What I was planning to do was to cut the 12 inch outflow pipe down to the same level as the 6 inch run through. Then take a 45 degree connector and a 20 foot length of pipe to get any possibity of heavy water flow well away from the levee. I was also gonna run a 20 foot length of 6 inch off the valve. Then lay a couple tons of very heavy rock right around where the pipes will discharge.
Another option I have seen done that would save you some serious cash and it looks really nice is instead of buying expensive 12" and 6" PVC buy one piece of corrugated black sewer pipe with the smooth inner wall (looks like pipe when you look inside) and cut it in half and tuck it under your outlet pipes and fill with dirt level across feathered out to all slopes and plant grass. I would put a 45 on the end of that 12" but it wouldn't be necessary to actually buy a seriously expensive fitting.
Cut your 12" pipe on a 22.5 at the height of your 6" and using a grinder work the cuts until you make a mitered 45 that lays inside the 1/2 piece of black corrugated "gutter" once you have a decent fit, tack the miter together with gorilla tape and pull the "gutter" out.............prime the miter and wrap a roll of PVC tape around the seam to hold it tightly.......then do the sand trick I described place the "gutter" back under the fitting and using a couple bags of concrete make a nice finished fitting and cover it with dirt and seed. If you want the concrete fitting to last for ever take a scrap of chain link or no climb fence and wrap it around the sand prepped 45 first which will act as rebar. Put a extra large Rainbird box over your 6" valve that is cut to form with the corrugated "Gutter" ...... back fill everything with feather dirt, throw some seed down and you have one classy looking finish for next to nothing money wise
A lot of excavation companies have "scrap" or remnants of nice pipe they are willing to sell for pennies on the dollar, we bought 40' of 24" 3034 pipe that was $25 a foot for $5 a foot DELIVERED for our latest pond!
