Ahh, ok. There's a park we un-fondly call "wino cap park" there. At Stainslaus x Jefferson. It was a very blighted park back in the 1970s/80s (needle junkies, winos, homeless encampments, etc...). The city came in and cleaned all that up. But it's still a nearly solid bed of wino screw caps and junk. However, back in the late 1800s, that was the upscale high end part of Stockton. So if someone cares to try to get underneath the junk, there's actually choice old silver in there.
Guys used to "snipe around" the junk. Eg.: small coils, going real slow, high disc. , going slow, and passing the cross-hairs where wino-caps show up, etc... And others tried a "strip-mine" technique which is to grid off an area 6 ft. square, and litterally dig every signal out. You'd eventually be rewarded with barbers and a seated or two. But again, very nerve racking.
So the crowning glory of b@llsy hunting was: A few friends of mine, during rainy moist season, would actually go out there with flat shovels, at 5am on a Sunday , or a federal holiday, and do the following: Cut out squares of turf, a foot or two across. Such that they can get underneath them w/o damage, and carefully lay on a tarp. They'd do 10 or so such cut-outs, so that it essentially became like they were "rolling back the turf", or "creating their own scrape". When they had a mattress size area dug out to 5" deep, they'd stop and detect it. Then when done, merely put the grass back in place, stomp it down, and ..... no harm done! Couldn't even tell they'd been there.
Naturally you could only do that in very moist times. And naturally they chose ... uh ... "discreet" times. But it paid off
