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travesable cuvert grates

State WI
Description Text

We had some field staff have a problem installing a steel traversable culvert grate on a concrete pipe (see photo). 

We and a number of other states allow the use of an adapter to connect the steel traversable culvert grade to concrete pipe. 

I was wondering if MwRSF has seen similar problems in the past or has come up with other possible solutions (e.g. traversable concrete grate comes to my mind...).


I know that the 4" object standard is difficult to apply on a slope, but it is the best published  guidance I know of 

Other Keywords fixed object; 4" chord
Date September 2, 2015
Attachment SlopeEndwall_PipeBell.pdf
Attachment sd-08f07.pdf

Response I have a couple of comments regarding the attached detail. 

1. I assume that the detail is for parallel drainage structures based on the pipe alignment which is why you are concerned with the step up at the attachment to the culvert pipe. If so, I would note that the detail shows 4:1 slopes for certain configurations. Currently, the best available guidance for traversable parallel drainage in the RDG recommends maximum slopes of 6:1 at speeds up to 80 km/h. 
2. With respect to the step up in height at the top of the culvert, the current best guidance for traversable parallel drainage would suggest that this is acceptable. Currently, the RDG recommends that the height of the first pipe on the culvert be mounted 4-8" above the culvert invert. Thus, if the slope grading remains consistent with the traversable culvert grate, then the step of of 6-8" at from the top pipe of the grate to the lip of the concrete pipe should present a similar traversable step. 

Let me know if you have further comments or questions.

Date September 14, 2015

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