Pursuant to Governor Charlie Baker’s executive order #562, Massachusetts Department of Environmental Protection (DEP) convened a stakeholder group to review public comments made regarding changes to Title 5 of the State Environmental Code. One of the comments recommended that DEP consider reduction of groundwater separation (separation between the bottom of a leach field and groundwater) in certain situations

As part of that effort, DEP teamed up with MASSTC to conduct a study to assess pathogen removal in soil absorption systems (leach fields).

Field Study

The objective of the study is to evaluate pathogen removal at varying depths in the infiltrative surface beneath a wastewater dispersal unit.

Pathogen transport is a primary concern of public health regulators nationwide for the obvious concern regarding disease transmission from both ingestion and indirect exposure though recreational and other activities. When Title 5 (310 CMR 15.00) was reviewed in the early 1990’s, MassDEP looked at the World Health Organization’s recommended 5 log removal (99.999%) of pathogens and reviewed available literature on pathogen removal (reviewed in the 1991 Technical Evaluation of Title 5 by DeFeo, Wait & Associates, Inc.) in order to determine the degree of removal that occurs at varying depths to groundwater for onsite systems. The 1995 revisions to Title 5 supported the longstanding requirement of a minimum of 4 feet of separation to provide a high pathogen removal factor in order to protect public health and groundwater as a drinking water source. The 1995 revisions further required a 5-foot separation for more porous soils.  DEP used 4 log removal, or 99.99%, as the basis for the 4-foot separation requirement.

The study will look at five indicator organisms:

  • Escherichia coli
  • Fecal (Thermotolerant) coliforms
  • Enterococci
  • MS-2 male-specific coliphage
  • Somatic coliphage

Fore more about this project, please explore the sections below:

Contaminants Addressed

  • Pathogens

Related Publications

More About this Project

Due to the nature of the analytes being used in the project - bacteria and viruses - the sampling ports had to be carefully located in easy-to-manage spaces that also prevent cross-contamination.

Phage Analyses Analysis for the two types of phage in this study – MS-2 and Somatic coliphage – will be...

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Each test cell in the study needs to receive a defined amount of wastewater each day, and that amount needs...

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To support the scale of this project, MASSTC received funding from Massachusetts DEP to procure and outfit an on-site laboratory facility capable of conducting the analyses required for the Groundwater Separation Study.

35 test cells were constructed to asses pathogen removal rates across a variety of depths of sand and two different wastewater distribution methods.

Indicator organisms are those that are used to detect and measure fecal contamination.