There are bad zoning cases, and then there are bad zoning cases like the one involving Falls Lake that was approved Monday by the Wake County Board of Commissioners. Yes, approved by a 6-1 vote, with all four Democrats and two of the three Republicans in the majority. It was bad enough to prompt a David Letterman-like list of the top 10 ways you know you have a very bad zoning case:

10. Commissioner Tony Gurley, the Republican who stole the chairman’s seat when Democrat Betty Lou Ward went to the bathroom, casts a heroic dissenting vote.

9. Ward, who chairs the commissioners’ land-use committee, says the case is nine months old, and it’s unfortunate that nearby residents, who have shown up to object, didn’t hear about it until a couple of weeks ago.

8. Ward is the nearby residents’ representative on the commissioners’ boardand their neighbor in the Falls Lake watershed.

7. The case isn’t even a rezoning. It’s an amendment (“text change”) to the county’s zoning ordinance designed to grease the way for a specific property owner’s redevelopment plans; the amendment was written not by the planning staff but by a private attorney representing a client.

6. One reason the planning staff couldn’t have written it: The commissioners recently abolished the position of county planning director.

5. The Upper Neuse Riverkeeper wants the amendment rejected.

4. Leaders of the Watershed Protection Council want the amendment rejected.

3. The mayor of Raleigh, the Raleigh City Council and the Raleigh planning director want the amendment rejected, saying it will undermine regional efforts to protect the Falls Lake water supply.

2. Before voting to approve the amendment, Democratic Commissioner Stan Norwalk calls on what’s left of the planning staff to figure out how the county can better protect the Falls Lake water supply.

1. What part of “shopping centers don’t belong in the Falls Lake watershed” don’t you understand?

Falls Lake, located in the Neuse River basin, supplies the drinking water for Raleigh and six eastern Wake municipalities. But it’s polluted”impaired,” the state saysfrom the development all around it, especially upstream in Durham County.

The pollution comes in with the stormwater (oils from the pavement, fertilizers from the lawns) and the wastewater (the sewerage is treated but not pure). The worse the pollution gets, the more it will cost to keep using the lake as a drinking-water source.

Thus, Raleigh and Durham are wrangling, with their respective legislators and state regulators in the middle, over how to clean the lake and prevent future degradation. Last year they came together to pass a law, titled “An Act to Protect and Restore Water Quality and Quantity in the Upper Neuse River Basin, Falls Lake and Other Drinking Water Supply Reservoirs,” under which the state is supposed to issue new Falls Lake rules in 2011.

Naturally, Raleigh wants the new rules to be tough on developers, especially in Durham. Durham wants the new rules to be tough, too, as long as they don’t get in Durham’s way.

So imagine Raleigh’s horror in the midst of trying to pressure Durham when it discovers that the Wake County commissioners are about to approve a scheme to build a shopping center in the watershedwith all the attendant cars and pollution.

That’s what this bad zoning case was about. There’s an 82-year-old lumberyard off N.C. Highway 98 that’s barely in business, and the property owner would like to sell it for development. But the watershed zoning is very restrictive, calling for one house per acre or a small (15,000 square feet, tops) commercial building.

Enter Lacy Reaves, a developers’ lawyer from Raleigh, who quietly approached county officials nine months ago. Let’s amend the zoning code, Reaves proposed, to create a special exception for any “nonconforming uses” in an R-40W zone. (The “W” is for watershed.)

Under the Reaves Amendment, if it’s a nonconforming usesay, a lumberyard that existed before the county had any zoningyou could replace it with something almost as big, like a shopping center, as long as the resulting pollution is substantially less than it was with the lumberyard.

In other words, the more pollution you used to produce, the more you can produce now.

Neighbors calculate that the amendment, which is complicated, may lead to a 160,000- to 170,000-square-foot shopping center. Reaves says it’ll be 120,000 square feet, max. There is, of course, no site plan.

“It’s a cleanup measure,” the artful Reaves told the commissioners Monday.

“It’s very good lawyer work,” Chairman Gurley responded.

But just because the lumberyardand an old cement plant is there, toowas a big polluter in its day, Gurley said, is no reason to permit another big polluter there now.

The property can be redeveloped under the existing zoning, he added, “just not as profitably.” There’s always a trade-off when there’s an old, undesirable use, but the owner doesn’t like what the zoning allows. “I’m just not willing to accept that the trade-off needs to be this large.”

That put Gurley on the same side as Raleigh Mayor Charles Meeker, Raleigh City Council and City Planning Director Mitch Silver, who all came out against the amendment when they got wind of it last month.

So did Lake Falls subdivision residents, who didn’t know the amendment was on tap (since it wasn’t a rezoning case, there was no notification to neighbors) until after a March 1 public hearing. “From my perspective,” said resident Rob Posgai, “the public has been left strategically out of this process.”

Even John Grace, longtime leader of the Watershed Protection Council, said he learned about the measure only when a county staffer mentioned it at an unrelated meeting in February.

Grace and other protection council leaders agree that something new on the lumberyard tract would be nice, but it shouldn’t produce more pollution than what the existing zoning would allow. “The lake shouldn’t know what’s there,” is the way Grace put it.

“What we’re doing is issuing a new set of rights to the property owner that no one else in the watershed has,” he said. “It won’t be long before other property owners want them, too.”