When Republican Larry Hogan beat Democrat Anthony Brown for the Maryland governorship last year, many pointed to outgoing governor Martin O’Malley’s “rain tax” as a big reason why. As one might expect, voters don’t like paying for rain, and they held Brown and other state Democrats responsible for charging them for something they can’t control, since it literally falls from the sky.

Maryland’s legislature is now in the process of rolling back the measure, which would make sense if the law actually does what Republicans warned voters it does. Of course, it doesn’t. The tax in question is a storm water remediation fee that primarily affects businesses in order to reduce the amount of pollution that makes it into state waterways — waterways that empty into the Chesapeake Bay. Maryland’s fee was passed as a way for the state to comply with EPA regulations established under the Clean Water Act, requiring states with waterways that fed into the Chesapeake to reduce its levels of nitrogen, phosphorous and sediment. Even if Maryland gets rid of its fee, it will still be required to take steps to reduce the level of chemicals and sediment in its waterways.

Taxing storm water runoff in order to pay for chemical reduction efforts is one of the best ways to do this. The Chesapeake Bay Foundation identifies storm water runoff as one of the Bay’s primary causes of pollution, and the only source of pollution that’s increasing year over year. The bulk of storm water runoff pollution comes from large parking lots in front of shopping malls or big-box stores and, to a lesser extent, suburban neighborhoods. When it rains, the water that lands on asphalt doesn’t soak into the ground, and instead picks up fertilizer, pesticides, pet waste, motor oil and sediment on its way to the drain, which empties into nearby waterways. As the CBF notes:

Up until about the 1980s, builders didn’t know much about the problems associated with polluted runoff. They just designed developments to flush the water off the property quickly. Now we realize runoff should be slowed down and soaked up to prevent pollution from running off developed areas and into our local rivers and streams. In fact, in the Chesapeake Bay region, this sort of pollution is the only major pollution sector still on the rise.

As Maryland has one of the country’s highest concentrations of “impervious surfaces,” like asphalt, where storm water can’t seep into the ground and instead has to be drained, pollution from storm water runoff is a bigger issue there than it is in, say, Pennsylvania, where a lower percentage of storm water is drained.

Rather than charging citizens for the rain coming out of the sky, storm water remediation fees simply treat the water running off from impervious surfaces as a utility, charging users for it as they would electricity or regular water. When you use more electricity, you pay a higher electric bill; when you account for more storm water pollution, you should shoulder more of the cost for cleaning it up. And while one big box store has a large swath of impervious surface, an individual homeowner has practically none — just their driveway and the stretch of road in front of their house, if that. So fees based on the amount of water draining off of each impervious surface — tied to whomever is responsible for that surface — barely touch individual homeowners.

Without directly taxing storm water pollution, citizens are going to have to shoulder the cleanup costs via other means, either through unrelated tax increases or cuts to unrelated programs. In short, if the storm water remediation fee dies, businesses will be shifting the cost of reducing storm water pollution away from them and toward the rest of the public.

The story here is familiar: Monied Republican interests did to the storm water remediation fee what they did to estate taxes, reframing them to make it seem like a tax that would almost entirely affect the wealthy would in fact put a financial squeeze on everyone else.

All so Wal-Mart doesn’t have to help keep motor oil out of the largest bay in the United States.