This really bugs me.
Nearly every grading plan (non DOT work) that I pickup these days, does NOT show a single bench mark. When I ask the Engineer, he refers me to the original surveyor. Some of the surveyors have replied with "It was not in our contract, and I'm not going back to the site without additional payment". They are often nice enough to provide me with their control points. Or tell me to use ManHole covers. I often find several tenths of vertical error in these points, yes 0.1 to 0.35 on the last project. It really looks like these surveyors leave the BM off intentionally, just to get the contractor to call them back for "additional work". But they don't like it when I call instead. In western NY there is a big battle between machine guidance contractors and some local surveyors/engineers. The surveyor/engineer holds back info, then when forced to release it they "bastardize the cad files". Instead of the surveyor getting the work they are so desperately trying to hold onto, they are actually pushing the clients away.
If the vertical control is off this much, just how bad is the topo. Errors like this could have an adverse effect on sanitary slopes, and other critical ties.
I can see these topo surveys are going cheaper these days.
A few years ago nearly every topo I tied into with grading plans were on State Plane Coordinates. Now they are all back to assumed coordinates, with no BM.
Vent over...
What do your state regs say? In NH we are required to show at least 2 benchmarks on a topographic survey.
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Very unprofessional and could lead to liability problems for the original site surveyor
and anyone who tries to use the bastardized data.
I don't release anything to machine guidance contractors.
Working mostly in the same area, I complain about the very same thing. Designers really dislike giving us control as we are a design/build(mostly build) firm utilizing machine control...
Just started a new job and couldn't even average out rims and lids for less than a couple tenths, project owner asked design engineer for some points for control, ended up using one for vertical that was a mag. Still seems as though there is half a tenth floating around, but it's only dirt!?
Give me more utility work...less competition with lots of regulation and specifications.
alphasurv, post: 362681, member: 1652 wrote: I don't release anything to machine guidance contractors.
Alpha,
Do you intentionally not show benchmarks on your topo surveys?
If the contract plans were to show enough information, then there would be no need to request anything from the original site surveyor. These contractors are signing liability waivers, and at times they are paying thousand of dollars for this bastardized cad file.
strizzy, post: 362682, member: 7236 wrote: Working mostly in the same area I complain about the very same thing. Designers really dislike giving us control as we are a design/build firm utilizing machine control...
Just started a new job and couldn't even average out rims and lids for less than a couple tenths, project owner asked design engineer for some points for control, ended up using one for vertical that was a mag. Still seems as though there is half a tenth floating around, but it's only dirt!?
Give me more utility work...less competition with lots of regulation and specifications.
Strizzy,
I'm specifically referring to the Rochester and Buffalo area. I setup machine guidance projects all over NY, and across the country. This is the only area where "professionals" put up such a strong front. Everywhere else I've worked, they are more than welcome to provide the information. In fact this area is quickly becoming my fastest growing clientele.
Have never done a topo without leaving a BM or showing that the elevations were from some offsite BM.
Apart from that, an elevation will be noted on some existing structure that appears on the plans.
Without a basis of elevations being traced to a BM, TBM or other reference on or off the plans, you got nothing.....
Reason for this omission is that BMs or CPs on construction sites more often than not are 'moved' during construction phase.
As you know, construction crews don't bother to check a BM with another BM to see if there was any movement before using them.
Had a similar problem in the past but instead of using my BM, they used a concrete nail found near my BM as reference point.
I and the foreman had no idea who established that point on the ground. Needless to say, a lot of finger pointing occurred
after that error.
What I did after that, was to note on the drawing the government BM/CP that was used as reference point to establish the BMs in the survey.
That way, you force the construction manager to either call the surveyor back for a recheck or have his foreman run
a verification survey (with their in-house surveyor) before using any reference point found in the project site.
I do a few topos a year for engineers/architects. I always show at least two vertically stable benches, outside of the area of any potential disturbance and clearly labeled and identified, on every topo. All I won't provide, unless specifically contracted for, are my sideshot points. The transmitted CAD file has line-work, horiz. control (without elevations - use the dammed BMs) & the contours/DTM. The signed & sealed hard copy rules.
That being said, I'm starting to shy away from them - the expected accuracy and the litigious atmosphere around the construction industry is just too stressful for an old dude. When I started surveying topo was transit & stadia, contoured by graduated rubber band, or plane table & level on really flat sites. Very large sites were flown and contoured photogrammetrically (is that a word?) $hit got built anyway. Nowadays, .05' & people go bonkers.
Did a topo for a proposed small apartment complex. Since the buildings were to be connected to the san sewer system, elevations were to be tied to it. As-built records for the two nearest manholes had been provided by the municipal engineer, a very fancy high end outfit - Swell office with eye-candy receptionist & lots of suits & ties. The records indicated the RIM elevations were within a foot of level with each other. Actually there was about 10' feet of difference (pretty obvious to the eye). QC? - we don't need no stinkin' QC.
But, their receptionist IS a major hottie.............
Depending upon where I'm doing a survey, I'll either use a local (city/county) benchmark from their records or I'll find some nearby NGS monuments to use. The BM is always offsite, and we will bring in temporary control points from which we can work (for topography and future staking).
I think my biggest frustration is when I send out a crew with a few datasheets and tell them to use one of those, whichever is easiest to access, then they don't tell me which one they used and I have to dig through the data files to see where their BM shot was and work backwards to figure out with one they used...
But I always put the BM information in my drawings.
FrancisH, post: 362723, member: 10211 wrote: Reason for this omission is that BMs or CPs on construction sites more often than not are 'moved' during construction phase.
As you know, construction crews don't bother to check a BM with another BM to see if there was any movement before using them.
Had a similar problem in the past but instead of using my BM, they used a concrete nail found near my BM as reference point.
I and the foreman had no idea who established that point on the ground. Needless to say, a lot of finger pointing occurred
after that error.
What I did after that, was to note on the drawing the government BM/CP that was used as reference point to establish the BMs in the survey.
That way, you force the construction manager to either call the surveyor back for a recheck or have his foreman run
a verification survey (with their in-house surveyor) before using any reference point found in the project site.
"As you know, construction crews don't bother to check a BM with another BM to see if there was any movement before using them."
That is a criminal offense in my mind... And I do mean criminal.
It should bug, it bugs me too,,,,,,,,,,,
Surveying 101, leave at least 3 (that would be a bare minimum) bench marks for any site.
If it's real construction, buildings, sewer, curb and gutter, ect.; then LEVEL through them.
Not putting critical information like the benchmark, renders the map useless and is totally unprofessional and not worthy of the paper or pixels that represent its image. I may be old school, and likely will take flack for this statement. I mean, why put your contact information or seal on it if you are willing to open yourself up to scrutiny or liability for the lack of data.
Several issues I think contribute to the lack of Benchmarks on a plan. Design engineers with no practical experience on what a BM is used for. Plans only produced for municipality approval.
Constructability takes a backseat to numerous plan checker wants. I have had apartment complex plans with no dimensions between buildings and/or the boundary and only dims to the setback lines. Also, the designer wants a "clean" drawing, existing topo and planimetrics is turned off in favor of drainage plans, lighting plans, landscape plans, etc. You may get an existing conditions page but it is bare minimum- probably copied from a previous surveyors work done years prior.
