In order to protect the wastewater treatment plant’s ability to continue treating wastewater during an extreme rainstorm, some of the excess flow (stormwater and sewage) that reaches the plant may need to be diverted around one of the plant’s many treatment processes.

Because the bypass process happens during storm events, the water is mostly rain water (often a ratio of four or five parts rain to one part sewage). All bypass flow continues to goes through:

  • screening
  • grit removal
  • primary treatment
  • phosphorous removal
  • disinfection

Bypassses can occur at the Ashbridges Bay and Humber Wastewater Treatment Plants, as these plants service older areas of the city with combined sewers (one pipe that carries stormwater and sewage).

The bypass reports are updated monthly, within 30 days of the end of each month.

Date Duration (hrs) Volume (m3) Reason
February 4-5 7.5 165,840 Excessive stormwater flow
February 24 5.3 50,843 Excessive stormwater flow
March 10 7.8 96,750 Excessive stormwater flow
March 14-15 2.6 40,120 Excessive stormwater flow
April 14-15 3.9 215,650 Excessive stormwater flow
April 19 3.0 58,330 Excessive stormwater flow
April 26 5.2 255,330 Excessive stormwater flow
May 25 2.9 54,980 Excessive stormwater flow
June 13 7.8 163,010 Excessive stormwater flow
June 20-21 5.3 189,830 Excessive stormwater flow
June 25 2.4 70,860 Excessive stormwater flow
June 29 2.3 99,220 Excessive stormwater flow
July 13 2.3 94,020 Excessive stormwater flow
July 17 10.2 342,850 Excessive stormwater flow
July 30 5.1 219,230 Excessive stormwater flow

Date

Duration (hrs) Volume (m3) Reason
February 4-5 2.0 2,599 Excessive stormwater flow
March 14-15 7.2 24,383 Excessive stormwater flow
March 30 9.4 (5.4 Active)* 16,555 Excessive stormwater flow
March 31 0.8 1,727 Excessive stormwater flow
Aprill 14 3.5 40,204 Excessive stormwater flow
April 19 1.7 5,419 Excessive stormwater flow
April 20 7.7 (5.0 active)* 16,877 Excessive stormwater flow
April 26 5.3 23,868 Excessive stormwater flow
May 1 2.2 9,520 Excessive stormwater flow
May 3 4.5 10,087 Excessive stormwater flow
May 25 2.7 23,828 Excessive stormwater flow
June 10 0.33 55 Excessive stormwater flow
July 17 7.1 69,573 Excessive stormwater flow

*More than one bypass occurred over this total amount of time due to one rain event. Active hours denote the time the bypass process was activated.

Date Duration (hrs)

Volume (m3)

Reason
January 12 4.25 90,709 Excessive stormwater flow
April 16-17 16.95 729,819 Excessive stormwater flow
June 24 4.10 99,410 Excessive stormwater flow
August 7-8 3.72 127,350 Excessive stormwater flow
November 1-2 7.55 244,510 Excessive stormwater flow
November 26 9.86 264,440 Excessive stormwater flow
Date Duration (hrs) Volume (m3) Reason
January 11-12  17.6 total (4.7 active)*  13,249 Excessive stormwater flow
February 20 14.9 total (7.6 active)* 14,131 Excessive stormwater flow
February 21 3.3 956 Excessive stormwater flow
April 3-4 6.5 31,962 Excessive stormwater flow
April 16-18 46.5 332,131 Excessive stormwater flow
April 25 4.6 142,65 Excessive stormwater flow
June 13 0.75 1,200 Excessive stormwater flow
June 24 3.5 23,772 Excessive stormwater flow
July 5 1.5 8,983 Excessive stormwater flow
July 22 0.5 1,377 Excessive stormwater flow
July 24 0.6 325 Excessive stormwater flow
August 6 1.8 11,556 Excessive stormwater flow
August 7-8 5.7 35,581 Excessive stormwater flow
August 17 0.8 2,207 Excessive stormwater flow
August 21 3.25 13,499 Excessive stormwater flow
September 10 2.7 1,428 Excessive stormwater flow
October 2 0.2 418 Excessive stormwater flow
November 1-2 8.75 43,713 Excessive stormwater flow
November 26 2.5 13,736 Excessive stormwater flow

 

*More than one bypass occurred over this total amount of time due to one rain event. Active hours denote the time the bypass process was activated.

Bypass information can also be found in the Ashbridges Bay and Humber Treatment Plant Annual Reports.