would work,” said Seilheimer of the DNR and FRNSA. “They felt better that it would be effective. The money is there to fund a transfer station operation like this on the lock. The state just needed assurance that it would be effective.”