Why is replacing wastewater collection systems in downtown areas often challenging?

Replacing wastewater collection systems in downtown areas is often challenging primarily because of the crowding of other underground utilities. In urban environments, multiple infrastructure systems such as electricity, gas, water, telecommunications, and sewage lines coexist in limited underground space. This congestion complicates excavation and replacement work, as care must be taken to avoid damaging the existing utilities during construction. Additionally, the close proximity of these utilities can lead to higher safety risks and necessitate more complex engineering solutions to navigate the constraints of the urban setting.

Although the other options may contribute to the challenges faced in urban infrastructure projects, the specific issue of crowded underground utilities stands out as a predominant factor that directly impacts the logistical planning and execution of replacing wastewater collection systems.