Back-pumping would give Lake O 'clean' water? Absurd

Thursday, July 12, 2007

It is absurd to describe water back-pumped from the Everglades Agriculture Area as "clean" water, as the vice president of King Ranch in South Bay did in a letter Tuesday ("Back-pumping into Lake O best option to restore supply").

Although less concentrated than current lake levels, back-pumped water contains more phosphorus than is healthy for the lake and adds to the massive sediment load. It also contains other pollutants that degrade the quality of water used in the drinking-water plants at the south end of the lake. The poor quality of back-pumped water and its impacts have been measured and reported since 1969.

South Florida Water Management District scientists studied water supply back-pumping impacts during the 1981-82 drought. Water-quality impacts were more widespread because of the low lake level. They found that back-pumping resulted in large increases in both specific conductance (a measure of dissolved pollutants) and in nitrogen concentrations at the south end. A large algae bloom then occurred in that part of the lake.

In a 1997 experiment, Dr. Karl Havens, a district scientist, added canal water from the EAA to lake water and measured an increase in blue-green algae. He suggested that the results were due to the increased nitrogen from the canal water. In an internal memo on Jan. 30, 2001, Dr. Havens, chief scientist in the SFWMD's Lake Okeechobee Department, stated his concerns regarding water supply back-pumping:

"Water supply back-pumping runs contrary to both the short-term goal of ecosystem protection and the longer-term goal of ecosystem rehabilitation. ... There certainly may be issues related to public health because the water supply intake structures for South Bay and Belle Glade are located quite close to the pumps ... "

Dr. Havens was right. Back-pumping during 2001 added 83,400 pounds of phosphorus to a lake already overloaded with phosphorus, and 3,197,800 pounds of nitrogen. Algae blooms were measured at a number of locations downstream from the back-pumping.

Trihalomethanes (THM) are carcinogens formed when the chlorine used to disinfect drinking water mixes with dissolved organic material such as that found in back-pumped water. Although none was done by the SFWMD, testing commissioned by The Palm Beach Post reportedly found THM problems at Pahokee and South Bay, with one sample in South Bay containing more than 12 times the THM water quality standard.

During the 2001 back-pumping, violations of the Class 1 water quality standard for total dissolved solids occurred in the back-pumped water, the lake and at the Belle Glade and the South Bay drinking-water intake pipes. Although most pesticides were detected at very low levels, a number were back-pumped into the lake. The lake's alligator population has exhibited some reproductive organ deformities, similar to those found in Lake Apopka, another highly polluted lake.

Often after droughts, the water level in Lake Okeechobee will rise rapidly. The 1981-82 drought ended during the 1982 rainy season when the lake rose from about 10.5 feet to about 17.5 feet in roughly a month. During the rainy season of 2001, the lake level rose about 6 feet. Back-pumping from the EAA added between 2 1/2 and 3 inches of that 6-foot increase.

Was that worth all those lake water-quality impacts? I don't think so. The Post was well justified in calling for an end to back-pumping in its June 28 editorial ("Forget back-pumping").

HERB ZEBUTH

The Acreage

Editor's note: Herb Zebuth retired from the state Department of Environmental Protection in 2004 after nearly 25 years as a regulator in its West Palm Beach office.