Due to some interference from furry woodland creatures, the marsh in my backyard is now a pond. This is causing water infiltration in my new addition’s cellar.
After pumping & vaccuming 5″ of water in the last two days, a newly rigged 1/2 horse sump pump is now keeping the cellars dry.
While I’m in discussions with the town boards about reducing the furry woodland creature’s contribution to this problem, I want to install a non-powered backup system to my new sump pump.
In short, I want to build a dam INSIDE the cellar. Actually, two of them – one halfway across the cellar, and another at the doorway connecting the old cellar to the new one.
Any ideas?
The only thing I’ve been able to think of is to find some pond liner to use as a moisture seal, then stack sandbags or stone or blocks upon the liner to create a 1’+ dam. The doorway dam should be about 5′ long, and the other will be about 25’+.
thanks,
TJ
Replies
Yes, I'm replying to my own thread, but with a question. I've located a source for the pond liner, and I've just ordered 300 empty sandbags. The new question is: How do I tell how much material to order? The sandbags are the standard 14" x 24" size, and are to be filled 1/2 to 2/3 full. Any suggestions?
thanks,
TJ
standard 14" x 24" size, and are to be filled 1/2 to 2/3 full.
Rounding, that's 1 foot by two feet by, say 1/2 foot, or about 1 cu.ft. per pag. That's 27 bags the cubic yard. My calculator says 300/27 is 11.1111 (adds up quick, don't it?)
Don't know if that will help your flooding, but at least you know what amazing quantity of sand to get from the yard. You may be better off with soft sand (versus mason's or sharp sand). Soft sand can later be used for sand boxes, volleyball courts or horse shoe pits--when/if it is not needed in the cellar.Occupational hazard of my occupation not being around (sorry Bubba)
Thanks, very helpful. May not need it all for the cofferdam, but my daughter's sandbox is always needing additions...
-TJ
Ordered the sand yesterday, and was a little suprised that the 11 yards will be delivered as 14 tons. The thought of schlepping 14 tons worth of sand isn't to uplifting, so I thought I should re-do the calculations.
HAving had time to reflect, I see the sandbag can be treated as a cylindrical solid, whose formula for volume is (pi)R(sqrd)H (R = radius of cylinder, and H is height. USing the 2(pi)R formula to calculate the radius from the circumference (28"), I got a radius of 4.5". Plugging this in to the volume formula, I get 0.85 cubic foot per bag. (pretty close, CapnMac!)
However, I'm only supposed to fill the bags 1/2-2/3 full: So, multiply by 300 bags, and divide by 27 to get cubic yards, and we get a range of 4.5 to 6.5 yards of material.
Called the supply yard back to halve the sand order to 6 yards/7 ton.
Pictures when the dams are done.
-TJ
Just a few thoughts:
1) What is the purpose of the dam in you cellar? Just to buy you some time in case of a pump failure? I'm wondering if the dam height is high enough to hold back the water. Obviously, water will seek it's own level eventually so if you're planning a contingency for being without power or a pump for a while, the dam spillover should be equal to the water surface elevation of the pond behind the beaver dam.
2) Any type of reasonably heavy poly (6 mil maybe) would work to waterproof the sandbag wall. I'm sure pond liner is fine but probably a lot more expensive. How do you seal it to the floor? If you can't seal it to the floor, why bother with the pond liner anyway? During times of flood, don't most people just stack up the sand bags and deal with the water that infiltrates through them?
Maybe I'm missing something.
I haven't shot the elevation of the pond versus the current cellar floor as yet, but from a rough estimate, the foot or so of height will take care of the problem.
The idea of the cofferdam is mostly for my peace of mind. I don't yet have any sort of backup for the sump pump, though it's been working fine for 3 days now - cellars are both pretty dry now.
I've already toasted my one spare working pump cleaning two 3" flows from the cellar system: New area of 26x40, plus old area of 32x36.
There has never been a water problem like this since I've owned the house, and I don't want a power outage to flood me out again. I need to look into power backup, but this will be a temporary solution.
As for the liner, I'm concerned about the possible state of 6mil plastic after dropping hundreds of sandbags upon it. Pond liner is designed to hold back water, and is often covered with rocks and stones to anchor it. The weight of the sand ought to seal it down pretty well. I also plan to put down some lines of silicon underneath the edge of the liner, to help resist infiltration.
Seems to me the dam project would put you well on your way to the cost of a small generator dollars-wise, and there's a risk that the dammed up water might only delay the problem of water forcing its way into the non-dammed part of the basement. If you've been thinking about a generator, this might be the time.
Pete
There is something to what you say; however, were I to go the generator route, I'd be putting the sump, house water, furnace & circulators, refrigerator and one or two light circuits on it. So, a big enough, auto-starting generator, fuel supply, auto-changeover switchbox, plus wiring work... Bit more than I feel I can swing just now.
Has to be auto-switchover because we both work.
Not that I'm not going to investigate such; maybe it won't cost as much as I think. But I need the backup solution NOW; just today there was something in the paper about regional power concerns for the summer...
thanks,
-TJ
by pond liner do you mean EPDM?
same as roof EPDM except that the pond stuff doesn't have the talc on it, or so I've been told.bobl Volo, non valeo
I got this stuff at a big garden supply center; this one has a section dedicated to 'water gardening' (Russell's, of Wayland, MA; if anybody's interested).
It's a 45mil rubber membrane. $1/sq foot. While the news and such always shows just sandbags being used, much of the on-line documentation I have been able to locate on 'how to sandbag' suggests use of 'Visquine ' (Polyethylene) as a barrier. Especially when walling up doors and such.