Investigation of Groundwater Flow Direction in Port Harcourt, Nigeria

The lack of reliable municipal water supply in the city of Port Harcourt has led to indiscriminate drilling of boreholes by the residents however, the direction of groundwater flow within the entire city has not been established. Hence, the research investigated the flow direction of groundwater in the study area in order to understand the best location for siting septic tanks and dumpsites with respect to the position of the existing or proposed borehole. This was achieved by determining the hydraulic heads (Hh) of twenty boreholes evenly distributed within the city by subtracting the static water level (SWL) from the corresponding earth surface elevation (E) with the use of a GPS and dipmeter. Results revealed that the hydraulic heads ranged from 0.14 – 23.16m while the surface elevation and static water level lies between 1.93 – 39.33m and 1.79 – 17.27m respectively. The contour map of the hydraulic heads indicated that the groundwater flows towards the southern and south-western directions hence, the residents were advised to take into cognizance when sitting dumpsites, landfills, and septic tanks with respect to proposed or existing boreholes.

Static Water Level and Elevation Analyses of Shallow Hand-Dug Wells in Ilorin Metropolis, Nigeria

Aim: This study was conducted to reveal the depth to water level and surface elevation in selected hand-dug wells within Ilorin metropolis to assist in planning and management of water resources within the study area. Place and Duration of Study: The study was conducted in Ilorin metropolis, North Central, Nigeria. Methodology: A total of twenty-six (26) hand-dug wells were sampled and relevant spatial information was acquired using a handheld GPS; data collected include: longitude, latitude, elevation and depth to water, then the static water level above sea level was estimated by the difference between depth to water and elevation. Statistical analyses such as mean and standard deviation were determined, also a base map, contour maps and 3-D elevation model of the study area were produced using ArcGIS 10.4 and Surfer 10 software. Results: The depth to water within the study area ranges between 1.6 m and 13.3m, while elevation were between 284.1 m and 377.9 m, then the static water level ranges between 270.8 m and 371.4 m. The static water level contour map showed a radial and multidimensional groundwater flow pattern trending in the NE–SW and NW–SE directions while the 3-D elevation model revealed an undulating terrain. Conclusion: The study concluded that the depth to groundwater is relatively shallow and this can guide proper development and management of groundwater resources within the metropolis.

Geotechnical Competence Assessment and Groundwater Prospect Deductions from Geoelectrical Sounding around Idanre Local Government Area of Ondo State, Southwestern Nigeria

Sixty vertical electrical soundings with maximum electrode spacing of 100 m; and seventy static water level measurements were undertaken in Idanre Local Government Area of Ondo State, Nigeria with the aim of assessing the engineering competence of the soil material to host civil engineering structures; and also establish notable point/location with groundwater prospect for borehole drilling and development. Typical sounding curves from the area include H, A, HA, KH, QH, and AA reflecting diverse lithological variations. The H, A, and HA curve types are the most preponderant constituting 30%, 15% and 25% respectively. The A (15%) and AA (7%) curve types suggest subsurface geoelectric configurations apparently favourable for foundation construction, as they showed an increase in resistivity (competence) with a corresponding increase in depth. The QH, KH, HA and H curve types constituting about 78% are favourable for groundwater accumulation and development. The topsoil is generally composed of sandy clay which is moderately competent soil material to harbour civil structures such as road, buildings. Although some degree of settlement is expected especially along traverses where the weathered layer is clayey. The study shows that 70% of the area in the upper 10 m is moderately suitable for civil engineering shallow foundation construction. The weathered layer is generally clay/sandy clay with resistivity less than 200 Ω-m, therefore can serve as earth medium for electrical material. The major aquifer units in the area are combined weathered layer and fractured basement (common in Aponmu and Jimgbe); a weathered layer (prominent in Imolumu, Ayefemi, Onipanu and Ajegunle) and fractured basement aquifer (found in Ajegunle and Odode). The maximum probable drilling depth to these aquifers varies between 15 m to 30 m. Areas with high static water level are characterized by thin overburden thickness (shallow depth to basement rocks). Also, areas with low static water level have corresponding thick overburden thickness (deep depth to basement rock/high depth of weathering). However substantial settlement may occur in areas with high static water level which could exceed the tolerable limit and threatens the integrity of structures during the raining season, coupled with the clayey nature of the weathered layer in many places.

PNEUMATIC HAMMER SOIL VAPOR PROBES AND MINIATURE PIEZOMETERS FOR GASOLINE SPILL DELINEATION AND CLEANUP

ABSTRACT In a new twist on an old procedure, pneumatically injected miniature well points may change soil investigations much as nail guns have changed carpentry. Soil vapor analysis has increasingly gained attention as a means of locating and monitoring subsurface gasoline spills. Accurate depiction of the plume position requires reproducible vapor detection and monitoring. In addition, static water level needs to be determined to understand flow direction. Miniature aluminum slitted well points can be mass-produced by computer-aided production facilities to create low-cost identical copies about 10 cm in length. The small points can be inserted into shafts and injected into the ground. The shaft is then pulled back, leaving a flexible teflon or polypropylene tubing attached. A gasoline spill at Falmouth, Cape Cod, Massachusetts, provided an opportunity to test the use of the injected “shield” points. More than 40 vapor points were installed in two days during four transects across a product plume located 10 m below grade.