I'm installing a sump pump and a bit of drain, in a clay soil basement that happens to have a spring. It is silty fine clay that has a habit of migrating with water and clogging everything.
What are the best drain rock types for this situation? Road base? Pea gravel? River rock? Crushed rocks? Can you supply references to tests or building science on this answer?
In this case it is possible to flush the area every few years with clean water, as it is possible for the gravel to reach the basement grade level. The hope is to dry out the soil in summer to reduce rust on the pipe and tree root growth.
Here's the temporary utility pump, used to lower the water level: