Probably the DUMBEST question on here in ages -- could I turn an old septic tank into a fish pond?

[Denninmi]

OK, I know this is a weird question!

My house was hooked up to municipal sewers back in the mid to late 1980s -- I think it was probably about 1987 or 1988. (Still have a well for water, though, YEAH!). At the time, the septic tank in the back yard was supposed to be pumped out (which it was) and "remediated" -- in other words, filled in. It was pumped out, but the contractor that installed the sewer line didn't come back and do part B. For some reason, no one ever pursued it, and the municipality didn't ever come check. Over the years, it just got ignored. I know it's under there, because when we have drought, that is the first place the grass starts to look bad, and the rectangular outline of the tank becomes clearly apparent.

OK, fast forward to now. The ground in the center of this area is beginning to settle down and form a depression, so its apparent the roof of this tank is now beginning to collapse. Per my mother, this tank is not a prefab unit, but was made in-place of concrete blocks and a wooden roof. The unit is approximately 4 x 8 feet in size, but the depth is an unknown -- my mother thinks it may be about 5 feet deep, but she doesn't know, and I have no idea what code would have required when this was installed (1949).

I have NO way of getting heavy equipment back there without doing significant damage to landscaping, which is something I don't want to do. So, I would have to fill it in myself, either with bulk or bagged soil. That sounds like a LOT of work. And, I'm not sure how many yards it would take 4 x 8 is 32 square feet, if it were 5 feet deep, that would be 160 cubic feet, which would be 5.92 cubic yards of soil. Yikes!

I was wondering if it would be possible to excavate it, cut off the boards, fill it partially so it's not extremely deep, stick a vinyl or rubber pond liner down there, and convert it into a pond.

What do you think? Pros, cons, dumbest thing you've ever heard in your life?

[ret5hd]

1. could you find out if said contractor is still in business?

[hlthe2b]

2. Septic tanks in many communities are highly regulated by public environmental health authorities

I have no idea if they must be consulted upon removal or modification of a non-functioning septic tank, but you might want to check, nonetheless. They also might be able to weigh in on your idea.

[TheMadMonk]

3. Just plead ignorance. At that age it's NOT going to be a major health hazard.

Not unless you do something dumb like lick the walls.

Smart trick would be to drop the top few courses of blocks into the bottom and then colapse the soil on top to give yourself sloped sides. Then it's just a matter of a few bags of sand and a vinyl liner.

[Vinca]

4. I don't know why you couldn't do that.

Your post made me laugh. Years ago my husband and I bought and renovated an abandoned farmhouse. One of the first things that happened was a collapse of the wood covering the septic tank . . . when my husband walked on it. We had the thing filled in and installed a modern septic system.

[HopeHoops]

5. Keep in mind that it will probably continue to sink. A vinyl liner will sink with it.

The leach field will prevent it from naturally becoming a pond, so a liner would be needed. I'd consult with a garden center that deals with fish ponds (Not a mega store like Home Depot). Also keep in mind that ducks will find it almost immediately and koi are one of their favorite treats.

Another consideration is mosquitoes and black flies. Without adequate circulation (such as a feeding stream), the larva will breed without control. You'll need some sort of minnow (or similar) population to keep that under control and you'll have to get used to frog croaking at night.

You really need to find someone who specializes in this sort of thing (and they're out there).

[Denninmi]

6. Yes, I gave up on koi after the "Great $1,000 Blue Heron Banquet of 2003".

Been there, done that. I just keep feeder fish in my main pond, and throw mosquito dunks in the little ones.

Our frog population has crashed precipitously around here, for whatever reason. Back in the 1990s I had tons of frogs in the pond. Rarely even seen a frog or toad now. Its creepy and sad.

[HopeHoops]

7. My dad lost his to ducks.