Geophysical and Hydrogeological Investigation Report
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GEOPHYSICAL AND HYDROGEOLOGICAL INVESTIGATION REPORT St Peters Catholic Church- Upendo in Kangawa, P.O. Box 230, Molo. Through The Catholic Diocese of Nakuru, through the Nakuru Defluoridation Co. Ltd P.O. Box 2943 - 20100 Nakuru Plot LR No.; …………………… Kangawa-Upendo Village, Kangawa Sub-Location, Kuresoi North Location, Mau Summit Division, Molo Sub-County, Nakuru County. Topo Sheet No.; 118/2 CONSULTANT: Samuel Munyiri, BSc, MSc. (Hons) R. Geol. (Registered Hydrogeologist; Licence No. WD/WP/254) P.O. Box 798-10101, Karatina. Cell-phone: 0723 623 766 E-mail: [email protected] Signed:_________________________________ Date:___________________________________ June, 2018 Hydrogeological and Geophysical Report St. Peters Upendo Catholic Church EXECUTIVE SUMMARY Introduction This report presents the findings of a geophysical and hydro-geological assessment carried out for St Peters Upendo Catholic Church-Kangawa on their 2 Acre parcel of land located in Kangawa Village, Kangawa Sub-Location, Kuresoi North Location and Mau Summit Division in Molo Sub- County of Nakuru County. The farm is located off the Molo-Londiani tarmac road section – at a distance of about 8km from Molo Town on the right hand side of this main road. The land can be accessed at the Kangawa Primary School junction and is about 1.8km west of this junction along a dry weather road. Water Demand and Use Kangawa-Upendo community is not served by any source of portable piped water, which would imply a near absence water supply on the client’s land. Apart from private boreholes and shallow wells in the area, there is no other feasible water supply. The community therefore relies on shallow wells, which have contaminated water due to percolation of fecal material from pit latrines. Residents with private borehole sell water to the community, making it unaffordable to the less fortunate. There is thus the need to provide a sufficient and reliable water supply to the farm to meet a domestic input estimated at 20.0m3/day. The Catholic Diocese of Nakuru, through the Nakuru Defluoridation Co. Ltd has partnered to sponsor a borehole facility and water reticulation system to the Kangawa-Upendo community. Geology Tertiary and Quaternary volcanics and sediments are the most dominant formations in the Mole area and basically in the entire Rift Valley region. The rift margins expose an older sequence of Trachytic and pyroclastics. Mau tuffs are exposed in the south and west of the Molo area. These materials comprise the majority of the Mau succession and are of unknown thickness. They represent a prolonged period of pyroclastic activity combined with a moist climate leading to fluviatile, mud-flow and lake bed deposits. Recent pyroclastics and sediments of the Mau Slope cover the Molo and Elburgon areas at surface, extending down onto the Rongai Plain to the east of the Molo area. Hydrogeology This groundwater potential investigation carried out on this part of the Kangawa area identifies two potential water bearing zones. There is the possible water strike associated with the sediment aquifer, whereas the other aquifer is associated with the fractured systems of the volcanic lithology. The lowlands suffice, as the recipients of terminal waters from the Mau catchments-due to the low topographical setting and in relation to the dip of the volcanic rocks; that would tend to push their terminal flows into the fractured and faulted rift floor rocks and lake sediments. The bulk of the groundwater supplies will have to be derived from the sediments that lie between different strata of the volcanic rocks. Conclusion and Recommendations It is thus recommended that a borehole be drilled at the location of VES 2 with UTM coordinates 36M 0799758m E and 9976624m N and, degrees 00° 12’ 39.6” S & 35° 41’ 33” E, with an altitude of 2595m to a minimum depth of 150m to a maximum depth of 200 metres. It is a mandatory requirement to obtain the necessary pre-requisite permits from the Water Resources Authority (WRA) and Water Resource Users Association (WRUA) prior to the commencement of the drilling program. There are two boreholes that are within the 800m radial distance to the proposed borehole. To avoid aquifer interference, we recommend that the proposed borehole be drilled to a deeper depth of 150-200m. Shallow aquifers above 90m should be sealed off to avoid aquifer sharing and subsequent depletion. May - 2018 II Kangawa Area, Molo Sub-County Hydrogeological and Geophysical Report St. Peters Upendo Catholic Church TABLE OF CONTENTS EXECUTIVE SUMMARY .............................................................................................................. II LIST OF ABBREVIATIONS AND GLOSSARY OF TERMS ........................................................ 1 1. BACKGROUND INFORMATION ......................................................................................... 3 1.1 Location ........................................................................................................................................................ 3 1.2 Objectives of the Survey ............................................................................................................................ 3 1.2 Climate, Drainage and Physiography .............................................................................................................. 4 1.3 Water Demand and existing water supplies. .................................................................................................. 5 2.0 PROJECT APPROACH AND METHODOLOGY .................................................................... 6 3.0 GEOLOGY .................................................................................................................................. 7 3.1 Regional Geology of the area. ...................................................................................................................... 7 3.2 Geological Succession ....................................................................................................................................... 7 3.6 Geological Structures ........................................................................................................................................ 8 4.0 HYDROGEOLOGY .................................................................................................................... 9 4.1 Surface Water Resources............................................................................................................................ 9 4.2 Groundwater System. ...................................................................................................................................... 10 4.2.1 Rainfall, Percolation and Recharge ....................................................................................................... 10 4.2.2 Mau Escarpment Faults and Hydrogeology: .................................................................................... 11 4.2.3 Borehole Data ...................................................................................................................................... 11 4.4 Groundwater Storage, Recharge and Discharge ......................................................................................... 12 4.5 Aquifer Parameters in the Study Area .......................................................................................................... 12 4.5.1 Transmissivity ........................................................................................................................................... 13 4.5.2 Hydraulic Conductivity ........................................................................................................................... 13 4.5.3 Safe Yield................................................................................................................................................... 14 4.5.4 Specific Capacity and Specific yield/storage coefficient ................................................................... 14 4.5.6 Groundwater Flux/recharge and Discharge Dynamics .................................................................... 15 4.5.7 Recharge .................................................................................................................................................... 15 4.5.8 Discharge ................................................................................................................................................... 15 4.6 Groundwater Quality ...................................................................................................................................... 15 5.0 GEOPHYSICAL INVESTIGATION METHODS ............................................................ 18 5.1 Resistivity Method ........................................................................................................................................... 18 5.2 Basic Principles ................................................................................................................................................. 18 5.3 Vertical Electrical Sounding (VES) ............................................................................................................... 19 5.4 Horizontal Resistivity Profiling...................................................................................................................... 19 5.5 Field Work .......................................................................................................................................................