California Highway Commission Monuments

[Jim Frame]

Can anyone tell me the length of the old 6"x6" concrete "C" monuments (typically with a brass pin in the center) that were used to mark state highway right-of-way lines? I'm working on a height modernization project, and at one of my network locations I'll have to install a driven-rod mark if I can't use the nearby "C" monument. Knowing its depth will help me assess its suitability for my project.

Thanks!

[Ian Wilson]

I believe they were about three or four feet from bottom to top. However, a foot to a foot and a half was sticking out of the ground.

Have you run into any of the ones made out of asphalt?

Ian

[Berk Blake, PLS CA]

Jim:

April 1938 detail from a set of plans that I have shows 6" x 6" x 42" with with sides chamfered to 12" below the top. It also says that the copper wire is 3/16" in dia. and 6" long.

[PLS7393]

Beware that the "C" Monuments stands for Construction.

These were set during the construction stage of a project by the construction crews, not necessarily set by a surveyor. To my knowledge and experience (6 1/2 years) with Caltrans, they may or may not have been set accurately at the right of way lines, so use them accordingly.

[Steve Martin]

Keith,

The monuments were prefabricated with the centered copper wire and the contractor placed them from references by the Surveyor. You can imagine having to dig a 3' hole and then perfectly centering a big piece of concrete and then evenly compacting backfill. Most of them are +/- 0.1' to 0.3'. Some have settled or have been bumped over the years too.

At times I have used a least squares adjustment to recreate the centerline from which the RP/ C mons were set from. It is not always straight forward, but it does give you a better idea about where the centerline originally was.

[btaylor]

Interesting nuggets of information on those. Thanks guys.

Bryan G. Taylor, PLS

[Jim Frame]

"Have you run into any of the ones made out of asphalt?"

I haven't. I wouldn't think asphalt would be very durable, at least the part that sticks above ground.


"It also says that the copper wire is 3/16" in dia. and 6" long."

I recall seeing one on West Capitol Avenue in West Sacramento that had been hit by a blade or hoe bucket. The top foot and a half had been pretty well shattered, but the pieces were held together and joined to the base by the brass wire. In that particular case, the wire may have run the length of the monument.


"Beware that the "C" Monuments stands for Construction."

I have no inside Caltrans experience, but I'm skeptical about this claim. I wouldn't think that so much effort would be put into monuments for construction purposes only. The "C" is prominent and somewhat decorative, and it would make sense to use something like that for a durable monument marking the right-of-way. At the same time, it doesn't make much sense to use a 42" decorative concrete monument to mark the approximate right-of-way only for construction purposes. I'd be interested in hearing from any Caltrans old-timers who might be able to substantiate or dismiss the construction contention.

[LA Stevens]

I worked for Caltrans for 8 years and have retraced some of these boundaries. I don't recall hearing about the "C" stamped on the monument, but it does make sense.

I was told by some of the old timers that the setting of the monuments was done by contractors forces from the design line set out in the field. These monuments in the bay area can be way off the right of way line (I've seen a few feet of error). I believe this was done this way in the 40's or 50's. During that time (the dates of which should be checked) the setting of the monuments were a contract item. I was told it was a very big mistake by the the Division of Highways because of the mistakes made in the location of these monuments. On the other hand, it probably makes a difference of what area you are working in and what control they provided to the contractor to establish the monument. You'd also have to apply the Combined Grid Factors used for the project. I'd say if you were within a few inches, that's great.

I'm curious if the 1938 detail had the "C" stamped on the side. That detail would have been before they were mandating the contractor to set the monuments. Could someone send me copy of that as well for my files. If the C was used before and after this time, it would have nothing to do with the accuracy of the monument.

[scarpa]

I have done numerous private surveys along old highway routes US 40 (I-80 corridor) and US 50 in California and Nevada. The concrete monuments I found in California were "stamped", as you say, with the letter 'C' and those in Nevada with the letter 'N'. I do not believe they had anything to do with construction since the ones we found were at angle points and points of curvature along the right-of-way.

Jon Scarpa

[Berk Blake, PLS CA]

Hopefully, there is a .pdf attached to this e-mail. I don' believe that I have ever seen a chc mon. without the C cast into the face. I have personally found them on maps dating back to 1913. The C certainly stands for California and not construction. Never perfect, but so much better than splitting rr tracks.

[Steve Martin]

I talked to a Surveyor from CALTRANS who worked on jobs where these monuments were set. He said that the monument locations were carefully offset with hubs, 3' offsets for example, and another hub was set at the monument location. The Contractor would then come in with a drill rig and auger out where the monument would go and set the monument. Surveyors would then check the monument locations. Like everywhere, some crews did a better job than others. He felt that if there were discrepancies in the location it was due to local movement of the surrounding soil, be it the backfill or slope stability in the 40 to 80 years since these monuments were set. He did mention that it was not unheard of for the contractor to drill out the wrong hub. I'm not sure how that would make it thru the checks and reviews. I personally never found one off by feet. I do know that sometimes the road is not always centered in the Right of Way, for example the Right of Way shows an angle point and the road is built on a curve or a minor alignment change completely within the right of way.

[LA Stevens]

I worked with many old time surveyors in District 4, San Francisco Bay Area. Many of which, who made the claim to be careful when retracing the Right of Ways, because they were not set accurately during the time frame in which it was a contract item. The routes I retraced, I found the original P-Line which created the Right of Way, but the accuaracy of the 6x6's were certainly not up to survey standards.

I don't think it was a requirement around here to check it, but it would of been a good idea. Or if it was, it fell by the way side. It certainly wasn't slope stability given some of the locations. They indicated to me that they had layed out the design line and the contrator would establish the location from the station and offset shown on the plans.


Who's your Caltrans contact and does he know when this was a contract item. Or better yet can he get a copy of the memorandums?

[Steve Martin]

Larry,

The story related to me about CALTRANS Surveyors setting references for the monument locations was related to me by the retired District Survey Engineer of Caltrans District 11 who had 40 years of service with DOT/ CT.

His experience related to District 11, other areas may have had a different standard of care.