What is a contributing factor to added sewer maintenance expenses caused by flatter sewer line grades?

Flatter sewer line grades can lead to a decrease in velocity, which allows solids to settle within the pipes. When the flow velocity is low, wastewater may not carry solid materials effectively, resulting in the accumulation of solids in the sewer line. This accumulation can lead to blockages and increases the need for maintenance activities, such as cleaning and inspections. Thus, the added maintenance expenses stem from the need to regularly clear and maintain the sewer lines to ensure they function properly, especially when solids settle and form deposits that could disrupt the flow. In contrast, higher grades and proper flow velocities can help keep solids in suspension, reducing the need for such extensive maintenance.