Foreword

The state of our groundwater resources is deteriorating due to the combination of depletion and pollution. Pollution occurs when the capacity of the subsurface to assimilate anthropogenic chemicals is exceeded and results in contaminant plumes that spread too far from the input locations. We use the groundwater environment as a waste receptor founded on the premise that the assimilation processes operating on the contaminants provide forgiveness. They provide much forgiveness but not enough to prevent deterioration of groundwater quality at many millions of locations across the globe where we leak, spill or dispose of waste in exceedance of the subsurface assimilative capacity.

One of the most striking examples of the failure of this premise comes from the widespread use of septic systems to make our household liquid wastes ‘disappear’. This is the subject of this book: Septic System Impacts on Groundwater Quality. The idea of the septic system originated in France around 1860, shortly after Darcy discovered his famous ‘law’ for groundwater flow. Our reliance on septic systems achieved official engineering credibility in the 1970’s via regulations of jurisdictions in the United States and beyond that standardized septic system design and installation. In the context of water treatment engineering, the purpose of the septic system is to infiltrate all of a household’s waste water through the vadose zone into the groundwater zone where, according to the inherent assumption, all of the potentially harmful constituents are fully attenuated and hence the front of the septic plume does not reach groundwater beyond the household property. This was the premise in the 1950’s when thousands of suburban housing developments were initiated throughout the United States, Canada and beyond.

Early on, except for nitrate and phosphate, the subsurface showed adequate assimilative capacity because typical household wastewater contained few hazardous constituents. However, the chemical makeup changed over the decades and now includes many anthropogenic constituents. In addition, the density of septic systems has increased substantially. Consequently, the formerly not so harmful concept evolved into the cause of common harm. Not only do septic plumes harm groundwater, they discharge nitrogen and phosphorus into lakes and ocean estuaries causing them to be choked with algal growth. A septic system that does not get all of the waste water into the groundwater zone is by definition a ‘failed’ septic system; while the other systems are deemed to be successful.

For the engineering and scientific community, the impact of the septic system on groundwater and surface waters should be a lesson in humility concerning our propensity to use the subsurface for waste disposal without rigorous prior assessment of its capability to fully attenuate harmful constituents. This book shows that small (point) sources can produce persistent and far-ranging groundwater plumes.

The author of this book, Dr. William Robertson, Professor Emeritus, University of Waterloo, Canada, is the leading scientific authority on the impact of septic systems on groundwater from the perspective of field investigations of septic plumes. He has published widely on plume studies and has developed alternative designs for treatment of household waste waters.

John Cherry, The Groundwater Project Leader
Guelph, Ontario, Canada, April 2021