State water quality regulators have tightened environmental restrictions on Santa Rosa's wastewater treatment plant in an effort to protect the health of the Laguna de Santa Rosa over the objections of city officials who questioned whether the tougher regulations are justified.
The new five-year permit governing the city's discharges of treated wastewater into the Laguna contain a controversial prohibition on the release of phosphorus into the Laguna, which is listed as an impaired waterway.
Phosphorus is a nutrient common in fertilizers and wastewater that when released into waterways can promote the excessive growth of algae and other plants and lead to low oxygen levels that kill fish and other aquatic life.
The new permit extends a rule known as "no net loading," which effectively requires the city to find ways to remove as much phosphorus as it puts into the Laguna.
"I think this permit is another step to protect and improve the water quality for the Laguna," said David Noren, chairman of the North Coast Regional Water Quality Control Board.
Noren commended the city for its work to divert 98 percent of its wastewater from the Laguna, one of the state's largest wetland areas, through industry leading recycling projects such as aggressive agricultural irrigation and the $205 million Geysers pipeline. He called it "absolutely astounding" for a system of Santa Rosa's size to at times not discharge a drop of wastewater into the Laguna, as happened in 2009 and so far this year.
But he and the other members of the board Thursday unanimously agreed the tougher rules were necessary to further protect a waterway that simply cannot handle any more phosphorus.
"Based on the science and data we have, it's appropriate for us to hold that line," Noren said.
City officials objected to the new requirement for phosphorus, arguing there is no connection between the plant's limited discharges during periods of heavy rain and the algae blooms in the Laguna.
They instead requested the board set a numeric limit on the amount of phosphorus the plant could discharge under the permit.