o.k. I just can't find the citation, so I'm going from memory. . .
Anders Bjarngard published his thesis and it had to do with the settlement of municipal waste landfills. Just like soil, there is initial "modulus-based" settlement (after all the trash does have some modulus value and there will be some immediate compression). There is also settlement as related to change in void ratio in the absence of change in effective stress - i.e., secondary compression. You see usually we are not dealing with consolidation as the landfill materials are usually not saturated and if so the permeability of the trash is pretty high.
Anders Bjarngard looked at historical data from landfills all over the place and determined that secondary compression (C-alpha) is similar to that for soil - problem is that the value of C-alpha INCREASES over time to some value, "C-alpha-max." He provides graphed data and values for C-alpha and C-alpha-max. I used to (likely still do) have a copy of his thesis. If you google Anders Bjarngard you will find ASCE publications that you can purchase and I think these publications must cite his original work. They have interesting titles and may be great publications, but I'm not spending the money to further engage in this discussion. I am interested in what you find.
I'm not taking anything away from what's already been posted. The variation in C-alpha is related to decomposition rate and all those anaerobic processes. I'm not sure that unleashing aerobic processes in a landfill is the right or wrong thing to do. If the debris has been in place for 30 years and you consider the extent of compression that's likely occurred, the forecasted settlement (compression) using secondary compression values may be manageable in conjunction with a soil raft.
Face it, you are not doing "generally accepted" engineering practice and your client should recognize this risk before you sell yourself as some engineering expert.
f-d
¡papá gordo ain’t no madre flaca!