Site Balence of Cut and Fill 2

[GoldDredger]

Hello,

I have a general question regarding grading plans. Say you have approved construction drawings with established grades, then your client (the developer) provides those drawings to the earthwork contractor.

The earthwork contractor indicates there is an excess of spoils that will have to be hauled off unless the site is raised so many inches (or for arguments sake, will require import and has to be lowered).

Although your analysis my show a balance on paper and through LDD, there are factors such as expansion, shrinkage and so forth which may throw off this balance.

The developer comes back and directs you change the grading plan to raise the whole site so many inches, so they may avoid this cost.

Typically speaking, would revising the entire grading plan with spot elevations and contours constitute and extra?

Have any of you come across this? Is this something you would outline in the original contract with the client? And if so, how do you do it.

GoldDredger

 

[GoldDredger]

Could probably start by spelling 'balance' correctly.

GoldDredger

 

[msucog]

are you referring to the extra going to you/designer or the contractor?

 

[PELS]

First off, you should always try to obtain soils information from:

1. Soils Report
2. Local grading contractors with experience in that locale
3. Discussions with other engineers or developers who have had projects built in that area.
4. Inspectors who have worked in that area.
5. Public Works personnel who have knowledge of past development in that area.

Those sources can usually tell you what was experienced in shrinkage/swell. Then you need to incorporate that information into your earthwork quantities prior to bidding. You are right that a balance on paper does not translate to a balance in the field, especially if you don't take shrinkage into account.

In your situation, there is no guarantee that the contractor's quantity is correct either. You also do not want to revise your plans just because your client told you it was recommended by the contractor. (Imagine if you did make his recommended revisions and the site still did not balance. Then finger pointing begins.)

The best thing to do for your client is to discuss the earthwork take-off methodolgy with the contractor. Try to come to agreement on whether the site can balance or not, then proceed on a plan to deal with the results. If it turns out you need to make UNIFORM adjustments to your design to effect a balance (i.e., raise or lower entire site or designated portions) and the amount of change is small (inches, as you said), don't change the design. Just make sure when it gets staked, the surveyor makes the adjustment in his cut/fill stakes. Then there is no plan revision costs. Adjustments can also be made during actual construction when shrinkage/swell amounts become apparent and real.

We have a section in our contract for construction problem resolution that is based on Time & Materials because it is impossible to predict unforseen problems. That's where we would justify compensation in this scenario.

If the adjustment is significant (feet vs. inches), then plan revision may be warranted. Whether or not the client pays for this depends on your initial contract and what is described in the Scope of Work. At this point, being flexible with your design and making adjustments to reach an earthwork balance saves your client much more money in construction costs than plan revision costs ever will. That's the justification I would try to make.

 

[civilperson]

The fact of excess spoils is more desirable than a shortage of fill. The excess can be used to raise individual lots above the planned distance to the top of curb or sold to developers with a shortage of fill. A shortage requires either a rework of the grading plan or import of material. Shrinkage and loss during grading is more common than expansion of material leading to a excess.

 

[francesca]

In my experience in land development design, the earthwork contractor was always very happy with an excess spoil condition, and would do lot grading to dispose of it. The only time we were ever asked to rework the grading plan was if there was insufficient fill material, or an inexperienced developer.

Who pays depends on many factors. Would the developer not agree to a soils analysis to determine actual shrinkage/swell factors? Did you make unreasonable estimates of these factors in your calculations? Would the developer not pay for an accurate topo?

Generally in site design, the developer tries to cut as many corners as possible, and if you can show that the inaccurate estimation was because the developer wouldn't pay for something up front that would have helped the accuracy of your calculations, you can realistically ask for more money for revising the grading plan. If you did not ask for a soils analysis or accurate topo, you're in a grey area. If you flat-out got it wrong, it's your responsibility to fix it. Regardless of who is at fault, if the developer hasn't paid his bill yet, you may as well suck it up and rework the grading plan or you may find it hard to get the bill paid.

 

[DarthSoilsGuy]

i agree with francesca about little excesses never come up. they just magically disappear.

also, what about suitable/unsuitable fill soils? raising the whole site will require more suitable soils for the areas where you need it. it's possible that you only have enough of the good stuff right now.

is there a lawn area where would be alright with some extra if the contractor comes back later saying i told you so? that way it could be handled by issuing an SK instead of revised plans.

invite the contractor to your office to go over the LDD calculation and his/her comps. if your surfaces, grid gen, and calcs are good, something was not considered and it is important that everyone is on the same page. also find out if they are working on any nearby projects.

if it's a big project with different subs, it's a good means/methods practice to leave the pad 2"-3" high anyway to protect it until slab prep.

 

[GoldDredger]

Thank you for the responses. I wrote a very generalized post on this, but as you can imagine, there are always qualifying factors. Let me try to supply more information.

With this project, there were considerable detention basins required, which were originally designed with retaining walls. The developer wanted to avoid retaining wall costs, and directed us to design with sloped gabions instead. This required an increase in the area of the pond and consequently increased the amount of spoils.

To resolve this, we all agreed to raise the site a uniform 4". The drawings would not be modified except by a separate addendum identifying this change. (And no, the earthwork contractor was not willing to just 'disappear' the additional fill. Must not have had a convenient use at the time)

Simple solution right? What a hassle it turned out to be for me. A variety of sub contractors, surveyors and independent tenants and their crews not well coordinated by the general contractor on this. Storm drain inverts remain the same, but curb inlets would change. Same with sanitary sewer vs rims. Driveways slopes tying to existing surfaces, you get the picture. Seemed I was taking a call or an email about it every day for a while there.

 

[civilman72]

Interesting post and discussion...

To answer your question on contracts, if the Owner requests that you revise any portion of an approved set of plans, I would almost always say this would be an extra. This is especially true if in having you revise the design, the Owner will be able to recover the design costs and save money on construction on top of that. This is of course assuming that you did present the correct earthwork numbers and did your best to economically grade the site.

A site design engineer may have a good swell factor to use, but there are so many other variables that truly determine if the site will ultimately “balance”. The cut/fill quantities calculated by LDD (assuming you created a stratum between existing ground surface and a finished ground surface) should not be your final cut/fill quantities that you supply to the Owner. Items such as topsoil removal & replacement and road pavement sections need to be calculated and integrated into your earthwork numbers.

I’m not assuming you forgot these things, but I do see some engineers that fail to take into consideration even these simple items. So if you have not considered these things, go back to the drawing board before you talk to the contractor. Here are a few other things that should be considered:

1. Spoils that are created from utility trenching.
2. The type(s) of construction equipment the contractor uses (and the weather) will directly affect the amount of soil loss during movement of the dirt. How can a site design engineer anticipate these losses? Most of the time you can’t, so include a limitation in your quantity estimate that states this was not accounted for.
3. In multi-family and commercial developments, the foundation design of buildings can significantly affect overall e-work numbers. Without specific foundation designs, it is difficult to determine the earthwork numbers associated with each building; this detailed information is usually not available when you are grading the site. If you do not have a detailed design, add another limitation note to your quantity estimate (see #2).
4. Some site design civil engineers “guess” at a shrink/swell factor. Unless you are very confident in the soils types, you need to rely on a geotechnical engineer to give you a recommended factor, and it should be based on actual on-site soil tests.

Experienced Owners generally know going into a project if they expect the earthwork numbers to balance, so when the contractor tells them it wont, no big deal. The problem is with the developers that just assume the design engineer will balance the site, and then blame us if we can’t. We all know this is not always possible. From my general experience, unless you can get really creative, it’s hard to not have a flat site require some import and it’s also difficult to design a steep site that does not generate export.

 

[civilman72]

Sorry, looks like my post was a little late, I see now where you are at.

One of the previous responses stated that if you only lower/raise the site uniformly a few inches you should not have to revise your drawings. I frankly cringed when I saw that. Unless you are working on a real small site, and with only a few contractors you are asking for trouble if you do not revise all the plans. I've worked with in-house survey crews, so the coordination between engineering and surveying was great. But on a big site, getting them to all remember the 4" vertical change and then calculate it correctly throughout the project would have kept me up at night.

GoldDregger, looking back, now that you've seen all the construction headaches and additional costs your Owner has endured, the question for you is, would he have actually saved money by paying you to re-design this a long time ago? I'd be curious to hear your response...

 

[DarthSoilsGuy]

saw a similar clusterf##k go down where a multi-story building addition was lowered maybe 2" inches to save the footings because all of the anchor bolts were set low (TOF was surveyed low for the 1st footing and it became a horrible "benchmark"). all the columns were fabricated so the 2" had to come out of the 1st floor ceiling space.... put that in your pipe and smoke it.

these across-the-board changes sound easier than they are. i bet the precast supplier for the storm sewer and sewer wishes you could raise a whole foot to throw in a riser.

 

[PELS]

GoldDredger:

Thanks for this post and your other two regarding "working with architects" and "dry utilities" design issues. Any engineer who has provided site design services has had to deal with all of these issues and more. Unfortunately, your experience must be chalked up to a learning experience rather that a profit-maker. The good news is that you will be much better prepared to deal with the next project in both your contract scope and client relations.

Good luck with your future endeavors.