[Amitaabh]

The water gutters in our house are patched by someone using a black tar with a bunch of rocks in it  (its probably some kind of asphalt with aggregate) black strips and a torch. I am worried that water reaching the ground through the gutter will have a large enough amount of impurities in it from running over the patch that the plants growing nearby will be unfit to ingest. The asphalt like thing that binds the aggregate just looks like the water will dissolve it pretty fast. I wonder how the asphalt even stays put, although it seems sticky I don't understand why it doesn't just get washed away. 

[curiouscat]

High molecular weight, large chain hydrocarbons are rarely  significantly water soluble. Most of it is hydrophobic, non-polar C-H bonds and rings.