Which of the following is NOT considered a prime sub in public works projects?

In public works projects, a prime subcontractor typically refers to a subcontractor who directly contracts with the general contractor to perform a specific portion of the work. In this context, prime subs are often associated with major disciplines or trades that are critical to the project's completion.

Electrical, HVAC (Heating, Ventilation, and Air Conditioning), and Plumbing and gas fitting all represent specialized systems that are essential to the functioning of a building or structure. Each of these trades involves substantial work that generally requires its own dedicated contractor due to the complexity and specialized nature of the work involved. These specialties are considered prime subs because they usually have a significant scope and are common in public works.

Mechanical Engineering, on the other hand, is more of a design discipline rather than a direct construction trade. While it plays a critical role in the planning and design phase of a project, it does not typically involve the hands-on construction or installation work that is performed by trades like electrical or plumbing. As such, it does not fit the criteria of a prime sub in the context of public works projects. This distinction is important in understanding the roles and responsibilities within the project management framework, particularly when it comes to contracts and project execution in public sector projects.