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Pin Cushions – The unpardonable sin
Ok. So maybe the thread title is a little extreme. But not by much. For years I’ve observed that some objects are detectable with magnetic locators and some are not. Recently I’ve been testing magnetic locators for a project and I’ve taken 5 rebar from the same bundle and each rebar produced a significantly different signal strength. The claims that an object of this size or that is detectable at this depth or that is somewhat misleading as there are plenty of examples of such objects that have no polarity or a weak polarity. It may be that you can detect a 1 inch bar from a depth of 5 feet. It may be that another 1 inch iron bar cannot be detected from a depth of an inch. Another issue is the direction of polarity, negative or positive. This affects the received signal strength. I don’t pretend to know all I would like to know about magnetic fields, but observation during my 20+ years of surveying has demonstrated that you cannot know that an object is not there simply because there is no signal from the locator.
I provide sales and support for some very advanced equipment. I use that equipment daily in my own business and it is what allows me to be productive as a solo operator. Having said that, I have said and continue to believe that the most important tool in a surveyor’s truck is the shovel. The second most important tool is the hammer. We are called upon to find or leave as set monuments that define the boundaries of real property. It’s the basis of what we do. The shovel, in many instances is the finder and the hammer is the setter. Both are important, but for retracement the shovel is king.
I recently took a small job (or what should have been a small job) finding the corners of a lot and staking one line. The lot is a simple four corner lot in town, 60’x170′. I found the first corner in a shared asphalt driveway fairly easily. I then worked my way down the street line. I was unable to find my other front corner and continued down the street, finding two more monuments that fit with the first. I always try to do this because it is possible that the first stake was not correct. I’ve even seen two front stakes be right with each other and wrong with the subdivision, so it’s good practice to tie in an adjoiner both ways if possible.
I then went to the back. I found one stake with old flagging on it, but it wasn’t the same character as the rest. It was an old carriage bolt with a 1/2″ diameter shank. The normal material for this subdivision is 5/8″ sucker rod (a smooth sided steel rod). I tied it in, but in my mind placed an asterisk beside it. I was unable to find the other back corner. I proceeded to other back corners. The next back corner was a 5/8″ sucker rod, but it was sticking up about a foot. This seemed uncharacteristic, so I collected it, but also placed an asterisk by it in my mind. I continued on and finally found a corner that had the right feel to it. I went the other way and found a back corner in the other direction that matched my expectations. The distance between them was within a couple of tenths of record. The carriage bolt was off by about 2 feet from the record, holding these two back monuments. I then used these to rear monuments and staked where I suspected the corner should be. Sure enough I found a 5/8″ sucker rod very close to record call. I then went to my other back corner and confirmed that it was gone by digging a hole. It was right beside a drainage inlet and was very likely removed when the box was constructed so I set a new monument.
Back to the front, I was now ready to set the front corner that I was unable to find. However before setting the stake, I navigated to the calculated position. I didn’t see any reason for this monument to be missing and the original surveyor clearly had marked the lots originally. So I dug the point also. Sure enough, only a couple of inches below the surface I found the 5/8″ sucker rod in place.
The only way to know for certain that a monument isn’t there is to dig. Now the question – how deep should a surveyor dig? I don’t have a definitive answer for this. There is a matter of practicality. Not just for the effort involved, but also a point where a deep, deep monument doesn’t offer much to property owners to know where the boundary is. Typically, I will dig a foot, use the locator and see if there is a signal. I also look at the soil to see if it appears to obviously be fill (coloration and debris).
Another thought about this job… I’m going to tell on myself. I gave a lump sum fee of $250 to do this. The lot owner thought it to be too high! In all, I spent about 5 hours in the field on this job – way more than anticipated. I don’t think that this entitles a surveyor to provide a less than excellent service. Even when you start seeing that you are down to minimum wage, you still dig the holes and you still set the stakes.
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