Troy, The floor of the pump house is one foot below water level. It does have a concrete floor with a drain in the bottom. The walls are concrete (a person could use cement blocks) up to ground level with small anchor bolts in the top to bolt a wood pressure treated plate for the top part of wood. The structure is about 46" x 46".

It sort of looks like the my broken pump. What doesn't look right are the two prongs sticking out of the side and the plug isn't flat like mine. Plus it the specs doesn't say it's a low voltage 12 volt pump. I'm thinking Rio doesn't make low voltage pumps any longer. I spent an hour looking on the web and could only find one internet site that carried a different brand of 12 volt pumps, so I ordered it. When it gets here I'll then try to figure out how to connect it up. Hopefully the plug looks the same as the one I have... This is what I ordered: Here is a link that might be useful: 12 volt pump

I have one of each as well as a very handy husband. this is an excellent combination! The external pump is a ? is it a Sequel? 750, and it's ultra quiet. It's at the far side of the pond, there are a few plants in front of it, and I only hear it when I walk around to the far side of the pond. We have a double settling chamber in front of it, which catches everything and has an easy valve for cleaning. Much recommended! It's all ground level, so the pump uses hardly any energy. The submersible is a small one on the skimmer. That one zooms softly, but it's small, so no issue. Taking the filter sponge out of the skimmer is messy, but because it's at the surface it's not hard to do. I always switch the little pump off for cleaning (daily in spring and fall), but even so, after reassembling the sponge and the leaf basket, little bits of stuff often get into the pump or through the pump to the spitters, where it clogs the spitter outlet. We never have anything get stuck in the external pump. DH is the one who brings the external pump in for the winter and puts it back outside in spring. Our winter cold would damage the external pump. We also bring the little internal pump in, since it's at the surface. If we had a big submersible at the bottom of the pond, we'd be able to leave it in the water (although not running) in the winter. :) Mary

If youre going to spend the time and effort to saw cut out the concrete to install a sump pump which will need a pipe for the discharge, you might as well take out the entire concrete area where the drainage problem is and replace with permeable pavers or put in a couple area drains in the pavers that drain to a low point beyond the retaining wall. Another option is to use a self leveling mortar to float out the low points and grade it away from the pool. Cut a narrow section of concrete out along the retaining wall and fill it in with gravel about at least 6" deep to help percolate the water.