Overindulgent Sloping Dam? Outside Sculptural Design? Overcharged Secluded Descent? Well, it's a little of all 3. An On Site Detention holds the water collected during a storm and restricts the flow into stormwater drainage (preventing creeks and rivers from flooding). An O.S.D works by restricting the flow via an orifice plate in the stormwater pit and providing extra storage for the water to sit until it gradually empties.
There are 2 basic designs: below ground - super-large concrete tanks placed underground and landscaped over. Above ground - water pools onto a contained, grassy area and is fed into a smaller stormwater pit.
The idea is that the O.S.D storage capacity is determined by the collection surface. Like everything else so far, the design has been really over engineered. But now it's passed through council, it's what we must comply with. Why didn't we negotiate a smaller detention area? Fewer stormwater pits? A more modest driveway design, you ask? Let's put it down to inexperience and too much faith in an engineer who took too long - we just had to get it through council.
Anyhoo, here it is. My amazing Dad spent 2 days building it to spec. All we have to do now is get a bobcat in to shape the earth around it - creating the correct fall, and lay some turf over the top. Easy peasy. It's also made a really nice retaining wall for future gardens. Watch this space for the 'after' photos.
