What D-1 actually is
D-1 is a crushed aggregate base course graded to the Alaska DOT&PF specification: a controlled mix of crushed rock from about one inch down to fines, with enough fines to lock together under a roller and enough rock to carry a load. It is what the state and the Municipality put under asphalt. The gradation is public: Table 703-2 of the state's standard specifications puts D-1 at 100 percent passing the 1-inch screen down to no more than 6 percent passing the No. 200, which is the fines window that lets it lock up. Around Anchorage it is sold by the ton, about 2,800 pounds to a loose yard, call it 1.4 tons, and our load calculator turns depth into yards and tons if you want to check our numbers.
What makes it different from a bag of "crushed gravel" is the gradation. Pea gravel and washed rock have no fines and never lock up; pit run has the fines but the rock is random. D-1 is engineered to compact. That is also why it costs more per yard than anything else on the pit price list, $22 to $30 depending on the pit.
Where D-1 belongs
- Driveway top course, four inches minimum, six on a slope or a truck driveway.
- Shop and garage pads before the slab, where it also gives the concrete crew a surface they can set forms on.
- Parking areas for equipment, where pit run alone turns to soup at breakup.
- Under pavers and patios, compacted, with a screed of sand on top.
- Trail and path surfaces where you want a hard, walkable finish that sheds water.
How much to order
Measure the length and width in feet, multiply, multiply by the depth in feet (four inches is 0.33), and divide by 27 for cubic yards. Add ten percent for compaction, because D-1 compacts more than it looks like it will. A 60 by 12 foot driveway at four inches is about 9.8 loose yards, close to 14 tons: one full 12-ton load and a small second one. Our load calculator does this for you and rounds to trucks.
| Depth | Coverage | Typical job |
|---|---|---|
| 3 inches | about 830 square feet | Walkway base, small patio |
| 4 inches | about 625 square feet | A 50 by 12 driveway |
| 6 inches | about 420 square feet | Truck driveway, shop apron |
| 8 inches | about 310 square feet | Equipment pad on soft ground |
Putting it down right
D-1 wants to be placed damp and compacted in lifts no thicker than four inches. Dry D-1 will not lock; soaked D-1 pumps. If it arrives dry, wet it with a hose before you roll it. A plate compactor is enough for a walkway; a driveway wants a vibratory roller, which the equipment yards in Anchorage rent by the day. Crown the driveway an inch or two so water leaves it, and do not seal the edges with a berm that traps water against the base.
The base under it matters as much as the D-1. Anchorage frost reaches well below three feet, deep enough that the Municipality requires footings at 42 inches, so a driveway over wet silt will heave no matter what you put on top. Strip the organics, put pit run or 3-inch minus down to get above the wet, then D-1. If you are not sure what is under your driveway, dig a test hole two feet down and look.
Delivery notes for D-1
- It is heavy. Our trucks carry 12 tons, about 8.5 yards of D-1, so a D-1 order runs out of weight before it runs out of bed. In spring weight-restriction season a load can be lighter still on restricted roads; see the breakup page.
- It does not pile well for storage; order what you will place within a few days, before it dries out.
- For the Mat-Su we load Palmer-side material, which is a different pit and a slightly different rock than Anchorage D-1. Both meet the spec.
Questions we get about this
Is D-1 the same as 3/4 minus?
Close but not the same. Both are crushed with fines; D-1 is graded to a state spec with a tighter, more consistent mix, and it compacts harder. For a driveway either works; for anything you will pave or pour over, use D-1.
Can I put D-1 straight on dirt?
You can, and on a well-drained gravelly lot it will hold. On silt, clay or anything wet in spring it will disappear into the ground in a year. Put a coarser base under it first.
How thick should a driveway be?
Four inches of D-1 on top of at least six inches of pit run or 3-inch minus, more where the ground is soft. That is a real driveway. Two inches of anything is a dust cap.
Do you sell by the ton or the yard?
The pit sells D-1 by the ton. We quote it by the ton and tell you the yards so you can compare with a supplier quoting the other way.