From quarry to waterfall

I went on my first ever tour of a working quarry last week. Given my main focus is on ecological architecture, the type of quarry came as a surprise.

Kelhead, located near Annan in Dumfriesshire, and owned and operated by Grange Quarry Ltd – which has several concrete plants and two quarries in Dumfries & Galloway, the Scottish Borders and Cumbria – mostly supplies aggregates and ready-mixed concrete. I went there in search of rocks for the water feature for the forest school nursery I’m designing near Dumfries.

Halvorsen Architects is turning its natural water-treatment system for the nursery into a playful and educational feature running across the site, starting with a waterfall on a steep sided bank and ending in an existing pond on adjacent land.

Kelhead is a limestone breccia quarry, supplying concrete aggregate and various forms of cement materials predominantly for road-building. It also supplies materials ranging from crushed rock fines to armour stone (mainly used for sea defences). A lime works and quarry and has been in operation here since the1820s.

Calcium agricultural lime, used to restore pH values to arable soils, is also produced here. Liming is a long-established practice in farming used to ameliorate acidic soils and improve ecosystems.

Breccia is a sedimentary rock made up of large angular fragments of minerals cemented together by a fine-grained matrix. If you’re wondering about what distinguishes breccia from conglomerates, they are in fact very similar, the main difference being in the shape of the large particles. In breccia, the large particles are angular but in conglomerates they are rounded. The angular shapes reveal that they have not been transported very far. Rocks that have been transported a distance by water or glaciers have had their edges worn down and rounded.

The rock, breccia, has very few uses. It can be used as a filling or road base where the technical requirements are minimal. It is rarely used in important projects because its composition is so variable. Some breccias are used for interior finishes.

However the rock is perfect for use in our water feature, given its durability and beautiful composition with many colours. Quarry manager, George Lowther, and I scrambled over large boulders looking for the perfect shapes for our project. It should make a fantastic water feature – it’s just a shame the children won’t live long enough to see the long-term effects of the water rounding the stones!

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