When reviewing drainage structures in particular, I am seeing a significant number of structure with different materials on the inlet and outlet.
Since there is only one field, I recommend adding guidance in the assessment to determine with side of the crossing. That way there is some rationale when only one material is chosen.
Another option would be to create a new category: mixed, mismatched, etc.
Henry,
I will talk to the Stream Crossing Steering team and let you know what guidance we come up with. I'll post it here.
Thanks,
Tom
The RPC team would also be interested in this once resolved.
Beyond different materials observed at inlet vs. outlet, we have also observed different inlet/outlet types (i.e. inlet with no wingwalls, but wingwalls at outlet, etc.) We have been mentioning this in the comments, but please let us know the best way to note if different. Thank you!
Currently the protocol is to focus on the inlet side for the structure material and type and mention the outlet materials, if different, in the comments. We can consider add outlet specific materials (and possibly structure type) parameters for next year, but the database and protocol for this situation is mostly set for this year.
I may have been responding to language in an older assessment guide when making the suggestion. Earlier versions did not explain to use the inlet condition at a mismatched crossing. From my perspective, this is resolved. This is an atypical situation and I don't feel we encounter it enough to treat it with an additional field or fields.
Yes, the protocols from 2017 and 2018 state to use the dominant inlet condition to describe the material and shape of the structure, and add in the comments that the outlet is different.