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In any event and whether the soil is easy or not, probably not the best choice of machine, but thats just an opinion. Your JD 450 is a crawler I assume ? Have ran the dozer version and lots of others as a full time operator. If that is so, at least you have the benefit of getting good traction, sounds like you are digging into a bank or a slope, not sure how level the site is, but you'll want to make your work area level for starters, including the stockpile area for the fill. After clearing, grubbing and leveling, lay out the footprint of the building, not sure if this is a tight lot, or your on acreage or what, but if a tight lot, best to have your surveyor give you the lot lines and use those known points to locate the building corners. Once you locate the building you can use offset stakes so you don't lose your reference point and can re-establish the corners anytime, because you will not have to excavate where the offset stakes are. Check your architectural drawings if you have a set for the job and do the layout, next you want to find out the elevation to excavate to and make sure you do not over excavate. Bottom of footing elevation + thickness of footing then the slab thickness on top of that will be top of slab elevation in the basement. Of course your foundation wall height is also taken from top of footing and will determine how high your 1st floor is above existing grade or what will be finish grade around the building. Check and see how much of the foundation will be exposed and adjust to your liking. You can excavate the entire footprint ( really have no choice with a crawler loader ) to bottom of footing elevation and form out the footings. Best to strip the footings, lay in the foundation drain(s), inside the footing and outside the footing, place something like a Mirafi filter fabric and stone #2s or #3s crushed stone or whatever you have locally around the perforated pipe, (basically pipe with stone surrounding it and wrapped entirely with filter fabric if you look at in section) make sure to put a slightly larger diameter pipe through the footing so you can let the inside drain pass through the footing, try to pitch all the pipe to the place it will exit the footprint of the building to ensure that water will run out, it doe snot have to be perfect, but if sloped properly, water will run right out.
Now that the pipe is in, you have drainage in case it rains, on the east coast, in areas I have worked, excavated areas can become ponds with one good storm, so it's good practice to do this asap and you will have plenty of access to all areas around the footing prior to the wall being formed and poured. The inside pipe is an extra precaution and the filter fabric is just a means to keep your stone clean, this is how I would do it to get max. drainage, your conditions may not necessitate it, but around here silt can choke up the stone and reduce drainage capacity, clogging up the voids. Next layout & form the walls, say one month after you pour the footing, concrete takes 28 days to reach full compressive strength, then it slowly gets stonger for many years, not much more than the mix design though, so you should wait a minimum of a week, so at least you have 1/4 strength and use a pair of #4 or #5 bars continously through the footing, your drawings should specify. Reinforcing bar dramatically increases the strength. Once your walls are formed/poured stripped ( make sure all pipe penetrations, beam pockets, and any other items that are connected to the wall are coordinated into the formwork, it's much easier to form it out than chop it out ! Check your drawings carefully, highlight & locate all of these 1st ! ) you may have to wait the 28 days to apply waterproofing, damproofing etc., check the mfr. instructions, most products require a full cure to get a bond. You most definitely want to wait the 28 days prior to back filling or risk causing the wall to crack or fail. Back to the excavating, once you establish where the building and work area is, you need to plan on where or what you are going to do with the fill, so locate the stockpile relative to the work and try and make a gentle "K" from where you excavate to and where you will stockpile, as you are backing out you should be turning so that when you go forward you go straight to the pile.
Soil, underfoot condtions, type of track pads, all contribute to the efficiency of the machine, relative to how fast you can dig, with a crawler, depending on the soil type it can be slow, especially if it takes a lot of break out force to get through it. Not much you can do to speed things up, if it's your only option, take your time, the harder you are on the machine, the sooner it will need repair. On that note, you'll want to make sure it is in good running shape, fluids are clean, changed, topped off, and everthing is in good running order, it will be working hard on this kind of work, grease those loader pins, 2x/ day is not overkill, run em dry and they wear quickly. I would want at least 3 to 4 feet between the excavation wall and the face of the foundation wall, minimum would be 2 feet, also, if your soil is not stable, you should shore it up or excavate the banks at a 45 deg angle of repose, to prevent a collapse, and remember if you are going to be in the excavation with the entire machine, make sure you have an escape route, or that a potential collapse could not engulf the machine, just read about a guy who was using a dozer to dig a trench to repair a dam, opened up a wet pocket of slop in the dam itself, which then collapsed, the cab door was against the trench wall and he could not get out, and did not get out, when his wife came to look for him, she was standing right above where the machine was with the property owner, and they did not even know he was under the water that filled the excavation in a few feet from where they stood. Best to take a wide cut and leave lots of room, common sense and thinking out your moves usually eliminates bad things from happening, just remember there are no second chances, so plan it out carefully, do a dry run mentally or on paper, make sure you have a plan, it always pays off. When you excavate, you will be increasing the volume of material by 15%-20% because it is no longer compacted when excavated, so your stockpile will be that much bigger than the excavated area. If you stockpile, and then plan to remove the material, you will handle it 2x, so if that is a consideration, build an area to get a truck in, with a JD 450 size machine, you'll need to build a ramp to get over the side boards of the dumpbody, but you will only handle the material 1x if you dig and load it out. If you will use the fill on site, plan out where you will use it and try and dump off as close to those areas as you can. Try to make your work areas as level as possible. I've spent a fair amount of time on Cat 955's & 977's, am very familiar with crawler loaders, you can make it work, but if you would like to keep the machine for a long time, better to rent something, save the wear on yours, I find that renting is extremely efficient around here, I can get a D-4 dozer for $375/day or a $420D rubber tired hoe for $800/week, you can do some serious work in a short period of time with these and the fuel economy is excellent. Not sure what excavators are going for, have not had to rent one, but even with shipping and fuel costs, you are way ahead, the job will get done, if yours breaks down the job stops. I do the lighter work with my own equipment whenever possible, areas of work that are not too stringent or hard on a machine, much less wear and tear to absorb. When you backfill, you should do it in 1 foot lifts and then compact, with a plate tamper or jumping jack, working your way up to the finished elevation, you may encounter settling and or voids if you don't. In any case hope this is some help, made a career in this area of work,and construction in general, so when time permits I enjoy helping whenever possible. Good Luck!
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