Hi Steven:

Clearing up ammonia or urea from CYA is straight forward, just slow and expensive.

1. Add borax till your pH is at or near 8.0
2. Add plain 6% household bleach --IN THE EVENING -- in 10 ppm chlorine doses (~2 gallons per 10K gallons)
3. Skip dosing if TC (total chlorine levels) approach 20 ppm.
4. Continue holding pH high and adding 10 ppm chlorine doses till CC is less than 1.0 ppm, and chlorine loss overnight is less than 1.5 ppm.

You can swim while this is going on, BUT the water may be irritating, especially to eyes.