Hi indycat:
Sorry to hear about your pond situation. My pond is only 1,000 gallons and I had a major blowup with my sprinkler system irrigation. It burst underground - right next to my new pond - and it leaked water into my pond and created a big flooded mess. This went on overnight and I had no idea it was even happening until I woke up the next morning to see my entire backyard flooded! Thankfully, I was able to get it fixed within a few days. At 1,000 gallons, it took 4 - 5 days to clear up where I could finally see the fish and bottom again. Since your pond is so large, it might take up to a month to clear up. It WILL eventually settle - just give it some time. After mine settled completely, I did partial water changes (20%) about every week with a wet/dry vacuum and it eventually got rid of all the mud at the bottom of the pond. You could probably start doing partial water changes now to get a jumpstart. I just waited it out until I could see that all my pondlife was ok. Good luck.

I think koi clay sprinkled around causes the siltation to clump and sink. It is very fine and doesn't add any volume to the material you have. Works great. Maybe someone can confirm this fuzzy memory?
Mike

The chemical is a flocculant. It does exactly what the guy told you. You put it into your pond, and it will cause the microscopic particles to clump together and sink to the bottom.

Thanks for the responses. I do have some Koi clay, can anyone confirm that this will help the situation? I may be able to add some this weekend

Ok I added some Koi clay a few days and did not notice any difference. Today I am doing a partial water change, if that doesn't yeild some progress, I'll get some of the clumping chemical, as a last resort

Other suggestions are welcome, we do have someone coming tomorrow to reroute future water on our property, regardless of what the neighbors do with their retaining wall