A sump is not required in a drainage system in which type of soils?

A sump is not required in a drainage system in Group 1 soils because these soils are typically well-draining and do not retain water excessively. Group 1 soils are characterized by having good permeability, which allows water to move through them quickly, reducing the likelihood of water accumulation that would necessitate the use of a sump. Consequently, in areas with these soils, the potential for flooding or standing water is low, making a sump unnecessary for effective drainage.

In contrast, the other groups of soils often have poorer drainage characteristics. Group 2, Group 3, and Group 4 soils tend to have higher retention of water due to their denser composition or clay content, which can lead to water pooling. In such cases, a sump might be needed to help manage excess water and prevent issues related to water accumulation, such as flooding or damage to structures. Therefore, the requirement of a sump is primarily influenced by the soil's drainage capabilities.