February 9, 2014. An earlier post described groundwater contamination and potential surface water pollution associated with coal ash impoundments in North Carolina. Last week, a Duke Energy ash impoundment in Rockingham County released an estimated 82,000 tons of coal ash into the Dan River. The ash, in a slurry of as much as 27 million gallons of water, leaked from a ruptured stormwater pipe running under an ash impoundment at Duke’s now-closed Dan River Steam Station. The spill continued off and on for five days as Duke Energy worked to temporarily contain the spill and then permanently cap the stormwater pipe. Duke Energy workers finished installing and testing the permanent cap yesterday. Early reporting on the spill can be found in stories by Charlotte Observer reporter Bruce Henderson here and here and by AP reporter Michael Biesecker here.
EPA staff have been on site since early last week. Although coal ash has not been classified as a hazardous waste, coal ash can contain a number of metals identified as hazardous substances in rules adopted by EPA under the Clean Water Act. Under federal law, a hazardous substance spill that exceeds thresholds set in federal rules must be reported immediately to EPA and to emergency response agencies. (You can find the rule listing hazardous substances regulated under the Clean Water Act and the reporting threshold for each substance here.) Although EPA must be notified immediately of a reportable spill, the person (or company) responsible can take up to 24 hours to determine whether the spill meets the reporting threshold.
Under state law (G.S. 143-215.85), anyone responsible for a hazardous substance spill must “immediately notify the Department, or any of its agents or employees, of the nature, location and time of the discharge and of the measures which are being taken or are proposed to be taken to contain and remove the discharge.” Both state and federal law also require immediate action to contain the spill, remove the hazardous substance and restore damage caused by the spill.
It is not yet clear how the spill will affect water quality and life in the Dan River. The nonprofit Waterkeeper Alliance reported that water samples taken by that organization close to the spill site showed high levels of arsenic and other metals. The Waterkeeper Alliance reported arsenic at levels capable of causing acute injury to fish and wildlife. You can find the Waterkeeper Alliance test results here. (Click on an individual sampling location in the box on the left-hand side of the page to pull up the test results for that sample.) Note that results have been reported as milligrams/liter (mg/L) and have to be converted to micrograms/liter (ug/L) for direct comparison to DENR sampling results.
DENR posted its complete water quality test results late Friday; you can find the DENR lab report here. Allowing for different sampling locations and units of measure, DENR’s results are generally consistent with test results reported by the Waterkeeper Alliance. A DENR water quality sample taken on February 3, 2014 at Draper Landing (about 2 miles downstream of the spill site) showed arsenic levels of 40 micrograms per liter — four times the water quality standard of 10 micrograms/liter. A sample taken on the same day further downstream (at the Virginia border) showed arsenic levels of 13 micrograms/liter. DENR’s results also show water quality standard violations in the Dan River for copper, aluminum and iron. By February 4, arsenic levels at Draper Landing had dropped back below the water quality standard and levels at the Virginia border were at the water quality limit of 10 micrograms/liter. Results for copper, aluminum and iron remained high.
Sampling immediately after a spill only provides a snapshot of water quality conditions and may not reflect long-term impacts to the river as metals leach out of coal ash settled on the river bottom. A year after the TVA coal ash spill, Duke University scientists found extremely high levels of arsenic in pore water (the water in river-bottom sediment) in Tennessee’s Emory River. Although surface water testing showed arsenic levels in the Emory River dropped just after the TVA spill, the contaminated sediment became a source of ongoing arsenic loading to the river in low oxygen conditions. (Source: Bruce Henderson’s report for the Charlotte Observer.) It will also take more time to get an assessment of the damage caused to vegetation, fish and wildlife as a result of the physical presence of ash in the water and on the river bottom.
There have been no reported impacts to drinking water. The Danville, Virginia water system has an intake in the river downstream of the spill site, but the water treatment plant had been able to filter out the ash and treated water continued to meet drinking water standards.
Some questions and concerns raised by the spill:
Public notice of hazardous substance spills. It doesn’t appear that either federal or state law requires the person (or company) responsible for a hazardous substance spill to notify the general public and that may be a gap for the N.C. General Assembly to fill. After notifying state and federal officials, Duke Energy put out a press release about the Dan River spill just over 24 hours after detecting the release. In the case of an immediate health and safety hazard, early notice would be better — although there may be a trade-off between early notice and the completeness and accuracy of information about the spill.
Conflicting water quality test results. Conflicting water quality test results created a significant amount of confusion about the Dan River spill — and some degree of suspicion. Mid-week, Duke Energy reported that river water samples taken downstream of the release showed only trace amounts of arsenic and other metals. You can find the Duke Energy water quality testing plan and results here. Note that Duke Energy reported water quality test results as parts per billion (ppb) — a unit that is essentially equivalent to the micrograms/liter (ug/L) used by DENR. (For purposes of comparing results, assume 1 ppb =1 ug/L.) Duke Energy also provides results for both unfiltered samples and filtered samples used to monitor treated drinking water quality.
Duke Energy’s instream results differ significantly from results reported by the Waterkeeper Alliance and by DENR. In the end, the Waterkeeper Alliance results and the DENR results seem to be generally consistent with each other; differences can most likely be attributed to selection of sampling locations. The extreme divergence of Duke Energy’s water quality test results calls for some explanation. Since state water quality test results lagged behind by several days, the Duke Energy results became the basis for early public statements about water quality impacts and that information proved to be unreliable. The inconsistent test results also suggest the public would be better served if the person responsible for a hazardous substance spill provided water quality test results to the state’s water quality agency for confirmation before releasing the information to the public.
Much of the water quality concern over the last week focused on arsenic levels in the Dan River. Another metal found in coal ash, selenium, can damage fish populations and present a health risk to people who eat the fish. DENR’s February 7, 2014 lab results for the Dan River did not find excessive levels of selenium, reporting selenium at the lowest quantifiable level. Preliminary lab results released by DENR on February 6, 2014 omitted the initial selenium results, indicating those samples would be given additional analysis because of suspected “interference”. The preliminary lab report did not explain the nature of the interference — which could mean another potential source of selenium in the Dan River or something related to the analytical process. Given conflicting data and general confusion over water quality test results from the Dan River spill, it would be helpful to have more explanation of the preliminary and final selenium results.
Delays in providing state water quality sampling results. DENR tested for more potential contaminants than either Duke Energy or the Waterkeeper Alliance, but that does not completely explain why results only became available five full days following the spill. Some analytical methods take longer than others, but it is important to know if inadequacies in the state water quality laboratory or other factors contributed to the delay. In this case, waiting five full business days for complete water quality test results probably didn’t cause additional harm, but the next hazardous substance spill may be different. The delay clearly did have one immediate result — it left an information gap that was filled by what turned out to be inaccurate water quality information.
Lack of information about conditions in old coal ash impoundments. Since older coal ash ponds have been largely unregulated, state and federal environmental agencies have very limited information about the impoundments. The Dan River spill suggests that utility company managers don’t have all of the information needed to manage environmental risk at these facilities either. Duke Energy struggled to find and fix the cause of the spill in part because the company believed the leaking stormwater pipe had been constructed entirely of concrete. Duke Energy employees could not find any damage to the end of the pipe and there was no obvious reason that a buried section of concrete pipe would have broken. It turned out that much of the buried pipe was actually constructed of metal rather than concrete, suggesting that corrosion caused the break.
The lack of accurate information on conditions at the Dan River Steam Station impoundment suggests the need for a joint Duke Energy/ DENR engineering review of existing ash ponds –including documentation of past construction, maintenance and expansion activities –to identify potentially high risk conditions.