Excavation contractor jobsite in King County, WA

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King County, WA Contractor directory

Excavation contractors in King County, WA

83 verified excavating and site work contractors serving King County.

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County excavation guide

Ground conditions and project requirements in King County

Use this local research to understand soil, seasonal constraints, permits, and jobsite logistics before choosing a contractor.

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Soil Regime ProfileEPA Ecoregion 2, 9, 10 (Coast Range, Puget Lowland, Cascades, Columbia Plateau)

Washington Puget Glacial Marine Drift, Columbia Plateau Basalt & Cascades

Dominant Soil Order: Andisols / Inceptisols / Mollisols / Aridisols
Parent Material: Puget Lobe Glacial Marine Drift (Hardpan and Loose Outwash), Columbia River Basalt with Loess, and Cascades Volcanics

Washington is glacial-marine drift, basalt plateau, and volcanic mountains. The Puget Lowland (Seattle, Tacoma, Everett, Bellingham) sits on the Puget Lobe's glacial marine drift: dense glacial till (hardpan) that excavators rip or break, over-consolidated lacustrine clay, loose recessional outwash that runs and needs shoring, and slope-failure-prone bluffs along the marine shoreline. Landslides in the drift bluffs are the region's recurring geohazard, and drainfield siting fights winter saturation: hydric soils and seasonal seeps are everywhere in the lowlands, with frost a non-issue (15-20 inches). The Columbia Plateau (Yakima, Spokane, Tri-Cities) is layered flood basalt: loess and Touchet beds over flows, rock excavation ordinary, and the famous loess-island topography of the Palouse adding deep, erodible silt. The Cascades add volcanic rock, deep snow loads, and lahar/mudflow mapping zones around Rainier and Baker. Shrink-swell is low statewide; volcanic-ash (Andisol) soils are well-draining and light.

Geographic Footprint:Washington's counties (Seattle, Spokane, Yakima, Vancouver) split between glacial-marine drift lowlands (hardpan, loose sand, bluff slides, wet winters) and basalt-and-loess plateau east of the Cascades: rock work on the plateau, hardpan and slope stability on the sound. The shallow frost line keeps footings modest.
Geotechnical Baseline

Physical Ground Conditions & Soil Properties

Shallow Bedrock (<50 in)
51.2%of county land area

High likelihood of bedrock refusal; hammer / ripper required for deep utilities.

High Shrink-Swell Clay
0.0%expansive soil

Low volumetric expansion risk in native subgrade.

Median Water Table Depth
26inches from surface

Moderate depth; seasonal wet perched water tables possible in spring.

Hydric / Wetland Soils
15.3%hydric coverage

Indicates poor natural drainage and potential jurisdictional wetland pockets.

Steep Terrain (Slope >15%)
16.9%of terrain

Predominantly gentle to rolling slopes suitable for wheeled earthmoving.

Septic Severe Limitations
93.8%severe rate

High rate of conventional drainfield limitations; engineered or drip systems often required.

Dominant Soil Textures:Sandy loamSilt loamFine sandy loam
Surface Stones / Boulders: 17.2% coverage
Compliance & Permitting

Earthwork Regulations & Permit Thresholds

Stormwater & Erosion Control
Construction Stormwater General Permit (Ecology); sites disturbing one acre or more, or less than one acre in a larger common plan; draft 2026 reissuance out for comment, permit number not verified

Administers NPDES stormwater discharge coverage for land-disturbing construction activities.

State Threshold:1.00 Acre
Local Threshold:Follows state
Onsite Wastewater & Utilities
King Local Health Jurisdiction

Jurisdiction over septic tank permits, soil evaluation perk tests, and drainfield sizing.

Housing on Septic:10.0%
Soil Evaluation:Soil logs sufficient for initial and reserve areas, by PE, designer or local health officer; soil scientists may perform soil evaluations
811 One-Call Requirements
Washington 811 (Dig Law, RCW 19.122)

Mandatory notice window: 48 hours prior to mechanized earthwork (excluding weekends and legal holidays).

Licensing & Clearing Permits
Weather & Ecology

Seasonal Constraints & Clearing Windows

Frozen Ground Days
0days / year

Typical days with sub-freezing soil conditions affecting digging.

Wet Season Months
January, November, December

Peak precipitation window requiring sediment traps and soil aeration.

Supply Chain & Hazards

Logistics, Aggregate Sources & Geohazards

Aggregate & Material Supply
Kangley Pit

Nearest active quarry: 4.9 miles haul distance.(60 active crushed stone/sand operations within 50 miles).

Flood & Hazard Overlay
FEMA 100-Yr Flood:16.9%(100% NFHL digital map coverage)
NWI Wetlands:43.8%jurisdictional coverage
Karst Terrain & Sinkhole Risk: Low

0.0% of county underlain by soluble carbonate rock formations.

HUC8 Primary Watersheds:Lake Washington, Skykomish, Snohomish, Puget Sound, Duwamish, Puyallup
Public conservation land: 11.2% (USGS PAD-US).

Area-specific FAQ

Do I need to call before digging in King County?

Yes. You should contact Washington 811 at least 2 working days before any digging so underground lines can be marked.

How deep do footings need to be in Washington?

In Washington, footings typically need to extend below the frost line, which is around 24 inches here. A local contractor will confirm the code requirement for your site.

Verified local listings

Excavation contractors serving King County

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