I don't think it's curly dock. Hard to put my finger on exactly why I think that, but it just doesn't look like the CD that I have.
Adding your general location to your avatar is helpful for figuring out weeds.
I have it in my field and gly with surfactant will kill it if the other plants around it are mowed. If they aren't mowed, it will only kill what gets reached. My sprayer isn't that stout if I use the atv, but has 50psi+ if I use the tractor and 3pt sprayer. There may be a better option than gly, but I haven't tried anything due to residual spray and it possibly hurting the next plot.