PROBLEM TO BE SOLVED: To provide a base material having remarkable restraining effect for clogging and increasing in pH, maintaining a good rainwater storage infiltration performance over a long period of time, having higher inter-pebble storage rate than a single grain ballast, and is usable widely as a versatile filler or a back-filling material.SOLUTION: A base material is constituted of a hard angular grain and an adsorption auxiliary material adhered to a surface of the angular grain via a mixture auxiliary material. The surface of the angular grain is covered with a coating layer having capturing function of an SS substance of mixture of the mixture auxiliary material and the adsorption auxiliary material.
