EPA, City Officials Expect New Treatment Plant Permits to Boost Boise River Water Quality

The amount of phosphorus pollution entering the Boise River during summer months from the City of Boise’s two wastewater treatment plants will be reduced by 98 percent under two updated discharge permits issued today. The EPA permits also contain new requirements to limit mercury and ammonia discharges and call for cooler water entering the River from the treatment plants.

The City of Boise currently discharges about 1,100 pounds of phosphorus each day from the two treatment plants. Once the plants are in compliance with the new permits, the City will discharge no more than 15 pounds each day. The City wasn’t required to remove phosphorus under the earlier EPA permits. The prior permits for the two plants had no limits for phosphorus, mercury, ammonia or temperature.

Under the permits, the city will remove the majority of the phosphorus within the next five years through technology upgrades at the two treatment plants. In the coming weeks, EPA anticipates that the City will propose to remove additional phosphorus from the Dixie Drain, an agriculture return drain 34 miles downstream. When the City submits its detailed proposal for the Dixie Drain “offset,” EPA may then reopen the permits and submit the Dixie Drain proposal for public review and comment.

“These new permits are good news for everyone who uses and enjoys the Boise River,” said Dennis McLerran, the EPA’s regional administrator in Seattle. “We’ve worked together to build strong permits while being sensitive to the cost to the City and ratepayers. We share the goal of clean water and support the City’s efforts to reduce the phosphorous and protect Idaho’s treasured rivers, lakes and streams.”

The permits, issued by the EPA, call for the City to make the pollution reductions and achieve the new permit limits for phosphorus and temperature within 10 years. The mercury and ammonia limits are effective when the final permits are issued. The permits for the Lander Street and West Boise Treatment plants, were last updated in 1999. Under the Clean Water Act, a National Pollutant Discharge Elimination System (NPDES) permit allows a facility, or “point source,” to discharge a specified amount of a pollutant into a river or stream under certain conditions. The conditions of the permits must ensure that public health, fish and other aquatic life are protected.

These permits will help restore impaired water quality in the Boise River and help achieve the water quality goals set out in the Snake River/Hells Canyon TMDL. Both the Lower Boise River and the Lower Snake River are listed as impaired water bodies due to excess phosphorus pollution and the Brownlee Reservoir suffers from large algae blooms regularly as a result of the phosphorus load in the system. The algae blooms greatly reduce oxygen levels in the reservoir which has historically led to fish kills.