Constructability Considerations for Dams and Spillways

Constructability is commonly referred to as the integration of construction expertise and knowledge into the design or preconstruction phase of a project. While there are numerous available references for constructability best practices, many of these are not well-documented. The project team’s goal of developing a constructable design improves project construction schedules, reduces construction costs, and provides the owner with high quality product. Although numerous dam projects are completed each year, valuable information is often communicated too late between the contractors and designers, and when potential constructability issues become difficult or costly to prevent. The sooner constructability challenges are identified, the easier and less costly these items are to address, resulting in reduced potential for schedule delays. This paper summarizes a variety of common dam and spillway design and constructability considerations. This paper is the culmination of observations and lessons learned from construction field personnel and engineers specializing in dam design and construction. The importance, challenges, and benefits of constructability presented are applicable to a wide variety of construction projects. However, the main focus of this paper is on constructability considerations for reinforced concrete spillways constructed in embankment dams. This paper focuses on common constructability challenges, such as rebar detailing, wall and slab geometries, concrete placements, and joint details It also provides examples of specific details, such as alternative weir designs (e.g., ogee, labyrinth, and piano key weirs), as well as energy dissipators, drains, wall penetrations, backfill compaction methods, and anti-seep walls. Examples and lessons learned are provided for the identified constructability concerns. The information presented in this paper will benefit those involved with design and construction of spillways and dams, including engineers, contractors, construction representatives, regulators, and manufacturers seeking safer, less expensive, and more durable spillways.