Decline

A tunnel driven at a gentle, steady downward gradient from the surface, or between underground levels, sized and graded for rubber-tyred vehicles to drive directly in and out — the modern, vehicle-based counterpart to the older, rope-hauled Incline, and an alternative to a vertical Shaft.

Historical usage

A recent development in mine access relative to the archive's usual period: declines became the standard way to open a new hard-rock mine only once diesel-powered, rubber-tyred loaders and trucks became practical underground, from the mid-to-later 20th century onward, and remain the normal choice for a new mine (or a modern reopening of an old one) today, in preference to sinking a new shaft where the ground allows it.

How it worked

Driven downward at a steady gradient — typically in the region of 8-15% — wide enough for the largest vehicle expected to use it, a decline lets trucks, loaders and drill rigs drive directly between the surface and the working levels, rather than being lowered down a shaft or hauled up an incline by rope. Comparative teaching material on mine access notes that a shaft costs roughly three times as much to construct as a decline (a 'slope', in some terminology) for a given depth, but that the decline's own tunnelling footage runs to roughly three times the shaft's in return, and that fitting large machinery down a shaft is far harder than simply driving it down a decline.

Why it was used

A decline lets ore, waste, equipment and people all move on wheels rather than being wound, avoiding the fixed load and headroom limits of a shaft cage, and it can double as a ventilation and services route for power and water lines. It suits shallow-to-moderate-depth mines particularly well, and is the access method Cornish Metals is currently using in South Crofty's redevelopment, where a 300-metre decline gives access to the upper workings alongside the mine's four older shafts.

Risks & limitations

A decline cannot easily support the continuous belt or rail haulage a shaft or a rope-hauled incline can, so at greater depth or higher tonnage a shaft usually becomes the more efficient choice again — declines suit shallower, vehicle-based operations rather than being a universal replacement for a shaft.

Regional variation

Called a ramp in Australia, Canada and parts of the United States for the same thing.

Mines associated with this term

5 examples chosen from 8 linked records — the term page is not an index.

• Glenbuck Colliery — East Ayrshire (well documented example)
  Named in this record’s history: “…before the club folded in 1931, the same era as the village's own decline. Chief among them was Bill Shankly, whose four older brothers all…”
• Maenofferen Quarry — Gwynedd (well documented example)
  Named in this record’s history: “…slate extraction was pioneered here in the 1970s-80s. Post-war decline, as synthetic roofing materials undercut demand for slate, reduced…”
• Blackhall Colliery — County Durham (well documented example)
  Named in this record’s history: “…sinking) in 1910 to a peak of 2,490 in 1950, before a long, slow decline to 1,353 by 1980. The colliery passed to the National Coal Board at…”
• Blaenavon Ironworks — Torfaen (well documented example)
  Named in this record’s history: “…to south Wales in the first place, and hastened the district's long decline. Iron production at the original furnace site ceased in 1904, though…”
• Boulby Alum Quarries — North Yorkshire (well documented example)
  Named in this record’s history: “…employed 355 people, 314 of them labourers. The industry went into decline through the 1850s as synthetic dyes and cheaper chemical routes…”

Sources

1. (secondary) Lesson 10.1: Orebody Access — Penn State, MNG 230: An Introduction to Mining Engineering
2. (secondary) Mining terms explained, A to Z: Decline tunnel — Anglo American

Record created: 27 August 2026 · Last researched: 27 August 2026