Doha South Sewage Infrastructure Project – Main Trunk Sewer

CEEQUAL Good – Sustainability Performance Assessment Design and Construct Award
Version 5 for Projects, June 2019 | Doha, Qatar

Client: ASHGHAL – Public Works Authority
Designer: AECOM/BYTP
Contractors: BOUYGUES/UCC JV
Sustainability/Environmental Consultant: Jacobs (CH2M)
Project Management Consultant: Jacobs (CH2M)
Assessors: Aza Elnimah and Tim Bell, KEO International Consultants
Verifier: Karl Pitman, Pitman Associates

Doha tunnel

Project Summary

The Doha South Sewage Infrastructure Project is a world class solution to upgrade and expand the sewerage infrastructure in Doha’s oldest area – the south catchment. The purpose is to accommodate the projected population growth for an additional million people. The project is strategic in nature and was developed to change the entire approach to foul sewer drainage in the Doha South catchment from a pumped sewer network to a gravity sewer network. The aim is to address, amongst other things, serious environmental and health issues resulting from undersized and aged sewerage infrastructure.

The Main Trunk Sewer (MTS) is a major element of the Doha South Sewage Infrastructure Project. The MTS is a gravity-based sewerage system that conveys sewage to the Doha South Sewage Treatment Plant (STW). It is designed conservatively to assure that it is self-cleansing during low flows without accumulation of solids, which could otherwise become a maintenance issue. MTS is also sized to meet projected flows for its 100-year design life. MTS has no pumps, valves or any other mechanical or electrical components within the sewer or associated structures. MTS was constructed using Tunnel Boring Machines (TBMs) which required a limited number of shafts, ultimately limiting adverse impacts to the environment.

By addressing and resolving serious environmental and health issues resulting from undersized and aged sewerage infrastructure, the Doha South Sewage Infrastructure Project both supports and contributes to achieving the Qatari National Vision (QNV) 2030. The Qatar National Vision 2030 aims to transform Qatar into an advanced country capable of sustaining its own development and providing a high standard of living for its people.

“The first project to achieve CEEQUAL certification in the Middle East, CEEQUAL has helped the project to set a new benchmark for other projects in the region in terms of sustainability, health & safety, team work, collaboration and innovative solutions”.

Maher Al Ajam,
Programme Director,
JACOBS/CH2M

Benefits of using CEEQUAL

The use of CEEQUAL increased the focus of the project team to be resourceful and efficient in the delivery of the project. In terms of the design, the project team reduced material purchased by optimizing the concrete lining of the shafts in relations to the geotechnical conditions.

What challenges did the project face?

The main challenge in this case was that the CEEQUAL Assessor was engaged after the concept design was complete. Therefore, there were aspects in the design and the evidence documentation that the Assessor could not influence. This was overcome by being very selective with the credits targeted.
Another limitation in terms of ecology and biodiversity was that the project wasn’t permitted by the municipality to improve the landscape as part of the reinstatement plan, everything had to be restored to its exact preconstruction condition. The project team organized a meeting with leading figures of the Public Parks Department to discuss opportunities for improvement to the landscape in future projects and the potential benefits associated.
The final major challenge was benchmarking/setting targets for energy and water. This is a major part of the CEEQUAL assessment and required for some points. This was challenging because the stage at which the CEEQUAL Assessor was engaged and there were no comparable projects in the region with available metrics to be reference. The projects carbon data now serves as a benchmark for future projects.

How did CEEQUAL influence the outcomes of the project? 

CEEQUAL influenced the practice of reducing carbon emissions during construction. The Carbon Footprint Management plan which included various resource efficiency strategies integrated requirements from the CEEQUAL assessment (specifically in section 8 and 9). Had it not been for CEEQUAL material, water, fuel, and waste tracking would not so integral to the reporting process. The urgency to optimize resources and reduce waste would also not be as pressing if CEEQUAL was not used.

“MTS is successful in providing a safe, sustainable, innovative and best-in-class sewage infrastructure, resulting in a higher quality of life for Qatar’s future generations, in alignment with the Qatari National Vision 2030”
Mahmoud Kamal
Environmental Manager
Contractor (Bouygues/UCC- KEO Consultants)

Achievements in Specific Categories 

Project Management

The Programme Management Consultant (PMC), formerly CH2M HILL (now Jacobs) developed the concept and preliminary design of the project based on their extensive international experience and best practices. The PMC carefully specified the materials in the structures to be durable for the maintenance-free 100-year design life in the aggressive sewer environment and Doha’s hypersaline ground conditions. The PMC also managed the development of the environmental impact assessment (EIA) and conducted all forms of stakeholder management.
Upon contract award, both the Contractor (Bouygues) and their designer (AECOM) had their own sustainability procedures implemented into their code of practice. This documented commitment supported the implementation of sustainability throughout the cycle of the project. Furthermore, both the designer and Contractor are ISO14001 certified meaning they each have their own effective environmental management system which lent itself to managing the detailed design and construction of MTS. At the project management level environmental risk and opportunities were identified, recorded, and prioritized according to their significance throughout the course of the project.
Finally, the whole project team understood the innovativeness of this project to the region in terms of ‘sustainability management on mega-projects’. In so, the team actively participated in sharing best practices and lessons learned with fellow members of the civil engineering sector. This was carried out through various media such as newspaper articles, presentations in conferences, and published research papers.

Land Use and Landscape

Due to the nature of the project being a tunnel, the surrounding land uses had a tremendous influence on the route and construction methodology of MTS. An optioneering study was conducted by the PMC whereby ten different route options were presented. The report included a Multi Criteria Decision Making analysis (MCDM) which looked at the environmental and social implications of each of the ten routes. Factors assessed included the characterization of the areas, environmental setting, sensitive receptors, historic land uses, social sustainability aspects, land use efficiency, as well as effects on neighbours. These factors were compiled on a scoring sheet, the scores for each option were assessed by multiple reviewers and the best performing route was selected. Subsequently, a geotechnical investigation was carried out for the selected route which was managed by the PMC. The site-specific subsurface geo-investigation and report ensured the client about the suitability performance of the chosen route. The land use and site selection for the route were rigorously assessed and the best-case scenario route in terms of environmental and social performance was selected. In so, land use efficiency was maximized for the MTS component of the Doha South Sewage Infrastructure Project.

The Water Environment

The design of MTS takes measures to protect groundwater from any potential contamination. The MTS tunnel is designed with three layers of redundancy to prevent leakage including grouting on the outside of the pipe, the pipe itself and an HDPE membrane inside the pipe. The EIA concluded that based on these design features the risk of potential leakage was of ‘no significance’.
In terms of construction, the protection of the groundwater is embedded into the contract. The contract states that ‘active dewatering is not permitted’. This condition had a tremendous impact on the project because it obliged the Contractor to use efficient construction methodologies such as diaphragm walls, vertical shaft-sinking machines (VSM), and grouting in the shaft construction. This significantly decreased the amount of dewatering required for the project ultimately minimizing groundwater depletion.

“The project will provide advanced solutions for transferring sewage water in Doha. The programme is designed to serve the city of Doha and its surroundings, where 90% of Qatar’s population resides. The city has seen a rapid population growth over the last few years, which necessitated the expansion of its sanitation system. We’re glad to have delivered a project which speaks to Qatar’s investment in building a sustainable future.”
Daniel Clert
Director of Construction
Contractor-Bouygues

Physical Resources – Use and Management

Energy

During the construction process the Contractor maximized opportunities to use energy efficiently. A Carbon Footprint Management plan (CFM) was produced and incorporated into the CEMP. The CFM included strategies to reduce overall energy consumption such as the selection and maintenance of efficient generators on site. Other strategies that were implemented were, the use of lithium ion batteries for the TBMs, the use of solar panels to operate all cameras on site, and the use of LED lighting in tunnel. Furthermore, fuel was tracked and reported on a monthly basis in order to benchmark the project and study trends.

water

Through its design, the MTS eliminates the use of water during operation. The MTS replaces the existing sewage pumping stations with a gravity-based sewage system. The MTS adequately conveys low flows without accumulation of solids and is simultaneously self-cleaning. The MTS has no pumps, or valves within the sewer or associated structures.

During the construction process, specific and measurable requirements were implemented to minimize the projects impact on water resources. Within the site offices, flow and flush fixtures were all low-flow and plastic bottles were completely banned.

Water was efficiently used for construction activities. As per the Dewatering Management Plan and the Water Quality Control Plan, dewatered water was treated and reused in order to minimize the use of potable water. A primary and secondary lagoon were set up on site to facilitate the groundwater treatment, reuse, and disposal process. Treated dewatering effluent was mainly reused for dust suppression, concrete curing, soil compaction, cleaning, as well as tunnel boring and grouting.

Furthermore, in order to maximize the efficient use of water the contractor collected and reused rainwater onsite. Rainwater was also collected by gravity into two underground tanks which were equipped with oil separators. The collected water was then pumped into a tanker and moved to the primary lagoon whereby it went through the same treatment process as groundwater. After this process, the rainwater was reused on site.

Materials

To achieve the required maintenance free design life of 100 years, the tunnel support system originally comprised a precast concrete segmental lining with a separate corrosion protection lining (CPL) comprising of a 250-mm thick sacrificial cast-in-place concrete layer integral with a HDPE membrane. The project adopted however an innovative lining system for big tunnel sewers by combining the segmental lining and CPL. This achieved a significant concrete lining thickness reduction of 200 mm, along with an associated reduction in the excavation diameter of 445 mm, which led to a 20% decrease in spoil to handle.
The tunnel segments and access shaft risers were all prefabricated and locally manufactured near the project site. Prefabrication provided precision in terms of material procurement and waste reduction.
Lastly material forecasts were carried out and reported on a monthly basis. The end of the project report shows that the planned quantities and actual quantities for major materials were consistently aligned throughout the duration of the project. The CEMP included logistic plans to support the material management approach such as transportation, laydown areas, and waste management.

Transport

The project is completely below ground and will have no impact on traffic in the operational phase. Nonetheless, measures were put in place during the construction phase to both minimize the traffic impacts on the local community and discourage car usage whilst commuting to work for staff.
The Contractor assigned specific routes and times of day for the transport of materials which was captured in the CEMP. Entrances to the project sites and diversion plans were arranged in a manner that they do not disturb the local community; this is captured in the Traffic Management Plan. From the onset of the project, site office staff were surveyed about their office commuting patterns and encouraged to carpool in groups based on the findings. Potential carpooling opportunities were identified and encouraged where possible. Lastly, during the winter months, the Contractor launched a ‘Bike to Work’ initiative whereby staff were incentivized with helmets and bike lights if they cycled to work. Staff were also permitted access an on-site shower if they cycled to work. The ‘bike to work’ initiative was promoted through posters and emails.

Metrics

Embodied carbon emissions 12,985,579 kgCO2 equivalent 16.8 % reduction achieved
Operational renewable energy potential Not applicable to MTS project since no energy is required when the project is operational.
Re-used material Generally, not tracked for the MTS however all excavated spoil (715,324 tonnes) will be reused for backfill on other Ashghal projects or for construction of berm around the NDS STW site.
Recycled material Not tracked for the MTS project.
Locally supplied material 153,808.42 m3 100 % of total material used
Potable water usage in construction 122,211 m3 34 % of total water usage
Potable water usage in operation Not applicable to MTS project since no water is required when the project is operational.
Waste diverted from landfill 26,317 m3 48 % of total waste