A Review of Borehole Construction, Development and Maintenance Techniques around Owerri and Its Environs, Southeastern Nigeria

Abstract

Borehole construction and development are techniques employed in the exploitation and management of groundwater. A review of the design, construction, development and maintenance of boreholes around Owerri was undertaken with the aim of finding a lasting solution to problems associated with borehole drilling in the area. Groundwater occurs abundantly in the coastal plain sands (benin Formation) which outcrop in the area with static water level (SWL) ranging from 8 - 65 meters depending on the location and the period of the year. The groundwater flow direction is north-south. The lithologic-log of boreholes in the area revealed that 0 - 5 meters are lateritic-sand followed by medium to coarse grained sand with clay bands occurring at greater depth. Well yield and drawdown vary from 54.24 - 231.50 m3/hr and 0.9 - 13.5 meters respectively, while the hydraulic conductivity is approximately 3.55 x 10-12m/sec. All these values indicate high specific yield and good aquifer performance. Groundwater from boreholes is the main source of water supply in the area, yet there are many failures. Some of the identified causes of borehole failure in the area include: poor geophysical survey, poor knowledge of the local geology, insufficient funding, improper borehole drilling supervision, unprofessional and inexperienced delivery of borehole drilling and post borehole completion problems. These problems can be remedied through proper geophysical survey, adequate funding, employment of professional and experienced drillers, proper well supervision and development as well as regular borehole maintenance.