Development of a conceptual framework for risk assessment of elevated internal temperatures in landfills

Samain Sabrin; Rouzbeh Nazari; Maryam Karimi; Md Golam Rabbani Fahad; Jess Everett; Robert Peters

doi:10.1016/j.scitotenv.2021.146831

Development of a conceptual framework for risk assessment of elevated internal temperatures in landfills

Sci Total Environ. 2021 Aug 15:782:146831. doi: 10.1016/j.scitotenv.2021.146831. Epub 2021 Mar 29.

Authors

Samain Sabrin¹, Rouzbeh Nazari², Maryam Karimi³, Md Golam Rabbani Fahad¹, Jess Everett⁴, Robert Peters¹

Affiliations

¹ Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.
² Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Environmental Health Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL, USA. Electronic address: RNazari@uab.edu.
³ Department of Civil, Construction and Environmental Engineering, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Environmental Health Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL, USA.
⁴ Department of Civil and Environmental Engineering, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 080828, USA.

PMID: 33839673
DOI: 10.1016/j.scitotenv.2021.146831

Abstract

Subsurface elevated temperatures (SETs) often occur in landfills and pose great threats to their structural and environmental integrity. Current landfill gas monitoring practices only recommend maintaining certain soil gases percentages, with no integrated strategy for predicting subsurface temperature. As a solution, this paper proposes a comprehensive risk assessment framework specific to SET mitigation. The risk model (R_SET) was constructed by incorporating independent gas variables (methane, carbon dioxide, oxygen, residual nitrogen, and temperature) identified in the existing literature as SET indicators, and analyzing gas-well data from the Bridgeton Landfill. Upon identifying these gas indictors and their safety thresholds, we found a significant association (p-value < 0.05) between safe-unsafe ranges of gas variables and subsurface temperature. Temperatures above 80 °C were found to be associated with 100%, 92.3%, and only 4% of the unsafe ranges of methane, residual nitrogen, and oxygen, respectively. As the correlation between gases and temperature seemed to vary for different gas combinations, we developed the R_SET by incorporating into these correlation coefficients event intensities specific to certain gas combinations, and then normalizing the R_SET scale over a 0-10 range. Over the study period, we identified 22.29% of cases as medium risk at the Bridgeton Landfill and 17.7% as high risk. SETs are governed by different combinations of safe-unsafe ranges of parameters rather than any individual parameters alone. Subsequently, we used a decision tree algorithm to assess the risk types associated with R_SET values. The proposed R_SET can serve as a monitoring and decision-making tool for landfill authorities for managing and preventing SET incidents.

Keywords: Elevated temperature; Landfill gas; Landfill subsurface fire; Risk assessment; Risk index.