**12. Case studies: application of electrical and very low frequency electromagnetic method to pre-construction investigations**

#### **12.1 Site descriptions, geomorphology and physiography**

The study area as shown in **Figure 1** is located within Igarra, Southwestern Nigeria expressed in Universal Traverse Mercator (UTM) Zone 3, and the study area is located within Northings 807054 mN and 807265 mN and Eastings 179000 mE and 179210 mE. The landforms are of two main groups, the high hills which are found in the north-eastern part of Igarra, while the other is low lying around north-western and south-western part of Igarra. The Igarra area is made up of untarred roads, footpaths, rivers, the tributaries converges at the point to form rivers which flows along the strike direction of the outcrops in the area.

#### **12.2 Brief geology of the study area**

Three major rocks overlie the basement complex in the Igarra area. The successions of the rocks are namely;

• Granodiorite which are rich in biotite and hornblende, diorite which are unmetamorphosised pegmatite which has large quartz clasts.

*Geophysical Investigations for Design Parameters Related to Geotechnical Engineering DOI: http://dx.doi.org/10.5772/intechopen.108712*

#### **Figure 1.** *Data acquisition map of the study area.*


The sequence of rocks in the Igarra area is made up of four main groups which includes Calc-silicate gneiss and marble, Metaconglomerate, Mica-schist and Quartzbiotite schist
