Water

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Client

Department of Environment and Natural Resources, Venezuela, South America

Scope of Work

Engineering, procurement, construction management, project financing.

Dessau completed a wastewater treatment project in the municipalities of Píritu, Puerto Píritu, Barcelona, Lechería and Clarines, in the state of Anzoátegui. The project included the construction or rehabilitation of 12 pumping stations, a surge chamber, two ocean outfalls (1 and 4-km) and a primary treatment plant, as well as the installation of pressurized and gravity

pipes with diameters ranging from 250 to 750 mm. The services provided by Dessau included making credit arrangements, conducting environmental and social studies, design, procurement, work supervision and comprehensive management of the project and the construction work.

Challenges

Install a sewer network below sea level.
Develop a construction and assembly methodology for the outfalls, accounting for strong ocean currents.

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Client

National Dams and Transfers Agency (ANBT), Algiers, Algeria

Scope of Work

Review the design, control and supervision of construction work.

With a capacity of 20 million cu. ft./d, the Sidi Lahdjel potable water plant is Algeria’s second largest. It is part of a major water transfer project that will provide drinking water to residents of the Mostaganem-Arzew-Oran corridor.

The plant has eight desilting units, a cascade aerator, six settling tanks, a 205,000-cu. ft. chlorination chamber and a 3.6 million-cu. ft. reservoir.

Challenges

Organize a complex, large-scale project.
Work simultaneously with another major project on the same site.

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Client

City of Montreal, Montreal, Canada

Scope of Work

Engineering, procurement, construction management.

The City of Montreal launched a major modernization and standards-compliance upgrade program for its water infrastructure – a colossal project that will take more than a decade to complete. After Dessau’s professionals conducted a number of studies, the City decided to make the Atwater, Charles-J Des Baillets and Pierrefonds water treatment plants their top priorities.

These two plants are among the largest in North America, with a combined daily output of 88 million cu. ft. of potable water.
Dessau is providing the preliminary studies, plans and specifications, project management, procurement, construction management, supervision and commissioning services.

Challenges

Maintain water production during works.
Offer a selection of technical solutions, taking into account construction and operation costs, as well as the cost of implementaing the solution in an operational plant.

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Client

City of Laval, Laval, Canada

Scope of Work

Engineering, procurement, construction management, operations.

The La Pinière water treatment plant helped restore the ecological potential of the Des Prairies River, a major tributary of the St. Lawrence River.

Treating an average of 8.5 million cu. ft. per day, this plant serves more than 280,000 people. Its maximum capacity is 21 million cu. ft. per day – equivalent to 200 Olympic-size pools.

The physical/chemical plant includes components for water disinfection, odour treatment and sludge treatment.

It also features one of the biggest lift stations in North America (98 feet deep with 16 submersible pumps and a unit capacity of 500 l/s). The 25-35 tonnes of sludge produced daily are dried then sold in granular form as fertilizer or industrial fuel.

In addition, Dessau has managed and operated the plant for over ten years.

Challenges

Complete the plant in fast-track mode over a 3-year period.
Cost-effective measures helped save $5 million on construction costs.
Respect emissions standards despite the fact that suspended particulate matter amounts were higher than expected.

Client

Rio Tinto Iron and Titanium; Tio Mine, Havre-Saint-Pierre, Canada

Scope of Work

Hydrogeological and geophysical study of the Tio open-pit mine.

Dessau’s mandate was to address two of the mine’s needs. The first component was to produce a hydrogeological model of the entire mine, define the groundwater flow dynamic and characterize the water quality of sub-surface effluents. The second component involved determining hydrogeological conditions of the open pit in order to define their effects on the stability of the rock walls.

Geophysical logs and constant-load injection tests made it possible to assess the degree of fissuration and the hydraulic properties of the rock mass. Dessau’s team was then able to demonstrate the need for active drainage through the creation of deep pumped wells in preferential fracture zones in order to the release hydrostratigraphic pressure that created a risk of instability.

Challenges

Dig inclined wells more than 328 feet deep in mine tailings.

Client

City of Laval, Laval, Canada

Scope of Work

Preliminary studies, design, supervision, construction management.

Dessau is working on the Chomedey filtration plant expansion and standards-compliance upgrade project. The plant's capacity will be increased from 6.4 million cu. ft./d to 8.9 million cu. ft./d, while new water treatment processes will be added. These upgrades include a coagulation step requiring chemicals at various injection points, retrofit of the

ballasted flocculation system's settling tanks, and optimization of an inter-ozonation phase using liquid oxygen. Dessau also implemented recommendations from the physical security master plan for improved access control and video surveillance of the plant.

Challenges

Maintain potable water production during work.
Execute works in an operational facility.

Client

Dominica Water And Sewerage Company (DOWASCO), Dominica, West Indies and Canadian International Development Agency (CIDA), Roseau, Dominica

Scope of Work

Technical assistance, engineering, project management and construction.

Dessau's contract included several missions to improve the management of water and sewer infrastructure in Roseau, Dominica’s capital. This work made it possible to support the organizational restructuring of DOWASCO, train local employees,

and plan, design and manage various construction and rehabilitation projects related to water infrastructure (mains, sewers and leak detection).

Challenges

Optimize knowledge transfer processes (technical and administrative knowledge).
Organize and manage several jobsites while minimizing the impacts on surrounding activities.
Develop an excavation program despite the absence of maps of existing mains.

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Client

City of Longueuil, Longueuil, Canada

Scope of Work

Management and maintenance of municipal infrastructure.

Working for the City of Longueuil, Dessau devised a methodology to improve the management and maintenance of municipal infrastructure while reducing operational costs. We first created an inventory of the water supply and sewer networks, as well as road pavement, and determined their degree of degradation.

We then developed a geographic information system (GIS) to compile and manage this information. Finally, we implemented a scheduled maintenance and investment plan for infrastructure in need of repair. This work-optimization approach earned Dessau several awards.

Challenges

Instead of spending money to repair broken infrastructure, the City of Longueuil now benefits from functional infrastructure and a regular, reliable budget for operations and maintenance.

Prizes and Awards

2005 IPAC Award for Innovative Management, awarded by the Institute of Public Administration of Canada.
2004 Technological Innovation Award, awarded by Quebec’s Ministère des Affaires municipales, des régions et de l'occupation du territoire.
Vectora Award of Excellence, awarded by the Quebec Municipal Geomatics Association.

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