The On-site Sewage Disposal Systems Standard as it relates to the Practice of Professional Engineering.
SPECIFIC THINGS THAT REQUIRE AN ENGINEER
The following is my personal interpretation of the Standard. I am a Professional Engineer who has been practicing in this field since 1985, and also teaches on-site sewage disposal to Engineers.
The Standard describes minimum requirements for selection, design, and installation on on-site sewage treatment for sanitary sewage in Nova Scotia. It can be found here:
Only Engineers can design systems less than 1000 L/day
Only Engineers can design systems greater than 1500 L/day
Backwash from water treatment devices is only allowed when an Engineer has accepted them as part of a designed system.
Clearance distances are provided for parts of a system that apply to non-engineers in every case, except where the Standard allows non-engineers or non-geoscientists to design and specify groundwater cutoff membranes in order to protect water supplies and foundation drains from untreated effluent and lessen those clearances. (this is a questionable activity in relation to Nova Scotia Engineering and Geoscientist legislation).
The Standard and Regulations allow non Professionals to select types of septic systems from pre-engineered tables, and then to certify that they are installed correctly. Currently, it is possible for an on-site sewage disposal system for a single family home to be selected, accepted by NSE, and installed, with no review by a Professional Engineer at any point. About half of Nova Scotians are served by these systems. If something goes wrong, like the effluent from a system contaminating groundwater and making people ill, the responsibility for this is undetermined, and may lie with the Municipal Engineer for the Municipality that issued a building permit, regardless of whether they, personally, even knew the system was going in.
DESIGN
There is a separate section that applies to Professional Engineers doing design for new systems.
A Professional Engineer must design a system using the “Low” permeability rates for ATU effluent in Table 3. There does not seem to be a release from this when a design manual for a product that uses a different soil classification system is applied. Table 3 should still apply, regardless, as it was developed for Nova Scotia conditions and uses the same classification system for soils as the Standard.
A non-engineer must use pipe hole spacings as provided in Table 12. An Engineer can design the pipe distribution system.
A Professional Engineer must use design criteria provided in a separate section of the Standard that non-engineers are not permitted to use or reference. This includes the design of systems that use engineered products (ATU’s) and sloping sand filters, a highly engineered type of sand filter.
The normal design section for Engineers requires that there be enough capability on the property to infiltrate the design flow. No excess discharge is allowed. Clearances must be met to comply with the Standard. This is for new construction.
MALFUNCTIONS
There is a separate section for addressing malfunctions and replacement or repair thereof. It is here that we see the main issues Professional Engineers have with the Provincial Department of Environment.
A non-engineer is permitted to do the work of assessing a malfunction and deciding if it can be repaired or needs to be replaced, and in cases where the lot size is adequate and all clearances can be met, they can propose a selected system solution.
On properties where the land area does not allow the normal required clearances to be met, a Professional Engineer must design a system.
The Standard then details a series of conditions and a protocols that the Professional Engineer must follow in order to remain compliant with the Standard. Those conditions are laid out in the final four paragraphs. The direction given is similar to standard engineering design protocol for most disciplines, providing an orderly hierarchy of issues to be addressed in the design process, in order to remain compliant with the Standard. That hierarchy is as follows:
Protection of groundwater, and mitigation of treated effluent flow to bedrock or high permeability soils is primary. This is required.
Horizontal clearance to water wells or surface watercourses is the secondary concern over other features where clearance is normally specified (i.e. lot lines).
When forced to compromise horizontal clearance distances to water supply and watercourses, locations where the effluent is released from the system to the natural environment are given priority over parts of the system where the intent is confinement. (i.e. keep effluent trench as far away from risk as possible, even if it means having a septic tank, pipe or pump chamber closer to a well or watercourse than the limits prescribe in a new system design).
If there is a case where none of the clearance distances can be met, they are to be maximized based on the above hierarchy. (do as good a job as you can).
Finally, and most wisely, the last paragraph of the Standard provides the ultimate direction to a Professional Engineer under the Standard, again, in order for the Engineer to remain compliant.
“A professional engineer must consider site specific conditions and incorporate protective measures in the system design to ensure that the repair or replacement will not cause an adverse effect.”
PROFESSIONAL ENGINEERING PRACTICE AND THE STANDARD
With this final clause, the Standard becomes applicable to all possible situations. It guides Professionals and non-professionals alike in a clear and responsible manner when site conditions are normal and new systems are being constructed. It provides a clear, cogent and orderly process for a Professional Engineer only to follow when addressing the rare instances when the normal requirements of the Standard cannot be meant. Most important, with the final clause, it acknowledges that, in some cases, all that remains to serve the public good, and protect the environment and public health, is the application of good engineering practice.
What is important is that Professional Engineers experienced in this Engineering design work understand and interpret this last clause as clear direction from within the Standard that once they have exhausted all other options, and they can only design a system where treated effluent must discharge to a surface water location off the property, if they design to “ensure that the repair or replacement will not cause an adverse effect”, their work remains compliant to the Standard because they have followed the Standard. They are not only permitted, they are directed to practice Engineering in the Standard.
The problem facing Engineers Nova Scotia now is that inexperienced, or non-engineering staff, in the NS Environment Department are interpreting that this, the only solution short of abandoning the home, somehow lies outside the Standard, despite direction in the Standard that clearly licenses the Engineer to do as best as they can in applying Engineering Judgement and care. That is, to do their job. Recently the courts tossed out their attempts to charge a Professional Engineer for practicing Engineering, but did so without establishing a precedent to protect Engineers from such future malfeasance on the part of NSE (being laughed out of court is, unfortunately, not recorded for posterity).
The distinction between when a design for an on-site sewage disposal system can proceed under a Notification or whether it requires an Approval can be simply described by the following test. If it is improving the environment and public health - for the public good - it is a Notification. If it isn't - allowing development where there is none now, and the standard (with no malfunction) cannot be met, then it has to be considered by the Minister for an Approval. After all, the "do nothing" alternative would exist. In the case of a malfunction, it does not.
A Professional Engineer wrote the Standard. In it we see a carefully constructed document focussed on ensuring that malfunctioning systems of any type are addressed as soon as possible and not subject to long wait times for Approvals that cause adverse effects to continue unchecked. Interpreted as it was intended, the Standard can continue serve Nova Scotians well.
