Aloha,
The Triple O is starting to take shape (See my keep-me-honest thread here.) For work reasons, I am at a pause, but I wanted some advice, anyway. The next step is to fill the raised garden bed. I am looking at about 14 cubic yards. Therefore, I only want to choose material once! Plenty of places offer "free fill" for a nominal delivery fee. I am on a budget, but money saved in the wrong place is money lost!
The depth of the garden is about 18 inches. Should I avail myself of this (much will include rock, sand, and other such stuff), or should I spring for the requisite amount of topsoil? Given the depth, is it possible to split the difference, filling half with larger, coarser material and the rest with topsoil?
Another design consideration is that the Triple O is to be an evolving project, with complexity of planting and buildings changing as our family ages. Thus, some future ability to add a pond or mountain, to rip up and replace track, or to repurpose a section needs to be considered. I am not sure if that matters so much where fill material is concerned, but I wanted to throw it out there.
Thanks as always for the advice! It is keeping me on a target to have a train running by Christmas with ballasting underway.
You could possibly save some money and fill material by first using concrete blocks to partially fill in the area, and cover them with the fill dirt or whatever you choose to use.
If you have a truck or trailer and know of a demolition project somewhere nearby, they may even let you have all the old, broken up concrete blocks and bricks for free.
Other possible sources of back fill.
In my area we have separated waste streams, The trash is hauled off to a landfill, the green waste is hauled to a place where it is ground up and composted into compost or mulch and is free to city residents. Hard waste is collected for use as back-fill. Concrete, brick, & stone & boulders. They charge three cents per ten pounds of waste to drop off, or fifty cents per truck load the pick-up for reuse. (For $2.00 they will have their bucket loader fill your truck.)
Pack it in tight! Eighteen inches of loose soil PLUS four years EQUALS soil compaction of 2 inches. Go to your local garden supply store, you are looking for a "dirt packer", a square metal plate about 10"x10" with a nice heavy handle. Pick it up by the handle and slam it into the ground, watch the dirt get packed down. Spread your (non-concrete & non-ROCK) fill in thin layers of about half inch or so. slightly moisten and pack it down as much as possible, repeat layer by layer.
YES! This is a LOT of work, but would you rather need to lift out the entire railroad in four years to put more dirt under it?
Tom Trigg
In this case I think the best answer is to do both. Fill partially with larger more solid fill (non compactible material, ie stone, brick, broken concrete, etc.) keeping in mind that what ever level you choose to stop at will be the deepest easy digging will occur later. Cover this with loose fill dirt, but only a couple inches above the top of the non compactible. Depending on climate (your greeting incicates Hawaii), you may let nature do your settling with rains, otherwise water with a sprinkler every couple of days for several weeks before putting in the next 3 or so inch layer. By breaking the process into smaller sections you will be able to considerably lessen final settling that will affect final track alignment.
Aloha, and good luck.
Thanks, everyone, especially for the admonition to go slowly and pack well! We have lots of sources of free fill here in the Islands, often with free or nominal fees. As my schedule clears, I will order the first upper body work out disguised as large, heavy, in-compressible objects!
Aloha!
Eric
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