Novel Improvement of Fate and Transport Considerations at a Closing Inactive CCR Landfill utilizing Next Generation Sequencing (NGS)
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Consumers Energy completed construction of the last phase of the final cover in December 2019 of an inactive Coal Combustion Residual (CCR) landfill located in Essexville, Michigan.

A robust program for postclosure care prescribed by state requirements for monitoring water quality during the postclosure care period is in development and will be executed next year upon approval of the closure construction certifications. As early as 1982, groundwater quality at the Site was determined to be impacted with a number of inorganic constituents, including arsenic. Administrative mechanisms providing for performance-based compliance permitted continued operations of the ash disposal within the areas of operation until numeric criteria groundwater surface water interface (GSI) was established in 1999 by the State. On February 14, 2002, Michigan Department of Environmental Quality (MDEQ) issued a Letter of Warning (LOW) indicating that some numeric water quality compliance criteria may not be achieved at the GSI – arsenic and low-level mercury were primary suspects. A detailed investigation culminating in a September 2005 groundwater characterization report outlined the nature and extent of elevated arsenic at the site and provided for a compliance monitoring program achieved through alternative monitoring points. This program was eventually adapted through a groundwater mixing zone authorized by MDEQ on August 26, 2009 and reauthorized with minor modifications on December 23, 2015.

This presentation will focus on recent monitoring results, investigative methods, and remedial approaches employed to maintain compliance with the groundwater mixing zone. One of the most recent tools used to analyze inorganic contaminants, and in particular arsenic, at the site GSI is Next Generation Sequencing (NGS). NGS enables identification of microbial community signatures which can be used to identify environmental changes that may affect water quality. This method of microbial detection is performed by extracting all the genetic material (DNA) from a sample and then specifically sequencing each 16s ribosomal RNA gene (16s rRNA) in the total DNA extract. 16s rRNA is universally used to identify bacteria because the sequence of nucleotides coding for the 16s rRNA molecule is highly conserved within a species and is always different among different species. This characteristic makes the 16s rRNA valuable for species identification.

NGS samples were collected during the August 2019 water quality compliance monitoring event. NGS and geochemical samples were collected from 13 sampling points, transecting four primary monitoring areas. Areas included: leachate generation, solid waste boundary, GIS compliance, and surface water. Preliminary results from this sampling event suggest a correlation between the change in lake elevation and arsenic solubility. While it is unclear at this time as to whether the microbial community is actively altering groundwater geochemistry or responding to environmental conditions that change groundwater geochemistry, substantial diversity of biochemical reactivity was detected from the biomass and analytical results from this sampling event. This indicates that the bacteria present may have an effect on the Site's groundwater chemistry, including the solubility of arsenic. By comparing the results of the NGS at locations that have long-term known geochemistry water quality data, spatial relationships relative to redox conditions were evaluated and a refined understanding of some of the key drivers of the fate and transport of arsenic were developed for further study.

Publication Summary

  • Geosyntec Authors: Andrea Rocha
  • All Authors: Andrea Rocha, Geosyntec Consultants; Harold Register, Jr., Consumers Energy
  • Title: The Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 5
  • Event or Publication: Event
  • Practice Areas: Natural Resource Monitoring
  • Citation: Andrea Rocha, Ph.D. (Knoxville) will present on "Novel Improvement of Fate and Transport Considerations at a Closing Inactive CCR Landfill utilizing Next Generation Sequencing (NGS)" at the at the Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 5 on August 27, 2020.
  • Date: August 27, 2020
  • Location: Webinar
  • Publication Type: Platform Presentation