Gravel, Stone and Soil Delivery in Federal Way, WA

Alderwood gravelly sandy loam over dense till

The USDA soil survey maps Alderwood gravelly sandy loam, 0 to 8 percent slopes, at the ZIP's center point. The Alderwood series fills 85 percent of the map unit. The top layer is gravelly sandy loam, a sandy soil with small stones mixed through it, which packs well and drains at a fair rate.^[1]

At about 35 inches down, the survey marks densic material, a layer so tightly packed that roots and water struggle to get through. Material like this is often called hardpan. Rain soaks into the loose upper soil, then stops at the dense layer and spreads sideways, which is why low spots can stay wet through a rainy season.^[1]

The survey rates the soil moderately well drained and puts it in hydrologic group B, moderate infiltration. Shrink-swell in the top 100 cm is low, at 0.7 percent. The soil barely moves with moisture, so the thing to manage is water sitting on the dense layer.^[1]

Long wet seasons at Tacoma #1

Weather normals come from the NOAA station at Tacoma #1, WA, about 6 miles away. It averages 40.8 inches of precipitation a year. Much of that falls as steady rain over many weeks, which keeps the soil above the dense layer damp for long stretches.^[2]

Tacoma #1 logs 27 days a year with a low of 32 F or colder. Freezes are fewer than in colder places, but water held in a base can still lift loose stone on a cold night.^[2]

The median last spring freeze at the station falls on March 8. The median first fall freeze arrives on November 14. Plant tender beds after the March date, and mulch beds before the November one.^[2]

The ground at the center point stands 410 feet above sea level, with slopes of 0 to 8 percent across the map unit. On a lot that tilts, water moving along the dense layer seeps out at the low side, so look for wet patches at the foot of a slope after rain.^[1],[3]

Work timing matters with this much rain. Gravelly sandy loam drains well in its upper layer, but after weeks of rain it can be soft enough to rut under a wheelbarrow. Plan base work for a dry spell in late spring or summer, and keep a tarp over a delivered pile of Road Base so it does not soak up water before it is spread.^[1],[2]

Drainage first, then the drive

On Alderwood soil, a drive is only as good as the drainage beside it. Strip the sod and topsoil, shape a crown, and compact the gravelly sandy loam. Lay a woven geotextile so the fines stay out of the stone during long wet spells.^[1],[2]

Spread Road Base or Crushed Concrete in compacted lifts. Top the drive with 3/4" Crushed Stone or Driveway Gravel. Angular stone locks in place and holds its shape through a wet winter, while Pea Gravel ruts and spreads.^[1]

Cut a ditch along the low side and fill it with Drain Rock wrapped in fabric. Because water rides on the dense layer at about 35 inches, a shallow ditch that reaches into the upper soil catches it before it soaks the base. Send the ditch to a lawn edge, a rain garden or a dry creek bed of River Rock.^[1]

Moss and puddles on an older gravel drive are signs that the base has filled with fines and no longer drains. Scrape the top layer, add fresh Road Base where the surface has dipped, and finish with clean 3/4" Crushed Stone. On a lot that slopes within the 0 to 8 percent range of the map unit, a shallow swale across the top of the drive keeps water from running down its length in a long storm.^[1],[2]

Federal Way homes in the Census

The Census counts 19,754 housing units in ZIP 98003. Detached single-family houses are 35 percent of them, and the median home was built in 1984. Owners live in 47 percent of the occupied homes.^[4]

Federal Way as a whole holds 37,479 housing units. The detached share across the city is 49 percent, and its median build year is also 1984.^[4]

The Washington State Department of Transportation sets its own rules for the stone layer under state roads, called Crushed Surfacing Base Course, in Section 9-03.9(3) of the Standard Specifications for Road, Bridge, and Municipal Construction M 41-10 (2027). Those rules are written for highway contracts.^[5]

With a median build year of 1984, many homes in the ZIP have drives, walks and drains that are now several decades old. Footing drains clog, gravel drives thin, and yards settle at low spots. A load of Drain Rock for a new trench, or a fresh base under a worn drive, handles most of those jobs.^[4]

Rain gardens, beds and wet corners

A rain garden suits ground where water stops at a dense layer. Dig a shallow basin at a low spot, loosen the bottom, and fill it with a mix of Topsoil and Compost. Plant it with species that tolerate wet feet, and line the inlet with River Rock so runoff does not scour the soil.^[1],[2]

For vegetable or flower beds, raised beds filled with Garden Soil sit above the wettest layer and warm up sooner in spring. Mulch with Brown Shredded Mulch, Black Shredded Mulch or Wood Chips to keep soil from washing out in steady rain.^[1]

Paths that stay firm through a wet season start with fabric and a thin compacted layer of Road Base. Top them with Walkway Gravel or #89 Crushed Stone. Small angular stone drains well and stays in place, even when the ground under it is soaked.^[2]

French drain or rain garden for a soggy yard

A soggy lawn on Alderwood soil has two common fixes. A French drain is a trench lined with fabric and filled with Drain Rock, often with a perforated pipe in the bottom. It collects water moving through the upper soil and carries it to an outlet, such as a ditch, a dry creek bed or the street edge. It works best when the trench reaches into the wet layer and the outlet sits lower than the wet spot.^[1]

A rain garden keeps the water on the lot. It works where there is room for a shallow basin and where the soil above the dense layer can hold the water for a day or two. Many yards use both: a French drain to move water away from the house, emptying into a rain garden at the low corner of the lot. Either way, a wide band of River Rock at the outlet keeps the flow from cutting the soil.^[1]