Civil Engineering ETDs

Ryan Webb

Publication Date

7-3-2012

Abstract

Coal combustion byproducts (CCBs) disposed of in unlined landfills can impact the quality of adjacent water resources. In previous studies, CCBs have been found to leach toxic heavy metals such as arsenic, mercury, and lead into groundwater. CCBs include fly ash, bottom ash, and flue gas desulfurization product (FGD gypsum). This investigation focused on determination of the saturated and unsaturated hydraulic properties of fly ash and bottom ash to then be used in order to develop a 1-dimensional unsaturated flow model. Ash samples from a power plant as well as core samples from buried CCB pits were collected for laboratory analysis. Saturated hydraulic conductivity was measured using falling head tests. Moisture characteristic curves were developed from hanging column tests, pressure plate tests, dew point potentiometer measurements and relative humidity measurements. Hydraulic properties were measured at various densities to simulate a range of conditions expected in the deep disposal pits. The measured hydraulic properties were utilized in a saturated/unsaturated hydrologic water movement model of flow through disposal pits containing natural overburden and buried CCBs. The model used historical climatic conditions at the ground surface, and estimated water infiltration through the CCB pits. Results display infiltration from surface water into CCB pits is most likely to occur in areas where ponding occurs. These results can be coupled with information about the chemical quality of CCB leachates to estimate the impact of landfill disposal of CCBs on the underlying ground water quality.

Keywords

Coal ash--Environmental aspects, Contaminated sediments--Environmental aspects, Sanitary landfills--Environmental aspects, Fly ash--Leaching, Groundwater--Pollution.

Sponsors

New Mexico Mining and Minerals Division

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Stone, Mark

Second Committee Member

Thomson, Bruce

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