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RE: Radiographic inspection

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Most testing labs use Pachometer's. A pachometer is actually nothing more
than a metal detector. In fact, Fisher is one of the companies that supplies
Pachometers for testing. Mel Fisher is also the treasure hunter that
discovered millions off the Florida coast a few years ago. Fish Metal
Detectors have been popular for years and serve a purpose for professionals
and hobbyists.
The depth of the detection is questionable. Certainly a couple of inches is
expected. In coin detection, it can be up to a foot or more depending upon
the mineralization of the soil (from my hobby days). I would caution,
though. I recently had a Pachometer study done on an infill in an
Unreinforced Masonry building and the results showed no steel rebar or
dowels. When the work began to remove the infill, rebar was uncovered less
than 4 or 5 inches from the surface. The lab that performed the Pachometer
study returned to the site with the equipment and did not detect the steel.
We still don't know why, but I do know that the testing tech was also the
owner of the Company and someone I've known for over twelve years and
trusted (also an engineer).
On a similar note, I was a Cross-Complainant in a law suit that arose from
the work done on a Unreinforced Masonry building owned by the Girl Scouts of
America. I was supplied a Pachometer survey which showed the building to be
Unreinforced. The lab was one that I did not respect, but who had been in
business specializing in Unreinforced masonry testing for years.
The roof was stripped and the contractor started to core the walls (this was
a blockwall building where the client wanted to Center-core the URM wall
rather than anchor through the face of the wall. The contractor hit vertical
and horizontal steel almost immediately.
I was notified, stopped the job and contacted the testing agency
immediately. They returned to the site and performed another study - to find
it reinforced to the hilt. They claimed that either the equipment was faulty
at the time of the original test or that their technician did not know
enough to check the batteries.
I was dropped from the suite (no liability insurance) and the Testing Lab,
Contractor and Roofer (the contractor and Roofer were Cross complainants
with insurance) were found liable and had to compensate the GSA for all
damages to the building.
IMHO, the Lab should have been the only one liable.

I've had Pachometers used on hundreds of buildings for veneer tie testing as
well as other needs without a problem. Generally the Pachometer can detect
the depth below surface, the spacing horizontally and vertically as well as
the size of rebar (I'm not sure how they do this).

Dennis Wish

Dennis Wish PE
La Quinta, California
ICQ# 6110557

"Silence is the virtue of fools."
Francis Bacon

|-----Original Message-----
|From: Powers, Tony [mailto:tpowers(--nospam--at)]
|Sent: Monday, March 30, 1998 9:19 AM
|To: seaoc(--nospam--at)
|Subject: RE: Radiographic inspection
|Tom Harris wrote:
|>       When walls or slabs above grade are too thick to use pachometer,
|> i have
|> used x-ray successfully.
|	[Powers, Tony]
|	How thick is too thick for a pachometer?  Where can I get more
|general information on pachometers and their use?  Thanks,
|	Tony Powers, PE
|	HDR Engineering, Inc.