Replacing Table 5-3 in the Design Guidelines for Sewage Works (2008) to update design sewage flow rates

Ontario is committed to supporting Environmental Compliance Approval (ECA) applicants for large subsurface sewage disposal works servicing seasonal occupancy sites by modernizing sewage flow rate estimates to align with updated research and operational data.

ECA requirements and replacing Table 5-3 in the 2008 Sewage Design Guidelines with Table 1 of the proposed Design Sewage Flow (DSF) Guide

Typically, owners of large subsurface sewage disposal works with a design capacity over 10,000 L/day, or that cross property boundaries, are required to obtain an ECA from the Ministry of the Environment, Conservation and Park (ministry) under section 53 of the Ontario Water Resources Act (OWRA) and Part II.1 of the Environmental Protection Act (EPA). These works include large on-site subsurface sewage disposal works commonly used in recreational trailer parks and campgrounds as well as residential developments.

The Design Guidelines for Sewage Works (2008) outlines technical guidelines for the design of subsurface sewage works in Ontario. In the absence of historical metered flow data, Table 5-3 in the 2008 Guidelines provides design sewage flow rates for new systems servicing various commercial and institutional uses.

To provide clarity and reduce burden to ECA applicants, the ministry has developed the draft Supporting Guide to Calculate the Design Sewage Flow for Subsurface Sewage Works Subject to s. 53 OWRA (DSF Guide). If the proposal for the DSF Guide is implemented, the proposed DSF Guide would replace the “Interim Fact Sheet MOECC Design Sewage Flow Rates for Seasonal Trailer Parks and Park Model Units, 2015”, which would be revoked. Table 1 from the proposed DSF Guide includes reduced design flow values for new systems serving seasonal occupancy sites. The updated flow rates are based on updated empirical data and consider seasonal operations and peak flow variability.

Accurate design sewage flow estimates are critical for:

• Proper sizing of treatment systems
• Preventing hydraulic overloads and system failures
• Ensuring environmental protection and compliance with regulatory standards.

We are proposing to replace Table 5-3 in the 2008 Design Guidelines for Sewage Works with Table 1 of the proposed DSF Guide.

Public consultation opportunities

This proposal has been posted for a 60-day public review and comment period. We encourage interested parties to make comments on this proposal to replace “Table 5-3 Common Sewage Flow Rates for Commercial and Institutional Uses” of the Ministry’s Design Guidelines for Sewage Works, 2008 with Table 1 of the DSF Guide.

Comments made on this proposal will be considered prior to making a decision on the proposed Table 1 of the DSF Guide.

This ministry is also consulting on the proposed Supporting guide to calculate the design sewage flow for subsurface sewage works subject to section 53 Ontario Water Resources Act under ERO number 019-2487.