I wouldn't advise it. Should the water main break the cement would have to be removed over the line that it covers. I had mine water main break and there was nothing but dirt over it and it was a 2,000 repair job.
To install the water return fitting above the ground pool, you have to switch off the source. After this you can then install the water.
Install a tarp to cover pool construction area. Install small sump pump at bottom of pool area
Do you have a pool light niche already installed in the pool? If not, you need a pool builder to do the job to code.
Yes you can retrofit a salt water pool system onto your existing pool equipment without too much trouble.
Install a floating pool skimmer
Yes, the pool can over-flow.
Yes there is no need to drain a chlorinated pool to change it to salt water pool all you have to do is add the salt install the new equipment and run it as usual.
One way would be to install drain tile in the yard around the pool deck to carry excess ground water away from the pool.
After selecting a location for the spa pool, it is necessary to build a base that will be strong enough to support the weight of the pool, water and occupants. It is then necessary to install an electrical connection to the pool. At this point, the pool will need to be filled with water and chemicals must be added until the water is "balanced". There are test strips that can be used to determine the correct chemical levels. http://www.ehow.com/how_4925553_install-spa-pool.html
Pump the water out or put a cover over the pool.
This question makes no sence!!! If you have groundwater and want to build an inground pool you need to install a "well point". a Well point is a plumbing line which runs underground and pumps out "ground water" under the pool. Once the pool is filled you do not need to worry about the ground water as much. the water in the pool pushes OUT as ground water pushes in.
Well, it could if ~ You install next to a foundation and you develop a leak in the pool. The extra water being splashed from the pool into the ground may also be causing a problem. It may pay to put an agg drain between the pool and the cellar to handle the excess water