howto dig hole for 300 gal septic tank...


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Old 08-05-03, 10:40 AM
Sc0rp10n
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howto dig hole for 300 gal septic tank...

hi all. i'm pretty close to doing the septic tank installation for my small deer camp. i'm going with a 300 gallon fiberglass spherical septic tank. it's roughly 4 feet tall and 4 feet in diameter, give or take a foot. i haven't purchased it, but those are the measurements. seems small for 300 gallons, but oh well.

the plan so far is to rent one of those personal back-hoes from the local rental place. it's one of those 1-man vehicles with the tank treads and the arm. not like the huge ones you see on construction sites, but smaller.

will this vehicle/machine be able to dig a hole sufficient for this size septic tank? do you have any suggestions on getting the hole dug?

also, when backfilling, would you recommend filling the tank with water as you backfill the dirt around it, or will it be fine without filling it with water? i've heard that a 300 gallon spherical septic tank doesn't really have to be filled with water as you back-fill.

anyway, thanks for any advice you guys can give.
 
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Old 08-05-03, 09:37 PM
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Danger exists when you did a hole that deep. You should have mechanical shoring holding up the sides of any hole deeper than 4', or you need to dig out the sides of the hole to at least a 45 deg. angle to keep it from killing someone.
 
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Old 08-06-03, 04:48 AM
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how can it be dangerous if nobody gets in the hole? i.e., the hole is dug and then the tank is actually placed into the hole? or are you talking about he sides caving in while someone is standing on the edge?

also, can that type of machine dig a hole like that?
 
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Old 08-06-03, 05:31 AM
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I'd fill the tank with some water before burying it. Spherical tanks are less prone to float out than square or rectangular tanks because of the surface area available for bouyancy. But what does a little water cost compared to doing it twice.

FYI: There are OSHA regs that refer to any trenching and safety. Basically, anything over waist deep needs shoring or walls cut in a way to stop cave-ins. It depends on soil structure. Just be safe in your work, if anyone gets in the hole, have someone else watch for dirt movement while the person is working.

The machine your using will do the job if you are in dirt, no big rocks, or large tree roots. When burying your tank, do not use any rocks but dirt or sand as the backfill material.

Take your time, have fun without alcohol until you are done. More questions, ask away and someone will answer them.
 
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Old 08-06-03, 05:35 PM
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It wasn't too long ago that one of our guys was working a backhoe next to a 5" deep hole, no shoring in the pit. The sidewall of the hole collapsed under the weight of the machine, that caused it to pitch forward into the hole, hurting the guy and damaging the rig.
 
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Old 08-06-03, 07:52 PM
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I had a guy get pinned up to his knees with loose dirt back in the early 80's. Ditch was just over mid thigh deep (36" to 40") and Billy couldn't move. Even with that little bit of dirt. Broke a bone on top his foot and twisted his left knee real good.

About 2-3 people a year die in KC metro area due to trench collapses a year. Could be water / sewer work or foundation repair.
Trenching can be dangerous unless you know a few things ahead of time.
 
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Old 08-07-03, 06:12 AM
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What you're talking about renting is what is called a mini-excavator ( a small track backhoe). For a project like yours, I would use a Terramite or compact Kubota rubber-tired backhoe. Both are readily available in my area (even Home Depot rents them). The advantage is that these have front end loaders that make backfilling easier. And I think the Kubota is 4 wheel drive. I, too, have heard of mini-excavators sliding off into the hole being dug. Less likely with the tractor style backhoes, IMHO.
 
 

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