Talk:750.7 Non-Hydraulic Considerations

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750.7.8 calls for Safety Slope End Sections on all drainage pipes greater than 21 in. that fall within the clear zone.

This seems overly conservative as the 2006 Roadside Design Guide (RDG) 3.4.2.1 states "If a foreslope is traversable, the preferred treatment for any cross-drainage structure is to extend (or shorten) it to intercept the roadway embankment and to match the inlet or outlet slope to the foreslope. For small culverts, no other treatment is required." The RDG goes on to define a small pipe culvert as a single pipe up to 36" or a battery of pipes up to 30".

Why are we so much more conservative than the RDG?

--Martik2 13:43, 23 March 2009 (CDT)

Dan Tschirgi: It appears that the current policy and the table on Standard Plan 732.10 are a "one size fits all" approach that applies to crossroad and parallel structures. This approach is outdated in the current approach of practical design. We will undertake some revisions to make the policy and standards consistent with the Roadside Design Guide. These revisions will be placed on the next available engineering policy ballot and if approved, could be effective by July 1. Please contact Joe Jones or me to provide additional comments for the revisions or to check on the status.

Thank-you for pointing out this inconsistency which will likely result in cost savings.

750.7.2.1 - Group C Pipe???

This section mentions that "Group C pipe should be specified for the portion of median outlet pipes outside the edge of pavement where such pipes are located on high fills requiring a break in flowline grade. Details for such installations are illustrated in Pipe Grades For Median Drop Inlets."

The linked application figure shows Group B pipe and not Group C as mentioned in the text.