On Aug. 28, the South Florida Water Management District (SFWMD) approved an emergency order allowing Florida Power & Light (FPL) to divert water from the district’s L-31E Canal system to help moderate unusually high temperatures and salinity that are occurring in the Turkey Point cooling canal system (CCS).
The CCS—an approximately 5,900-acre network of unlined canals at Turkey Point—is used to provide cooling water for FPL’s two 820-MW nuclear units located 25 miles south of Miami. Under routine operations, there are no active surface water inflows needed to maintain CCS water levels, temperature, or salinity. This year, however, numerous factors have contributed to higher than usual inlet temperatures in the CCS, which have approached 102F.
The plant’s original operating license included a requirement limiting CCS water temperature on the intake side of the nuclear units to 100F. FPL received temporary approval from the Nuclear Regulatory Commission to deviate from the water temperature requirement as it pursues a permanent change to the plant’s operating license. The company seeks to increase the CCS intake water temperature limit from 100F to 104F.
There is no immediate end in sight for the factors that are contributing to the problem. FPL reports that typical annual rainfall at Turkey Point ranges between 50 inches and 75 inches. In 2013, the annual rainfall accumulation measured less than 20 inches. Through July of this year, the total rainfall was less than 26 inches as measured at the CCS.
Additionally, FPL data indicates that high evaporation and losses to groundwater have resulted in more water leaving the CCS than is being provided from the aquifer or rainfall, which is concentrating salinity in the CCS. FPL reports that CCS salinity has reached levels near 90 ppt, compared to historic levels of approximately 60 ppt.
An algal bloom has also added to the problem. The algae concentration—prior to treatments that began in mid-summer—was as high as 1.8 million cells per milliliter, far exceeding the historical average value of 50,000 cells per milliliter. The turbidity associated with the algae bloom has caused unusual amounts of solar energy to be absorbed in the CCS, thereby increasing CCS temperatures.
The SFWMD operates the L-31E Canal system, which is part of the Central and Southern Florida Flood Control Project. Water from the system is discharged to Biscayne Bay through several coastal structures, with the quantity and timing of discharges controlled through the operation of canal network gates.
The SFWMD approval authorizes FPL to connect to the L-31E Canal and conditionally withdraw stormwater for use in the CCS. Limits prohibit withdrawing water that is reserved for fish and wildlife. The only water available is water that would otherwise be discharged to the bay. The SFWMD will determine daily the amount of water withdrawn and the timing of FPL’s operation of pumps based on “flows to tide.”
—Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)