Brother's property in Cupertino CA was built on hardpan. This is clay baked by 1000 summers into pottery. The builder brought in dirt and spread it over the ha

Brother's property in Cupertino CA was built on hardpan. This is clay baked by 1000 summers into pottery. The builder brought in dirt and spread it over the hardpan to make the lot look attractive. He wanted to plant bushes, rented a motorized post-hole auger. A 4' tall auger with a motor and frame mounted on top, you start the motor which sounds like a bomb going off and with your brother on one side and you on the other, wrestle the thing into the ground, the auger twisting and snarling like an angry animal. After getting through the foot of imported soil it began to bang and shake. I shut the motor off, said "We must have hit a water pipe!" He laughed. No, we'd just got to the hardpan layer. It sounded exactly like banging a hammer into an old iron pipe. Eventually we broke a hole through and even drilled another foot or so after that (the hardpan was just a couple of inches thick). Ultimately it was futile: all the rain (what there is in CA) would run across the hardpan and drain through the holes we drilled that day. The bushes would sink through the holes, leaving the property looking like some Mad Hatter had placed tipsy plants at random angles. So a little clay? Count yourself lucky.