Gravel, Stone and Soil Delivery in Seattle, WA

What lies under ZIP 98101

The USDA soil survey maps the center point of ZIP 98101 as Urban land on 5 to 20 percent slopes, and it rates 90 percent of that map unit as paved or built over. Alderwood soil fills only 5 percent of the unit, so the native profile shows up in scattered patches between foundations and pavement. When an old slab or a tired lawn comes out for a new project, the material underneath may be disturbed fill as often as true soil, and a quick test hole with a spade tells you which one you are working with before any stone arrives.^[1]

Where the Alderwood profile is intact, its top mineral layer is a gravelly sandy loam. The survey calls it moderately well drained and places it in hydrologic group A, the class where water soaks in fast and little runs off. That is friendly ground for an open stone surface, because rain falling on a gravel pad can sink through the base and into the soil instead of racing across it toward the street.^[1]

Water does meet a limit lower down. A dense, compacted layer that soil scientists call densic material sits about 35 inches below the surface at the center point, and roots and water pass through it slowly. During a long wet spell, water can collect on top of that layer, which is a good reason to lay a perforated pipe in a trench of Drain Rock along a basement wall or beside a sunken patio. Shrink-swell in the top 100 cm is low, at 0.8 percent, so the soil barely moves as it wets and dries and a well-packed base stays where you put it.^[1]

Rain, cold nights and the working calendar

Weather figures here come from the NOAA normals station at Seattle Boeing FLD, about 6 miles away, which averages 36.5 inches of precipitation a year. Much of that can come as long gray stretches of light rain, and steady rain is hard on any surface that holds water. Fines in a gravel drive stay damp, soft spots open where tires turn, and a flat mulch bed can stay soggy for weeks. In each case the cure is to give water a slope and a way out.^[2]

The Boeing Field station logs 30 days a year with a low of 32 F or colder. At that station, the median last spring freeze falls on March 13 and the median first fall freeze on November 17. Those two dates frame the easiest months for setting pavers, seeding over fresh Topsoil or laying a new bed of Brown Shredded Mulch. A gravel pad can go in during any month, though packing a base in cold, wet weather takes more passes because damp fines resist the plate.^[2]

Laying a parking pad on gravelly loam

Gravelly sandy loam drains on its own, so a pad here does not need the heavy fabric and extra-deep base that clay ground demands. Strip the sod and loose dark topsoil down to firm ground, then shape the subgrade with a slight crown or a steady fall away from the building. A light geotextile is still worth laying wherever old fill or soft pockets turn up, since it stops the base from mixing into whatever lies below.^[1]

For the base, Road Base or 1-1/2" Crushed Gravel goes down in thin lifts, each one misted with a hose and run over with a plate compactor until it stops creeping. Angular pieces lock together under the plate, while rounded stone would keep rolling. On ground mapped as mostly built over, expect buried brick, old concrete or rubble near the surface, and pull anything large out before the first lift goes in.^[1]

The top layer is where you choose a look. Driveway Gravel or 3/4" Crushed Stone gives a firm, clean surface that cars can turn on without digging ruts. #57 Crushed Stone drains even faster but shifts more under a tire. Where a site tilts, steel or stone edging keeps the surface from creeping downhill a little more with each storm.^[1]

Courtyards, planters and shared yards

Fast-draining soil and a damp climate pull a garden bed in two directions. Rain keeps the bed moist through much of the year, yet a gravelly loam lets nutrients wash downward quickly. Mixing Compost into the top layer, or filling a raised bed with Garden Soil, gives roots something that holds water and food between storms. A cover of Black Shredded Mulch or Wood Chips softens the drip of rain onto bare soil and keeps weeds down in shaded corners where moss would otherwise take over.^[1],[2]

Plenty of projects in a dense neighborhood start with no native soil at all: a planter box on a deck, a strip beside a walkway, a tree pit cut into paving. For those, bring in Topsoil or Garden Soil rather than digging up what sits under the pavement, which is often compacted fill. A layer of #57 Crushed Stone at the bottom of a deep planter lets water leave the box after a long rainy week.^[1]

For a footpath between beds, Walkway Gravel or 3/8" Crushed Stone packs into a smooth tread that stays firm when wet. Pea Gravel feels softer underfoot and suits a sitting nook, though it rolls on a slope and rides out on shoe soles. River Rock under a downspout gives roof water a place to land without carving a hole in the bed.^[1]

Holding a sloped yard in place

The map unit at the center point covers slopes from 5 to 20 percent. On a yard that tilts like that, every hard rain tries to carry loose material downhill, and bare soil goes first. A low wall of stacked stone or timber, backfilled with #57 Crushed Stone so water seeps through instead of pressing on the wall, turns one steep bank into two gentler terraces that are easier to plant and mow.^[1]

Riprap pieces set into the face of a steep bank break up running water and keep gullies from starting. Between them, Wood Chips or Brown Shredded Mulch shield planted soil while new roots take hold. Skip Pea Gravel on any real slope, since the round stones roll and gather at the bottom after the first big storm.^[2]

Homes in ZIP 98101

The Census counts 13,585 housing units inside ZIP 98101, and only 2 percent of them are detached single-family houses. Seattle as a whole has 393,918 housing units. Detached houses make up 37 percent of that citywide total.^[3]

Housing in ZIP 98101 is young by local standards, with a median build year of 2000. The median for Seattle is 1976. Owners occupy 14 percent of the lived-in homes in the ZIP, so many orders here may come from building managers and landlords as well as residents.^[3]

For reference, the Washington State Department of Transportation names its standard stone layer under pavements Crushed Surfacing Base Course, listed under Section 9-03.9(3) of its Standard Specifications for Road, Bridge, and Municipal Construction M 41-10 (2027).^[4]