Tomorrow is the final facilitated joint session of City Council and County Commission. Last time they got into the details of the plan, and I learned something new.

Mark Donaldson described the density swap concept differently than he has before. He spoke of a density "budget" that is calculated based on the acreage in different slope categories. It's not a new concept, just a clearer way to describe it. However, he also spoke of a "clearing budget," and it turns out the clearing restrictions work the same way.

This means developers have maximum flexibility when doing site planning.

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Here's how it works:
Since this plan primarily applies to subdivisions, not single homes, I'm going to pick an example parcel big enough for a subdivision. Let's say we've got 10 acres under 15%, 4 acres of 15-25% and 1 acre over 25%.

We compute our density budget:
10 ac. X 6 units = 60
4 ac. X 2 units = 8
1 ac. X 0.5 units = 0.5

Total 68.5 units

We compute our clearing budget:
10 ac. X 100 percent cleared = 10 ac.
4 ac. X 50 percent cleared = 2 ac.
1 ac. X 15 percent cleared = 0.15 ac.

Total 12.15 acres

We can now pick the easiest 12.15 acres to clear and fit the 68.5 units on them however is best. Better still, if we leave a flat acre wooded because a creek runs through it, we can spend that acre of our clearing budget upslope. This could be especially useful for parcels steeper than in my example.

In any case, we end up able to clear 12.15 of the 15 acres and build 5.64 units/acre. Allowing for roads, that gives everyone about a fifth of an acre. It would also be possible to mix in smaller duplexes for retired couples who want less house and spread your single-family homes further apart.

In short, what the plan does is preserve most of the development capacity of a given parcel and add flexibility in how that capacity is sited on the land. For every example of a parcel that loses potential there are probably five that gain potential from the added flexibility. It's good for smart developers and not so good for those who work fast and leave mudslide hazards and runoff messes in their wake.