Draft permit would let Fairbanks discharge 11.2 million gallons a day into the Tanana

Fairbanks could keep discharging up to 11.2 million gallons of treated sewage a day into the Tanana River under a draft permit the state posted Sept. 8.

The permit would let the city and Golden Heart Utilities keep running their shared wastewater plant, with a "mixing zone" near the outfall, a defined patch of river where the discharge is allowed to exceed water-quality limits before it dilutes. The zone covers ammonia, copper, temperature and overall toxicity to aquatic life.

The daily ceiling has climbed. It was 8 million gallons in the 2015 draft and rose to 11.2 million, a figure a later proposed permit kept. Meanwhile the state has flagged $6.7 million in work to add ultraviolet disinfection so the plant can meet stricter chlorine limits, upgrades that would affect both the water going into the river and sewer bills for Golden Heart customers.

Mixing zones are contested. State policy requires them to stay as small as practical and bars them from creating a health hazard or harming aquatic life, with extra limits where salmon spawn. Environmental groups and some tribes argue the zones concentrate pollutants in habitat that people downstream depend on. The state calls them a regulated tool for protecting water.

A formal 30-day public comment period is coming, though the state hasn't set the dates.