Gravel, Stone and Soil for Multnomah County, OR
Oregon Rock Supply sells gravel, stone and aggregate delivery in Multnomah County, OR by the ton or by the yard. Across the Willamette Valley and Portland Basin, the ground is deep slackwater silt the ice-age Missoula floods left behind, and it stays soft through the wet months.
That ground is why 3/4 minus, the local name for 3/4-0 crushed rock, is the starting point for most base work here. It is crushed rock graded 3/4 inch down to fines, so it compacts and locks up instead of shifting under a load.
Ground Conditions Across Multnomah County
Across the Willamette Valley and Portland Basin, winter brings 35 to 45 inches of rain, almost all of it between November and March. That water lands on tight silt and clay that sheds it slowly.
A base that was not built for that slow drainage will pump and rut by February. The base course has to carry the load, and the water has to have somewhere to go.
Erosion follows the same pattern across the region. Winter rain runs off bare silt, scours banks on the Willamette and its tributaries, and moves soil on steep foothill slopes.
Timing matters too. Portland treats October 1 to April 30 as the wet weather season and requires bare ground stabilized within two days.
From May 1 to September 30 the window is seven days, so base and paving work concentrates in the dry season.
Frost heave is a minor concern here next to winter saturation and soft subgrade. Short freezes do little damage compared with a subgrade that never dries out.
Materials Delivered in Multnomah County
Base work starts with a minus rock that keeps its fines and compacts. Drainage work starts with a clean, open stone that has had those fines screened out.
3/4 minus is the standard Oregon base under driveways, parking pads, shop floors and shed bases.
Oregon specifies base material by top size with a minus notation. The Oregon Standard Specifications for Construction place dense-graded base aggregate in Section 02630.10 at sizes from 2 1/2 inch - 0 down to 3/4 inch - 0, and Section 00641.10 states that base aggregate is dense-graded unless otherwise specified.
Choosing the Right Material
Washington County sits on the same ground as Multnomah County: slackwater silt on the valley floor, Jory series clay and silty clay loam in the foothills, river gravel along the Willamette and its tributaries. The same minus base and the same drainage layer apply, and there is no difference in the material choice.
Clackamas County spans more than one ground region, covering both the Willamette Valley and Portland Basin and the Cascade Range and Hood River Valley. Where its ground turns to the higher, stonier side, base and drainage choices shift with it.
Hood River County is different ground entirely. It sits in the Columbia River Gorge on young volcanic ground: andesite and basalt with pumice, cinders and ash over it, orchard soils on volcanic ash in the Hood River Valley, and thin stony soil at elevation.
That volcanic ground drains and compacts differently from the deep silt here, so a base that works on ash or cinders is not the same answer as a base on valley silt. Match the material to the ground under it.
Delivery Across Multnomah County
You order online, choose a quantity by the ton or by the yard, size the load with the calculator on the product page, and pick a delivery date at checkout. A dump truck then tips the load on site in one pile.
Bulk delivery covers Portland, Gresham, Troutdale, Fairview and Corbett. The truck tips the material where it lands, so think about where the pile should sit before the delivery date.
Order 3/4 Minus and More for Multnomah County
3/4 minus is the base most ground in Multnomah County is built on, and Oregon Rock Supply delivers it along with drain rock, 1/4 minus, Natural Pea Gravel, river rock, riprap, sand, topsoil and bark dust. Order online by the ton or by the yard and a truck will tip the load on site.