Grade
Moving dirt is the first real cost a scheme incurs, and it is invisible in almost every student project. Load a site's real terrain (the same USGS 3DEP grid Surveyor samples), then reshape it — a building pad or a stepped run of benches — with side slopes that daylight back to existing grade. Read cut, fill, net import/export, truckloads, and the balance elevation at which nothing leaves the site. Cut volume is not fill volume: soil swells in the truck and shrinks in the fill, so the tool reports bank, loose and compacted separately and tells you which one the trucks are paid for. A screening-resolution grid model, not a grading plan.
Sources & methods
Method. A grid (prism / "borrow-pit") volume between two surfaces: the USGS 3DEP bare-earth grid and the surface you draw. Four-corner prism per cell; cells the cut/fill line passes through are subdivided so cut and fill do not silently cancel; every volume is printed with its cell size and a convergence error bar. Swell and shrink come from a handbook range for the soil class — cut (bank), loose (truck) and compacted (fill) are three different numbers, and trucks are paid for loose.
Slope defaults are drawing conventions, not stability analysis. The real limit is the soil's shear strength — determined by a geotechnical engineer against a factor of safety. "Angle of repose" describes loose granular material poured in a pile and is the wrong concept for an engineered fill; it appears in this sentence and is then never used as a design criterion.
- Fill batter: 1:3 (33.3%) — conservative for uncompacted common earth; also mowable
- Cut batter: 1:2 (50%) — typical for firm soil in a temporary/permanent cut
- Mowable / maintainable slope: 1:4 (25%) — the practical landscape limit, not a stability one
- Accessible ramp: 1:12 (8.33%) — ADA/ANSI A117.1 ramp limit, with landings
- Accessible route without handrails: 1:20 (5%) — the running-slope threshold above which it is a ramp
- Parking / paved area: — (5%) — 5% max comfort ceiling, ~1% min drainage floor
Not modelled: topsoil strip and respread (often the largest single quantity on a real earthwork schedule), unsuitable material and undercut, rock excavation, dewatering, haul distance, compaction lifts, retaining structures, erosion control, subgrade prep — and cost, deliberately: truckloads are the unit of felt magnitude here. SSURGO bedrock/water-table flags are mapped soils, not borings. 3DEP and SSURGO are US-only. Out-of-coverage cells are excluded from every volume. USGS and USDA products are US Government public-domain works with their own no-warranty statements; place search © OSM contributors (ODbL).
The swell/shrink table is handbook-typical and UNVERIFIED (2026-07-30): ranges are shipped wide and must be checked against the Caterpillar Performance Handbook, Peurifoy, or a state DOT earthwork manual before teaching with them.