Comments on: Decatur UDO Idea #2: Missing Middle District

By: Ch

Ch — Thu, 16 Jan 2014 03:10:40 +0000

By: BikeBoy

BikeBoy — Wed, 15 Jan 2014 02:31:21 +0000

They are all technically called detention since you are temporarily detaining the stormwater. All of these systems have some sort of controlled outlet that releases the water at a controlled rate. Some ponds do retain some water until it evaporates off, but most underground systems fully discharge.

By: So Many Books...So Little Time

So Many Books...So Little Time — Tue, 14 Jan 2014 15:07:43 +0000

Is there a difference between Detention and Retention? We have a space near our house that I always referred to as a Retention system. Are they the same thing?

By: BikeBoy

BikeBoy — Tue, 14 Jan 2014 02:15:35 +0000

Currently in Decatur, it’s not the case that all new single family construction requires a stormwater detention system.

The are a few rules that determine whether or not stormwater detention is required.

If you subdivide a lot into multiple lots that were not previously separate lots of record, you’re required to do detention.

If your impervious coverage exceeds 4,058 sq ft (regardless of your lot size), you are required to do detention.

If your total disturbed area during construction exceeds 10,000 sq ft (regardless of your impervious sq ft and regardless of your lot size) you are required to do detention. And as a extra little pat on the back, you’re also required to install a water quality system in your water detention system.

I completely agree with you that not considering lot size in making this determination is crazy. You used to be able to do a lot size calculation to make the max impervious calculation, but apparently too many people were using the slightly complex formula in a way that made the City Engineer not happy.

We redesigned our current build to come in under 4.058 sq ft after reading the language of the required easement that the city requires you to grant it to access your new detention system it forced you to build on your own property.

Hopefully the UDO will have a more coherent and rational detention policy.

By: BikeBoy

BikeBoy — Tue, 14 Jan 2014 01:54:02 +0000

Currently you’re required to do water detention if you subdivide a lot that has never previously been two lots of record. If the property used to be two (or multiple) lots, then combined, you can split them back to their previous lines and not have to do water detention. The detention requirement isn’t based on how many homes you’re building at one time, but seems like it since developers have frequently been buying and splitting larger lots.

Water detention doesn’t have to be, and fairly often isn’t above ground. There are plenty of new homes in Decatur that have underground detention. Above ground is cheaper, but almost always uglier because of the fencing requirements. Spec house builds rarely spend extra money in designing and implementing aesthetically pleasing detention systems.