how to determne grade for a new driveway

[RNeumann]

Robot Check

OP said he’s tried a “sight through inclinometer”...........he’s having a hard time all the way around with this one.

I’ve had the hand level for years. With a story pole on both sides it’s amazing how close you can get. It’s a great tool for a lot of folks- especially TBNers.

 

[muddstopper]

to answer a few questions. Power will be all underground. The goal is to keep from cutting as many trees as possible. Overhead power lines require a very wide clear cut right of way. That I am not going to allow. The power will be buried in the ditch line of the new road. Yes long slopes will drain a lot of rain water. Culverts will be used to redirect the water so it doesnt run all the way from the top to the bottom. A 60ft elevation change in 1000ft isnt that steep a slope. I just need to know the exact elevation change so I can lay it out with the right slope. As for letting grading contractors lay out the road, I know many good dozer and excavator operators. Most build really nice roads. Most want to do it the way they want it done, not the way I want it done. Never seen one yet that didnt change the direction they where grading when they started getting off grade. Roads tend to have their ups and downs when a straight line would have been better. Its easy to cut a straight slope when you can see the other end, not so easy if you are grading around a bend and cant see how high or low to go from the operators seat. Most can follow a flagged line pretty well and that is what I want to do is flag the center line. I have already had a guy from the USFS try and layout the road and he does it all the time for loggers. The road he laid out went from 6 degrees to 15 degrees. He laid it out and flagged it twice, first time he came out way low resulting in a sharp turn and steep grade to get to the top. Second time he came out way high also with steep and shallow slopes. Not what I want. I am not exactly inexperienced in this type of work and am not trying to be unreasonable. I know what is involved and the difficulty in getting there. I have a lazer transit and lazer level. I dont have someone to hold the stick, but if I can determine the distance and elevation change. I can set the levels up and hold the stick myself. I am not exactly able to run back and forth all day making changes and adjustments and want to try to do the right setup the first time.

 

[mapper]

Used to work with a guy that was an absolute master in spotting grade for building logging roads, his roads never broke grade, ever.
The tools he used were pacing for distance, an anaroid barometer for elevation change, and an abbney level or clinometer to spot the actual grade.
He would start by zeroing the barometer at the starting point, then walk to the end point counting his paces. At the end the barometer would give the elevation change. He would then calculate the grade needed to get from start to end, set the grade on the abbney level and mark the grade back to the start point. If he came out a bit off the grade was adjusted and he would work his way back the other way. Rarely saw him take more than three passes to get it right on the money.
Marking grade was always done on the uphill side of the proposed road, about the same level as the operators eyes seated on the dozer. A colored paper card stapled to tree trunks or flagging wrapped around the tree trunks will work also. This operation is a lot easier to do with two people than one!
A word about GPS for elevation, the signal from the navstar satellites is very weak any thing in the line of sight to the satellite will block the signal, so an open sky is very important. Elevation is the weakest of the three coordinates and requires the maximum number of satellites to be visible and with a wide dispersion across the sky to get a good solution. Your elevation jumping around on your phone is most likely caused by satellites appearing and disappearing from view as you move giving you different solutions for elevation, unless you know how many satellites are visible and where they are you have no way of knowing what's good or bad.

 

[muddstopper]

Finally found a google map that shows the topo contor in 20ft increments instead of 100ft. The starting point is @1580elv and the 1620 contor line runs right thru the house site. So it looks like I have a 40ft elevation change unstead of the 60ft number we had been trying to use. 20ft makes a lot of difference in slope when your strecthed out 1000ft. No wonder we kept missing. I was also able to zoom in the map to see actual landmarks I can recognize on foot. That will make it much easier I think. I can draw the road out on the map, look for the landmarks and just measure with a stringbox to get a close approx distance. The elevation tops out about a 100yards from the actual house sight. This point is sort of in a small gap of the mountain. From that point I will run the top of the ridge with the road. Already a logging road there, just have to clean it up. I can measure from the gap of the ridge to the starting point, use the 40ft elevation to determine the slope and just sight it with the inclinometer and lay flags.

 

[747driver]

Sounds like you found the source ! What is the google map you used ? You are at the same elevation we are here in TN. Can you find someone local to help you for the day in plotting it out ?

 

[JDAOWNER]

YOU MIGHT TRY A LAND SURVEYOR. THEY USUALLY HAVE MODERN EQUIPMENT THAT SHOULD HELP YOU. IF YOU HAVE TIME AND WANT TO DO IT YOURSELF, GET SOME TUBING AND MAKE A WATER LEVER.

 

[muddstopper]

Sounds like you found the source ! What is the google map you used ? You are at the same elevation we are here in TN. Can you find someone local to help you for the day in plotting it out ?

I found it on the county mapping site. I just had to find the right button to push to get 20ft contor lines instead of the default 100ft line. I had it all along, I just didnt find the option to change it until this morning. Old men and computers always need grandkids to show them how stuff works.

I did consider a water level, but I didnt want 1000ft of hose to make it work. I could have done 100ft at a time. Make 10 measures and came up 4 ft at a time and been really close. I just didnt know it was 40ft and not 60ft that I needed to raise in grade.

 

[mapper]

So it looks like your driveway will be +/- 4% grade. That's not bad at all!

 

[ericm979]

The contour lines on topo maps aren't all surveyed. They may not be as accurate as you'd like.

 

[muddstopper]

The contour lines on topo maps aren't all surveyed. They may not be as accurate as you'd like.

I think I have a plan. Actual grade will depend on total distance. I Think I can put together a 50ft water level and start with the 4% number on one end and just see how close it comes out at the other end. The 50ft stations will give me a total distance traveled, and I can then just measure the difference in the end results and the desired results and make the needed adjustments for a final centerline. Once the centerline is flagged I can then use the water level to determine the heights of the high side cuts and lower side fill, based on the width of the road. This should give me some ideal as to how much timber needs to be removed. This is something I can do without waiting for another person to help.

As for the topo maps being accurate or surveyed, they probably havent had a actual physical measurement made. I dont know what kind of device or instrument those mappers use to come up with their numbers. I do know that trying to use a sight inclinometer, and guessing at slope wasnt working. To much changing directions and correcting grade to get where you want to be. If it wasnt for going around a hill side, the inclinometer might have worked pretty well, but its hard to sight around a curve.