Section 5. The commissioner shall, in a manner and to the extent provided by this chapter, control and supervise any building project to be undertaken by a state agency or building authority when the estimated cost of the project exceeds $250,000 and involves structural or mechanical work. The commissioner may, upon request of a state agency or building authority, delegate project control and supervision to that state agency or building authority over projects involving structural or mechanical work whose estimated cost is less than $5,000,000 if the commissioner determines that the agency or authority has the ability to control and supervise such project. Except as otherwise provided in this section, any state agency or building authority shall control and supervise its own building projects when the estimated cost of such project is less than $250,000, or if the project does not involve structural or mechanical work. Notwithstanding the foregoing, the commissioner may delegate control and supervision over projects involving structural or mechanical work with an estimated cost of less than $10,000,000 to the University of Massachusetts if the commissioner determines that the University of Massachusetts has the ability to control and supervise such project. As used in this section, ''estimated cost'' shall mean the estimated construction cost stated in a study or program prepared in accordance with section 59.