Is there an effective test method for a large HDPE pond liner?

[edsun10]

I am looking at a repairing a defective evaporation pond liner which is made up of 2 layers of HDPE with a proprietary drainage membrane between them. The top layer is damaged and we have a contractor in place ready to remove and replace this. The scope of works calls for the bottom liner to be visually inspected but I feel defects and damage could be near impossible to spot with the naked eye. A vacuum box test only does where it touches and is usually limited to the welds. I understand that a holiday test won’t work as the bottom liner is on the ground and the test will short out. Is there another test I can do on the entire liner (approximately 35,000 sq m)?

On a slightly different tack, we have found water between the HDPE liners on the outside of the pond berm. The pond is 225m x 150m and the water is usually 1.5 m deep, the berm is 2.5m high. I would have thought that any water between the liners would not have gone much above the pond water level. An office wag has ventured that the water in the pond must have pressurized the water between the liners and forced it over the top of the berm. Is that possible?

 

[Ron]

If the HDPE is non-conductive (which is generally the case), a holiday tester will work...it's supposed to short out...that's how you find the holes.

 

[bimr]

Identifying leaks in landfill liners

http://www.clu-in.org/products/intern/leaklnfl.htm

 

[edsun10]

Ron

Apologies, I should have chosen my words a bit better and used grounded rather than shorted. The contractor is saying they can’t perform a holiday test on the bottom liner because it is contact with the ground. It is in effect earthed and they can’t get the current to pass through it.

Bimr

Thanks for the info.

 

[Ron]

Edsun...that's not the way a holiday tester works. If the tester is grounded to the ground, and the brush probe is pushed or pulled across the liner, if there is a hole in the liner, a spark will occur, since the liner is non-conductive and creates an insulation to ground. What is happening, is that the circuit is completed through the hole, not through the liner.

 

[48as52]

On a slightly different tack, we have found water between the HDPE liners on the outside of the pond berm. The pond is 225m x 150m and the water is usually 1.5 m deep, the berm is 2.5m high. I would have thought that any water between the liners would not have gone much above the pond water level.

Eng Tips Rocks

thanks,
kk

http://cubuilt.com

 

[Ron]

The volume space between the liners is small enough and there is enough water in there that it is being "squeezed" outward by the head pressure of the water in the pond. The volume space is a closed system, so not subject to static head of the pond.

 

[Ron]

Sorry...need to be a little more clear.

The space is not subject to the limitations of static head.

 

[edsun10]

kk = Thanks for the advert.

Ron - Thanks for the input. Met with the contractor this morning and he is does not think he will get a return signal through the soil and will not attempt a trail, so the holiday test is out and we are inspecting visually . . . marvelous.