Borehole Rehabilitation: A Case Study in the Dunkwa Mining Town

Rehabilitation works were carried out on boreholes in the Dunkwa Mining town in the Central Region of Ghana. These works were carried out because the boreholes had lost their original yields due to clogging, corrosion and encrustation and had been abandoned for a long time. The cost of drilling a new well and assessing the productivity of the well is $4,500 which is more expensive that carrying out rehabilitation works which is cheaper, about$800. Also, the initial yields of the boreholes were very high according to the feasibility report which is not a common characteristic of the rocks in the area. Camera inspection followed by rehabilitation, pre and post pumping tests were carried out to assess whether there has been an improvement in their yield after the exercise and that the yield obtained will be adequate for a water supply design. Results show that all the boreholes had an improvement in their yields (57.19 - 259.80 %) after the rehabilitation. It can therefore be concluded that rehabilitation is effective in restoring boreholes to their original yields. Organisations drilling boreholes to communities can take advantage of rehabilitation of the existing boreholes located in the communities which are high yielding, thereby reducing project implementation cost. Keywords: Borehole Rehabilitation, Borehole Yields, Borehole Camera Inspection, Pumping Tes

Efficacy of Geophysical Techniques for Groundwater Exploration in the Volta Basin, Northern Region of Ghana

Abstract Groundwater, traditionally extracted from hand-dug wells and boreholes is the main drinking water source in the Northern Region of Ghana. Many boreholes have been constructed in the region to increase accessibility to potable water mainly as part of rural water supply projects where borehole siting has to be relatively cheaper.  These projects have resulted in low success rates of borehole drilling because of the application of inefficient and simple geophysical techniques supposed to be cheaper. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. The surveys were conducted at stations of existing dry and positive boreholes. Results show that the three geophysical techniques are efficient to identify groundwater accumulation zones. The ERI, EKS and 222Rn are efficient to identify discontinuities, calculate hydraulic conductivity of discontinuities and identify areas of water circulation respectively. It is recommended that the ERI be used to obtain discontinuities and weak zones for drilling on rural water supply projects in the VB. The EKS and 222Rn should be conducted to evaluate these features when high yield boreholes are required.   Keywords: Geophysical Techniques, Volta Basin, Borehole Drilling, Success Rate

Assessment of Groundwater Quality and Health Risk of Heavy Metals: A study from the Tarkwa Mining Area, Ghana

This study seeks to evaluate the hydrogeochemical characteristics of water in the Tarkwa mining area using the Piper and Chadha plots and to carry out a health risk assessment using the US Environmental Protection Agency (USEPA) health risk assessment model. A total of 39 groundwater sample points were used for this study. Results from the Piper and Chadha diagrams show that the dominant water types in the study area are Ca-HCO3 and Mixed Ca-Mg-Cl water types which indicates that groundwater in the area can be classified as fresh water. The hazard quotient (HQ) value for heavy metals estimated, suggested an acceptable level of noncarcinogenic inimical health risk. In relation to the HQ value, the Hazard Index (HQ) calculated was less than 1 suggesting that inhabitants will not be exposed to a potential health risk for the injection of heavy metals. Carcinogenic risk estimated for As (1.80×10-4) was higher than the acceptable risk. The carcinogenic risk estimated therefore indicated that, drinking of groundwater over a long period will increase the probability of cancer. It can be concluded that currently the groundwater in the Tarkwa area is safe for domestic purposes.   Keywords: Hydrochemical Characteristics, Human Risk Assessment, Tarkwa Mining Are

Hydrogeological Properties of the Rocks in Adansi Mining Area, Ghana

Groundwater is an important resource in the Adansi mining area as some communities in the area are not connected to the Ghana national water network. These communities therefore utilise groundwater for potable water supply. The hydrogeological properties of an aquifer coupled with climatic conditions and geomorphology determines how much groundwater exists in that location. A hydrogeological study of the rocks in the Adansi area was carried out to obtain the aquifer hydraulic properties. Drilling and pumping test analysis information were used to assess these properties. The average borehole depth in the area was 44.3 m whilst the average static water level is 10.75 m. There is a general decrease in yield with an increase in borehole total depth. There is also no strong correlation between aquifer saturated thickness, yield and drawdown. Transmissivity of the aquifer decreases from the phyllite, argillitc sediments, granites to sandstone. Three hydrogeological regimes (> 0.9 m/day, 0.9 – 0.09 m/day and < 0.09 m/day) were also realised based on the hydraulic conductivity. The spatial distribution of the hydraulic properties suggests the influence of geological structures on the occurrence of groundwater in the area. Keywords: Hydrogeological Properties, Mining, Hydraulic, Drilling, Groundwate

Groundwater Vulnerability Assessment of the Tarkwa Mining Area Using SINTACS Approach and GIS

Groundwater vulnerability assessment to delineate areas that are susceptible to contamination from mining and anthropogenic activities has become an important element for resource management and landuse planning. In view of the extensive mining in the Tarkwa area, quality of groundwater has become an important issue. This study estimates aquifer vulnerability by applying the SINTACS model which uses seven environmental parameters to evaluate aquifer vulnerability and geographical information system (GIS) in the Tarkwa mining area. Sensitivity analysis has also been carried out to evaluate the relative importance of the model parameters for aquifer vulnerability. The SINTACS model results show that the intrusive rocks within the Tarkwaian and the Birimian rocks are dominated by very high vulnerability classes while the Banket Series is characterised by high vulnerability class. The Huni Sandstones have moderately high vulnerability. In addition, the Kawere Group and the Tarkwa Phyllites displayed medium vulnerability. Analysis from the variogram model shows that all parameters used in the SINTACS model have a strong spatial structure. From statistical analysis, depth to water parameter inflicted the highest impact on the vulnerability of the aquifer followed by effective infiltration, vadose zone media, soil media, aquifer media, topography and hydraulic conductivity in the order of decreasing impact. Sensitivity analysis indicated that the aquifer media, hydraulic characteristics and topography cause large variation in vulnerability index. Depth to water and effective infiltration were found to be more effective in assessing aquifer vulnerability. Keywords: Groundwater, Vulnerability, Tarkwa, SINTACS, GI

Combined Electrical Resistivity Imaging and Electromagnetic Survey for Groundwater Studies in the Tarkwa Mining Area, Ghana

The major source of potable water in Tarkwa is the Bonsa Treatment Plant sourced from the Bonsa River. The activities of illegal miners along the banks of the Bonsa River has resulted in pollution of the river. This has resulted in high treatment cost and irregular supply of water to the Tarkwa Township and surrounding communities that are fed by the Bonsa Treatment Plant. In view of the difficulty in getting frequent and regular potable supply of water, people have resorted to construction of boreholes and hand-dug wells. However, the success rates and borehole yields are low especially in the hydrogeologically difficult terrains in the Tarkwa area. The aim of this paper is to investigate the hydrogeological conditions of the Tarkwa area using both the Electrical Resistivity Imaging (ERI) and Electromagnetic (EM) geophysical techniques to determine the electrical resistivity and conductivity values that are related to groundwater accumulation, so that potential water-bearing zones can be identified. Results from electrical resistivity show that the general resistivity distribution in the Tarkwa area is between 32 Ωm and 100 000 Ωm. Water-bearing zones in the Huni Sandstone occur to a depth of 35 m with an average resistivity value of 400 Ωm, at a depth of 60 m and a resistivity of 600 Ωm in the Tarkwa Phyllite, at a depth of 55 m and a resistivity of 600 Ωm in the Banket Series and 50 m depth with resistivity value of 500 Ωm in the Kawere Conglomerate respectively. The electromagnetic conductivity values also show that the general conductivity distribution in the Tarkwa area is 3 – 32 S/m. The application of electrical resistivity and electromagnetic techniques separately gives success rate of 80 % and 65 % respectively. An improved success rate of 86 % is achieved combining the two techniques. Keywords: Electrical Resistivity Imaging, Electromagnetic Method, Groundwate

The utilisation of End-of-Life Plastics for the production of paver blocks: A waste management and disposal strategy

The volume of municipal solid waste in developing countries continues to grow, yet disposal and management have become significant challenges.  As a result, a proper disposal strategy is required.  The feasibility of making paver blocks from plastic waste for construction work was investigated in this study.  Paver blocks manufactured from plastic waste (PP and HDPE) and sand in varied proportions were evaluated for compressive strength, water absorption, and abrasion resistance.  Paver blocks were manufactured with plastic (PP and HDPE) to sand ratios of 30:70%, 40:60%, 50:50%, 60:40%, and 70:30%, or PP30, PP40, PP50, PP60, and PP70, and HDPE30, HDPE40, HDPE50, HDPE60, and HDPE70.  The paver blocks were inspected after 28 days.  Compressive strength, LA abrasion, and water absorption of paver blocks increased from 30% to 40% HDPE, then fell to 70%.  As paver block PP content grew from 30% to 70%, abrasion and water absorption decreased.  The compressive strength of PP paver blocks declined from 30% to 50% PP, then increased somewhat, and then fell to 60% and 70% PP.  PP60 and HDPE40 paver blocks had the highest compressive strength, abrasion value, and water absorption.  HDPE40 pavers have lesser water absorption and more abrasion than PP60 pavers.  PP60 water absorption and abrasion were 0.53% and 11%; HDPE40 was 0.03% and 24.2%.  PP60 and HDPE50 have compressive strength, abrasion resistance, and water absorption of 20.09 MPa, 11%, and 0.53%, respectively, and 13.06 MPa, 12.1%, and 0.03%

Mining and Metal Pollution: Assessment of Water Quality in the Tarkwa Mining Area

The quality of water in mining communities is uncertain since metals associated with acid mine drainage are known to saturate these waters. Previous studies in Tarkwa, an area noted for gold and manganese extraction, have reported large concentrations of aluminium, arsenic, cadmium, copper, lead, manganese and mercury in water samples. This research aimed at investigating the chemistry of groundwater with special focus on the contamination status of trace elements. It also compared levels of metal concentration with those that were determined in previous research works, to identify changes that might have occurred. Thirty-eight water samples from boreholes, hand-dug wells and streams, within the Tarkwa area were obtained and analysed. Results show that 90 % of water in the area is acidic and Eh was determined to be positive, depicting oxidizing conditions. Mean groundwater temperature was 28.9 ºC. Thirty-two samples had either temperature or pH values falling outside the range recommended by the World Health Organisation (WHO). Thirty samples had at least one metal concentration exceeding the WHO guideline values. Among the list of elements that exceeded the guideline, arsenic, manganese, nitrate, nitrite and iron were the most predominant. The dominant ions in the samples were sodium and bicarbonate. High concentrations of Fe and SO42- in some parts of the study area point to the influence of acid mine drainage (AMD). Comparisons of results of metal concentrations with findings from previous research in the area showed a reduction in concentration. Hydrochemical modelling with PhreeqC attributed this reduction to sorption processes. Comparison of levels of metal concentration in the different water supply facilities (borehole, hand-dug well and stream) showed no significant variations. Keywords: Water Quality, Drinking Water, Hydrochemical Modelling, Heavy Metal

Mechanism(s) Underlying Interactions Between Cattle Manure and Mineral Fertilizer in a Maize Field Soil in Ghana

A 70-day laboratory incubation study was conducted to unravel the mechanism(s) underlying synergistic interactions between organic and inorganic nutrient inputs to the soil. Soil from a maize farmer's field at Kpongu in the Upper West Region of Ghana was amended with a factorial combination of 0, 50% and 100% levels of the recommended rates (RR) of inorganic fertilizer and cattle manure and incubated at room temperature in plastic cups. Deionized water was added to maintain soil moisture at 70% field capacity throughout the incubation period. Cups were covered with gas-permeable parafilm. Soil sampling was done at 7, 28, 42, 56 and 70 days after incubation. The soil was analyzed for available phosphorus, organic carbon, microbial biomass carbon, nitrates, ammonium, soil urease activity, iron, and copper at each sampling. The addition of 100% RR NPK + 50% RR manure often results in higher amounts of the measured parameters,synergistic interactions and supply of nutrients to the soil, with longer residual effects. While all the under-studied mechanisms (improved nutrient synchrony, priming effects, general fertility improvement fertility) contribute to synergistic interactions, the improved nutrient synchrony mechanism is the most prominent. Farmers can therefore manage the timing of the nutrient inputs well to capitalize on this mechanism for improved soil fertility.&nbsp

Groundwater Vulnerability Assessment using Drastic Index and GIS in Kumasi Metropolitan Assembly, Ghana

The assessment of groundwater vulnerability to contamination has become an important element for landuse planning and groundwater resource management. This study aims at estimating groundwater vulnerability using an integration of Geographic Information System (GIS) and DRASTIC method in the Kumasi Metropolitan Assembly (KMA). The groundwater vulnerability map was prepared using index and overlay analysis with the aid of Arc GIS 10. The DRASTIC Index (DI) computed ranged between 70 and 164 as the lowest and highest contamination potential respectively. The eastern and western flanks and north-west tip of KMA are underlain by the granites which bear water due to the combined effect of weathering and fracturing and are dominated by "Very High", "High" and "Moderate" vulnerability based on the vulnerability index computed. The "Low" and "Very Low" vulnerability are located at the northern, central and southern parts of KMA which are underlain by phyllites. These suggest that boreholes located in the Birimian metasedimentary units which comprise mainly phyllites would be less likely to be vulnerable to contamination than those located in the intrusive rocks dominated by the granites. Keywords: Groundwater Vulnerability, Soil Media, Hydraulic Conductivity, Overlay Analysi