IN THE PROCESS OF EXCAVATING A POND...THAT IS BELOW A KEYSTONE WALL I HAVE COME TO A PROBLEM AREA. TRY TO VISUALIZE THIS...A 4 FOOT WALL...THAT I BELIEVE WAS INSTALLED IMPROPERLY...THEN IN FRONT OF IT 3 FEET THE HOLE FOR THE POND ABOUT 3 FEET DEEP..I KNOW ITS EXTRA DEEP..BUT THATS WHAT WAS SPEC'D. ANYWAY WHEN DIGGING FOR THE POND WE HIT DRAINAGE STONE IN FRONT OF THE WALL..I AM CONCERNED ABOUT UNDERMINING THE WALL...HERE IS MY PLAN...BUILD ANOTHER WALL INSIDE THE POND AREA...USING A PINABLE WALL SYSTEM AND SECURING THE BASE COURSE TO THE GROUND WITH 3 FOOT PIECES OF REBAR...MY THINKING IS THAT BETWEEN THE REBAR AND THE PRESSURE OF THE CLOSE TO 3500 GALLONS OF WATER THAT WILL PUSH ON THE WALL I SHOULD BE OK...LET ME KNOW WHAT YOU ALL THINK...
Fireman, should be no problem with the wall, IF you install fabric in front of the buried block. This is done along rivers or lakes all the time. The fabric will hold back the drainage sysem and base, make sure you extend it down below the water line then cover it with rip rap, The cover should be #5 stone if the water moves, if not you can get away with 3" angular stone.
A good 5 to 6 oz. fabric should work might look to a woven type for this is soils are clay type, but any fabric would work as long as it's heavy enought.
Fireman - when you say pond, are you talking about the Aquascapes type pond? If so, rip-rap is probably not advised. If the rip-rap is either beneath or above the pond liner, there'd be great potential for liner tears. Here's my 2-cents, for what it's worth: I'm assuming this is the type pond that has a skimmer, pump, biofalls, liner, etc. For what you describe, I think your idea of building another wall inside the pond to retain that soil is a good one. For this kind of pond, if you didn't, the customer may let the water evaporate, leaving no water pressure to press against the soil/stone beneath the retaining wall. But I wonder if you could change the plan to make the pond less deep near the wall - less wall for you to build, less chance for washout, better chance for sleep at night . As for the rebar into the ground, I talked once to a civil engineer about something similar, and he told me that those thin pieces of bar, when acted upon by something like a retaining wall, will cut through the soil like a knife through butter. In other words, they won't provide extra stabilization for your wall. Bury more courses if you want to add stability.
STONEHENGE, THANX FOR THE INPUT, NO IT ISN'T AN AQUASCAPES POND(I PREFER THOSE) THIS IS A VERY FORMAL YARD AND THE A** OF A LANDSCAPE DESIGNER THAT DID THE PROPERTY SPECED EVERYTHING TO BE CERTAIN WAY.. AND THE HOMEOWNERS THINK HE WALKS ON WATER SO I GUESS I'LL HAVE SOME SLEEPLESS NIGHTS BUT I'M HOPING FOR THE BEST.
