Clean up act for coal4 January 2010
The Environmental Protection Agency in the US is assessing the integrity of coal ash impoundments following a spill of combustion residuals last year
The December 2008 release of coal ash from Tennessee Valley Authority’s (TVA) Kingston, Tennessee facility flooded more than 1.2km2 of land in the US, damaging homes and property. Coal ash from the release flowed into the Emory and Clinch rivers, filling large areas of the rivers and resulting in fish kills.
As a result of this the Environmental Protection Agency (EPA) is currently involved in two separate efforts regarding the management of coal combustion residuals from coal burning electric utilities. These are: A nationwide assessment of current management practices; Drafting a proposed rule for public comment by the end of 2009.
In March 2009, EPA issued information request letters to electric utilities that have surface impoundments or similar units that contain coal combustion residuals. The letters requested information to assist in the evaluation of the structural integrity of these management units.
EPA, working closely with other federal agencies within the different states, is reviewing the information provided to identify impoundments or similar units that need priority attention. As part of this assessment effort, EPA will inspect many of the units to ensure that they are structurally sound. Appropriate remedial action will be required at any facility that is found to pose a risk for potential failure.
Response from electric utilities
EPA has received responses to the information request letters and posted all of the responses on their website, with the exception of information claimed as confidential business information. This covers 219 facilities and 584 surface impoundments and similar management units.
In summary, the 219 facilities that responded are located in 35 states. Of the 584 surface impoundments and similar management units covered in these responses 194 units (33%) have been given a potential hazard rating under the National Inventory of Dams criteria. Of the 194 units that have been rated:
• 49 units (25%) are rated as high hazard potential.
• 60 units (31%) are rated as significant hazard potential.
• 77 units (40%) are rated as low hazard potential.
• 8 units (4%) are rated as less than low hazard potential.
On the other hand, 390 units (67%) have not received a hazard potential rating. The hazard potential ratings do not assess the stability of these units; the ratings assess the potential for loss of life or environmental and economic damage. Units rated as high hazard are those where failure will probably cause loss of life.
In addition, of the 584 surface impoundments and similar units covered in these responses, 405 (70%) were designed by a professional engineer and 134 have been inspected by a state inspector in the last year. The units show considerable variation in height:
• 75 units (13%) being reported as greater than 15m in height.
• 120 units (20%) are greater than 7.5m, but less than 15.5m in height.
• 251 units (43%) are greater than 1.8m but less than 8m in height.
• 38 units (7%) are less than 2m in height.
• 100 units (17%) being reported as having no height.
Based on the initial information and site visits to date, the agency has not encountered any issue which required immediate action or attention on the part of the utility or federal or state government. That is not to say that the site visits haven’t noted some areas that should be addressed, such as maintenance activities and correcting the low areas of the dam crest by placing engineered fill. Any recommendations that EPA believes are appropriate will be provided to the company, as well as placed in the final report that will be made available to the public.
Coal ash reports
Final contractor reports were also carried out at 22 facilities to assess the structural integrity of 43 surface impoundments or similar units which had a high or significant hazard potential rating.
The reports have been completed by contractors who are experts in the area of dam integrity, reflect the best professional judgment of the engineering firm, and are signed and stamped by a professional engineer.
The reports are based on a visual assessment of the site, interviews with site personnel, and the review of geotechnical reports and studies related to the design, construction and operation of those impoundments, if available. The engineering firms also reviewed past state/federal inspections of the impoundments.
EPA contractors were not authorised to conduct any physical drilling, coring or sampling while on site. However, they did review studies which may have included such information. The contractors were asked to rate the impoundments as satisfactory, fair, poor, or unsatisfactory. Expert experience has shown that only impoundments rated as unsatisfactory pose immediate safety threats. None of the impoundments assessed received an unsatisfactory rating. Impoundment ratings noted in the reports should be taken in the proper context, since a unit may be found to be structurally sound while it may receive a fair or poor rating based on other factors.
Draft copies of the reports have been reviewed by the facilities and the states for factual accuracy and their comments on the draft reports have also been posted. EPA continues to review the reports and the technical recommendations, and is working with the facilities to ensure that the recommendations are implemented.
EPA has provided a copy of the final report to each facility and has requested that the recommendations are implemented and action plans are provided. Should facilities fail to take sufficient measures, EPA will take additional action, if the circumstances warrant, and will be devoting special attention to those facilities receiving a poor rating.
In summary, the assessments have rated the impoundments as follows: Satisfactory – 22 units; Fair – 15 units; Poor – 6 units; Unsatisfactory – 0 units; Total – 43 units
As they become available, additional reports can be found on the EPA’s website www.epa.gov