Final Rule: Disposal of Coal Combustion Residuals from Electric Utilities:
The United States Environmental Protection Agency (USEPA) signed into law its final version of the Disposal of Coal Combustion Residuals from Electrical Utilities (rule) on December 19, 2014. The rule was later published in the Federal Register on April 17, 2015 (USEPA, 2015b)
The Coal Combustion Residuals (CCR) rule provides requirements to electrical utility providers regarding applicable criteria for the disposal of coal combustion residuals (aka. coal ash), from coal fired-power plants. The CCR rule mandates that coal ash landfills are to be regulated as solid waste landfills under RCRA Subtitle D and require a groundwater monitoring program and corrective action programs. The rule states that groundwater monitoring and corrective action programs are implemented at CCR landfills no later than October 17, 2017. An annual groundwater monitoring and corrective action report is required for a CCR landfills that documents groundwater monitoring activities and corrective actions over the previous year and detail project updates for the following year.
Groundwater monitoring at CCR landfills presents a unique challenge for environmental professionals in that the final rule requires specified groundwater sampling parameter requirements. Measurements of groundwater characteristics including temperature, conductivity, dissolved oxygen, oxygen reduction potential, pH, and turbidity are taken during low flow groundwater monitoring events. The CCR rule has specific requirements for turbidity levels prior to sampling which can be difficult to obtain in areas with natural geologic formations that produce naturally high turbidity and in wells not properly constructed (i.e. material and purging). Groundwater sampling at CCR sites must measure total recoverable metals with a sample turbidity of less than five (5) nephelometric turbidity units (NTUs) and without using field filtration. It has been argued that without field filtering (0.45 micron filter) the sample would be biased higher (for metals) in wells that have high turbidity. The USEPA counter-argues that proper well construction and implementing proper low flow groundwater sampling and purging methodology should limit turbidity thereby reducing the transfer of solids into the wells (USEPA, 2015a).
Applied Geology and Environmental Science, Inc. (AGES) recently presented at the Utility Solid Waste Activities Group (USWAG) CCR Workshop in Washington, D.C. regarding approaches in well design to limit turbidity in groundwater samples. AGES described a method in which wells were, “drilled with the Rotasonic method and designed with pre-packed screens, consisting of an inner layer of food-grade nylon mesh over a 0.01-inch slotted Schedule 40 PVC screen; an inner filter pack of 0.0165-inch sand; an outer layer of food-grade nylon mesh, and an outer filter pack of 0.0165-inch sand. The filter sand size was selected based on sieve/hydrometer analyses of the aquifer material in the area” (AGES, 2016). The well design in combination with low flow sampling methodology appears to achieve lower turbidity levels in groundwater samples in compliance with the Final CCR rule.
1. Applied Geology and Environmental Science, Inc. (AGES). AGES Present at the USWAG CCR Workshop in Washington, D.C. 2016. http://www.coalcombustionresiduals.com/index.php/about-us/2016-01-08-15-25-36/ages-presents-at-the-uswag-ccr-workshop-in-washington-d-c
2. United States Environmental Protection Agency (USEPA). Hazardous and Solid Waste Management; Disposal of Coal Combustion Residuals from Electric Utilities. Washington, D.C. April, 2015a. https://www.epa.gov/sites/production/files/2015-04/documents/redline_version_of_ccr_final_rule.pdf
3. United States Environmental Protection Agency (USEPA). Final Rule: Disposal of Coal Combustion Residuals from Electrical Utilities. Washington, D.C. October, 2015b. https://www.epa.gov/coalash/coal-ash-rule