It's all about systems of checks and consistent communication between the instrument man and rodman.
For RP's, our practice is to set the RP's with a total station and record the as staked elevation. The instrument man reads off the point number as "Point number fifty two", after it is written down, the rodman reads off what he wrote in a different manner "five two".
We write the point number on the back of the lath, then run differential levels over the RP's and utilize them AFTER they check with the total station elevations.
Then two guys walk around writing all of the elevations on the lath.
The guy with the cut sheet reads off the point number and the elevation. The guy writing on the lath verifies he is at the correct RP and reads off what he wrote.
The guy with the cut sheet checks what was written and placed a dot next to the information on the check sheet to indicate it was checked.
Good communication is critical. If this procedure is followed closely, we never have a bad stake. Where problems occur, is when the contractor disturbs the RP and tries to put it back or puts the stake at the wrong RP.
Hub Elevations vs Machine Control
Anybody wish to make a parallel? I see it quite clearly.
We still set the control, we still get to certify, we still get paid, and it's a heck of a lot easier than pounding hubs into 99% compacted soil.
Underground, curbing, building foundations... naw. Bad idea. But what about getting the roadway and mass grading real close. As in REAL close, with the right outfit.
> Okay,
>
> It seems that contractors seem to want the hub elevation for our layout points recorded on the back of our lath. Seems they like to use them as TBM's or they like doing the math to come up with design grade without looking at the plans. This just seems like another way to open myself up to liability. Is this a common practice now days?
John,
I have been working on a 64 Mile pipeline for the past few years. I was asked to place offset hubs with station and elevation on the laths for the pipeline construction. All worked out good for a few months until the clean up crew started working the whole line back and fourth. The mudman putting the mortar on the pipe joints was using my laths for something I not sure of and was throwing them on the side of the ditch. Along comes the cleanup guys and picks up the lath and proceeds to the other work area 23 miles down the alignment. Somehow the lath was used again out of the back of the truck and was thrown to the side next to a fallen lath next to a set hub. ...............wait for it............... Ring Ring Ring!!!!!!!!!!! Contractor " Your stakes are way off and I have to have you out here now to check everything that has been done since Noah built that cool yacht thingy"
Fireman mode!
I head straight to the lath and turn it over infront of the contractor showing the station numbers corresponding to 23 miles back........... He bought lunch
My suggestion would be, If needing elevations on the lath, give enough information on the lath so that it can not be mistaken for any other position on the project. For some that is a point number system, for other it can be a descriptive code and location.
Mine typically read side 1 "LINE A STA 100+00 O/S 15' N", side 2 "HUB ELEV 1901.12"
Have a good day,
WQ