Topographical and geological maps for materials

Construction materials (aggregate, sand, gravel, boulders, clay, limestone) must be found close to the project, in sufficient quantity and quality. Maps are the first tools in this search.

1. Topographical (and aerial) map

• Shows contours, rivers, terraces, slopes, roads, villages and land use, helping to locate accessible sites and estimate haul distance and area.
• Shows landforms such as river terraces, fans and floodplains, which are likely sources of sand and gravel.
• Aerial photographs and satellite images show vegetation, outcrops, river channels, landslides and tonal contrasts that indicate rock or soil types, and allow measurement of area.
• Contours help to estimate overburden thickness, slope for quarry benches, and drainage.

2. Geological map

• Shows the type, age and distribution of rock formations, and the attitude (strike and dip) of beds, faults, folds and contacts.
• Helps to choose the formation suitable for aggregate (quartzite, limestone, granite, gneiss), cement raw materials (limestone, clay) or building stone, and to estimate thickness and extent, thus reserve.
• Shows weak, shattered and weathered zones (faults, shear zones) to be avoided.

3. Engineering geological map

• Shows rock/soil engineering properties, weathering grade, joint spacing, rock mass classes, slope stability, groundwater and geohazards.
• Allows direct selection of the best site considering quality, safety of quarry slopes, stability and environment.
• Shows areas to be avoided (landslides, active gullies, flood zones) and areas for waste disposal.

Together the maps narrow the search from the regional scale to the quarry or borrow site, which is then confirmed by field mapping, test pits and laboratory tests.