Excavation contractor jobsite in Coos County, NH

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Coos County, NH Contractor directory

Excavation contractors in Coos County, NH

17 verified excavating and site work contractors serving Coos County.

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County excavation guide

Ground conditions and project requirements in Coos 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 59, 82 (White Mountains, New England Uplands-Longfellow Mountains, Northeastern Highlands)

New Hampshire White Mountains, Glacial Uplands & Merrimack Valley

Dominant Soil Order: Spodosols / Inceptisols / Histosols
Parent Material: Glacial Till and Outwash over Littleton-Mealhill Gneiss, Conway Granite, and Paleozoic Metasediment

New Hampshire is glacial till over granite-and-schist, with the White Mountains at its core. Soils are thin, stony, and acidic; bedrock ledges sit within a few feet across most upland lots; and glacial boulders are the everyday excavation surprise. Slopes run 20-70 percent in the mountain counties (Coos, Grafton, Carroll), so access drives, bench cuts, and contour septic lines dominate those sites. The Merrimack Valley and the southeast (Manchester, Nashua, Concord) are the working lowlands: glacial till and stratified drift over schist and granite, hydric soils in the streamside basins (20-35 percent), seasonal high water, and the state's fastest-growing excavation market. The Stratified Drift aquifers beneath the valleys carry sand-and-gravel trench stability issues and strict aquifer-protection overlays. Shrink-swell is negligible statewide. Frost runs 42-60 inches, the deepest in New England

Geographic Footprint:New Hampshire's counties (Manchester, Concord, Laconia, Berlin) are stony glacial till over granite and schist: bedrock ledges and boulders everywhere, steep White Mountain slopes to the north, wet valley drift aquifers south, and 42-60 inch frost. Rock and slope shape the mountain work.
Geotechnical Baseline

Physical Ground Conditions & Soil Properties

Shallow Bedrock (<50 in)
58.1%of county land area

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

High Shrink-Swell Clay
1.2%expansive soil

Low volumetric expansion risk in native subgrade.

Median Water Table Depth
20inches from surface

Shallow water table; active dewatering or sumps needed for deep trenching.

Hydric / Wetland Soils
20.2%hydric coverage

Indicates poor natural drainage and potential jurisdictional wetland pockets.

Steep Terrain (Slope >15%)
41.9%of terrain

Mountain/hilly terrain; terracing, benching, and tracked haulers frequent.

Septic Severe Limitations
93.3%severe rate

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

Dominant Soil Textures:Silt loamFine sandy loamVery fine sandy loam
Surface Stones / Boulders: 33.8% coverage
Compliance & Permitting

Earthwork Regulations & Permit Thresholds

Stormwater & Erosion Control
EPA NPDES Construction General Permit (2022 CGP), NH coverage number NHR100000 (EPA-issued; NHDES does not issue a state CGP, inferred from EPA Appendix B pattern and not individually verified for NH). One acre or more, or smaller if part of a larger common plan. State layer: NHDES Alteration of Terrain (AoT) permit.

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

State Threshold:1.00 Acre
Local Threshold:Follows state
Onsite Wastewater & Utilities
NHDES Subsurface Systems Bureau

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

Housing on Septic:55.0%
Soil Evaluation:Permitted designer submits test pit logs and percolation results under Env-Wq 1000; percolation tests at each 4,000 sq ft area
811 One-Call Requirements
Dig Safe System (811)

Mandatory notice window: 72 hours prior to mechanized earthwork (excluding weekends and legal holidays).

Licensing & Clearing Permits
Weather & Ecology

Seasonal Constraints & Clearing Windows

Frozen Ground Days
120days / year

Typical days with sub-freezing soil conditions affecting digging.

Wet Season Months
October

Peak precipitation window requiring sediment traps and soil aeration.

Supply Chain & Hazards

Logistics, Aggregate Sources & Geohazards

Aggregate & Material Supply
Guildhall Plant

Nearest active quarry: 12 miles haul distance.(8 active crushed stone/sand operations within 50 miles).

Flood & Hazard Overlay
FEMA 100-Yr Flood:4.1%(100% NFHL digital map coverage)
NWI Wetlands:12.9%jurisdictional coverage
Karst Terrain & Sinkhole Risk: Low

0.0% of county underlain by soluble carbonate rock formations.

HUC8 Primary Watersheds:Saco River, Lower Androscoggin River, Ammonoosuc River-Connecticut River, Upper Androscoggin River, Headwaters Connecticut River, Passumpsic River
Public conservation land: 100.0% (USGS PAD-US).

Area-specific FAQ

Do I need to call before digging in Coos County?

Yes. You should contact Dig Safe New Hampshire at least 2 working days before any digging so underground lines can be marked.

How deep do footings need to be in New Hampshire?

In New Hampshire, footings typically need to extend below the frost line, which is around 48 inches here. A local contractor will confirm the code requirement for your site.

Verified local listings

Excavation contractors serving Coos County

17 verified listings

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