I went out to an industrial park to bid on cleaning their parking lot and it is covered in these stains. I have seen them before and muriatic acid wouldn’t even remove them. They seem to be coming out of either the expansion joints in the curbs or the flat surface. Some of the spots were wet so I assume that the stain is an ongoing situation. I was thinking that is may be coming out of the soil, maybe from the fertilizer that is being used. If anyone has run into this before and has any idea how to get it up, I could use some help on this one.
Black goo that bubbles up from the soil and leaves tough stains on concrete? My WAG is you struck oil. Natural or otherwise.
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