Wednesday, January 19, 2022

Illegal sand mining to negative river eco-systems

Department of Geological Survey official Vincent Lekula says the demand for river sand in Botswana has increased dramatically over the past decade; generated by the high rate of development within the greater Gaborone area.
Lekula said these developments need high tonnages of river sand mined illegally from the river beds all over Botswana to meet the demand. Giving identification and assessment of industrial mineral resources for construction aggregates during September Electra Mining Botswana sand has negative environmental impacts as the river eco-systems are deteriorating due to the prolonged extraction.
“For this situation to be addressed the Ministry of Minerals, Energy and Water Resources (MEWR) through our Department is responsible for resources exploration used mainly for the purpose of construction in Botswana as an alternative. The ultimate goal lies in providing sand which will be cheap, environmental friendly, meeting the industry’s demands,” he said.
“Our major objectives, among others, are to provide Batswana enough machine sand and construction aggregate, to meet the ever growing demands in the Greater Gaborone area.”
DGS has been conducting researching on end to identify and assess suitable rock types for the manufacture of machine-sand for use by Botswana’s construction Industry. There has also been a financial strategy to improve the quality of life of Batswana by availing affordable construction raw materials.
“We have also mounted a huge campaign, promoting citizen participation in mining and empowering Batswana through Small Scale Mining (SSM). As mentioned previously, without promoting environmental protection awareness by reducing illegal sand harvesting, the result would severe land degradation, as is the scenario where there has been uncontrolled sand mining”, he said.
DGS’ sand mining methodologies have involved field sampling, geo-physical probing and laboratory tests. The Department’s geo-physical methods utilizing the regional airborne gamma radiation (GR) has covered most of Eastern Botswana. However, in the erstwhile, GR did not cover most of the greater Gaborone area.
During the procedure, total radiation was measured at outcrops at the sampling locations, using the GR spectrometer. The Activity indices (I) were measured to find suitable rock aggregates, using K, U and Th values. The country-wide high resolution aeromagnetic map was helpful in delineating rock units of interests. The magnetic susceptibility also was measured on the outcrop at every sample locality, providing 8 separate readings at every location. As Dolerite and Felsite have high magnetic content, hence the depth and lateral extents can be estimated using aeromagnetic map.
According to the Geologist, “Laboratory test involve bulk density, water absorption, aggregate impact value (AIV), aggregate crushing value (ACV) and 10 percent fact, grading, Los Angeles Abrasion (LA) and Methylene Blue.
“A total of 57 rock specimens have been sampled with focus on the rock types that are most likely to do well on road/building construction for example, granite, felsites, dolerite and Gabbro. “Recommended quarry sites include Molepolole, Modipane, Moshupa, Ntlhantlhe, Kgomokasitwa, Mmankgodi and Metsimotlhabe.”

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