Sand supply in The Gambia, recommendations for resource management
Bide, T.; Mitchell, C.J. 
ORCID: https://orcid.org/0000-0002-5911-5668; Watkins, I..
2024
Sand supply in The Gambia, recommendations for resource management.
Nottingham, UK, British Geological Survey, 36pp.
(OR/24/052)
(Unpublished)
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Abstract/Summary
This report discusses the critical issue of sand supply in The Gambia, highlighting its importance in construction and the potential environmental impacts associated with its extraction. It emphasizes the challenges posed by rapid urbanisation, the need for effective regulatory oversight and the potentially negative consequences of sand mining such as erosion, habitat loss, and pollution. Without sustainable resource management, the future supply of sand in The Gambia cannot be guaranteed, which may result in serious impacts to both infrastructure projects and economic growth. The work summarised by this report was completed as part of the International Geoscience Research Programme (IGRD) programme in BGS, under the ‘Sand and Sustainability’ project. The Gambia was deemed an ideal case study for application, and testing of, good practice guidance produced by the BGS, due to the ongoing work in-country by stakeholders to improve the resilience of the national sand supply chain. Coastal sand resources, which were historically the main source of sand in The Gambia, are now virtually depleted. Alternative sources of sand include inland and offshore deposits of sand. The inland sand deposits are of variable quality and face considerable opposition to their development from local communities. The marine (offshore) sand deposits could provide good quality sand, but their extraction must be carefully managed to avoid coastal erosion and environmental damage, considering predicted shoreline retreat and the country's reliance on tourism. Good resource governance is a complex issue that requires the collaboration of all interested parties. The first step is ensuring a good baseline understanding of the geological extent and physical properties of known sand resources. This report covers key geological formations known to be suitable for construction sand in The Gambia and gives a brief overview of their physical properties based on field observations and laboratory analysis of sand samples. Although systematic sampling was not conducted as part of this project, a number of sand samples were collected and analysed to determine their particle size distribution (PSD). The particle size data was compared to UK and European industry standards for construction sand to give an indication of relative performance. The geological assessment of resources in The Gambia highlights the dominance of fine-grained clastic sediments. These resources are subdivided into inland, coastal and marine (offshore) sand deposits. Based on particle size and compositional analysis, the inland sand deposits sampled are classified as medium to fine sands mainly composed of quartz grains. These are too fine to meet current European and British standards required for concrete. The coastal sand deposits sampled are classified as medium to fine sands. Depending on the amount of reworking of these deposits, either by coastal processes or heavy mineral extraction, the coarser size fractions are dominated by shell or lithic (rock) fragments. High shell contents are considered deleterious for aggregate use as shells are considerably weaker than quartz or other lithic fragments. Processing to remove shell fragments would be required for the sand to be made suitable for use as a construction material. The marine sand deposits sampled mostly consist of medium grained quartz sand with a high proportion of shell fragments in the coarse size fractions (>1mm), of both unprocessed and processed materials. Processing to remove weak shell-fragment material would greatly improve the quality of the sand; however, the current processing (washing) plant is not effectively removing the shell-fragments from the marine sand. Further discussion of the sand samples collected in The Gambia is provided in section 3 of this report. This report explores various alternatives and new sources of sand supply to address the critical shortage in The Gambia, including marine sand, new onshore deposits, manufactured sand and recycled materials. The following could help improve sand supply sustainability in The Gambia: • Increased geological understanding: Enhanced understanding of onshore and offshore sand resources through geological characterization and mapping, including the creation of regional-scale sand potential maps. • Improvement of industry practices: Investment in basic washing plants to process sand, thereby improving product quality and broadening end-uses. Knowledge sharing with stakeholders from the UK's minerals industry may facilitate this. • Research into alternative materials: exploration of alternative construction materials, such as clay or earth blocks, in collaboration with local academics and the construction sector. This is a complex issue that has social, environmental and land use planning considerations which are outside the scope of this work. Before such considerations can be properly assessed, baseline data on the physical availability of materials need to be understood.
| Item Type: | Publication - Report |
|---|---|
| Funders/Sponsors: | British Geological Survey |
| Additional Information. Not used in RCUK Gateway to Research.: | This item has been internally reviewed, but not externally peer-reviewed. |
| Additional Keywords: | IGRD |
| Date made live: | 06 Nov 2024 10:31 +0 (UTC) |
| URI: | https://nora.nerc.ac.uk/id/eprint/538332 |
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