Dip In Road 1

[xroy]

hi,

does anybody know what a dip in road is? when is it best to use and what should be the specs.

i am designing an access way for the utility area of the project i'm working on and this particular access way will block all possible drainage going to the ditch around that area. our client wants to use a dip in road to solve the drainage problem of that area.

xroy

 

[msquared48]

"DIP" stands for Ductile Iron Pipe, which requires less cover under traffic load than either concrete, PVC or CMP pile.

Then again, a "dip" in the road is a depression, or a really stupid person standing there...

Mike McCann
McCann Engineering

 

[xroy]

hi msquared48,

actually, Ductile Iron Pipe was the first thing that came in to my mind. But according to our client, it's not.

I agree that it's a road depression. I just wanted to know
what are the specifications for this type of design. A drawing detail would be the best answer.

thanks


chris

 

[PELS]

From your very brief description of the circumstances, it sounds like you would be better off using a culvert in the roadway rather than a "dip" or depression. The culvert allows the drainage to flow through the roadway without having a low area. If this is a low traffic volume access road, there are very economical pipe types such as CMP or HDPE that can be used for the culvert.

 

[sam74]

If it is a public road then you would want to look at K values for the vertical curve. Minimum design K values can be assigned for vertical curves in the roadway which have variables involving design speed, algebraic difference in grades, and length of vertical curve. See the link for a chart for sag curves and google vertical curves and K values to find more info.

http://www.nj.gov/transportation/eng/documents/RDME/figure4j.shtm

 

[francesca]

The design of a structure to convey storm water is dependent upon the volume of storm water to be conveyed. This is true if it's a culvert or a "dip."

Even if this road is a temporary structure for during utility construction it needs to withstand at least a 2 year design storm, possibly a 10 year design storm. If the road will not be surfaced, then a "dip" or traversable ditch (ford) would need to be armored with riprap, concrete or asphalt, all of which would likely cost more than a culvert.

 

[xroy]

Actually, the original design was to use a culvert but our client wants to use the dip instead.

Tnx for the advice.

 

[RWF7437]

Dips are widely used in the desert southwest of the U.S.

Try searching for standard drawings in the DOT websites for Arizona, New Mexico and possibly California and West Texas.

good luck

 

[PELS]

I must confess I have not heard of this "dip" concept. Apparently it is used quite frequently in the design of forest roadways. There is some minimal design criteria and graphics in here:

http://ttap.colostate.edu/Library/MISC/USDA 077 1803-SDTDC.pdf

 

[xroy]

Hi Pels,

Thanks for posting the link. It's really is very helpful.

Chris

 

[cvg]

here is the phoenix detail for dip crossing

 

[rconner]

I was just curious --is an effective "shoulder" transition maintained with these things?

 

[ptmoss]

A dip in the road is simply that. Come down about 5" or so about 8-10' in off the edge of your main road. Then your utility road heads uphill. Obviously this wouldn't be needed if the utility road drops away from the main road.

If there is a ditch along the main road then you'll likely have problems matching the depth of the dip to the bottom of the ditch. I have property owners ask to do this all the time on their driveways when they're too cheap to put in a culvert.

The only time I relent is when the driveway, or in your case the utility road, is at the crest of a hill along the road. In this case the water from the driveway ditches will flow off in opposite directions downhill and the dip will divert water that might come down the driveway so it doesn't flow out into the main road.

If the utility road does not come off a crest like this and there is a ditch to cross then you need to design a culvert.