Answer:
The positive impacts are simple- jobs. Mining, drilling, and other exploratory resource harvesting companies have historically brought abundant employment opportunities. They can also revive dying towns/cities that are the brink of financial ruin.
The negative impacts however, are sometimes far greater dependent on the type of operation, and the environment in which these operations take place.
Example: while the pebble mine in Alaska gives abundant employment and financial benefit to those that take part in it, the estuaries of which Salmon have used those streams for a millenia are threatened by the toxic drainage. If this operation is regulated carefully, an entire link in the environmental cycle there can be broken and could have devastating long term impacts on the entire area and surrounding communities.