Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia

Kirubel Molla Bazezew; Wahaj Khan; Belay Sitotaw Goshu

doi:doi:10.11648/j.sdenv.20260102.11

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Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia

Kirubel Molla Bazezew

, Wahaj Khan, Belay Sitotaw Goshu^*

Published in Science Discovery Environment (Volume 1, Issue 2)

Received: 5 February 2026 Accepted: 24 February 2026 Published: 5 March 2026

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Abstract

The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.

Published in	Science Discovery Environment (Volume 1, Issue 2)
DOI	10.11648/j.sdenv.20260102.11
Page(s)	110-131
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Basalt Foundation, Deep Weathering, Seepage Control, Foundation Treatment, Risk-based Optimization

References

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APA Style

Bazezew, K. M., Khan, W., Goshu, B. S. (2026). Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Science Discovery Environment, 1(2), 110-131. https://doi.org/10.11648/j.sdenv.20260102.11

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ACS Style

Bazezew, K. M.; Khan, W.; Goshu, B. S. Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Sci. Discov. Environ. 2026, 1(2), 110-131. doi: 10.11648/j.sdenv.20260102.11

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AMA Style

Bazezew KM, Khan W, Goshu BS. Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Sci Discov Environ. 2026;1(2):110-131. doi: 10.11648/j.sdenv.20260102.11

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@article{10.11648/j.sdenv.20260102.11,
  author = {Kirubel Molla Bazezew and Wahaj Khan and Belay Sitotaw Goshu},
  title = {Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia},
  journal = {Science Discovery Environment},
  volume = {1},
  number = {2},
  pages = {110-131},
  doi = {10.11648/j.sdenv.20260102.11},
  url = {https://doi.org/10.11648/j.sdenv.20260102.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sdenv.20260102.11},
  abstract = {The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.},
 year = {2026}
}

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TY  - JOUR
T1  - Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia
AU  - Kirubel Molla Bazezew
AU  - Wahaj Khan
AU  - Belay Sitotaw Goshu
Y1  - 2026/03/05
PY  - 2026
N1  - https://doi.org/10.11648/j.sdenv.20260102.11
DO  - 10.11648/j.sdenv.20260102.11
T2  - Science Discovery Environment
JF  - Science Discovery Environment
JO  - Science Discovery Environment
SP  - 110
EP  - 131
PB  - Science Publishing Group
UR  - https://doi.org/10.11648/j.sdenv.20260102.11
AB  - The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.
VL  - 1
IS  - 2
ER  -

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Author Information

Kirubel Molla Bazezew

Department of Geology, Dire Dawa University, Dire Dawa, Ethiopia

Contact Email

http://orcid.org/0009-0004-4918-4338
Wahaj Khan

School of Civil and Architecture Engineering, Dire Dawa University, Dire Dawa, Ethiopia
Belay Sitotaw Goshu

Department of Physics, Dire Dawa University, Dire Dawa, Ethiopia

Contact Email

http://orcid.org/0000-0002-6887-7218

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APA Style

Bazezew, K. M., Khan, W., Goshu, B. S. (2026). Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Science Discovery Environment, 1(2), 110-131. https://doi.org/10.11648/j.sdenv.20260102.11

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ACS Style

Bazezew, K. M.; Khan, W.; Goshu, B. S. Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Sci. Discov. Environ. 2026, 1(2), 110-131. doi: 10.11648/j.sdenv.20260102.11

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AMA Style

Bazezew KM, Khan W, Goshu BS. Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia. Sci Discov Environ. 2026;1(2):110-131. doi: 10.11648/j.sdenv.20260102.11

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@article{10.11648/j.sdenv.20260102.11,
  author = {Kirubel Molla Bazezew and Wahaj Khan and Belay Sitotaw Goshu},
  title = {Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia},
  journal = {Science Discovery Environment},
  volume = {1},
  number = {2},
  pages = {110-131},
  doi = {10.11648/j.sdenv.20260102.11},
  url = {https://doi.org/10.11648/j.sdenv.20260102.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sdenv.20260102.11},
  abstract = {The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.},
 year = {2026}
}

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TY  - JOUR
T1  - Geotechnical Site Investigation and Foundation Characterization for the Legeoda Earth Dam, Dire Dawa, Eastern Ethiopia
AU  - Kirubel Molla Bazezew
AU  - Wahaj Khan
AU  - Belay Sitotaw Goshu
Y1  - 2026/03/05
PY  - 2026
N1  - https://doi.org/10.11648/j.sdenv.20260102.11
DO  - 10.11648/j.sdenv.20260102.11
T2  - Science Discovery Environment
JF  - Science Discovery Environment
JO  - Science Discovery Environment
SP  - 110
EP  - 131
PB  - Science Publishing Group
UR  - https://doi.org/10.11648/j.sdenv.20260102.11
AB  - The Legeoda Dam project, proposed in eastern Ethiopia’s Dire Dawa region on the Halo Busa Lege Odamirga watershed, aims to provide irrigation water for downstream agricultural development. This geotechnical feasibility study addresses foundation challenges associated with deep tropical weathering of Oligocene flood basalts overlain by uniform alluvial deposits. Twelve boreholes along the 520 m dam axis, supported by extensive laboratory testing (index properties, shear strength, compressibility, permeability) and in-situ SPT, revealed a consistent stratigraphic sequence: 1.5 m topsoil, 2.5 m clay, 4.0 m sandy silt, 7.0 m highly weathered basalt, 10.0 m fractured basalt, and sound basalt below ~25 m depth. Key findings include uniform overburden thickness (39.9–40.1 m), progressive strength increase with depth (SPT N = 5.5–78.8), high untreated settlement potential (6251 mm), and significant seepage risk through fractured basalt. Seepage, stability, and settlement analyses confirmed technical viability following targeted foundation treatment. Novel contributions include quantitative risk-based treatment optimization and cost-benefit evaluation specific to Ethiopian basalt terrains, demonstrating benefit-cost ratios exceeding 3.0 for integrated cutoff and grouting measures. The study concludes that the site is highly suitable for a zoned earth-rock embankment dam with standard foundation improvements. Recommendations emphasize deep cutoff penetration into sound basalt, selective grouting, and comprehensive instrumentation. This work advances sustainable dam development on flood basalt foundations in rift-margin settings.
VL  - 1
IS  - 2
ER  -

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