The perfect villain in Deschutes County may be the contamination of groundwater in south county by nitrates.

It’s there. It’s known it’s there. And not much is being done about it.

Nitrates are creeping slowly underground. More are being added with every flush of the toilet. Many people rely on private wells for their drinking water. And it goes without saying that people should not be drinking what other people flush.

The earth in the area is sandy and porous. It’s fertile ground for contamination. More and more wells in south county are likely on track to be unfit to drink at some unknown point in the future — maybe distant and maybe not. Land-use laws designed to protect the area from development make it difficult to fight the contamination with better sewer systems.

The Oregon Department of Environmental Quality and officials at Deschutes County have told county and state leaders again and again about testing data and the modeling of what is likely to come. They did it again on Monday.

There are some 10,338 lots in the area in question. A total of 6,914 have been developed and 3,424 still vacant. Of the developed lots, 5,698 rely on conventional septic systems. That is another way of saying 5,698 homes rely on septic systems that continue to do a good job of adding more nitrates and giving the villain a helpful boost.

The cost of upgrading to modern septic can run about $30,000. What are the incentives to switch over? About $3,700. For many families, that’s not much of an incentive when you think about the total cost.

County Commissioners wondered Monday where they might find more money to get people to switch their septic systems.

Meanwhile, the villain below keeps growing.