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Monitoring Effluent Plumes

Monitoring of the effluent plume from an onsite sewage disposal system

July 06, 2007      

During the last decade or longer, claims and counter-claims have been made worldwide by many inclusive of several professional consultants, regulators and others regarding the longevity and effectiveness of onsite disposal systems.

During the summer of 2000, an excellent 2-page article was published in the USEPA (United States Environmental Protection Agency)-sponsored Small Flows Quarterly, titled "Monitoring Effluent Plumes". The article was by David Pask MEng PEng, Engineering Scientist with the USEPA’s Small Flows Clearinghouse at the University of West Virginia.

It was indeed the brilliant David Pask PEng who had developed the contour beds. It was his Master’s Degree project (1983) under the expert supervision of the now retired Prof. Dan Thirumurthi PhD PEng at TUNS, Halifax.

One can note the extreme details and monitoring that is necessary in order to establish with confidence the plume progression and the resultant pollutant dispersion/sorption over the years/decades. Further, numerous sites have to be monitored in order to be statistically relevant in almost every sub-watershed!

In addition, lab analysis of soil adsorption properties for phosphorus will not be relevant in the real field situation over time! This is because of the existence of paths of differential conductivity as well as the presence of macropores in the soil.

Further, it will be difficult to simulate saturated and unsaturated conditions in the laboratory on temporal/spatial scales which exist in the field among other problems.

An important and informative email from David Pask MEng PEng; January 15, 2001