I have been asked to locate a basement that extends into the street.
This is "Main St" and with all research shows ROW and Boundary going to face of building +/-.
These are old mill buildings dating back to the 1800's(still researching when they may have been built)
I can go into the basements and measure out from what I believe is the "face" of building above.
This is one particular block (about 200 feet)but could turn into all of down town(about 2,000 feet each side).
The question that was asked of me, "Is there a way to measure through the sidewalk(ie: ground penetrating radar was a thought) to determine the location of the limit of the basement?
Oh yea, and they want the info yesterday. LOL
Any thoughts or ideas other than accessing the basement and rough measuring would be greatly appreciated.
Jim in Southern NH
test pits
we locate undergourd pipelines almost everyday and use these.
http://www.locateunderground.net/home.php?cat=263
You could probe the limmits of the building then check by measuring the inside of the structure.
I have been told that when using GPR what you are looking for has to be within 6-7 of the surface.
I have never seen one of these used but it is a possible option
http://www.ssilocators.com/specialty-products/all-materials-locator/
That looks like it would work great, however, I believe the OP has stated that the area above the basement extension is paved.
Is there anywhere you can drop a plumb line down from the ground floor to the basement, and then measure the extents of the basement, etc.?
How deep through the sidwalk? Vacuum bores can get pretty deep but your dealing with a 6" hole so you may need a few to find the end of the basement and then it may be hard to tell what your actually looking at in the hole.
You going to have to measure it.
The existing sidewalk is paved with brick inlay.
Someone had the bright idea back in the 80's to do it this way. 2" pave with 4"x8"x1" brick inlay.
The reason that this is an issue is that we are replacing the mast arms on Main St. and they hired a company to bore out the locations.
They are approximately 2-3 dia and 9-10 feet deep.
The crew was boring the other day and hit this basement.
It is approximately 2 feet below grade to the top of the basement.
I have not gotten a clear answer as to what material the basement is made of (concrete, granite block, etc) but will be verifying soon.
Jim
I wouldn't do anything invasive until I had consulted a structural / geotechnical expert......
These "basements" were probably coal chutes or storage areas. They are also referred to around here as "sidewalk vaults".
First, does the municipality keep track of these vaults? Usually, they involve some kind of fee or tax, as an encroachment into the City street.
Around here the NYCDOT kept records, usually index cards with size, depth and extent.
GPR ought to give you a fairly good idea where voids under the sidewalk occur.
Around my parts, the City kept a record of the encroachment or issued a License Agreement for Sub-space within the public right-of-way. You may wish to check the City Real Estate Owned file...if it exists. I would also check the old Samborn Fire Protection maps as this may provide you an estimate of the sub-space size.
That is a toughie. Measuring from the inside, at best, gives you the location of the inside of the exterior wall but no clear definition of the location of the outside of the exterior wall. That might be 8 inches or 24 inches or more depending on construction materials and techniques used at the time.
Effective GPR depth could be less than 6 feet depending on what type of soil you are trying to 'look' through. My experience is that GPR does not like clay at all.
Probe rods, shovels and vac excavation would seem to be the best bet.
In a coal mine, we would typically locate two plumb lines on top and bottom and start a traverse from there or run a traverse down a slope, (or stairs in this case) to transfer coordinates to the basement.
Are there any pipes, ducts, chutes, or other openings/pass-throughs between the first floor and basement ceiling you can use as a point of reference? I did something similar where I mapped the first and second floor, then used a couple of points of reference to line up the floor diagrams. That would give the dimensions of how far the "air space" extends past the face the building, but of course, as mentioned above, the width of the outside wall could be an issue.
Jim,
GPR might work but you may want to do a combination seismic, resisitivity survey along the street. A 5 ft grid would also show most of your sewer,water and other utilities. email me and I will send you our underground locating manual which will show the geophysical methods available for this type of project. It beats digging holes and we use these methods when we have worked in Cities and power plants to map utilities.
Jerry K. Price
DES Resource Groups Inc
www.DESRG.com
email; gPsprice@aol.com
