We're laying out BMs in preparation for a 16 mile level run. Our new way to set BMs is to countersink them into concrete. This will, hopefully, prevent them from being damaged or destroyed. As soon as I reduce the size of the pictures I took yesterday, I will post them.
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As a retired DOT surveyor of 47 years my pet peeve is doing quality leveling to marks that have a short life span. We started increasing intervals to half a mile and setting or recovering NGS style markers used for N E Z control. A handfull on the construction side complained but overall the response is that it is about time. The problem with temporary marks is stability over time and the time it takes on some projects from control survey to build. It was causing the construction surveyors to pick and choose which marks to hold and which to update. Most of them prefer a greater interval to having that task. I like the idea of countersinking provided the mark has a chance to survive for a while. Otherwise its wasted effort. Better to focus on locations that may remain untouched than to set a well constructed mark in harms way.?ÿ
As a retired DOT surveyor of 47 years
Retirement must have been fairly recent??ÿ Congratulations.?ÿ Fully retired, or going into private practice?
?ÿUsed a specific corner of the base of Birdie Bone's headstone in a cemetery in 1995.?ÿ Bet it hasn't moved 0.01 since then.?ÿ?ÿ
?ÿmarks that have a short life span
I'm afraid too many of the GSVS14 series will be moving vertically.?ÿ Probably stable horizontally, but I've noticed some of the large diameter rings (for the gravity meter to set on) have broken away from the central post, probably from frost heave.?ÿ If they don't break away, then does freezing under the ring lift the central post and disk??ÿ
I know NGS considered them to be mostly for the one project, but a little piece of sonotube separating the post and ring would have been an easy precaution for future stability.
@norm congrats on your retirement
As soon as I reduce the size of the pictures I took yesterday, I will post them.
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(5) Grinder with grinding bit. Got good deal ($10) on bit on Amazon.
(4) Two-part epoxy.
(3) Countersunk hole.
(2) Centering template and hole depth checker.
(1) Set 3-1/2" aluminum disc.
The regional advisor and I were disappointed with the GSVS monuments altogether. They set a rod in a sleeve every so often but even they were not driven to refusal yet they could potentially hold. Yes we have noticed movement in many of them. A pity to let 1st. order leveling marks become no good so quickly. But the GSVS had a budget just like everything else and choices had to be made.?ÿ
Damn youngsters keep retiring.?ÿ Makes the rest of us look bad for planning to still be at it three days prior to our funeral.?ÿ Because we want to, that's why.
Our new way to set BMs is to countersink them into concrete.
Are you leaving the dome proud of the concrete surface??ÿ If it's not, anyone using a wide-base invar rod will have to use a spacer, which is both a nuisance and a potential blunder source.
@norm- I??ve been retired for just short of 2 years. I work full time for a consulting firm. ?ÿ ?ÿI figured if I had to work full time till I??m 63, I might as well be drawing retirement and a 2nd check.
This was always our procedure for DOT control and level runs. Set control away from proposed dirt work 1500' inter-visible intervals. Drive screw together rods to refusal, dig a hole for a concrete collar with a wider bottom than top about 2' deep, set the cap on the rod just a few hundredts higher than the concrete, I would use a pvc collar for the concrete. Of course that's the gold standard, some of those rods were plus 20' deep. Often refusal was when my arm refused to pound anymore.?ÿ
You are in florida?
I would not use curb or concrete here as a base cause of frost heave, but often what's going under the concrete, even without frost, can be iffy.?ÿ
I would love to do a 16 mile level run.?ÿ
There is something to be said about boots on the ground.?ÿ
Are you leaving the dome proud of the concrete surface?
Yes.
You are in florida?
Yes. We are setting Stability 'C' Class BMs on top of curb inlets, flat grade inlets, headwalls and overpass walls. I don't like the later because I don't think anyone can do a good job of holding a level rod very plumb on walls, even if it's only one section of rod. The BMs you mentioned are called Stability 'B' Class. Do you use the same naming conventions?
My city of 100,000, 20 square miles, has no benchmark network of its own. There are some benchmarks that were long ago set by the county surveyor, but these are gradually disappearing.?ÿ There is a line of marks set by the DOT along the highways that cross our town. Same for them. And there are a couple of NGS marks remaining.?ÿ So any potential building site is apt to be a good long run from the nearest BM.
I'd like to install benchmarks across our city with some good levelling between them. Very roughly, I figure such a project would cost at least $100k. So I'm searching for a justification that the bean counters can understand (ie/ compelling demand, pay back time).?ÿ ?ÿ
SO... Field Dog ... and others ... I'd like to hear the story about what lead up to the decision to run 16 miles of Benchmarks. Is this for a specific project? Or a groundswell of demand from the community??ÿ?ÿ
@norman-oklahoma?ÿ If you're really careful, you can use their dedicated countersink bit to set the Bernsten BP Series Markers for Concrete in marble tile on a site like this....
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