RedDirt
Gold Member
- Joined
- Dec 4, 2007
- Messages
- 469
- Location
- Northern Idaho
- Tractor
- Kubota BX23, Wards 16HP HST Garden Tractor, (previous) D2 Logging Cat
Anyone with a hoe always, or should always, fret "What's down there?" before they dig. Keeping a record of what you place in the ground can avoid some costly mistakes later. A accurate As-Built record can also assist developing the next underground project because you will know what is in the ground and where.
At "work" we keep track of all major underground utilities by taking and recording as-built shots of the pipes/conduits with a digital theodolite while the trenches are still open. This gives us an x,y,z location and I'm confident I can later find any of these points underground within a hand shovel (+/- 2 or 3 inches). At "home" I still use the method I developed before work became so sophisticated: crossed tapes. Carefully done, this method can yield almost the same accuracy, especially in the x,y plane. Basically this is a simple navigation exercise.
I start with a rough plan view sketch of the underground work and permanent locations I'm going to measure these point from. The sketch doesn't need to be precise. It only serves as a "key" to your dimensions. On the job we call it the cartoon.
The permanent locations can be the corners of buildings, fence posts, even trees (that you don't expect to cut down). I mark these A, B, C, etc on the sketch. (If you use a tree among other trees be sure to label it 36" OAK, 18" Maple, or similar so you can positively identify it later.)
Then I label the points I am measuring. These are usually the "turning points" (the 45/90 degree fittings or "T" intersections) of underground pipe/conduit or random points along a curved line. On my sketch I mark these points 1, 2, 3, etc.
Next I make a handwritten three column spreadsheet.
The first column is for the point number. The second two columns are for the points I measured from (the letters) and the associated dimension.
Next take a tape measurement from a nearby permanent "above ground" location to the pipe. Now take another measurement from a different permanent "above ground" location. It is most accurate if the lines of these two tape measurements intersect at about 90 degree angle plus or minus 30 degrees. I'm speaking here of the angle formed by the two tapes, not the angle between the pipe and the tape, that's immaterial.
The spreadsheet is filled in as you take the measurements. Thus:
1 / A-30'-5 1/2" / C-20'-2"
2 / A- 45'-8 1/4" / D-58'-4 3/4"
3 / B-18'-2" / D-20'-7"
etc.
The fixed points you measure from and the points you are measuring can be added to the sketch and spreadsheet on-the-fly as needed.
Next time you are digging in that area pull out your sketch and spreadsheet and you can re-create with the crossed tapes what you have buried underground. You'll know really close where your hazard zones are. If you've measured each "turning point" and intersection (and random points along a curve), the remainder of the piping lies between these points. Like a "connect-the-dots" drawing.
Two tapes used simultaneously make this task quicker. Mostly I use a 100' and a 300' tape but shorter tapes will still work; you may just need more points to measure "from". I usually tack the end of each tape at two of the locations I'm using and literally cross them over the pipe intersection I'm measuring. When the angles between the tapes gets "too narrow" (less than 60 degrees, or 45 degrees "in a pinch") I move the end of one or both tapes.
If striving for accuracy you can hand hold a plumb bob at the intersecting tapes and and adjust the intersection until the bob is just above the measured point.
If you have a builder's level you can measure and record the depth of the underground pipe from a bench mark elevation. Typically "at home" I just add a fourth column to the spreadsheet labeled "BG" for "below grade" and simply tape measure to about where I think finish grade will be.
You can actually make a fairly decent drawing from the spreadsheet data especially if you have a good plan of your property showing the buildings. But remember, if you are measuring on a slope, the plan will not be an accurate "horizontal" representation. If your land is reasonably level your finished plan can be quite accurate. You can plot a lot of items (including the points you are measuring "to") using crossed tapes.
By the way, for re-creating your underground work later on the surface it doesn't mater if you first measured "along the slope" of the land. As long as you measure the same way later the point you previously recorded will lie below the intersecting tapes.
Is this record keeping tedious? Yes, a bit. But the first time you hit your 220volt service or water main you'll wish you'd taken the time.
I hope this saves someone a future catastrophe.
At "work" we keep track of all major underground utilities by taking and recording as-built shots of the pipes/conduits with a digital theodolite while the trenches are still open. This gives us an x,y,z location and I'm confident I can later find any of these points underground within a hand shovel (+/- 2 or 3 inches). At "home" I still use the method I developed before work became so sophisticated: crossed tapes. Carefully done, this method can yield almost the same accuracy, especially in the x,y plane. Basically this is a simple navigation exercise.
I start with a rough plan view sketch of the underground work and permanent locations I'm going to measure these point from. The sketch doesn't need to be precise. It only serves as a "key" to your dimensions. On the job we call it the cartoon.
The permanent locations can be the corners of buildings, fence posts, even trees (that you don't expect to cut down). I mark these A, B, C, etc on the sketch. (If you use a tree among other trees be sure to label it 36" OAK, 18" Maple, or similar so you can positively identify it later.)
Then I label the points I am measuring. These are usually the "turning points" (the 45/90 degree fittings or "T" intersections) of underground pipe/conduit or random points along a curved line. On my sketch I mark these points 1, 2, 3, etc.
Next I make a handwritten three column spreadsheet.
The first column is for the point number. The second two columns are for the points I measured from (the letters) and the associated dimension.
Next take a tape measurement from a nearby permanent "above ground" location to the pipe. Now take another measurement from a different permanent "above ground" location. It is most accurate if the lines of these two tape measurements intersect at about 90 degree angle plus or minus 30 degrees. I'm speaking here of the angle formed by the two tapes, not the angle between the pipe and the tape, that's immaterial.
The spreadsheet is filled in as you take the measurements. Thus:
1 / A-30'-5 1/2" / C-20'-2"
2 / A- 45'-8 1/4" / D-58'-4 3/4"
3 / B-18'-2" / D-20'-7"
etc.
The fixed points you measure from and the points you are measuring can be added to the sketch and spreadsheet on-the-fly as needed.
Next time you are digging in that area pull out your sketch and spreadsheet and you can re-create with the crossed tapes what you have buried underground. You'll know really close where your hazard zones are. If you've measured each "turning point" and intersection (and random points along a curve), the remainder of the piping lies between these points. Like a "connect-the-dots" drawing.
Two tapes used simultaneously make this task quicker. Mostly I use a 100' and a 300' tape but shorter tapes will still work; you may just need more points to measure "from". I usually tack the end of each tape at two of the locations I'm using and literally cross them over the pipe intersection I'm measuring. When the angles between the tapes gets "too narrow" (less than 60 degrees, or 45 degrees "in a pinch") I move the end of one or both tapes.
If striving for accuracy you can hand hold a plumb bob at the intersecting tapes and and adjust the intersection until the bob is just above the measured point.
If you have a builder's level you can measure and record the depth of the underground pipe from a bench mark elevation. Typically "at home" I just add a fourth column to the spreadsheet labeled "BG" for "below grade" and simply tape measure to about where I think finish grade will be.
You can actually make a fairly decent drawing from the spreadsheet data especially if you have a good plan of your property showing the buildings. But remember, if you are measuring on a slope, the plan will not be an accurate "horizontal" representation. If your land is reasonably level your finished plan can be quite accurate. You can plot a lot of items (including the points you are measuring "to") using crossed tapes.
By the way, for re-creating your underground work later on the surface it doesn't mater if you first measured "along the slope" of the land. As long as you measure the same way later the point you previously recorded will lie below the intersecting tapes.
Is this record keeping tedious? Yes, a bit. But the first time you hit your 220volt service or water main you'll wish you'd taken the time.
I hope this saves someone a future catastrophe.
