BALTIMORE (WJZ) — Rain on the roof. That’s often a comforting sound.

But Alex DeMetrick reports, soon it’s going to mean money out of your pocket.

The nickname is rain tax, and the more hard surfaces you have–like a parking lot–the harder it’s going to bite.

When rain falls on rooftops or other hard structures like driveways and parking lots, it scours away chemicals from air pollution, eventually running off into the Chesapeake Bay.

It’s a big source of those poor grades given to the bay’s health in annual report cards.

“The Chesapeake Bay and its rivers and streams are overloaded with too much nitrogen, phosphorous and sediment,” said Will Baker, Chesapeake Bay Foundation.

That destroys water quality and feeds algae blooms that create dead zones. So Maryland’s legislature has created the impervious surface tax.

“The impervious surface tax would have an enormous impact. We have 200 sites throughout the state of Maryland. If you look at Our Daily Bread for example, the proposed fee would be $5,000,” said Bill McCarthy, Director of Catholic Charities.

And that’s for just this one property of Catholic Charities.

The tax would also hit every church and nonprofit roof and parking lot in 10 surrounding counties.

Fees would also be imposed on individual homes and driveways–with the highest in Baltimore City–$48 to $144 a year depending on the home’s and driveway’s size–and $72 per every 1,050 square feet of hard surface on businesses, private schools and nonprofits.

For those 200 Catholic Charities properties:

“I would hate to say it’s hundreds of thousands of dollars a year,” said McCarthy.

Money raised from the tax would be spent on improving stormwater runoff systems–a fix that will cost billions.

Maryland has set a deadline of July 1 for 10 counties and Baltimore City to formally establish rain tax rates.