# Forum Home Renovation Paving  Hydrapave

## sundancewfs

Anyone used Boral's Hydrapave pavers?
Easy to prep and lay? http://www.boral.com.au/BS/hydrapave...bility&site=CI

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## Planned LScape

I havent used those products but I have used a similar one by C & M. It was shaped like a dog biscuit and had little gaps on the joins that were filled with fine sand and quarter minus screenings to allow water to penetrate into the water table and limit runoff into drains. They were easy to lay (same as any other pavers) but we were wondering why such a paver was used on a frequently used driveway into a set of units. It was all done to plan- stabilised crushed rock used underneath 150mm thick and compacted, but for a thoroughfare into a set of units I would of thought concrete would be longer lasting that didnt allow water into the base layer. 
For patio areas would be fine, only thing is fine dirt will over time find it's way into the gaps and weeds and mould will grow through.

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## sundancewfs

Hmm interesting thoughts, I was looking for something for our driveway. We don't have a "Legal Point of Discharge" so we have to contain our stormwater on our block (as much as is reasonable) One plan is to build a 20m3 rockery/dry creekbed with crushed building rubble in the bottom and feature rocks covering it. As we have young children I don't want anything that can have standing water. The Hydrapave looked like a good idea to minimise the amount of runoff of the 300m2 or so, of paving and driveways. The roof run off will be controlled by a 30,000 litre tank plumbed into everything but the kitchen sink. Any thoughts on stormwater control? Any sites that would give the hydraulics of dry creek beds?

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## Planned LScape

Do you ever have dramas with flooding with no stormwater outlet, or is it a steep block? 
A dry creek bed could be ideal, falling the yard to it with subtle swales with plantings etc along it. Becomes both a feature and aids drainage too. Just make sure the end of it is directed somewhere where it wont cause damage or issues with neighbours

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## sundancewfs

Not too steep a block, the front has a 10deg slope for about 20m and then the back 70m has about a 1m fall over the 70m. The driveway is going to be on about 1/2 and 1/2 
I was wondering if there is some sort of resouce for working out the size of retention required for a given amount of paved area. The way I see it the variables would be the amount of rain per hour and how much water the surrounding soil can disperse for a given moisture level. The constants I can see would be the size in cubic metres/litres of the retention device, the size of fill used in the retention (displacement of water compared to the overall size of retention) I would like to build something "big enough' but not do unnessecary work by making it too big.

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## Dan574

on my last house I had to do the same thing, we were told we had to have 2 rubble pits 1m3 in size, I had 1 either side of the house, the downpipes where they went into the ground were then connected to slotted pvc to form an ag drain before any over flow went into the rubble pit, there is a formula to work out how much drainage is needed. 
From memory they worked out how long my ag drains need to be versus the roof area.

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## sundancewfs

Ok Dan574
Thanks for that. I'm on 1/2 an acre so I have a fair bit of room to play with. I'm thinking to make it as "natural" looking as possible and can afford to dig up 3x4metres or so.

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## sundancewfs

Well after a bit of digging around online I came up with this....    

> Underground systems must be 2.5 times greater than the desired water volume to account for an
> approximate 60% loss of void space by rock fill. Infiltration is a method to completely retain a desired
> volume of stormwater onsite by allowing it to percolate into the substrate.

   

> The bottom of
> infiltration trenches are assumed to clog quickly and therefore considered impervious; design plans for
> infiltration trenches should take into consideration that only the sides will allow percolation of
> stormwater. Long deep trenches provide the most efficient percolation because of the high surface area
> on side walls.

  From the following article....  http://www.usc.edu/org/seagrant/Publ...rmWaterRpt.pdf

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## Planned LScape

True, when you get a machine to dig into clay soil the bucket virtually polishes the dirt (especially clay) and it holds a heap of water

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