I don't have a complete answer, but it is an interesting topic. I envision your main flat rock at a slight angle, lower toward the stocktank, with the desire for water to sheet across its upper surface, decant around the edge, and drip off the bottom. My first thought is to drill the main rock for the tubing, making it easy to hide under the main rock. Seal the tubing to the rock with polyurethane sealant. Use liner under, with pipe boot, just as a precaution. Place another flat rock over tubing thru main rock to cover the unsightly drilled hole and to deflect water into the space provided between the two flat rocks. Landscape as necessary for aesthetics and function. That's just a first thought, sometimes they are just plain stupid and sometimes they stimulate further constructive thought.

Landscape fabric with mulch on top? No way in hell. The mulch becomes dirt and then weeds grow on top. I use a shovel to remove weeds. So much easier. But cant use a shovel with landscape fabric. What a pain in the arse. I saw a gardening program on tv a few years back and the guy was using a sawzall to divide the grass. He made it look so easy. Im going to be dividing my clump this year, so maybe Ill go rent a sawzall and buy the demolition blade. Wish me luck !

If only it were that simple designing septic systems would be easy. Where the water goes is totally dependant upon the local geology. In an arid desert region such as you suggest the soil does absorb the water, however desert plants tend to have a vast root network just slightly below the surface. In fact, a 20ft high suguaro cactus has a root system that covers 20 to 30 acres. In many regions such as in the midwest they have 10" to 40" of topsoil over a thich hardpan yellow clay subsoil that is almost impervious to water. As the water leaches out of the leachbed it saturates the topsoil horizontally and slowly moves up to the surface by capilary action where it is either absorb by vegatation ground cover or is evaporated into the atmosphere. Anyone who lives in that area can tell you firsthand that the first indication of a problem with a leach line or sewer line will be a continual wetspot on the lawn which will progressively get worse until you end up with a swampy area filled with foul stinky standing water on the surface. Now in regards to Fallingwaters original post, he/she is describing a "mound system". Years ago before you could start building on a lot the performed a "Perk Test" to determine how well the soil would absorb water. If your land did not meet the minimal standard on the perk test you simply could not build on that land. But in recent years the septic system technology has changed. In regions where you have a high water table and the land will not perk they now permit two solutions. 1. An aerobic septic tank, which is a normal septic tank that has a third chamber installed with an air pump and areator nozzles in the bottom of the third chamber. With this type of system the aerobic bacteria that would normally be found in the leach lines are in the third chamber and air is supplied via the pump and areators. With this type of tank the liquid discharged from the aereator chamber is pure water and may be discharged directly onto the surface watershed or into a nearby waterway. (In some jurisdictions they are required to have a chlorinator on the discharge line.) 2. A mound system is an above grade septic tank. In some installation. In some localities they require you to construct a retaining wall around an enclosure about 30' x 70' and the septic tank is installed sitting on the ground inside the retaining wall, then the enclosure is filled with sand up to the top of the wall (about 4') and the leach field is then laid on the sand. They then continue covering the leachbed until the sand is piled high in the enclosure with about a 45deg slop on all sides, and the sand is then covered with sod to prevent erosion. In some areas the tank is partially embedded with the discharge line at grade level and the leach bed is then run on the surface and finally covered with 3' to 4' of sand and finally covered with sod. The sod has a two fold purpose, it absorbs a substantial portion of the water and dissipates it to the atmosphere, while also preventing erosion of the sand covering. In most areas where they permit mound systems they do not allow any activity on the mound that might be detrimental to the growth of the sod. That means no picnic tables, lawn chairs or childrens outdoor recreational equipment tht might increase foot traffic and cause bare footpaths in the sod.

Thanks! Other than the initial tile selection, there really isn't anything else I would change. I thought I was well informed before signing the contract but I realize now how little I really knew. I feel very fortunate to have selected a builder that made the "right" decision for us time and time again. From design to equipment selection to fixing the small things throughout the process I always felt like their primary goal was to make me happy. My advice is to make sure you pick a reputable builder, ask lots of questions, and try to be home as much as possible during the build. It's amazing what the subs will do for you if you're nice to them and don't mind footing the bill for lunch and drinks occasionally.