The documents said there were two valves in the middle of the front yard -- one for zone 10, and the other for zone 11 (the section between the driveway and the sidewalk). So we continued to dig from the known valve (zone 10) until we found the valve for zone 11. From the stone retaining wall, we knew where the irrigation line went under the sidewalk, so we assumed it was a pipe from the valve to the sidewalk.
In fact there were two pipes -- one main supply line for Zone 11, and a feeder line for zone 10. We removed them both.
Then we kept digging until we hit rock.
And from there we expanded the width of the trench towards the street.
Scrape the dirt off, and cart it off to the back part of the yard, to expose even more rock.
Break that rock up into manageable pieces and move it out to enlarge and deepen the trench.
Repeat this process -- scrape off the dirt, haul it to the back part of the yard, to expose more rock.
Break that rock up.
Lift the rocks up out, and move the dirt out, and we have a trench of maybe 8 or 9 feet in width. We have about 7 feet to go to the curb.
Part of the process is lifting out the large rocks and putting them by the curb. These can be used as "landscape" rocks; people will come and get them for retaining walls or just for decoration.
For the lesser rocks, they are sorted out of the dirt, down to about the size of a walnut, and moved to the driveway, and I try to get people to come take them away as "fill".
The dirt that remains is mixed with grass and leaves, to increase its organic material, and try to make it better dirt. Then it is moved to the side until I can bring it back after all the excavation is down. We have been using bags and bags of leaves.
The remaining soil to dig up no longer has any large solid rocks -- I believe this ground was all dug up for the construction of the road some 35 years ago.
What we have is a top layer of dirt -- relatively good dirt, although it can use more organic material (so we will mix it with leaves). This top layer is about 12 to 14 inches deep. Under it is a layer of a mix of limestone dust and rock, the buried by-product of creating the street, curb and such. This is very very poor "soil", but if we mix it with leaves and then mix that with the comparatively better soil that was on top of it, it should be passable. Sorting out the rocks and any other construction debris, of course. We have found a lot of broken up pieces of asphalt.
This excavation has taken about 2 months, from early October to late November. We hope to finish it off within another month, if the weather holds.