I'm afraid my reply is not of much use for this painting, but first thing I see is that there's no or very little white of the paper visible. If you have a nice white paper, and you leave the white untouched here and there, it will immediately give a much fresher and crisp look.
Trying out a color on another paper than your painting first, allows you to see how it looks.
Another thing is to avoid mixing too many colors and use pure ones as well. When mixing, two to three colors max will be best to avoid mud.
When looking at your photo, I don't really think your colors look muddy though. It seems to me that you just overworked the image a bit too much. Leaving areas white, and trying as much as possible to do less (but accurate) maybe is the key. Although that is also the hardest!!
You could also try out using different kinds of paper, different amounts of moisture etc. Some paper is very easy to overwork.
Finally, when looking at this picture, I find that my eye tends to go to the brighter, yellowish green spot in the painting. Probably this is also for a next painting, but maybe it would look nice if there's also a yellow-green patch in the foreground on the right, and one a bit closer to the mine, so you'd lead your viewers eye to the mine. That would also help to make the color brighter.
I actually found some more info on muddy watercolors in the Watercolor section of WetCanvas. I give you the link below:
Hope this helps!