Flat concrete slab

[Surcharged]

My client is an industrial wood processor. Several years ago they constructed a 200' x 200' concrete slab (8" thick) to store pallets on. They have a large forklift that moves the pallets. The slab was built 3' below natural ground and has retaining walls on all 4 sides. On one side is a gentle concrete swale approx. 6" deep that moves water to a pipe in the side of one of the retaining walls. The water then moves off-site. The problem is that the slab is almost perfectly flat from one end to the other. When the water gets deep enough it spills into the swale. After a rain there are large puddles of water everywhere and they must work in the water until the sun evaporates it. They want to fix it without starting over. My initial thought was to put in another gentle swale perpendicular to the other swale. THis was shot down by the company because it will be too rough on the forklift driver. My next thought was to install an industrial type trench grate perpendicular to the swale. Any thoughts?

 

[civilperson]

Survey the puddles, mark with paint and add topping at these locations.

 

[Surcharged]

THat may be good idea civil but the area in question is big. According to the forklift operator the puddle is about 1/3 to 1/2 the site. Apparently there must be some type of small ridge holding the water. There are also 6 sets of railroad tracks that run perpendicular to the swale. There are no cross ties on the track but the tracks stick up so that it prevents water from draining in one direction. The company rep did state that the tracks werent used anymore.

 

[cvg]

can you remove the tracks and install the trench drain in the slot?

 

[PELS]

Assuming the pipe "in the side of one of the retaining walls" is deep enough, connect another underground pipe to that pipe and run it back to the center of the puddle and put in a drain inlet (or two) slightly below grade. Then the water will drain directly to the drain inlet instead of the swale.

If the pipe isn't deep enough, you need to find a point where the water will release (where does it go now after it gets into the pipe?) and run an underground pipe from the drain inlet to the point where it can either be released or connected into a larger drainage system.

It sounds like this site was not designed by a civil engineer.

 

[Surcharged]

The "engineer" was fired after this fiasco. The pipe isnt deep enough to run another pipe - thats why I was going with the trench grate.

 

[PELS]

Where does the pipe (in the ret wall) ultimately discharge? The grade at that location should be your control point to determine if you can run a pipe to it.

 

[Surcharged]

The client has asked about creating a slope by adding concrete to the existing concrete slab. I am concerned about the bond between the new and old concrete and how durable it is. Any thoughts?

 

[concretemasonry]

Adding a slope by pouring a feathered slab is not a viable solution.

The turning of a forklift exerts some horrible forces that will quickly destroy the thinner portions. Once this progressive effect happens, you have created the same dreaded step the any forklift operator hates, especially when trying to spear and align pallets.

Dick

 

[655321]

Could you grind down the slab in places and create a little slope to a point where you can drain it out?

 

[Surcharged]

Grinding may work. We could start at the main puddle and grind a path to the swale. As long as we dont create a bump for the forklift. How do you grind concrete?

 

[655321]

You could rent a grinder, but if you didn't know what you were doing you could make a big mess. I would find a contractor that specialized in it. There should be one in the phone book, or ask someone that does flat work. We have it done all the time in parking lots and streets that aren't draining properly.

 

[Surcharged]

How wide is this grinder? What does the finished product look like? And how much does this usually cost per sf? THanks for the idea.

 

[655321]

I've never seen a price for this work as it is usually a fix that we allow the paving contractors to do at their expense, instead of replacing a slab. The price would probably very greatly depending on what you need done, you should get contractor to look at it and give you an estimate. But, if I had to guess, maybe somewhere between $5.00 and $10.00 a SF, and again this is a complete guess. The end result I have seen has been suitable for parking lot and street pavement. I think the final quality depends on how fine or polished you need the concrete to be, smoother is more expensive.

Grinders come in all sizes, some are small enough to push, other you drive.

Please write back and let us know how it turned.

 

[655321]

I meant to say $5.00 to $10.00 a SY, not SF. Still a guess though.

 

[TDAA]

Start by finding the low point of the puddle, and then figure where you want to take the water to. Do a flatness survey of that direstion. This will give the guys grinding an idea of what would have to be removed.

This type of method is often used by highway contractors if they have an evenness spec.