Saturday, May 21, 2022

Bald Head Island addresses arsenic spikes in RO discharge near marina

According to the island's utilities director, the exceedances derive from four groundwater wells following an unprecedented amount of rainfall from Hurricane Florence. The recent exceedances are well-diluted, according to the DEQ.

Bald Head Island's reverse osmosis system exceeded state-permitted arsenic levels in December 2018, January, and April. (Port City Daily photo/Mark Darrough)
Bald Head Island’s reverse osmosis system exceeded state-permitted arsenic levels in December 2018, January, and April. (Port City Daily photo/Mark Darrough)

BALD HEAD ISLAND — At an outfall located the entrance of the Bald Head Island Marina, the island’s utility system has exceeded its state-permitted monthly water discharge arsenic limits three times in five months.

The island’s utility director emphasizes the arsenic is naturally occurring and is showing up in reverse osmosis discharge concentrate at higher-than-average levels as a result of Hurricane Florence’s excessive rainfall.

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These exceedances are not being recorded in the island’s drinking water; rather, they’re being discharged just outside the Bald Head Island Marina.

They are also well-diluted and rare, according to the Department of Environmental Quality (DEQ). However, it remains unclear what’s causing the increased levels. While Bald Head Island’s utilities director said rainfall from Hurricane Florence was to blame, the state’s environmental agency said that wouldn’t be the case unless the village’s drinking water wells were damaged.

Exceedances

The most recent arsenic discharge exceedance was recorded last month — the island released 21 micrograms per liter of the naturally-occurring chemical, about twice as much as it’s permitted to release. The Division of Water Quality (DWQ) at the Department of Environmental Quality has not yet issued a Notice of Violation for Bald Head’s April arsenic exceedance, as it’s still awaiting the island’s most recent monthly report.

DWQ issued two notices of violation for the island’s arsenic exceedances in December and January. Arsenic discharges in December exceeded the utility’s daily maximum contaminant limit — at 38 micrograms per liter, nearly four times its allowance. This followed the island’s first startup of the water plant after Hurricane Florence, according to Bald Head Island’s response to the violation.

In January, the island’s utility system twice exceeded its permitted daily maximum contaminant levels; on Jan. 15, the island released 23 micrograms per liter; on Jan. 28, it released 12 micrograms per liter — marking a monthly average of 17.5 micrograms per liter, over its permitted 10 micrograms per liter limit.

Before the recent uptick, the island exceeded its daily arsenic maximum in discharge waters in March 2016. The exceedance, recorded at 14 micrograms per liter, resulted in a state violation.

Bald Head Island's reverse osmosis concentrate solution is discharged at an outfall located at the mouth of its marina. In December 2018, January, and April, the concentrate exceeded its state-permitted arsenic levels. (Port City Daily photo/Courtesy Department of Environmental Quality)
Bald Head Island’s reverse osmosis concentrate solution is discharged at an outfall located at the mouth of its marina. In December 2018, January, and April, the concentrate exceeded its state-permitted arsenic levels. (Port City Daily photo/Courtesy Department of Environmental Quality)

Utility’s response

Kennith Bowling, Bald Head Island’s utilities director, said the source of arsenic derives from Hurricane Florence’s unprecedented rainfall.

“We are managing the arsenic levels by monitoring our wells and operating them in a way that minimizes concentration,” Bowling wrote in an email Monday.

Bald Head Island residents receive their drinking water from 16 groundwater wells located around the island. Three reverse osmosis units treat the water and discharge a concentrate solution at an outfall location at the marina’s entrance. Of the 16 wells, Bowling said four have shown “some elevated levels of arsenic” since Hurricane Florence.

The island’s consultant, Environmental Chemista, informed the utility that the December 2018 exceedances were caused by the elevated rainfall and a system that laid dormant for two months.

Levels lowered, but still exceeded permit limits, by January. In February and March, Bowling said the island recorded levels of arsenic within its permit limits, at less than 10 micrograms per liter. However, Bowling said the utility will submit April’s exceedance in its forthcoming Discharge Monitoring Report, which it is required to submit to the DEQ.

Arsenic in groundwater

Arsenic is a naturally-occurring mineral in groundwater. Sarah Young, a DEQ spokesperson, said the mineral should not be higher because of the hurricane unless there was damage to the well as a result of the storm.

“Reverse Osmosis (RO) systems have a filtrate side and a concentrate side. The concentrate side is discharged to surface waters in this case. The RO concentrate will consist of the same constituents that are in the well water, just higher concentrations.”

In Bald Head Island’s case, Young said its discharge point is well-diluted. The 10 micrograms per liter limit is based on the surface water human health standard, which is based on fish consumption. Young said.

“If the discharge was consistently above the standard, and was in an area that did not flush well, there would be more of a concern based on fish consumption,” Young wrote in an email Friday. “In this case, the exceedances are rare and the discharge point is well diluted.”

Dilution of the concentrate solution is taking place at the mouth of the island’s marina.

“Generally speaking, when the discharge enters the rivers, dilution will reduce the arsenic concentrations within [a] certain distance,” Young said. “That distance varies depending upon the discharge flow and the river flow, among other parameters.”


Send tips and comments to Johanna Ferebee at johanna@localvoicemedia.com

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