Technical Consultancy Services for the "Chalkida Bypass and Psachna Bypass" Project

The first phase of the project has been successfully completed. It involved the provision of technical consultancy services for the assessment of the stormwater drainage and road drainage infrastructure along the highway corridor. Consortis contributed to the technical substantiation of the proposed solutions, the review of their completeness and compatibility, and the identification of critical issues affecting the project’s safe and effective operation.

The services covered all Geographical Sections of the project, extending from the North–South Evia Connecting Arterial Road to the optional Psachna Bypass section, including the dedicated flood protection infrastructure at Lake Doko.

The Challenge

The alignment traverses catchments exhibiting diverse hydrological and geomorphological characteristics, encompassing multiple drainage basins, natural watercourses, and receiving water bodies with varying hydraulic constraints. Limited natural discharge capacity in specific locations, combined with the need to safeguard the roadway against inundation and ensure efficient stormwater management, required an integrated assessment of the drainage and flood mitigation infrastructure.

The solution 

A comprehensive technical review was undertaken for all hydraulic works, structured by Geographical Section and functional asset category. The assessment included the evaluation of watershed delineation, receiving water body conditions, hydraulic interactions between individual drainage components, and compliance with the Greek Road Design Guidelines (OMOE-ASYEO).

The review specifically covered:

• Cross-drainage structures, including reinforced concrete box culverts and pipe culverts.
• Longitudinal drainage infrastructure, including roadside ditches, stormwater pipelines, and subsurface drainage systems.
• Specialized drainage systems for tunnels, interchanges, and deep cuttings.
• Slope protection, erosion control, channel stabilization, and watercourse rehabilitation works.
• Flood protection infrastructure at Lake Doko, including the detention basin, pumping station, rising main, and outlet structure.

Particular emphasis was placed on verifying the consistency of the hydraulic design philosophy, including the adopted design return periods of 50 years for cross-drainage structures and 25 years for longitudinal drainage systems, as well as confirming the hydraulic adequacy of reinforced concrete box culverts under the 100-year design storm. Hydraulic analyses were reviewed based on the continuity equation and the Manning–Strickler flow resistance formulation, ensuring consistency with accepted hydraulic engineering practice.

Project Benefits

The consultancy services supported the technical verification and maturation of the hydraulic design, contributing to:

• Improved completeness, robustness, and technical consistency of the hydraulic studies.
• Verification of compliance with applicable design standards, technical specifications, and regulatory requirements.
• Enhanced technical readiness of the project prior to implementation.

Through an independent technical review and specialized hydraulic engineering consultancy, Consortis delivered significant added value to a complex transportation infrastructure project, strengthening both roadway resilience and flood risk mitigation while supporting the long-term operational safety and reliability of the highway corridor.