# Estimating dirt quantities for dirt jumps

Lee,

It has come to my attention that people often ask questions about dirt quantities for dirt jumps. I can come up with numbers for this. Basically it’s a routine that is used for civil engineering for building roads and such. It just needs to be applied for dirt jumps. I have been involved with one project thus far and have a second one coming up. If you want you can direct people my way.

Thanks.

Dave

Dave, right on.

Do you want to tell me the equation (I’ll give you credit of course), or do
you want people to ask you directly?

Braaap,

— Lee

Lee,

Its a little more complicated than an “equation” It’s an earthwork calc’ in AutoCad, basically you design the jumps w/cadd create a 3d model than use that model to figure out the dirt required. There are other elements to consider- compaction percentages and such, but at least you can get estimates.

Dave

Dave, thanks!

Everyone else, here’s Dave’s email: gunnifreeride@yahoo.com

5 replies
1. 970 says:

why do you need math to build dirt jumps?

2. leelikesbikes says:

Hey Andy.

There are two types of people in this world:

1. Those who jump in and do things.

2. Those who measure and plan, then go for it.

If you’re a Type 2, and especially if you have to estimate dirt quantities for a city-sanctioned park, you gotta do some math.

All you Type 1s: Just start digging and hope for the best …

3. Glen says:

I am a civil engineer and I do earth work quantities frequently. The shrinkage factor you would want to use is 10-15% which for the amout of dirt will be a very low number. but the rest will just be the cubic area of the jump. if you have a 4′ wide 5′ high jump with a base of 3′ the cubic area would be 1.1 cubic yards and with a 10% shrinkage factor your talking about 1.21 cubic yards.

Cubic Yards = (ft2 * depth ft) / 27

4. cmc says:

Woah!!!

You guys are forgetting that a dirt jump does not have to be all dirt.

UNDER THOSE JUMPS CAN BE:
1) Logs