Investigating old dams

Abstract

Summary Examples are given of three dams, two rather old, water impounding dams, the other, more recently constructed, for retaining industrial waste. All three dams suffered some degree of failure and, as a result, were investigated more fully than would otherwise have been the case. At Lluest Wen, following emergency grouting and other work, a detailed examination disclosed so many imperfections in the puddle core that a new slurry trench cut off was provided. A 20 ft diameter shaft at the draw-off works was partly investigatory, partly for remedial works. The industrial waste dam developed alarming symptoms during its construction and suffered a partial failure. Following investigations, remedial works were put in hand. Even during the progress of these, there were further untoward events but finally, the dam was stabilized. Tittesworth dam suffered a downstream slide during works to raise the impounding level. The original site investigation failed to find foundation weaknesses which were not fully disclosed until excavations were made during the course of the reconstruction. A search of the owner's records showed that the slope had slipped during the original construction.

Defra research into Internal Erosion

“…Approx 1 ton/year. (Little, 1977) RATE OF INTERNAL EROSION -PREDICTION AND RISK ASSESSMENT It is suggested that the level of detail which is appropriate to apply to the assessment of vulnerability to rapid internal erosion should be on a risk based approach. This considers whether the Undertaker has reduced risk to as low as reasonably practicable (ALARP), namely whether the measures taken have been proportionate to the reduction in risk that could be achieved.…”