Making boreholes work - rehabilitation strategies from Angola

In areas of the world where primary water supply is obtained from boreholes drilled in fine grained drift, there is potential for ‘sand’ or ‘media’ intrusion. This can result in clogging of borehole screens, damage to submersible pumps and blocked handpumps. Many boreholes encountering this problem of media intrusion are abandoned due to expensive rehabilitation procedures. This paper discusses field solutions adopted in Kuito, Angola where boreholes are highly susceptible to fine media ingress. Findings presented are based on the authors field experience between 1993 and 2002 whilst working for Oxfam GB in Angola. It outlines three remedial measures, namely, internal gravel packs, geotextile stockings and telescoped borehole design.