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Question DetailsAsked on 8/10/2016

Laying a rubber liner over a cement creek. Any problems? Any chemical reactions? Should I lay dirt over concrete?

It is a fake creek. Concrete not shaped properly, so plan to add a bit of dirt on sides to grade down to middle for water slope. Am concerned about possible rubber/concrete chemical interaction? Should I cover all concrete with a shallow layer of dirt, then lay on top the liner?

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1 Answer


You say a "fake creek" - since you are interested in sloping it to drain, I presume you mean it does serve as a drainage channel, not purely an architectural feature, so what you put in it has to be non-erodable.

Rubber (would not be real rubber for this - would be a synthetic rubber like used on oudoor conveyor belts) can be in contact with concrete without a problem, though if there are any low spots you could get stagnant water under the liner which could cause an odor issue - plus the possibility if it does not seal tight that vermin could take up habitation under there. Also, standing water under the liner can cause biodegradation - so normally pond liners of this type are designed to either be totally immersed in the liquid at all times, or be fully drained with filter drain material under them - generally speaking a sand-gravel mix that will not wash away from under it in the limited flow that will go through it. Plus in a channel environment measures would be take to ensure water flowing down the channel could not get in under the liner and wash away the bedding material or lift it up and tear it.

A liner like this, rated for direct sun exposure (to last more than a couple of years) is likely to run you at least $1/SF and probably more - plus it would still not take care of the out-o-level issue so would trap water in the low spots as stagnant ponds unless there is constant flow through it.

I am lost as to why the liner - expensive, and I don't see how it helps the situation, plus not very pretty. The normal solution for this would be gunite (like commonly used to make in-ground pools) or shotcrete - these are sprayed on cement mortar mix or sprayed on concrete, respectively, the choice between them depending on whether there is going to be any significant flow through it (shotcrete if yes). Can be placed from a fraction of an inch to a foot or more thickness to even out the uneveness in the surface - cheaper if left rough of course but can be hand and/or machine floated or troweled to a smooth surface.

Another possibility - especially if flow is always low and slow so erosion is not a big issue, would be using a shot rock or cobble liner to improve the appearance (though would require consideration of whether that added flow resistance would make the channel undersized, and would support vegetation growth eventually).

If this is an actual drainage channel like a floodway, you likely have to get a permit from the appropriate drainage district, or possibly from the Corps of Engineers depending on size, whether a regualr stream flows through it, etc. hyour local drainage district or Planning and Zoning department should be able to get you started in the right direction. Might even be they are responsible for maintanance of it and will take care of any functional (though not just appearance) problems with it. Also, if actually a floodway or such, you should have a Civil Engineering firm experienced in floodway/channel design handle the design and materials selection for you so there is a good chance of a reasonably long life for this (typically about 5-15 years for synthetic liners, about 20-50 years for concrete).

Because this is concrete, unless just a small runoff collection swale in your yard, I really think you need a Civil Engineering firm (google for Site Development Engineer - not an Angies List category) to look at your situation and give advice. After finding out who owns this and is responsible for it - if more than just a small on-site runoff control swale, likely belongs to city or county or state road department, a state or federal lands agency, an erosion / drainage control district, railroad, or such entity depending on wht it is adjacent to and what it drains from and/or to.

Answered 3 years ago by LCD

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