Environment

Design of Small Wastewater Systems

Background:

There has been an ongoing effort to reduce the level of involvement of professional engineers in the design of small community wastewater systems with sub-surface disposal of the treated effluent. Persons licensed as individual sewage treatment system designers (ISTS) have successfully lobbied for an exemption from engineering oversight for systems of this description under 10,000 gallons per day (gpd). If improperly designed, they could pose a serious hazard to the public's health through discharge of untreated or partially treated wastewater to ground and subsurface waters. 

ACEC/MN Position:
Wastewater systems play an important role in protecting the public’s health and the environment. All systems serving over 3 homes should be designed by a licensed professional engineer. The determination of what system best serves a group of homes should be made by an engineer, who does not have an interest in a particular system, rather, is seeking the best solution to the owners needs.

Systems that involve multiple households have numerous engineering challenges that ISTS designers are not trained to address. These include the design of pumping and piping systems, roadway restoration, grading between households, easement aquisition and an understanding of hydraulic principals. The expertise of the ISTS designer is limited soley to understanding the sub-surface disposal and dispersion of the treated water.