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Alaska cruise regulators have sent five more notices of violation to cruise ships for discharging unpermitted levels of pollutants into state waters during September.

That brings the total number of such violations to 20 for this year. The most common violation was for ammonia, a component of urine.

September violators were the Holland America Westerdam; Princess Cruises’ Sapphire Princess, Diamond Princess and Island Princess; and the Silver Shadow, owned by Monaco-based L’Aigue Marine, according to the Department of Environmental Conservation.

This summer was the first season cruise lines discharged wastewater under a general permit, which a 2006 ballot initiative required the state Department of Environmental Conservation to write.

Unlike many municipal dischargers, cruise ships aren’t allowed a mixing zone. DEC enforcers sample the wastewater for pollutant levels at the end of the pipe, before it becomes diluted in seawater.

Cruise lines have been fighting the permit. They predicted this spring they wouldn’t be able to comply for some of the listed pollutants.