Cinders and Ballast. I have studied that question and mixture for 30 years and must say they do not mix. The worst damage is done by attempting to dump ballast over a cinder roadbed track and them failing to really lift the track up above the cinders so that the good ballast falls under the ties.
Cinders are a great roadbed for the narrow gauge track as they compact hard as rock directly under the tie but are loose and drain between the ties.
An example was a track across a salt marsh, washed over by a storm flood and the cinder between the ties washed away down to one foot below the bottom of the ties but a column of cinders remained packed below the ties.
Picture the lifting of the track, rails and ties, three feet above the ground and what do you have left? You have the indents that I call “Pockets” in the cinder roadbed and columns of dirt at the top of the columns between where the ties were located and blocked ends for drainage. Now, if you try to make a 3- inch rise of track with new ballast and want to tamp it in what will happen? The junk material at the top of the column will fall into the “pocket” and not the good clean stone. If the area under the tie, the pocket, is not fully filled, it then becomes a basin for water in the next rain and will make a great mud puddle, and bad surface. That is followed by bent rail and rough track.
When you want to change from a cinder roadbed to a ballast roadbed it would be best to skid the track in attempt to level the cinder and dirt into the pockets and make that the smooth sub-grade. Then spread a car-load per car length of any clean ballast and tramp several inches under the ties. That will last a long time and save the rail. A skid is a small under track plow that you drag by a locomotive or machine.
I would recommend the C&TS save and use every pound of cinders from Chama ash pit to replace old cinder locations on the track with it. And also buy other cinder style fine stone, such as the local volcanic rock in the area that will also drain and mix well with the present cinders. You want something with similar compression factors. Granite is not necessary for the C&TS axle loading but good dolomite is great and what I used to ship for my company. ( I dispatched 1.5 million tons a year of mostly grade A and some grade B in my career)
Some of the worst wet sections should be considered for the skid method and a good dump of stone ballast like the D&S has used in the meadows. This is where good price study of the local suppliers needs to play into the methods.
I just stress to not to try to tamp ballast into the dirt and junk under the ties without filling the pocket fully with good stone. The Jordan spreader should cut the mud off end of ties to open the pockets so water will not lie in any basin under the tie. Wish I were there again to supervise the improvements.
