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Home>>Diagnosis and rehabilitation of the Macarez Valenciennes wastewater treatment plant

Diagnosis and rehabilitation of the Macarez Valenciennes wastewater treatment plant

Rehab STEP Macarez Valenciennes - Le film

Altereo was commissioned in early 2014 by the Syndicat Intercommunal d’Assainissement de Valenciennes (SIAV) to carry out a civil engineering diagnosis of the Macarez Valenciennes wastewater treatment plant (WWTP) to determine which installations would be retained as part of the station’s rehabilitation project. The mission was renewed for the Project Management phase of the rehabilitation of the WWTP.

An exemplary project for the management of complex works in continuity of service, under permanent drawdown of the water table and within tight deadlines, which has now been successfully completed and is the pride of our teams.

Meeting of Altereo and SIAV

The Valenciennes conurbation in the North of France has been committed for more than twenty years to a modernisation process with the idea that the future can only be prepared for by integrating the four pillars of sustainable development at all levels of its action: economy, environment, social and governance.

In 2010, this approach led to the development of ATHENA 2020 objective, a demonstrator of the sustainable city of Valenciennes. The Syndicat Intercommunal d’Assainissement de Valenciennes (SIAV), a major player in the implementation of the demonstrator, had the ambition to place, at the centre of this large-scale sustainable urban development project, the construction of a new wastewater treatment plant with a capacity of 160 000 inhabitants, extendable to 200 000 inhabitants.

This facility was intended to be resolutely futuristic, almost utopian since it is a zero-waste and positive energy facility, with eco-construction criteria anticipating future standards, very low-cost operation, maximum use of the energy produced, and integration of the social aspect of sustainable development, a World-first..

The main idea was to fight against energy insecurity in the Valenciennes region by recovering fatal energy sources, in particular by recovering heat from raw and treated water and by validating a new model of waste water treatment that would reduce the user’s bill. The project’s budget was around €50 million excluding tax.

This project, matured over nearly 15 years, led to the creation of a jury in 2013 to participate in the devolution of the works within the framework of a European call for tenders. Altereo was a member of this jury, where its Business Director for Asset Management and Works, Denis Savoye, sat as a expert engineer in civil engineering for the water sector and a voting member.

At the beginning of 2014, following a change in governance, this ambitious project was abandoned in favour of a complete rehabilitation of the Valenciennes Macarez wastewater treatment plant.

The Macarez Valenciennes wastewater treatment plant

Altereo was commissioned in early 2014 by the Syndicat Intercommunal d’Assainissement de Valenciennes to carry out a civil engineering diagnosis of the works of the existing Macarez Valenciennes WWTP in order to determine which installations would be part of the station’s rehabilitation project.

This WWTP with a nominal capacity of 70 000 inhabitants, up to 100 000 inhabitants at peak, is of the activated sludge type and includes 2 biological treatment lines, i.e. 2 aeration basins and 2 clarifiers. Altereo carried out the field investigations while the works were in service (the diagnosis was carried out on the external emerged parts).

STEP Macarez - image1
STEP Macarez - image3

The diagnostic report on the civil engineering of the Valenciennes WWTP was submitted at the beginning of September 2014. Altereo offered to complete the diagnosis by examining a line that had been emptied for the occasion (operation of the WWTP in degraded mode).

A new mission was therefore entrusted to Altereo. The SIAV had decided to set up a revolutionary process on an experimental basis in a clarifier and thus to empty the works on a biological line to carry out this mission.

STEP Macarez - image6
STEP Macarez - image4

At the same time, the SIAV wished to launch the project management for the rehabilitation of this WWTP of Macarez Valenciennes.

This complex work (civil engineering and equipment upgrading) and involving multiple partners was to be completed before the end of 2015 and allow the facility to operate normally until 2030, the end of the depreciation period. Altereo won the call for tenders for this new mission, which is exceptional in terms of its complexity and the extremely risky timeframe for the studies and work.

Complexity of the operation

A continuous service and permanent lowering of the water table, within a tight deadline, made the work complex, involving: the application of a synthetic binder waterproofing coating on the pre-treatments, crack injections, replacement of reinforcement, resumption of superficially degraded concrete, hydro-demolition, reinforcement additions, shotcrete, and general protective coatings.

STEP Macarez - image7
STEP Macarez - image10

Complementary mission

Mission of research and analysis of documents related to the construction and the previous expertises concerning the respect of the existing design and execution rules during the construction of the clarifiers of the wastewater treatment plant.

After observation of a significant degradation of the civil engineering at the level of the sails of the 2 clarifiers built in the 1990s (presence of numerous vertical cracks and spalling with reinforcement corrosion spectra on the external facings of the emerged parts of these sails (above the natural ground) and the diagnosis carried out in 2014, revealing undersizing at the level of the outer layer of the sail of each clarifier, the SIAV decided to establish a more precise diagnosis of the undersizing and, at the same time, to check whether design and implementation faults had been found so as to enable it to make a claim against the original manufacturer of these structures if necessary.

The SIAV therefore entrusted Altereo with a mission to support the precise survey of the constructive provisions on the walls of the two clarifiers.

This survey was carried out in two phases during the partial hydro-demolition operations of the sails carried out as part of the civil engineering rehabilitation operation.

Interview Veronique Dupire SIAV

Véronique Dupire, President, SIAV

Interview Hakim Haïkel SIAV

Hakim Haïkel,  service manager, SIAV

Interview Denis Savoye Altereo

Denis Savoye, business manager, Altereo

A look back at this complex project management

The civil engineering rehabilitation of the Valenciennes MACAREZ 100,000 population equivalent wastewater treatment plant is finally completed. This project, which was carried out in continuity of service, with permanent drawdown of the water table, was carried out on behalf of the Valenciennes Intercommunal Sewerage Syndicate (SIAV), the installation being managed by GESAV (Saur). The BALESTRA/IVEBAT consortium carried out the work.

The complex project was managed by GESAV (Saur). The minimum objective for the durability of the rehabilitation is 25 years.

This operation, costing more than €2 million (excluding VAT), was carried out by Altereo’s Hauts-de-France agency, with exemplary rigour and team involvement, under the supervision of the Property Management Department.


Criteria Quanttity Unit
Duration of implementation studies 15 weeks
Duration of the work 12 months
Maximum number of employees 23 people
Average man-days 11
Number of simultaneous workstations 6 U
Repair mortar 35 Tons
Hydrodémolition de béton 65
Shot concrete 380 Tons
Cast concrete 65
Length of treated cracks 520 ml
Laminated organic binder coating 400
Number of meetings 52 U
Number of stopping points 48 U
Final cost 2 000 000



“This has initiated a real sense of partnership within the utility-project manager-constructor triad”

Hakim HAIKEL, service manager

Diagnosis of the civil engineering of the WWTP at Macarez (100,000 P.E.)
Project support for rehabilitation (2M€ of work, 190K€ of project support)

The SIAV (Valenciennes) is confronted with a preponderant issue concerning the integrity of its sanitation system with the prolongation of the service life of its treatment plant at Valenciennes (100,000 P.E.). Several civil engineering infrastructures suffer from major disorders and require rehabilitation using sophisticated techniques.

To this end, the SIAV assigned Altereo the mission to conduct diagnosis studies and to carry out project support. The Altereo team of Hauts-de-France, backed up by the expertise of Denis SAVOYE, was able to produce high-quality output by carrying out project studies and preparing tender documents for enterprises, in particular the production of the technical specifications from scratch, which is very rare. The pathologies encountered were identified and addressed with technical responses guaranteeing the required additional service life of at least 20 years.

The follow-up of the execution studies and the works in progress is ongoing with an increased presence and an always relevant analysis of the vagaries of site. The work contract resulting from the studies being clear and balanced, a real partnership has been established within the utility–project manager–constructor triad ensuring the success of the rehabilitation operation.