Mini Ex sheet piling or shoring

HI , Have a site that has long history of site contamination.... I am removing 5 old style car hoist (1 large cylinder in center) in a large auto service garage ie 12 hoists. The issue, is even before it was installed there was environmental issues on site. The excavation is: 8" thick concrete floor, 30" "A" gravel, (here is issue) 6 feet of 3/4 Clear stone and 36" steel corrugated culvert on vertical with the hoist cylinder inside unknown back fill.... likely some concrete but could be 3/4 stone....

Total depth is approx 8 to 10 feet.

1 hoist is started
there is 8 ft sq hole for each hoist cut in floor. We can see undermining back 4ft at 4 ft depth ie 45 deg....

Looking for solution to retain 3/4 so we don't under mind floor....

Sheet piling w Mini Ex ? I don't think trench box will work as 3/4 will move before the trench box drops??

Site is in auto garage with 14 ft high ceiling and its only $3k job so I cannot get too crazy w $$

thankyou

What is your scope of work ,to remove the parts of the hoist only or to remove both the hoists and the contaminated soil as well?Has the site been tested,if so what are the contaminates. If your planning to dig a hole deeper than 4' it will need to be shored or sloped 1:1.Is there ground water to deal with?The magnitude of the shoring will be dictated by the depth of the hole,if you are going down 8' that will require substantial shoring.This will require an engineers input to begin with . 14' ceilings would probably make this a low headroom sheet pile job, meaning your going to drive short sections and splice them as you go down and cut them apart as you extract them. If the contamination was serious enough to require full remediation it you would probably have to demo the building to do the ground work. If im clear that your budget for this work is 3000.00 i would remove the hoist components or cut them off below floor level and restore the floor if this is possible. Leave the excavation alone even though the digging itself seems simple the bureaucracy is overwhelming ,3 k wont even get the consultants to the site to begin with.

Trench box it or demo the building. You could use the hoe to help push down the box. If you are already undermining the slab you have some bigger problems. The remediation sounds like the larger issue here. How are you going to know when you are meeting your cleanup requirements? I assume you have a P.I.D. meter and lined rolloffs boxes with a proper clearance for disposal?

Does the three foot corrugated pipe have to come out or can it stay in place?

I think there a couple ways to do it, but 3K is not enough money in my mind.

KSSS said:

I think there a couple ways to do it, but 3K is not enough money in my mind.

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I agree.

$3K is not even enough to cut 5 hoists 1' below grade and pour back the floor, leaving everything else in the ground.

Yeah, but he's in Canada, so if it 3k in canadian loonie's, he's working with even less $$$ than you guys are thinking. $2,260 in USD right now.

I think if everything has to come all the way out, you've got issues.

I think I might try to just make a hole in the concrete just big enough for the top of the cylinder (3'x3'), weld a bar across the top and a 20 ton bottle jack on each side and jack the cylinder loose. Then pull it out the rest of the way with forklift. Backfill the "cylinder" hole with clean, then remove your 8' x8' concrete and repour.

Depending how the hoists are made, some are really difficult to cut off 1' down. None of this works if the culvert has to come out and all the "contaminated" soil.

crane operator said:

Yeah, but he's in Canada, so if it 3k in canadian loonie's, he's working with even less $$$ than you guys are thinking. $2,260 in USD right now.

I think if everything has to come all the way out, you've got issues.

I think I might try to just make a hole in the concrete just big enough for the top of the cylinder (3'x3'), weld a bar across the top and a 20 ton bottle jack on each side and jack the cylinder loose. Then pull it out the rest of the way with forklift. Backfill the "cylinder" hole with clean, then remove your 8' x8' concrete and repour.

Depending how the hoists are made, some are really difficult to cut off 1' down. None of this works if the culvert has to come out and all the "contaminated" soil.

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LOL!!!, I was just thinking along similar lines to 'crane' them out cause anytime you got 'contaminated' around here it gets ridiculously expensive/time consuming/paperwork hassles!!! and the second you 'touch' some dirt that test positive... it can NOT!!!! go back into the ground!!!! PERIOD!!! even though it had been in the ground for 50 years or more before that... so then you need suitable fill... which usually means suitable structural fill..... properly compacted and probably tested with a nuke or something... so now you gotta have an abatement guy on site and a soils guy there to make sure you fill it properly... I doubt 30K would be enough for a job like that.... the last job we were on that had 'dirty' dirt... we had to chase it down 10 more feet and three truck loads

I would walk out front door and keep on walking and not look back

HI Guys
Sorry for slow reply....

My scope is to remove hoist and its concrete base (if any).
Floor has been cut by others... I am just excavator.
$3k is simply for removal of steel and concrete

I have done 2 other similar job. 1 hoist per site... less than 4 hrs work

Corporate property owners are paying for all soils testing and if needed safe and legal disposal.
Pile any soil removed for testing.

Yes they know if soils fail they have huge bill.

It was very easy job on the other sites as soils were stable.
Hole stayed small...
This clear stone is the issue.

Will trench box work with Existing 3/4 clear stone?


In regards to slopes... we will not be down hole.
Soil samples will be taken from bucket of Ex.

Restoration is separate quote/scope...

When Soils Engineer decides what we can back filled with (after Lab tests, paid for by others)

Yes, they know if soils fail they have huge bill.

If Soil fail, We can use Clear stone to back fill and a hoe pack to "consolidate" the stone.

Then thought was concrete lean fill to manage any un-mining of concrete floor...
If this is not possible, We may need to cut and remove floor, but again this is not that large of area... worst case is still less than thousand sq feet....

Have you approached property owners about extra cost?

It is pretty much impossible in my view to put lean crete under the slab and get it tight unless you drilled holes in concrete floor and backfill it that way. The way I think I would do it if I understand the project correctly is ex out the 3/4 clean stock pile it. Remove the cylinder and place back the 3/4, given your less than 1000 sf of concrete, I would remove it as needed based on the slope of gravel. By the time you figure out how to put pilings in with a mini, I don't see it worth that little amount of concrete that is required.

Thxs...
BLS repairs... yes customer is prepared for extra cost...

Thxs KSSS... This is not first job where pilings are discussed for slope control....is there any piling solutions that work for mini ex? Whats min cost for this kindof setup?

Started dig yesterday, removed 2 of 5 hoists... 3/4 clear stone just keeps moving, real pain.

But in regards to environmental, no issues. They say, they can not test "granular " . And there is no visiable contamination. They had "sniff tester" and was getting "zero reading"

Plan A is to dig out hoists and then cut remove any floor that is under mined and re pour removed floor area.

Still looking for shoring options??

I have not seen anyone doing that with a mini. Doesn't mean it is not possible, but I have never seen it. I am sure it is a pain having to move way more material than is needed but still likely cheaper than driving pilings with a mini, which would likely be a bit difficult and take awhile.

Would be easier to drill and inject grout for shoring... but you'd need the pumping equipment and a small drill rig...

I agree with the grout idea ,but if you are are really into sheet pile an Ape # 6 vibro ,weights 750 lbs and has about 4 tons driving force. You check the specs on Apes web site or call Ape in Edmonton. That hammer would drive light sheets or some chanel iron of what ever lenght the headroom you have will allow. They also make an excavator mount thats a bit bigger . Still an expensive operation. If you can rent a grout pump and push some 1" shd 80 pipe thru hole in the concrete around the perimeter of your excavation that might work, but its still a complicated experiment.

Yep, APE was still open for business this morning

Tugger2 said:

I agree with the grout idea ,but if you are are really into sheet pile an Ape # 6 vibro ,weights 750 lbs and has about 4 tons driving force. You check the specs on Apes web site or call Ape in Edmonton. That hammer would drive light sheets or some chanel iron of what ever lenght the headroom you have will allow. They also make an excavator mount thats a bit bigger . Still an expensive operation. If you can rent a grout pump and push some 1" shd 80 pipe thru hole in the concrete around the perimeter of your excavation that might work, but its still a complicated experiment.

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I've seen guys do similar on jobs we've been at in the past but can't remember the details... just know they drilled down and depending on the stuff they were going through they would adjust there hole spacing up to a max of about 2 feet then push grout as they removed the feed line. I'm sure it took some experience to get the fillin correct but was a cool operation and didn't even need much in the way of equipment!