OPTI Canada Inc./Nexen Canada Ltd. (OPTI/Nexen) developed a constraints map for their proposed Steam Assisted Gravity Drainage (SAGD) project near Anzac, Alberta. Constraints mapping is a graphical representation of the suitability of a land area for construction purposes. The objective of a constraints mapis to provide information that will allow reduction of a project's footprint in areas of higher constraint to trigger elevated levels of site mitigation and avoid "no-go" areas. OPTI/Nexen used the constraints map as a key planning tool during the conceptual and detailed designphase for their project to balance the placement of surface facilities with environmental and cultural land use sensitivities. A constraints map is a dynamic tool that can be used over the lifetime of a project, from initial screening at the beginning to detailed facility siting for future phase updates. Constraints maps take into consideration regulatory requirements; raw data such as disturbances, wetlands, field survey data, traditional use, historical sites, soils and air photos as well as derived data such as wildlife Habitat Suitability Index modelling results. They may also include subsurface environmental, surficial and subsurface engineering, and temporal constraints. Fundamentally, constraints mapping utilizes the same information as the Environmental Assessment process, however it processes the information in a slightly different manner.


In December 2001, OPTI Canada Inc. and Nexen Canada Ltd. (OPTI/Nexen) retained Golder Associates Ltd. (Golder) to develop an environmental constraints map for their Long Lake Project lease area near Anzac, Alberta (Figure 1).

What is a Constraints Map?

A constraints map shows areas of high to low environmental and cultural importance based on sensitive features in the area. Sensitive features may include the habitat that animals and fish use for food or shelter, areas where rare plants are found, and protected places such as parks, traditional land use sites and cabins.

"Constraint" means to restrict. An area of high environmental importance will be highlighted on the map as an area of high constraint, meaning that a disturbance to the land in this area could have a considerable effect on the sensitive features. Areas of moderate to low environmental importance will be highlighted on the map as having moderate to low constraint, meaning that disturbance to the land in this area could have less effect on the sensitive features. The constraints map also takes into account the combination of overlapping areas of importance. For example, if two or more sensitive features were found in the same area, such as a cabin and a berry-picking area, this location would have a higher environmental constraint than a location with just one sensitive feature.

The constraints map is produced by a Geographic Information System (GIS). The GIS is a type of computer software that is designed to develop, manage, analyze and display spatial data (where things are) and attribute data (what things are) in a digital format.

Why is a Constraints Map Important to OPTI/Nexen?

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