Not familiar with your area, but how does DG get to be the soil? Is it installed, or is this some natural phenomenon? If compressed DG is literally the soil, it seems like it could be the base and you only needs a proper setting bed. What's up with this Californians?

In that form, does it make a stable base?

Depends on the area, many areas require permits, the permits are concerned with permeable vs imperable and run off mitigation. Usual construction includes terracing.

Thanks for the replies. Yep, around here what ain't DG is boulders lying about on the ground. (Aside from these mystery chunks of clay I find - perhaps fill from the developer 30 yrs ago). Some of the hills look like a giant was piling up car sized pebbles.

On an earlier 50 ft temporary pathway I just scraped away 2 inches of dirt to make way for the pavers, ran a compactor over the dirt and set the pavers. After five years this "temporary" pathway shows only slight settling (but it does show settling which would be unacceptable in a permanent installation).

For this permanent install I wanted to do it by the book. I am pretty confident this existing compressed DG won't move, but I am worried that the compacted aggregate being 4" deep in some spots and only 2" deep in others would give me trouble in the long run.

Your answer about the "temporary walk" seems to indicate that you will have the possibility of settling over time. I'm not familiar with your conditions so can't say (and I didn't understand what Jim Mat meant about "it depends ...") If a jackhammer would work on the base material, why not rent one? (We know nothing about the details of your project.)

Ask the yard where you're buying the pavers for the contact number for their area rep. I have (not very) fond memories of using a jackhammer with a spade bit to dig irrigation trenches and plant trees when I lived in SD. I know that in areas of the country where there's shallow rock ledge you can treat that as your base, but I don't know if your hardpan behaves like rock, or if it moves (expansion, etc) with rain. Your paver area rep will have a much better sense of what the people installing thousands of sq ft of pavers per year are doing in your area.

Our standard is that unless dynamite is required to get the full depth of base called for in ICPI specs, we suck it up and chip our way down.

I have never heard of DG as a natural occuring material so I have no idea. I actually prefer decking to paver patios.

I wouldn't take the slight settling on my quickie pathway job as a condemnation of DG (nor an endorsement - I am not an expert on DG as a base). The area for that path was a former lawn, and my only prep was to scrape off the top couple inches, sprinkle some loose DG over the surface in place of sand, put the pavers on it and compact. That there was only minor settling of the pavers with such an ugly prep job I thought was pretty good.

As for renting a jackhammer - no need. After watching pros get a lot of mileage out of their jackhammer in my front yard (irrigation ditches and tree planting, as Revolutionary Gardens mentions) I went out and bought one. With 1/2 acre of backyard for my DIY projects, I've gotten pretty good mileage out of mine too, but also not fond memories.

Thanks for the info!

It makes sense that if the existing material is hard and compacted already, that you need to make sure that whatever fill you put back in is as compacted as possible so as to eliminate or minimize potential settling. Since DIY, it may be a case of paying your money and taking your chances. At the worst case scenario, if awkward settling occurred down the road, at least it could be fixed by adding material & recompacting, which is not as bad as having no way out at all.

To your point, I've been thinking about it from a risk/benefit perspective - how confident am I that I won't have to pull up pavers to fix this later? If the hard layer were nice and smooth I might go for a thinner aggregate layer, but I don't feel good about having the aggregate vary from 4" to 2", so I'm gonna invest the time now to chip away at those high spots and bring it all to 4" depth.

I'm glad I found this thread, because I have a similar problem where I live on the east coast of Queensland Australia. Based on what I've read, I think I'm going to dig down to where there are patches of sandstone, fill any gaps with road-base, then compact it all down so the area looks level. Then I'll add paver sand for final levels. Would appreciate any added advice though...