Bridge Construction

[buckry]

Part of my new pond design includes a bridge across it. In Indiana the only wood available for outdoor projects is pressure treated pine. I'm very worried that when it rains the chemicals in the wood will drain down into my pond. Is this something that will happen and if so will it be a problem? I would hope that my filter would do some good with this sort of thing, but I guess any foreign chemicals in the water at all is a bad thing. If I paint the bridge first will that lock in the chemicals? If that's no good I'm just going to buy normal wood and paint that. Paint is no problem once it's fully dried and cured right?

 

[sissy]

They now use salt to treat some of the new pressure treated wood .I have a bridge across my pond also

This is a fence made of the new wood that i built last summer and i am rebuilding my bridge top from this stuff as soon as I get the time .

 

[Bullfrog]

Go to a specialty wood shop and buy cypress or Redwood, something naturally resistant to rot if you are concerned. Others have PM'd me that they have used treated lumber with no problem after the purists lectured me not to do it when I asked the same thing.

 

[Waterbug]

Depends on the chemical used. Today you should only run into ACQ treatment. The older CCA treatment is still used but only for certain applications and you shouldn't find it in a big box store. ACQ is copper based and that would be a problem for fish and generally not something filters remove. Your best choice would be ACQ Type D which is a common type.

The chemical doesn't leech out in great amounts, that would defeat the whole purpose of using it. Most leeching happens the first year. If you wash the lumber with slightly acidic water, like 4-5 pH, you can remove most of this first year leeching. Soap isn't a help, it's high pH.

There have been many studies on ACQ and leeching, but not a lot specifically on your case. This is not the kind of thing that kills all your fish after the first rain. More of a long term risk issue. Less of an issue if you're doing regular water changes, so depends on the pond too.

Here's something I don't think most people consider...the biggest danger will come from saw dust. Building the bridge near the pond, the saw dust gets into the pond. Or saw dust on the structure washes off and into the pond. The wood in the dust rots and all of the chemicals are left behind. Could be a much larger dose than normal leeching.

No absolute answer. More of a question of how much risk you want to accept. Someone with $20K worth of Koi in a pond wouldn't let PT wood any where near the pond.

Paint is no problem when dry.

If you're really concerned you could nail EPDM liner to the underside of the bridge so runoff went into the soil at the sides of the pond instead of in the pond. That would reduce chemicals by a great amount.

Big box stores may not carry redwood, cedar, etc., but I'll bet you have a wood specialty store that carries it...for a price.

 

[sissy]

I buy the salt treated wood at Max Kendal lumber yard here .I look at the label and went online as it tells you all the ways lumber is treated now and what to look for on the label to tell the difference .!2 inch wide board by 20ft long salt treated lumber that is rot proof and holds it's color is around 10 dollars at the lumber yard and can be painted if you want to with out peeling .primed first of course .

 

[buckry]

Ok, I think you guys answered it awesomely and I feel like it's a totally reasonable risk, especially since I will be doing regular water changes, and my fish are all $3 koi, and only 2 months old, at this point, I'm not out anything if I have to buy 3 or 4 new ones, in fact, a few of them are quite ugly I would actually LOVE the chance to replace them. Thanks so much, I'm going to move forward with the treated lumber.

 

[sissy]

If you prime it and then paint it you should be fine .

 

[taherrmann4]

I have used pressure treated lumber for the supports of the bridge and untreated poplar on the top, have never seen any problems. But mine was also wood that was lying around outside for several years before I used it. Go for it.

 

[buckry]

Ok, the wood is bought, $100 worth of pressure treated pine. Should have a bridge later tonight. Thanks again for the input all.

 

[sissy]

good luck are you making it a arched bridge or just straight .I had to use 2x 12 's to get my arch and then had to double them up so it would not crack at the weaker points .I even used metal cut to an arch and bolted that inside the bridge .I could have tripled the 2x12 but the metal was stainless steel and it was only 10 dollars and they did the bend free and did the holes for the bolts and we got 2 from one piece of stainless steel .Wish i would have put it on the outside of the bridge as the metal looks pretty .

 

[buckry]

Arched. I bought a 12" piece of pine. I'm going to cut a 6" or 7" arch out of it. I have a bunch of 2x4's that I'm planning on making a support frame on the inside out of. The 2x12's will more than likely be decorative, not structural.

 

[buckry]

Here is the completed bridge. Need my wife to help put it in place and she already helped me move it out today so I'll get it in tomorrow and post some pictures of it.

 

[j.w]

Nice and that is gonna look nice across your pond

 

[Waterbug]

What took you so long? Let's not tell my DW about this. She's come to expect a job like this to take a few months.

 

[sissy]

I like open bridges because I like to sit in the middle and meditate at the beginning of the day and the end of the day .I think it grounds you and refreshes you .I did add top rails on mine only to help me get back up .I just like sitting in the middle and looking down on the fish when I feed them .Guess your wife will have to be hands on for this part of the pond .I used a 2 - 2x10's across the pond and slowly slid the bridge across them .You have to think on your feet when you are doing it by yourself .