Since someone resurrected this - Here is another update:
Angry neighbor sent a letter from a lawyer last august asking us to water the arena or they would sue. We purchased a water tank with spray boom to pull behind my side by side (kawasaki mule). It took almost 2 hours to water the arena and 2 trips to refill the tank. We did this before every time I taught. It was time consuming and not super helpful in the heat of the summer when it sucked the water right out of the sand.
After I consulted 2 different lawyers we responded to the neighbor with our own letter. Short and sweet addressing their “issues” and how we may take action, and also how they may take action to alleviate their frustrations. Mind you these visits with the lawyers cost me time and money.
Neighbor responded again saying that our watering was not good enough and that we needed to figure out some other way to reduce the dust.
At this point we had done everything legally on our end to protect ourselves, the lawyers said the case would not hold up in court as we were very reasonable in our responses and taking action. The angry neighbor was unreasonable. So we ignored their second letter and stopped watering as we were into fall at this point and the arena would stay wetter for much longer.
The neighbor was also harassing me and my students (minors) during this time by yelling and cussing me out while I was teaching. I finally called the cops one day after my students became very upset ( I was good at just ignoring him). We haven’t heard boo from him since that day.
Since then I have talked with other family members who assured me they wanted no part in a lawsuit, it was just the angry older gentleman who pushed for the lawyers. What a sad way to spend the later years of your life, angry and yelling. His children have had nothing but nice things to say about my horses and students. His grandchildren and great grandchildren love watching the horses when they visit. I am still kind to his children that have been at his house recently, but just ignore the older man instead of saying like hello and chatting like I did before this entire thing happened.