Anchor trenches for MSW landfills subject to various uncertainties arising from inconsistency in parameter measurement and determination, placement of fresh waste on the geomembrane (GM) liner, improper compaction of cover and backfilled soils, construction practices, assumption of relative slippage, and invention of new design methods. A wide range of variability is associated with the design parameters of the anchorage. Conventional factor of safety approach cannot account for the uncertainties involved. The drawback can be well addressed through reliability based approaches. The objective of the analysis discussed herein is to produce estimates of the probability of anchor trench failure as opposed to the conventional factor of safety. Therefore, a framework for the target reliability based design optimization (TRBDO) methodology is presented for the design of anchor trenches. This paper emphasizes the importance of allowable design strength of the liner considering the variability for rectangular and L-shaped rectangular anchor trenches. © ASCE.