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Utilities: Drought causes rise in salinity at water plant
By Charles Swenson
Drought and high tides combined this week to cause a spike in salinity levels at the plant that provides drinking water for the Waccamaw Neck. Georgetown County Water and Sewer District shut down the plant during the high tides and used stored water to meet demand, said Larry Dickerson, the utility’s assistant executive director.
Water use is up this summer from 2010, mostly because customers are irrigating their landscaping, he said.
The district treats water from the Waccamaw River at its plant off Sandy Island Road. The river is still affected by the tide although the intake is 12 miles from Winyah Bay and 26 miles from the ocean.
Water begins to taste salty when the salt content hits 1,000 microsiemens per centimeter. The utility’s treatment plant can operate up to 1,100 microsiemens. But the salinity hit 6,500 microsiemens at the high tide on Saturday night.
“We shut down the plant for a couple of hours on either side of high tide,” Dickerson said. “We’ve got a number of wells that we continue to operate.”
The district stores water in aquifer wells in Murrells Inlet and DeBordieu in the offseason to help meet peak demands in the summer. “The ground acts as a big storage tank,” Dickerson said.
Since the last serious drought in 2007, the utility adapted the water treatment plant so it could bring in reverse osmosis filters to remove the salt from the river water. That would only be done in “a very prolonged drought,” Dickerson said. “It’s another tool in the arsenal.”
In 2007, the salinity at the water plant’s intake peaked at 10,000 microsiemens. This year, the flow of water in the Pee Dee River basin, which flows into the Waccamaw, is higher than in 2007, Dickerson said. “They’ve had more rain in the upper part of the basin than here,” he said.
The 2007 drought prompted the district to draw up a plan to use treated wastewater from its plant on Waverly Road to irrigate area golf courses. A couple of courses bought drinking water from the district for irrigation in 2007.
But that project proved too costly for the courses, which would have to improve their storage ponds to meet state regulations.
“If the drought situation persists, they might reconsider,” Dickerson said.
The utility board last week approved an agreement with DeBordieu to sell up to 192,000 gallons of water a day for golf course irrigation. The course will pay the same rate as a residential customer, $2 per 1,000 gallons.
Earlier this year, the district completed a project that allows treated wastewater from the DeBordieu sewage treatment plant to be pumped to the Waccamaw River rather than sprayed on the golf course. That system is designed to avoid putting treated effluent on the course during wet periods that could create runoff into the pristine North Inlet estuary.
“We haven’t put any water back into the river since May,” Dickerson said.