Land subsidence in built-up marshland

Severe land subsidence has been observed in a residential area in Ottawa built some 15 to 20 years ago on marshland. Subsidence varies from 12 to 18 in. (30 to 45 cm), affecting streets, sidewalks, driveways, fences, garages, and other structures supported on the ground surface. Houses were not affected because they were founded on shallow bedrock. Accelerated decomposition of the peat and the underlying marl is believed to have started when the area was drained for development, and this is believed to be responsible for the severe subsidence observed.On a observ\ue9 un affaissement grave du sol dans un quartier r\ue9 sidentiel d'Ottawa construit sur un sol mar\ue9cageux il y a 15 ou 20 ans. L'affaissement varie entre 30 et 45 cm (12-18 po.) et affecte les rues, trottoirs, entr\ue9es, cl\uf4tures, garages, et autres constructions \ue0 la surface du sol. Les maisons n'ont pas \ue9t\ue9 touch\ue9es par l'affaissement puisqu' elles reposent sur un fond rocheux. On estime que le drainage du secteur en vue de la construction a entra\ueen\ue9 la d\ue9composition acc\ue9l\ue9r\ue9 de la tourbe et de la marne, ce qui aurait \ue9t\ue9 la cause de l'affaissement.Peer reviewed: NoNRC publication: Ye