Anti-channel drain baffle

Does anyone know what this additional fitting is used for in a tank?

It is mentioned as an option when specifying an API 12F tank.

Sounds like a 'box' on the end of the low point drain* inside the tank.

Is it about sediment or keeping oil out of this drain. Oil that is floating on top of the water. Thus only letting the last bit of water out of the tank.

/ DLK

You are on target* it keeps some sediment back as well as oil and allows water through due to the 1" minimum gap at the bottom. It is a minimum 64" periphery * (16" x 16" box)
I acts a little like an anti-vortex device.