Onsite detention system

Anyone have an idea of how much for a onsite detention system? and where i can get some prices? tx

 

Many variable to consider to determine price. Maybe @Leo2413 has an idea having recently built one.

 

Nauru is worth a call

 

I have allowed for up to 50k for mine.

 

Where is the project?
Any designs done?

 

Zak, how did you go with you looking for prices for OSD ?

i think i will need it too for my build.

Iam also curious how much?

Like tiles and bricks they charge per m2.

So for a OSD how much do they normally charge per m2?

Who do i talk to find out prices??!?!?

 

We have always done ours very simply and cheaply. You merely use your rainwater tank as part storage and part detention. Say you need 3000l for BASIX then you may need a 5000l tank so you have 2000l for detention. A smaller size overflow is drilled at the 3000l height which restricts the overflow rate in heavy rain. Only an extra few hundred dollars for the larger tank + some extra plumbing work.

 

That's what I was thinking when I saw the title.
Mediocre minds Bob...

 

are we just talking soak Wells here? you sydneyssiders use some weird terms, between this and that squares nonsense instead of square metres

 

Buckets with holes don't cut it over east OSD'S store the water then pumps release it to the storm water network (pipes running to creeks waterways etc) slowly after the storm event.

For the easty's. WA use soak wells, an osd tank with holes in it basically. They store the water the it dissipates into the sandy soil. No storm water pipes to be seen. It just goes back down to the water table, instead of flowing to creeks rivers etc

That's my rough understanding

 

The higher pipe is the standard 100mm overflow. The lower pipe has a much smaller hole (usually 30 - 60mm depending on the maths) so the water can be released at a slower rate. Our engineer designs this type of detention system for us as common practice. This has always been acceptable to council standards. (Byron Shire)
I has to be gravity feed to the street.

 

From reading the council stormwater management manual it says something the lines of...

There are above and below ground on site detention.

Above ground are usually water tanks as shown by rockstar above

Below ground can be a basin or adsorption trench or a concrete swimming pool like structure with holes as Bob pointed out. This tends to be more expensive.

However, council requires capturing of water not only to roof areas but to all hard surface areas such as driveway, pavement, etc.... so therefore the above ground will not work for surface water on ground and needs to be lower than the hard surfaces and below ground OSD.

This is how i see it...

Above ground OSD "Tank" = roof

Below ground OSD "like swimming pool with holes" = ground surface areas


The hydraulic engineer will work the area of the roof, ground hard surfaces and determine what size and type will be required.

Rockstar how much did it cost you to put that water tank in?

Any one know much for the below ground OSD?

 

@Rockstar is there a pump to? Can you use the water?

@TML below ground can vary significantly depending on the design of the pits, size depth, ground conditions. Plus pumps and electrical work involved.
Above ground would be fairly "fixed" as it's just plumbing it up varying sized tanks. The outlet is just an orifice plate (a specific sized butt hole ) that is sized to control the release rate of water

 

Yes and Yes. The water below the smaller diameter overflow (3000l) is used for household purposes like toilet, washing machine (cold) and any outdoor taps. The pump is necessary to pressurise this rain water to these outlets as is the case with most domestic rainwater systems. The tank overflows go to the street kerb via gravity.
Our engineer tries to put as much detention as possible into the tanks (ie: all of the roofwater) so we minimise pits for the concrete driveways. To date I haven't been required to use anything larger than standard 600 x 600 lidded pits (gal lids/plastic pit) that driveway channel drains feed into to provide some detention prior to draining to the street kerb. I have seen one duplex done with a dished capture area in the concrete driveway with a drainage pit at the lowest point so in a heavy downpour the driveway dished area would back up (fill up) and discharge at a slower rate.

 

@Rockstar much cheaper option going the larger tank over the underground pits plus the future maintenance, provided you have the room for a big tank of course.

I'm not so sure about the dish capture idea, mould, mozzies breeding, drowning. Ok in a public area like Park detention basins but on private property I'd be considering other options

 

The tanks are just standard plastic. It's probably no more than 30 min extra work for the plumber. PVC pipe is cheap as chips. We actually connect both outlets to one overflow pipe these days rather than 2 separate overflows and put a Fernco coupling on each outlet to prevent cracking of the pvc due to any ground movement.

 

It probably only filled up to around 200mm at the deepest point in the centre before overflowing into the garden and it all drains quite fast once the heavy rain passes. So no worries about mozzies or mould since the water doesn't sit there for long. From memory it was an area of around 100sqm or so.
Having said that I would avoid this method unless absolutely necessary.

 

Yeah, we've never had to go more than a 5,600l duraplas. Mainly we do it in 5000l. I think you can get slimline tanks up to 5000l if space is an issue for a 2m diameter tank.

 

Thanks Rockstar. So how much did your rain water tank costs?

 

I bought my last 5000l round squat Clarke tank through Bunnings for about $820 delivered. (with my power pass discount)