Excavation variables: HOW MUCH TIME?

[ericscher]

I'm struggling to put together an estimate for a customer who wants a new parking area. Normally when I do this I am just laying in material on top of a pre-existing construction drive. This time I need to excavate the area myself.

The excavation is fairly simple in that I'm only going down about 10 inches and I expect to produce about 100 yards of spoils before it fluffs.

Soil is former farmland converted to residential and likely to be pretty moist. I have no test holes to see if I'll be dealing more with soil or clay, nor will I be getting them.

I'm using 30" ditch bucket with a roughly 5 cubic foot capacity and a 3500 size dump truck that will handle 3 ton loads.

Spoils are being disposed of on site and no single trip is likely to be more 100 yards, so my ratio of digging time to waiting time should be pretty good. At LEAST 40:20, and that's being conservative.


My work doesn't involve a whole lot of excavation and almost all of it is just culvert work so I don't have the amount of experience needed to answer one simple question...


Under the described circumstances, how much TIME will it take?


Even if I price this open ended at $XXX/hr, the customer will still want to know a range.


Going on just the math and assuming 6 bucket loads per yard that would be 600 buckets. Assuming it takes 5 minutes to load 6 buckets that's 1 yard in 5 minutes and 8 yards in 40 minutes, or 8 yards per hour if I the 40:20 work to idle time is correct.


That's 12.5 hours to excavate 100 yards, assuming all my assumptions are correct and nothing goes wrong.

At $150/Hr that comes out to $1,875.

If I bid the excavation work at $1,000/day for two days that should cover it.

SHOULD.



But are my assumptions worth a damn? Am I just pulling this out of my 4th point of contact? (old paratrooper term)


What do you guys think?

 

[movindirt]

I have one question, what are the rough dimensions of the area you're digging? Its 100 yds. overall, but is it long and narrow or a square, that will also help with your time.

 

[Scrub Puller]

Yair . . .

ericscher

Just getting my head around it. No mention of what has to be done to spoils . . . do they have to be levelled or dressed?

Cheers.

 

[ericscher]

movindirt -

It's like a rectangle with a chunk cut out of it because it's supposed to butt right up against an existing driveway and garage.

I drew it out as two adjoining rectangles of 22' x 121' and 13' x 32'

I guess you could also think of it as a 22' x 153' rectangle with a 9' x 32' chunk of corner missing.

Excavation depth will be about 10 inches as measured from the surface of the adjoining driveway.




Scrub Puller -

Leveling or dressing the spoils isn't part of the bid. We'll be dumping along a tree line in the back. We'll tidy up of course,but nothing fancy.

 

[RBMcCloskey]

3,078 SF. x 1.0 / 27 = 114 CY. ===> SAY 115 CY. Say: 2 Days = 16 Hr. x $150 = $2,400. = $21.00 CY. +/-
That should cover Labor, Equipment, Fuel, Coffee & Lunch (2 days), Insurance and Profit

 

[ericscher]

Interesting...

I had done some more thinking and decided that two days should do it but I wanted another half day for safety, so I came up with $2,500.

But I like the formula. More importantly, I like the result... $21/cuyd

That gives me a good way to quantify it. Thank you.

 

[Shimmy1]

I want to come do business where you do. Around here, excavation and transport for 100 yds goes around $3-5 per yard. Yikes.

 

[RBMcCloskey]

Can you do the work as described for $300. to $500. and make money?

 

[Shimmy1]

I don't think I could spend much more than 2 hours on this. It takes me roughly 5 min to load 20 yds³ on my side dump. That's 25 min loading time. Let's say it takes 10 min per load to go dump. There is 50 min. That leaves me with 45 min for cutting the grade. I never said the entire job would be $300-500. Just the excavation. I'd also have my mobilization costs into that.

 

[RBMcCloskey]

Look at it as described, using his equipment and methods.

 

[Shimmy1]

I'm just saying I can't take my Bobcat to dig a waterhole. Yes, I could do it. Yes, I could probably bill 3X what it would cost to do with my excavator. But, I would not be in business very long. Around here, production has it's hand on the throttle.

 

[ericscher]

Different places, different circumstances, different realities.

That's intended as nothing more than an observation, BTW.


If I had no excavator, I would need to rent one.
A comparable excavator would cost $295/Day, plus tax & Insurance. Call it 325. Add 220 for two way transportation because it's cheaper for me to have it delivered than lose the man-hour productivity.
Say $550.

If I didn't have a dump truck I'd have to rent one of those, which actually changes the excavator calculus. Dump truck is $225/Day so that basically replaces the delivery cost on the Excavator, only now I have to rent a trailer because all of my trailers are in use. That adds 50 bucks.

So now I have $600 in equipment costs per day.

Now I need to excavate a shallow ditch and move the spoils without driving on the adjoining driveway because it looks like 2" of asphalt on an unknown base. I also don't want to tear up any more of the lawn than absolutely necessary and a dump trailer has size issues that matter. And this is a residential neighborhood on the corner of a sort-of 4 way intersection with narrow-ish roads.

With the equipment I have I would not be able to finish in a single day. Plus, we often have to deal with a sticky, dense mud that rapidly reduces bucket capacity and I don't know if I will be hitting that stuff without test holes that I can't dig.

So, two days... $1200


I already have the equipment, so I don't need to rent but I do have to maintain and eventually replace, so I need to make enough to pay the overhead and the profit AND set aside for taxes and equipment.


That's just the situation I have to deal with.

 

[lumberjack]

I see a few things that don't make sense to me.


5 minutes to load 6 buckets with an excavator. When I'm loading out of pile, I can make 6 passes in a minute, give or take 10 seconds... the ctl gets material loaded faster. Cutting a tight grade with an excavator sucks, so I assume it's got a reasonably generous tolerance. A pass shouldn't take thirty seconds. With one person in the truck and the other in the ex, the ex stays working cutting and piling while the truck is gone. This means when the truck is getting loaded it's hopefully mostly out of a pile instead of loading from the cut.


With 2 people, $150/hr seems reasonable or possibly even low. With one person it seems high.


What is the tolerance on the grade and how are you measuring it? The tighter the tolerance the longer it takes.


What about any over dig? If the parking area is 22', I'd want ~23' cut at least to make sure the fill is good to the edge, more if the vertical cut edge crumbles.


Price wise, I would be around $1.5-2k for a day. I don't know if I'd use the CTL, ex, or both, depends on the situation. Dirt isn't my focus; my hourly rates are higher than the average straight dirt guy around here (dirt leaves other more expensive equipment sitting).

 

[ericscher]

The time consumer will be the cutting, not the lifting into the dump truck. I'm not bad on an excavator, but I'm not as good as I would be if this was all I did all day.

We'll be loading from the cut, not a pile.
Everything about making this work depends on a very neat, clean excavation.
Also, the equipment I have is what I'll be working with. Not meant to be snippy, just stating a circumstance.

Two people, one excavator, one dump truck.

Tolerance matters a LOT because if I am off more than a small amount I will be buying a lot of material out of my pocket. Worse, the tight delivery access means no 20 ton trucks, which increases the cost. I am making NOTHING on the gravel.

I'll be UNDER digging in a manner of speaking. 10" hole and 11" of material. The 9" of 411's wont pack much, the 2" of #4 or #57 limestone will pack a little. I want to intentionally end up visibly but slightly above the driveway surface.

I'll be sending the bid within the next few minutes and I will be charging $2,500 for the excavation, for which I am budgeting two days. Day one will include some layout, marking, setting strings, etc... Day two will include laying in the GeoGrid.


I'm actually feeling better about this bid because of the back and forth here. Thank you all.

 

[lumberjack]

Good luck!


You make nothing on the gravel itself or nothing on the gravel including installation?

 

[Remodman]

Hi Lumberjack

You mentioned in one of your posts that you knew of a good GEHL dealer, is he still around?

 

[CM1995]

Are you adding a mobilization charge?

BTW - I move this thread from Shop Talk to General Industry Questions.

 

[DoyleX]

Sounds like you know how to figure your cycle times and quantities. Some variables to consider. Swell factor with a smaller bucket compared to the big boys 1.4 And what about underfoot after 30-40 rounds of a gorged 3 yd tipper. The going might get tough when the haul road blows out.

Gives me a chuckle writing about hauling with a 3yd tipper. Did some sub work digging and ran out of spoil room. Boss man grabs his dumper and with 2 yd of wet clay away he went. That only went for a few rounds as I could tell it wouldn't make the day so 1 yd it was to the end.

 

[ericscher]

Good luck!


You make nothing on the gravel itself or nothing on the gravel including installation?

Nothing on the gravel itself.

I pad the price slightly as a protection against the loaders at the yard overfilling the trucks. Like if you want 20 tons you might get 19 or you might get 21 in any given truck.

On the gravel I take my price, add tax and round up to the next dollar. On delivery I add two dollars per ton, so on 100 tons I make $200.


I do this because the price is so variable all over the area and too easy to check.

I make my money on the labor. I generally try to make sure that whatever I'm going I'm netting a thousand a day. Of course, I mean SUB net, no technology joke intended. I do a pretty substantial set-aside for taxes and machine maintenance/replacement.

 

[ericscher]

Are you adding a mobilization charge?

BTW - I move this thread from Shop Talk to General Industry Questions.

Oh, that's OK.
Sometimes it's hard to know exactly the right forum, so it's good to know someone is there to correct it if I guess wrong.


I'm afraid I don't know what a mobilization charge is. Or perhaps I use a different word...?