I'm working on a boundary survey of a parcel through which Interstate 5 runs, and need to tie into Caltrans monuments to nail down the ROW.?ÿ This segment was built in the 1960s (I think), and I've learned from experience that during that time in this area Caltrans set nice bronze disks in large blobs of concrete to reference the ROW.?ÿ The problem is that they tended to set them below grade by a foot or two, and in my experience with a dozen or two they didn't put any iron in the concrete to aid in recovery.?ÿ
This morning I set out to look for one aided by a search position calculated from a couple of recorded survey maps a few thousand feet distant.?ÿ I had staked out the position yesterday, but after chipping ineffectually at the baked clay surface I decided to come back today with a battery-powered rotohammer to break through the crust.?ÿ Because I had to cross a dry canal and ascend a steep levee to get there I didn't bother taking the Schonestedt on either trip, figuring it wouldn't be useful.?ÿ I just started to dig at the staked-out location.
I was about a foot down when the shovel hit something hard.?ÿ Not in the bottom of the hole, but on the side.?ÿ I started enlarging the hole and saw that it was a 5/8" rebar, the top about 6" from the surface.?ÿ Huh, maybe the last guy to dig this up raised it with a rebar.?ÿ More clearing revealed the rebar to be set in concrete, and more clearing yet revealed the nice bronze disk surrounded by 4 each rebars, obviously set by the monumenting crew in order to make a Shonestedt scream.
I should have taken the pin finder along, could have saved myself some digging.?ÿ (Digging, by the way, on a 90?ø day while wearing an N95 mask because of all the smoke.)
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I've never seen that before. Maybe they put a rebar cage around it after the 4th time it got tractored out by the Cats LOL. Then cut the rebars off at the end of construction.
The foolishness of burying such things without some iron to help find it has always amazed me.?ÿ Back in the 1800's, sure.?ÿ There were no handy dandy Schonestedts available then.
?ÿin my experience with a dozen or two they didn't put any iron in the concrete to aid in recovery.?ÿ
It isn't what you don't know that gets you -- it's what you know that's wrong.
I'm working on a boundary survey of a parcel through which Interstate 5 runs, and need to tie into Caltrans monuments to nail down the ROW.?ÿ This segment was built in the 1960s (I think), and I've learned from experience that during that time in this area Caltrans set nice bronze disks in large blobs of concrete to reference the ROW.
I worked for CalTrans for 17 years and there's some nuances here.?ÿ You're referring to ROW obelisks (some poorly obelistic) and (recently, last 40 years) they were set by the construction contractor or one of his subs, not by the supervising surveyor's personnel.?ÿ They have a rich history, some being set in the 1920s by actual surveyors, others, not so much.?ÿ They were obviously expensive so the practice died out by the 80s, to be replaced by iron pipes?ÿ or rebar.?ÿ Some early County Routes set obelisks which control if CalTrans acquired the ROW later.?ÿ I think that's where CalTrans got the idea to set big concrete ROW monuments.
Now for the good and bad of it.?ÿ In flat country, farmers would cultivate right up to the road shoulder if they could butt a big chunk of concrete standing proud kept them out of the ROW.?ÿ But they attracted vandals for the brass disc & some farmers just backhoed them out of the way.
I've found dozens of them especially in the desert where they all were proud by at least a foot (two feet typical) and some sticking out in the middle of a poison oak patch which protected them.?ÿ It's hard to imagine alluvial coverage would obliterate them in such a short time span but you work in a different clime.
I've found none for miles on a project where one can conclude the contractor blew off setting them (still got paid?), there were much worse problems with the contract, and the record shows set monuments where it was never done.?ÿ I've found pristine ones that are 50' off based on calculations (usually in stationing) where it's obvious a contractor had his crew set a mon at ROW width um, near the BC of a giant curve for example based on a wing-ding and cloth tape from construction control by contractor's personnel.?ÿ And so many are missing (the hard ones to hoof concrete & water to) one might suspect the contractor only set ones the inspector could see with little effort and sign off on the monuments tick list.
So "CalTrans Obelisks" though historical have a spotted history and when found should be viewed with a jaundiced eye.?ÿ I've declared ancient CalTrans mons 100s of feet off and everybody agreed.?ÿ Might be the same in other States.
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Supposing you had buzzed for this thing before digging. It's hardly uncommon to find all kinds of metal junk in a highway right of way.
Hobbyist metal detectors are designed to signal for non-ferrous metals. If you have a lot of copper or bronze objects to search for, it might be a worthwhile purchase.
You're referring to ROW obelisks (some poorly obelistic) and (recently, last 40 years) they were set by the construction contractor or one of his subs, not by the supervising surveyor's personnel.?ÿ
Maybe I'm just lucky to be in the right area.?ÿ The stretches of I-5, I-505, I-80 and SR113 that I'm most familiar with were subject to post-construction monument surveys that seem to have been carefully executed.?ÿ
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Some of them even have adjusted coordinates listed.
And even though they predate NAD83, the orientation closely matches.?ÿ As an example, the 2 monuments I've tied on the current survey are about 3700' apart, and I'm missing the Caltrans bearing by 3 seconds, easily within the error budget of my RTK positions.?ÿ (The distance misses by 0.07'.?ÿ I can live with that.)
So I guess the reliability of the monumentation depends on the Caltrans district and construction era.?ÿ The one thing I do know for sure is that around here you need a shovel if you hope to find any of them.
Thanks for sharing this Jim. ?ÿI too, at age 50, after 38 years on the job, continue to make what I call rookie mistakes. ?ÿIt is nice to know that I am in good company.
I had a job some years ago (EDM days) that involved a rock quarry that fell in multiple sections with rough terrain.?ÿ I had a copy of an older survey that referred to an "original stone" way back in the back, over a mile from the nearest road.
I had the crew pack everything in that we would need to find and tie this corner in to out survey:?ÿ pick, shovel, pike bar, sledge, machete, theodolite, legs, EDM, reflectors, chain and a plethora of pins, flagging, nails and paint.?ÿ The truck was almost empty when we started our trek.?ÿ
When we arrived at the corner it was evident as to it's location.?ÿ There were 4 treated wooden corner posts placed in a square around the stone that had various ages of withering flagging flapping in the breeze.?ÿ A faded lath had written on it "SEC COR".
It was high on a bald steep slope.?ÿ At about the same time we all looked back to the east to see what we would need to clear to tie this corner to the survey...
From this high point you could plainly see our truck parked by the side of the road adjacent to our control point a mile away.?ÿ We could've sent one man in there with the reflector and dispensed with all the crap we dragged in.
Dragging everything back out was not fun.?ÿ
Might be the same in other States.
It IS the same in other states...
If it isn't, I'd like to hear the story...
The local DOT would set aluminum caps in concrete for control points. They would be spaced at 1500' intervals plus or minus. They began the practice using NAD27 control. The problem was that the aluminum caps were placed on screw together aluminum rods, the concrete had no iron in them just like Jim describes. The things had to be surveyed to be found. At least they were flush to the ground and not buried. Once GPS showed up the control got switched to NAD83 usually with some rebar added. Of course along a right of way there are normally good spots for control and you would end up with an 83 point close to a 27 point. Still to this day you can get a set of plans and you better pay attention or you could end up setting on a old NAD27 control point thinking it's the NAD83 point.?ÿ
1960s? They should have put rebar in the concrete instead for much less confusion.
I think these are more like control monuments, they have a reference to the layout line station and offset.?ÿ They aren't necessarily on the R/W.?ÿ It is not common in my experience.?ÿ They have them on US50 from Downtown Sacramento going east too.
Usually Caltrans has lots of control but none of it is referenced to the R/W AAARRRRRRRRGH!
