Arjo Dedessa Irrigation Project Feasibility Study Summary
Project Overview
Project: Arjo Dedessa Irrigation Project Feasibility Study
Client: Federal Democratic Republic of Ethiopia - Ministry of Water Resources
Date: May 2007
Consultants: Water Works Design & Supervision Enterprise in association with Intercontinental Consultants and Technocrats India Pvt. Ltd.
Report Structure
| Volume | Content |
|---|---|
| Volume I | Survey and Investigation (Annexures 1-3) |
| Volume I(a) | Topographic Survey, Geomorphological Studies & Geological & Geotechnical Investigation (Part I - Report) |
| Volume I(b) | Geological & Geotechnical Investigation (Part II - Appendices) |
| Volume II | Natural Resources (Forestry, Energy & Catchment Development Plan) |
| Volume III | Water Resources (Meteorological, Hydrological & Hydrogeological Studies, Dam & Appurtenant Works, Hydraulic Structures) |
| Volume IV | Agriculture (Soil Survey, Land Evaluation, Agricultural Planning, Livestock, Fisheries, etc.) |
| Volume V | Environmental and Socio-Economic Aspects |
Geological & Geotechnical Investigation Appendices
| Appendix | Content |
|---|---|
| A | Bore Hole Logs |
| B | Photographs of Core |
| C | Field Permeability Tests |
| D | Variable Head Test |
| E | Test Pit Log |
| F | Laboratory Test Results |
| G | Geophysical Investigation |
| H | Piezometer Installation Detail |
Key Findings from Borehole Investigations
The document contains detailed borehole records from multiple locations including:
- Dam axis (left and right banks)
- Original spillway
- Saddle dam axis
- Quarry site
Example Borehole Data (AD4 - Right bank, Dam axis)
| Depth (m) | Strata Description |
|---|---|
| 27.00 | Pinkish grey, moderately weathered, highly fractured, medium strong vesicular TRACHYTE |
| 28.00 | Greenish grey, highly weathered and friable weak TRACHYTE |
| 29.00 | Light grey to pinkish, moderately to highly weathered, highly fractured, weak to medium strong porphritic TRACHYTE |
Discontinuity Report Findings
The discontinuity report identifies various fracture zones and joint patterns in the rock formations, including:
- Closely spaced joints
- Incipient fractures
- Fracture zones with various apertures
- Mineral-filled joints (calcium, gypsum, iron staining)
Permeability Test Results
The document includes numerous Lugeon tests and variable head permeability tests with results such as:
| Borehole | Test Depth (m) | Lugeon Value | Permeability (cm/sec) |
|---|---|---|---|
| AD2 | 3.80-13.40 | 26 (average) | - |
| AD3 | 14.00-17.00 | 3.88 (average) | - |
| AD3 | 5-8 | - | 5.53E-04 |
| AD6 | 5-8 | - | 5.19E-04 |
Core Photographs
The report includes extensive photographic documentation of core samples with:
- Yellow color blocks indicating samples taken for laboratory testing
- Red color blocks indicating core loss areas
- Detailed depth markers for each core section