Thinking about Delay, Disruption, and the Cumulative Impact of Multiple Changes

Change is any addition, deletion, or revision to a contract (Ibbs and Allen 1995). This may be a design or construction contract, and it may affect the scope or administration of that contract. Such change often causes an adjustment to the price of the contract, its duration, or both, and regularly occurs on projects. These cost and time dislocations may stem from the impact change has on labor productivity, which, when lowered, will require more labor hours to perform a task. With that increase in labor hours comes an increase in the costs and time required to complete the work. In turn, this may reduce or eliminate the contractor’s profitability and impair the owner’s return on investment and the utility of the project. This may lead to friction, acrimony, and even litigation between the owner and contractor. The problem gets even worse if many changes occur on a project because a special condition called cumulative impact may result. Cumulative impact may result from changes that delay the critical path or disrupt the work to such an extent that their sequences or means and methods are changed. Disruption may not impact the critical path of a project, but may still damage productivity. Delays and disruption may occur in any phase of a project (e.g., an owner’s acquisition of property, permitting, design, or procurement) and ripple through to hurt the productivity of a later stage of the project (e.g., construction). Cumulative impact has gained popularity (or, in the minds of some people, notoriety) in recent years, but it is often poorly understood, poorly explained, poorly demonstrated, and poorly quantified. The subject has become so important that the American Association of Cost Engineers (AACE) has even seen fit to address it in one of their recommended practice guides. There is a clear need to better understand cumulative impact.