Gold coins under a paved lot?

[bobg0719]

I just heard a story from a very credible source about gold coins found on a property while ecavating a lot to pave it. About 20 years ago the owner of a paving company and hid crew were excavating a lot where a former bank once stood in preparation to pave it. while running the machine the owner noticed burlap bags in the dirt. When he got off to check them, he found numerous amounts of $5, and $20 gold coins from the early 1900's in them and on ground around them. He and is workers split the find without officially notifying anyone about the find. After they split it, his workers never showed up and he had to finish the paving job himself. He says that he didn't really have time to search for any more coins due to a time schedule to complete the job. I am just curious if there is anything under that lot still left, or in the unpaved ground around it. I know that I can't dig the blacktop if there was something there, but is there anyway to accurately detect for gold coins under a paved lot? It would love to know if there is anything there.

 

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[Tom_in_CA]

Bob, I work with paving and pavers a lot in my business (a street sweeper company that works explicitly with construction and paving industry). So here's the scoop: The pavement, when done on virgin dirt for the first time (which is the scenario you describe as the lot was "first generation" when they installed it) is laid on a compacted bed of decomposed granite base. In other words, they don't just lay asphalt on top of virgin dirt (for any sort of engineered spec's anyhow, but I'm sure anyone can do anything they want). If you talk to this paving fellow again, and ask him, I'm sure he'll confirm that there is a fill-layer under the asphalt. Therefore the actual terra firma would be under that. In other words, the depth to go through the asphalt (several inches for parking lots which handle lighter loads than streets) and the DG fill layer (6"? more?) will be prohibitive.

In the older days, perhaps less prep. was done. Like, concrete sidewalks laid on virgin dirt with little to no preparation, and thin asphalt layers laid right on existing dirt too perhaps. But today, there is usually that fill-layer for proper compaction, drainage, etc... So odds are, you will not be able to reach down to individual coins at the depths to get through that deep. And bear in mind too, that having one layer of minerals (the asphalt composition), then chaning to the DG layer (another mineral composition) to regular dirt/soil (yet another mineral composition) will give your machine fits. The machine will be tracking and adjusting to the topmost level, and can "hit a brick wall" at the next level. The most depth is had when the soil is consistent mineral composition all the way down, IMHO.

But heck, for gold coins, I'd still give it a try anyhow. If the actual depth down to the native dirt isn't as much as I'm saying (check with him to see if he recalls the spec's), and if you did get coin-size hits with your detector, you could actually dig them up. Here's how:

A lot of people consider asphalt (as is used on streets) is a hard substance, impenetrable, etc... But this is not the case. Asphalt was invented (to replace the earlier use of concrete for roads/streets) because it is more permeable, maleable, (more elastic, so-to-speak). It actually expands and contracts moreso than concrete will, during extreme hots and colds. So while concrete streets used to crack during freezing and thawing, ashpalt would "give". For example: if you went to an asphalt street during a day of 100* temperature, I bet you could stick a steak-knife straight up and down in the soft asphalt, right? Thus I have heard of bottle diggers, for instance, actually probing their bottle probes right through asphalt! (you could never do that with concrete). And then I've seen bottle diggers actually dig in asphalt, where they sort of "cut a plug" (so-to-speak), do their digging, and then replace the man-hole sized plug when they're done. They did this in an abandoned lot, in a blighted neighborhood, where I'm sure no one cared. So I'm not suggesting the property owners where you're at would approve of this. But I'm just saying ....... for a coin-sized divot, if your signal was only a few inches deep....... for what is likely a gold coin ......... just sayin' ....... 8)

 

[bobg0719]

Thanks for the reply. I figured it was a long shot but I may give it a try anyway. The bags of coins were broken open while he was scrapping and leveling the lot. There is a good chance that there are coins still there. I will try and find about about the thickness of the asphalt and any layer of dirt that may be on top of the coins. It amazes me how these were left behind when the original bank closed up and was torn down. I wonder if there are anymore bags deeper in the soil.