Specifications often require the mixing of round river stone with native materials at the invert of stormwater culverts. Does anyone have a standard ratio of mixing these items?
This mixture is in the culvert. The Ministry of Fisheries often ask for the invert of culverts to be lined with native material and/or stone, to protect the aquatic life from the abrasiveness of the culvert material. The outlets here in Ontario Canada are generally Rip Rap material.