Field performance of a leachfield: evaluation problems

Robert P. Chapuis

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: GEOENVIRONMENTAL - I Landfills , Contaminated Soils & Groundwater

ABSTRACT: Several principal, secondary and seasonal residences are equipped with septic systems and leachfields for treating household wastewater. The properties of the soils receiving the wastewater are important for the treatment performance and also the property value. A poor treatment may contaminate a river or a lake by discharging bacteria, nitrogen and phosphorus. During the past decades several organizations have tried to improve domestic sewage systems, but with uncertain success. The authors had an opportunity to assess groundwater parameters around a leachfield, which had been classified as poorly performing according to an appreciation done for the municipality, with a single shallow auger hole, without taking any soil samples and without taking groundwater samples and of course, analyzing them. The authors carried out a detailed field investigation including several hand-augered holes, to sample the soils and install small monitoring wells with data acquisition sensors, and then groundwater sampling for field and laboratory analyses. The gathered information was compared to that of the municipal appreciation. Major differences were found, and listed. Several technical and economical comments are presented to explain the origin of differences and improve the systems.

RÉSUMÉ: De nombreuses résidences principales, secondaires ou saisonnières sont équipées de fosses septiques et de champs performance du traitement et la valeur de la propriété. Un mauvais traitement peut contaminer une rivière ou un lac en Dans les dernières décennies, plusieurs organisations ont s domestiques de traitement, avec un succès mitigé. Les auteuraluer les paramètreeau souterr"peu performant" suite à une évaluation faite pour la municipalité, avec un seul sondage à la tarière, sans prendre échantillons de sol ou u souterraine et donc sans analyses. Les auteurs ont réalisé une investigation détaillée incluant plusieurs sondages à la tarière manuelle, pour échantillonner les sols, et puis échantillonner pour des analyses sur place et au laboratoire. Linformation colligée a été comparée à ation municipale. On a trouvé et listé des différences majeures. Plusieurs commentaires techniques et économiques sont présent et améliorer les systèmes.

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