Gyr_Falcon, thanks, that's it. Rugbyhukr, thanks for the attempt. =)

If this is a slab that is 4 inches thick and all that is below is some kind of soil then remove the concrete and dig into that soil under it and look closely at that soil to determine 1. how much organic matter is there. 2. how well that will drain. 3. how well that soil will retain moisture. 4. what the tilth of that soil is. 5. what kind of life is in that soil. These simple soil tests can help find that information, 1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top. 2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up. 3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart. 4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell. 5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy. and can guide you in determining what you need do to make that into a good, healthy soil. You want between 5 and 8 percent organic matter in any soil that is used to grow plants.

I've got a track system on which I'm putting some WAC 802 Low voltage fixtures which take MR16 bulbs. In an area along the track I'd like to use them for generalized lighting. I'll be using an Ushio bulb with a 38 degree beam angle. With an 8 foot ceiling, how do I calculate how far apart the fixtures have to be so they overlap to give me generalized lighting? Here is a link that might be useful: The WAC fixture I'm using

That appears to be a configuration that is no longer sold due to not having a polarized connection.