Dew, you say
"Digging a few tabs in some of the parks might be work the time."
The operative word here, Dew, is "few", right? If there were truly a "few", then sure, no one would dispute that it's worth the time, and you'd be right. But what I was talking about, is not "a few". Let me give you an example:
There was an old town blighted park, in the bad part of San Francisco, that got a large portion scraped off with heavy equipment, to make way for artificial turf soccer fields. Some friends and I got in on that one several years ago, and had a blast. Since it was basically a demolition site, we put our mindsets in "relic mentality" mode, and dug everything (except iron). Because afterall, no fear of holes. On some days, the entire top 6" was uniformly gone, so it was strictly old coins. But as the project progressed, unfortunately new soil got mixed back up with the deeper soil, so now clad and old was mixed together, with no "rhyme or reason" as to depth/age correlation. But still though, easy digging meant we still dug everything!
Here's the point though: I saved every single target I found, over 2 weeks of solid hunting every night after the workers would leave for the day. When it was all over, I inventoried all the coins, to gold, to junk ratio, just for the fun of it, and for an article we wrote for W&E magazine about that event. The aluminum junk to gold ring ratio was utterly staggering. It was a rare look at what ratios would be like, if a person had the liberty to "dig all" in junky urban blighted ghetto parks. We're talking on the order of 300 to 1 ratio, of any gold item, to all the foil, tabs, slaw, slag, etc.... This is simply not an option at un-disturbed turf, IMHO. Well, SURE, you can do it (go have a blast), but tell me honestly, if a guy had that much energy (and that much gonads to go dig 300 holes in turf for a single gold ring), why not simply find swimming beaches, sand volley ball courts, and other such hunt sites where the ratios are much better per their nature, and the digging is much easier per the nature of the material? I mean, why bother? I happen to live near the ocean, which might be easy for me to say. But it holds true for swimming or recreation beaches at even fresh-water lakes inland too.