Therefore, utilization of this adverse gas by reactive soil liners to improve their strength and hydraulic performance as well as their self-sealing efficiency through mineral carbonation seems a logical option and an innovative technique for counteracting the anthropogenic emissions of CO\({}_{2}\) and simultaneously preventing the contamination of groundwater and soil, as well as environmental degradation. According to ASTM D5370, olivine is a sustainable, cost-effective, and widely available pozzolanic material (material with the ability to form cementitious compounds in the presence of water after reacting) with the potential to enhance soil strength characteristics owing to its strong affinity for CO\({}_{2}\) adsorption leading to the formation of stable carbonates with strength enhancement properties [10, 35, 36]. Olivine carbonation has been and is still a leading mineral for the sequestration process, which involves converting magnesium-rich minerals to stable magnesium carbonate precipitates after reacting with CO\({}_{2}\) in the presence of water [37]. The carbonated products may potentially bond the soil particles together, increase strength and reduce hydraulic conductivity. Recently, studies on carbonated olivine-admixed soils focus mainly on the strength characteristic [38, 39, 40]. However, few if any studies have evaluated the hydraulic conductivity of carbonatedolivine soils, which is one of the most critical parameters in assessing the suitability of a material for liner application. Moreover, knowledge about the required olivine particle size to be utilized for carbonation to achieve significant hydraulic conductivity reduction is also lacking. Furthermore, no study has attempted to employ a global optimization technique to optimize the control factors (olivine content, carbonation time, and carbonation pressure) so as to achieve maximum hydraulic conductivity reduction for the carbonated olivine-treated soil. As a result, the right combinations of the control factors for optimum reduction in carbonated-olivine treated soil's hydraulic conductivity are not obvious. In view of this, the purpose of the current study was to assess the suitability of CO\({}_{2}\) carbonated olivine-admixed marine clay for use as a bottom liner material in engineered landfills to reduce leachate migration while sequestering CO\({}_{2}\) from the landfill. The influence of carbonation time, carbonation pressure, and olivine content on the hydraulic conductivity of CO\({}_{2}\)-carbonated olivine-admixed marine clay was assessed using the attainable region (AR) and response surface methodology (RSM) techniques. The AR method was used to optimize the olivine particle size during the grinding process to get olivine particles in a defined particle size class (\(-75\) um) before treating the marine clay. The RSM approach was used to design the experiments, analyze the performance, and optimize the factors responsible for achieving significant hydraulic conductivity reduction of the CO\({}_{2}\)-carbonated olivine-admixed clay. The findings of this study will assist geotechnical and geoenvironmental engineers in designing a smart liner material that would be economically viable, socially acceptable, and environmentally sustainable with the potential to sequester landfill CO\({}_{2}\), thus making it superior to the current conventional compacted clay liners. The findings of the study would also promote the use of marine clay typically considered as construction waste to value-added application as a liner material in engineered landfills. The results of the study would also open up a promising perspective for the use of AR and RSM to define the optimal olivine particle size and olivine content in targeting optimum hydraulic conductivity of the olivine-admixed soil during field application.