Why are people writing 打井 (dǎjǐng) = "to dig a well" on this construction site wall? Near campus, there are construction sites for apartments, and one of them has this writing on it:



Repeatedly written is 打井 (dǎjǐng) = "to dig a well", along with a phone number.  It's possible that these are all advertising some kind of well-digging service, but it seems an unexpected place to choose to advertise, especially when there's more than one of them.  It makes me think there's more to this story.

Question: Why are people writing 打井 (dǎjǐng) = "to dig a well" on this construction site wall?

The other words seem to be:


降水井 (jiàngshuǐ jǐng) = precipitation well
收废品 (shōu fèipǐn) = waste collection
I myself as a Chinese can tell you that they are all advertisements for well digging, as those places are near the countryside where some villagers might need well for water, therefore those people with the equipment seek those opportunities by these advertisements. The number follows are phone numbers.