At Aldercrest, homeowners didn't know they were putting down roots on a slope that geologists say has moved, off and on, for probably thousands of years. Three years ago, he and his wife, Mary invested a lifetime of savings in a new Aldercrest home, one they were forced to tear down, leaving them financially devastated. It's hard to say. But I don't think that should ever have been built on. Despite the warnings, no evidence exists that a study was ever conducted.
Slide goes undetected The slide remained undetected for years.
After the development was approved in 1973 the city began to rely on a new slope stability map that indicated most of Aldercrest was built on stable ground. However, the map also contained a disclaimer that it was intended as a guide only and that complete soils reports be conducted to determine stability. When water draining through the soil reaches an impermeable clay layer, it pools and forms a slick failure surface. Naming the culprit Burns, the PSU geologist, said the fine-grained Troutdale is the culprit in landslides that have damaged homes on Oregon City's Holly Lane and caused Clackamas County officials to stop development in parts of the Beaver Lake subdivision. Where it's filled with clays and silts, however, as in parts of Milwaukie, Oregon City and parts of Clackamas County, it is more prone to fail.