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Permeable paving will handle the amout of runoff you design for it. Just as all of us in the hardscaping industry, we always tell our customers that each job is different and special considerations need to be taken, so it isn't as easy and handing over some specs and calling it good. One thing for permeable paving that is a constant is the fact that you will be using 2 or more sizes of aggregate for the system. The bedding layer is usually 3/8 to 1/4". This isn't that hard to set pavers on, so your concern with with getting pavers level on large aggregate isn't as tough as you think.
Compaction is key with permeable pavers, just as it is with normal pavers. Just because that you don't have fines included into the base doesn't mean you don't obtain 95% proctor, you absoulutly do. Most systems will have 3 different sizes of aggregate, and the main purpose of this is to create a choking layer so that smaller aggregates in the bedding layer don't migrate down into the sub-base (which usually is 2 to 3" sized aggregate). This subbase when fully compacted will typically have 40% void space for storage of stormwater. Each permeable paver will have an infiltration rate for their system, so when you are looking for that info, just look to the manufacter.
Installation of permeable pavers realitivly the same as any other paver application, it comes down to a thicker base installation. There is a little more care taken in making sure you don't let fines into the system and not compacting the soil base, but nothing that can't be taken care of.
Paul, your question on slope is easy, it is designed to be on a slope. I'm working with a driveway currently that has a 5% slope and we will be using permeable pavers. Special considerations need to be taken so that when the water hits the bottom of the slope the excess water has an exit, which in this case we are using corrogated pipe to discharge the water out towards a rain garden. It would be nice if we could have simple solutions to everything, but we can't. Just takes a little more thought and considerations to make special circumstances work.
Andy
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