I'm considering doing a pump and dump system.  I am building a 6000 sqft house near the the Canadian border in MT where it gets VERY COLD in the winter (all radiant floor heat).  I have a 30-60 gpm well that I was planning on pulling from for the geo system on an open loop.  I have a small "valley" that I could build a dam on, but it would require some serious planning on my end.

The slope is probably 10-degrees and assuming a 10-ft max depth, I could build a dam 60'x100' (probably 5' avg. depth).  I thinking this is about 30,000 ft3 of water capacity or 225,000 gallons.

Question 1
Is this enough area to store the water from my system?

Question 2
Would I be pumping enough water to fill my dam (I know there are 100s of variables (soil, evaporation, perc, etc.), but in general)?  Is there enough water to keep it full?

Question 3
What happens when you pump water into a pond that is frozen above?  Does the water just push the ice up?  Do you get to a point that you can't pump any more into it?

Question 4
Is a drywell a better solution? 

Question 5
Assuming a -20 degree day, how many gallons would be pumping and dumping?

Thanks!!!

These questions are so site-dependent that accurate answers are difficult to give online.

1+2) Impossible to answer for reasons you cite - too many variables.

3)Pretty sure ice floats - streams run happily into frozen ponds in nature all the time.

4) same as 1+2

5) Flow depends on system tonnage and GPM needed per ton. 6000 SF house could require anywhere from 5-20 tons of HVAC, though I'd hope for the lower end of that. If it needed 10 tons and 2 GPM / ton that would be 20 GPM. Worst case day might be 16 hours of operation, on the order of 20,000 gallons of water needing somewhere to go. Relating gallons to pond volume, 1 cubic foot = 7.5 gallons.

Have you had your water quality tested? You need very high quality water for an open system. I looked into it for my home and the well water is to hard, I would get mineral build-up in the heat exchanger and have to clean it too often.

As far as the pond is concerned, I would not put in a pond that could not sustain itself on it's own. Consult a pond builder or Agriculture extension agent in your area.

You may want to consider a pond loop if you have the area

As others have said, a lot of variables here. On the coldest days, you could be pumping 30,000 to 45,000 gallons per day.

Moving water doesn't freeze so if your question is will your plan work, then probably yes as long as drain is higher than water discharged or water is stored deep enough to keep drain below frozen water.
Water can lift ice, but mother nature's streams are more powerful than a well pump. It's not un heard of to have to knock a hole in the pond around here in January.
As was pointed out make sure of the water quality, that's the biggest thing.
Not sure of your heat load, but water usage could easily be 3 Million Gal/yr and 30 GPM. As long as you have room an experienced excavator can make water go away, but if you spend too much on a pond or injection well it can really close the gap between open and closed loop. Find out what each costs before you make your decisions, weigh in reduced maint. cost and longer well life.
Good Luck,
Joe

Thanks for all the great answers!

I'm getting my soil tested out in the next couple days.  I'd really like to do the pump and dump system, but I'm just concerned that I will overload my dump area.   I was thinking it's more like 1-4 gallons per minute the system is running, but from what I hear you all saying, it's a lot more.  1-4 gallons was doable for me, but 20-30 GPM seems like a LOT! 

One big concern I would have is even if I built a pond large enough to hold that capacity, you are pretty much toast if your line out dies or freezes, right?  If it's -20 degrees and it poops out, you're in for a terrible winter as I see it. 

Hmm... I need to think this one through better.  To hold that amount of water, I really would need a pond about 8 times the size. 

Do you have any other suggestions to get rid of so much water?  I don't have any natural water source to dump into.   I guess I could dump back into another well?  But I would kind'a like to get usage out of the water once it's pumped up.   

Maybe if I add a little more detail to my site, this could help with some suggestions.

In my dreamworld bubble, this is how I envisioned my geosource heating to work (and be very green in the process).  Instead of pumping the water up from the ground and back into a well, here was my idea.

I have 20 acres on slightly sloped ground.  The house sits high on the hill next to the timbers.  2/3s of the property are open where I intend on putting a 50- to 100-tree orchard and garden.   The orchard happens to be in the lower section (perfect for gravity fed water).  The orchard area is probably 60' vertically from my home site and pond elevation, and maybe 300' away.

USAGE #1
I would pump my water from my well to heat my house.  (Electricity used once)

USAGE #2
The water gets discharged into my pond that is just below my house and right in the line of my views.  So the pond would add great aesthetics to the property and besides the beauty of a body of water, it could be used for swimming, duck habitat, little paddle boats for kids, etc.  I had also planned on using this as a rainwater storage area, but that's a talk for another thread probably.

USAGE #3
This this would be virtually "free" water (assuming you only pay for it once to heat your house), combined with the harvested rainwater, it would be great to gravity feed this water from this "storage tank" to water the trees and garden.  If in a dry season I drain my storage pond, then I can just use my well water to fill in the gaps.  But if I can make use of my harvested rain water and geothermal discharge, why not?! 

USAGE #4
Well, I eat and sell my organic fruit and veggies....  Yummmm!

See any flaws in this line of thought?  Maybe I should still proceed, but make plans on enlarging the storage pond. 

QUESTION #1
But is there a point that I could drain my aquifer and end up with very angry neighbors?  At 20 GPM x 16 Hrs/day x 7 months = 4 million gallons.  Even at 20 gals/day for my trees (say 100 of them) for 5 months of the year is only 300,000 gallons of water needed.  So I'm going to have a large surplus unless I peculate and evaporate 9/10ths of the water...

QUESTION #2
HELP!!! I'm starting to see my dream pop!  Not a question, I guess...  A plea!

Let's start with the heat load.
J

For what it's worth, my HVAC guy says it is going to require a 10-ton system.

Not quite a complete answer. I don't think your bubble has to be burst here, but we need to proceed with data (as Engineer says). The other thing is that while geo can do most anything you want, there are always trade-offs (no free lunch). Your idea of using discharge water for horticulture appeals to me and has been done (discharge one place in winter and sprinkler system in summer). Actual heat load (not one contractor's opinion) gives us a water quantity we're working with.
J

Probably another incomplete answer, but until I get the heat load calcs, I'll provide you with this:

I had 6 different guys gid it and they all said between 8-10 tons are required.  It is going be run as radiant floor heat (either in concrete or gypcrete) for the entire 6000 sqft. (4000 house, 2000 garage/shop).   The house is long, going East/West to take advantage of the southern exposure which is fairly unobstructed by trees (now if I could just get rid of those pesky winter clouds.....).

Lots of windows, 11-13 foot ceilings throughout (ok, not very green, I know).  2.5 levels.

I'll try getting some harder facts together to post here tomorrow.

What does your state Environmental Dept have to say about this? Here in Idaho the DEQ and Water Resources Board are turning thumbs down on pump and dump because of aquifer depletion concerns if the water isn't returned to underground.

I have heard, or read, that an adequate dump region can be created by using a drain field like a septic system.

Lord; when can we get politicians to stop imagining that water goes away. MI makes you cap artesian wells if you hit them. You may also have seen a recent thread where local gov. would not allow removal of heat from a flowing well (no open loop allowed) so the energy available continues to spill on his lawn while he burns propane. What a sin.
J

Actually dmaceld actually raises a very good point. Last I had heard, MT has rather strict regulations on water gathering because people downstream locations are losing water as glacier melt is less and less each year because the average temperature year round is more and more.
While I agree with Joe that when you use geothermal, the water is going to go away like using the water for crops, the state may still have regulations requiring you not to draw out that much water.
Not really sure why with 20 acres you can't find room to have a closed loop system that's less maintenance. I don't mean to interject into how you build your home, but it seems like if you're building 6000 sq ft with radiant flooring, the loop budget shouldn't be what kills you. Also, since you're in process, you might be able to get the back-hoe to cut you deal when you're building the foundation.
Lastly, have you considered what kind of construction the home will be? You might be able to bring the unit down in size if the home is constructed with a very tight energy barrier, such as SIPs and ICFs, but that's another forum.

Here's an idea that maybe hasn't come up yet here before.    What about installing BOTH a closed loop and an open loop system--on the SAME system.  With a couple of ball joints and bypasses you could manually open and close the valves when you wanted to.

The thing that scares me a little is just what was mentioned above--draining a significant amount of ground water and not having enough area to dispose of it.  The appealing idea on a open- and closed-system for me is that I could potentially get the best of both worlds. 

I could fill up my pond (oversized storage tank) with just the water that I will need for my orchard in the summer (and all the other "USAGE" points I mentioned above) and when I've reached that mark, I could open/close a couple valves and start running it through the closed loop system.

Moreover, I could potentially start off on the closed loop system until I suck out a lot of ground heat and drop the performance level and then switch over to the open-loop for a month or so and give the ground time to warm up from the surround ground and then switch back over--thus improving the overall efficiency.

If I go with a closed loop system ANYWAY, the additional costs to make it a dual system (open and closed) are pretty nominal--a couple of valves, some extra pipe, MAX 8 hours of labor.  I'm thinking $1000 MAX!  Unless I'm missing something. 

See any flaws with this idea?

Cross between open/closed loop actually has greater efficiency. Open loop is better for heating and closed better for cooling. If your inspectors are on the ball however, either must have capacity to be exclusive making dual system rather expensive. i don't recall the radiant floor design mentioned before. That has impact on sizing as most water to water systems are not graduated 1 ton at a time.
Again, let's start with the heat load, then the design criteria.....
Can't help you with partial information.
J

Why not run a standing column system and run the bleed off into the pond?

Sounds like you have a great productive well. While 8-10 tons will require a relatively deep well, you can trade some of the depth for a larger bleed off.

Using a standing column system, you would cut your water dump amount by roughly 90%.

Do you know of any local legislature regarding responsible standing column systems?