runoff from salt would not be helpful. If no potential from runoff, probably not an issue. It will poison the soil its applied to for a while. Personally, I'd use Roundup.
Round up or killex. Anything containing 2-4-D will wipe em out. But be careful not to get it on flowers or your plants. If your in Canada these products are banned for use on dandelions and other broad leaf weeds but it is available for use on poison ivy. You will need to ask for it as it's usually locked up.