What should be the condition of soil above bedrock for a DIS?

The correct answer states that the soil must be at least 3 feet above bedrock for a Drainage and Infiltration System (DIS). This requirement is crucial because adequate soil depth above bedrock allows for the effective treatment of sewage effluent before it reaches the underlying rock layer. Soil serves as a natural filter, breaking down harmful pathogens and nutrients through biological processes.

If the soil is insufficiently deep, such as being less than 3 feet, there may not be enough soil material for adequate filtration, which can lead to environmental contamination and system failure. The 3-foot minimum ensures that the effluent is treated effectively, reducing the risk of groundwater pollution and ensuring compliance with health regulations.

The other options do not meet the established guidelines that prioritize effective wastewater management, thus failing to provide sufficient soil for treatment purposes.