Well, when I first encountered wood chips at a totlot, King TotsaLot gave me some FANTASTIC advice! I saved it and here it is, to sav His Majesty having to reprint it.
I don't know much about *where* the best areas (apart from around the play-on structures) would be, but I'm sure KT will add to that question.
Here's what he said about wood chips.
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Here is what KT does and has learned.
Wood chips rot and compact, and an older lot has layers based on this phenomenon. The wood chips on an old lot will be dark brown...if they are lighter colored then either the lot has had new chips added, or it is a newer totlot.
The stratification typically consists of some thin zone of loose dry dark colored chips...and then you hit the compacted zone. KT finds most of the coins at the top of this compacted layer and simply rakes the inch or so of loose chips back with his shoe. Almost all clad is readily visible against that dark background, except pennies, which quickly take on the same dark look as the wood chips...I think it is tannic acid from the wood coloring the copper.
Anyway, KT rakes with his foot on the spot of a signal, and reswings the MD over it...at least 50% of the time the item is in the loose wood chips then and not on the spot. But if on the spot, out comes the PinPointer and KT locates the item and digs it. If the mulch is damp, it will come out in layered pieces....find the piece the item is in with the pinpointer and break it down to extract the item. If you don't hit it initially with the pinpointer, then back across it with the MD coil and push in your digger and pop out a mass...it will be loose and fall apart...check hole, if no signal, you got it in the mass, if signal then you got a problem in the hole. Most totlots KT has worked on, have a bottom...covered with a fabric or mesh liner...if the signal is below the liner, forget it and move on...9 times out of 10, it is a pop can that was crushed and covered by the liner. KT dug a number of these early in his MD career and won't do it now. Too much trouble and poor results on goodies preclude it. Most detectors under good conditions will detect a popcan at 8 to 10 inches deep...most totlot liners are 8 to 10 inches deep!
How to fill a totyard mulch/chip hole? It makes a sorry looking mess digging, but can pretty easily be repaired. The first stuff to go back in the hole is the damp, soggy stuff that was the last you dug out...you will have a bit of excess simply because it was compacted before so you will have to mash it down as you fill it up...once all that stuff is in the hole, then stand up and use your foot to rake/scatter the loose wood chips you pushed to the side across the site...it will look reasonable...remember..the first rain will wash away any evidence of the disturbance. And what looks damp on the surface will dry in a few minutes due to it being exposed to the air...and it will take on the appearance of the dark dry wood chips.
On some school totyards, KT has dug over a hundred holes in an hour and a half and before leaving only the last few he dug are even noticable....The first time kids are back across the site, playing, jumping, dragging their feet, and falling down, the surface is completely compacted and changed and there will be so much disturbance that KT defies anyone finding evidence of an MDer ever being on it.
Just do not leave open holes where a kid could trip and fall, that is the main thing...KT has actually seen a couple of squirrels actively digging on one of his totlots, either burying acorns or digging them up! THEY make a bigger mess than KT leaves! And kids dig in the mulch too, for what reason, KT does not understand! Maybe cause they realize they lost something??!
On a new mulch totlot, you will have a different problem...the new mulch will give you splinters! KT has a hard time understanding how kids don't get a lot of splinters when these lots have additional mulch added to them. If you come across a newly mulched totlot, it is possible that the old mulch with its collection of coins and jewelry was stripped out and you will have to wait for the goodies to be repopulated by the kids! That could take monthes. Or the goodies are buried too deep for you to find with your detector.
Anywho, the problems with mulch is that it is not like soil which has a binder to hold it together...so just realize you will never "dig a plug" in mulch...it just fragments and comes all apart. Just keep the different colors separated so you can put them back into the hole in the right sequence.
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Thank you again, Your Majesty!
SageGrouse