Ammonia is easy to contain by: Tarping the component that is releasing ammonia is effective, especially for outside releases.
Allow ammonia to dissipate to atmosphere if people downwind are adequately protected or evacuated. Best overall method of handling a release is to control ventilation and reduce pressure by releasing to atmosphere (from containment within a building or under a containment tarp).Tank of ammonia, unless exposed to extreme heat (warmer than water from hose stream).
Consider using portable exhaust fans to divert or diffuse vapor instead of water. Spray water at rates of at least 100 gallons per minute with two hose streams located at each flank (narrow fog stream) over the top of invisible vapor located just after the visible cloud. Use a dilution rate of 10 to 1 water to ammonia (2 to 1 for maximum dilution of ammonia to water). NEVER put water on ammonia liquid or an aerosol stream or aerosol dense gas cloud. Avoid using water unless absolutely necessary to protect life (evacuation or rescue).