Swimming pool water?

Can old water still be sitting in a filled up swimming pool?

• We had moved into our house a little over a year ago. The backyard use to be a hill with a bunch of trees and plants. We decided to have all the dirt removed and a retaining wall put up and sod on the ground. All of the dirt had been removed (about 3 months ago) and now we are finally getting ready to have a retaining wall installed. From the bottom of the ground the dirt stands about 4 ½ feet tall. Behind our yard is the neighbor’s fence which sits up much higher then our house. The other day the strangest thing had happened, the side of the dirt wall had become wet (about the size of a football). The spot started about 1 foot up from the ground. Over the next few days this spot has grown (probably about 5 feet in length and there is also a small puddle of water on the ground). We have also notice another water spot forming about 6 feet over from this spot. We went to the neighbor’s house behind ours and told them that they must have a water leak. They said that they do not think that they have any type of leaks and do not hear water running when the sprinklers are shut off. One thing that they did mention is that there use to be a swimming pool in the backyard, but that had been filled in years ago. We had a small earthquake 6 days prior to seeing any water. Do you think that there might have been some water left behind in this old swimming pool and this earthquake might have put a crack in the pool or pipes and now the water is draining out into our yard? I just wasn’t sure if water would still be sitting in an old filled up pool after many years. Or does it sound like the neighbor’s might have a broken pipe in there sprinkler system? If anyone could shed some light on this situation I will appreciate it.

• Answer:

  If the pool was "filled in", there wouldn't be any water -- it's not as if they would have buried it with the water in it. You're instincts are likely correct - there's probably a leaky sprinkler system pipe somewhere in there. I'd dig down into the wet spot to see if you can find where it's coming from. A leaky pipe or sprinkler head won't really make any noise unless you've got super-hearing. Or, the second likeliest explanation is that by doing your earth-moving, you've messed up the yard's drainage. Have you been getting more rain lately or running your sprinklers longer to compensate for summer temps? Has your neighbor? A lot of puddles, etc. can be caused by changing the drainage pattern of your yard. Hacking a bite out of the hill exposed deeper ground which might usually get wet - water tables shift throughout the year. If this is the case, I'd install a french drain before putting up a retaining wall. Much less likely is the earthquake caused a fissure in the bedrock allowing water from the water table to seep up in that spot - that would be a one-in-a-million situation though. the simplest explanation is usually the right one...