In 1989, Haights Creek Irrigation Company replaced 730 linear feet of 24- and 27-inch-diameter RPM (reinforced plastic mortar) pipe because of several failures. Bureau of Reclamation personnel examined the pipe before and after exhumation, the surrounding soil conditions, and measured diametral deflections. Major longitudinal cracks in the pipe invert appear to be the result of hard spots in the pipe foundation. Some of these hard spots were caused from mounding, or using a mound of soil under one end of the pipe to bring it to grade without providing an equivalent uniform support along the remainder of the pipe.
United States Department of the Interior, Bureau of Reclamation, "Haights Creek RPM Pipe Failures" (1994). Water. Paper 10.