From derelict quarries into aquaculture goldmines
By Muturi Githae
As the real estate boom in Kenya continues unabated, so has the demand for construction materials levitated with stone quarrying and cement factories enjoying blooming business. The discovery of titanium, rare earths and niobium in Kwale County and coal in Mui Hills in Kitui County is also expected to increase mining activity in the country.
Mining is a temporary activity, with the operating life of a mine lasting from a few years to several decades. The legacy of mining activities has characteristically been land restored to wildlife, like the Haller Park in Mombasa that was once a Bamburi Cement mine or, at some sites, ruined to such an extent that it is inappropriate for any other use.
Progress towards sustainability is made when value is added in terms of the ecological, social and economic well-being of the community. According to Mining Facts, mine closure occurs once the mineral resource at a working mine is exhausted, or operations are no longer profitable. Besides remediation technologies such as constructed wetlands,
Abandoned mines and quarries could be used for a key source of sustainable economic activity; fish farming. Most environmentalists are alarmed about toxic mess left behind once mining activity ends.
However, the Worldwatch Institute report entitled “U.S. Fish Farms Tap Former Coal Mines for Water,” by Ben Block explains that fish farmers in the Appalachian mountains of West Virginia are using water from the abandoned coal mines to raise trout, catfish and salmon.
According to Block, sometimes the water in the mines is clean enough without treatment. But in others the coal companies have been required to add treatment plants to the mines, and these are effective at turning the water crystal clear. Either the healthy water is carried by pipes to the fish farms, or the treatment plants themselves are adapted to accommodate aquaculture operations. Streams near to the mines are also being used to raise fish for recreation purposes.
Among other benefits, aquaculture may provide a much-needed source of revenue, employment and, in some cases, food to communities impacted by mine closure. Further, aquaculture in a controlled closed environment may be more acceptable to critics of fish farming who are concerned about fish escapes and viral transmissions to wild populations.
Despite the would-be benefits, aquaculture in flooded mines is not without its complications — it requires a site-specific design approach that must consider issues ranging from metals uptake by fish, to the long-term viability of the aquatic system as fish habitat, to the overall contribution of aquaculture to sustainability.