2.1 Assessment of borrow pits excavation Method
Field investigations covering the environs of Ado Ekiti were undertaken to study some geo-environmental impacts as a result of borrow pits. Four borrow pit sites were identified in some areas of Ado-Ekiti, Ekiti State and were each investigated by direct measurements and use of photographs. Two of the borrow pits are active and identified as BPA1 and BPA2 while the other two are abandoned and identified (Inactive) as BPI1 and BPI2. A reconnaissance visit was initially made to the sites and other features around sites for proper observations and survey to determine the normal state of the sites during mining (for active sites) and after mining has been done (for abandoned sites). Continual removal of soil and the three-dimensional state of the borrow pits were measured and modelled. Also, the longitude coordinates, latitude coordinates and elevations of the pits were measured with E-Trex Geographic Positioning System () and recorded. The height of the borrow pits at different points were measured using levelling instrument and the average height of the pit was determined. Photographs of the four sites and areas around the sites with the infrastructures (buildings, roads near the site) present were taken. The potential environmental impacts and hazards such as landslides, debris flow, erosion, flood and runoff pool of both the active and abandoned borrow pits were also assessed through visual inspection and photographs taken.
Data generated by the GPS were used to generate 3D maps for the sites using surfer software and AutoCAD. The data retrieved from the maps were then used to determine the volume of overburden that has been excavated from the borrow pits using Equation 1. The maps generated were used to calculate for the areas and volumes of the borrow pits.
\(p\left(z\right)=p_{o}+g\int_{o}^{z}{\rho\left(Z\right)\text{dz}}\)(1)
The average depths (Z) for each of the pits were measured at different points to get the soil overburden. Soil samples were collected from each of the sites to determine some geotechnical properties of the soils.

2.2 Determination of Borrow Pit Area and Volume

The shape of the borrow pit is not a regular manner. Therefore, to calculate their area and volume, different points around the borrow pit were gotten and used to create a diagrammatic representation of the surface of the pit using AutoCAD software. The area was calculated both manually and automatically using the scissors principle (or scissors method) and AutoCAD respectively. The scissors method is diagrammatically represented in Fig. 1.
Area of borrow pit is thus calculated as:
\(C=\frac{A\ +\ B}{2}\) (2)
Where A is the\(\sum{Northing\times Easting\ of\ arrows\ facing\ right}\ \)
Where B is the\(\sum{Northing\times Easting\ of\ arrows\ facing\ left}\ \)
Where C is the Area of selected borrow pit.
Volume of borrow pit is thus calculated as:
V = C * \(h\) (3)
Where \(h\) is the difference of the average height at the top of the borrow pit and the average height of the bottom of the borrow pit
Volume of water pooled into the borrow pit is calculated
\(V=A*D\) (4)
The coordinates (i.e. longitudes and latitudes), elevations and heights of both the active and abandoned (inactive) borrow pits identified as BPA1, BPA2, BPI1 and BPI2 respectively are presented in Tables 1 and 2.