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.
Ashbridges Bay Treatment Plant Bypasses (2025)
Ashbridges Bay Treatment Plant Bypasses (2025)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
March 5 |
10.3206 |
251,770 |
Excessive stormwater flow |
March 16 |
6.7083 |
126,320 |
Excessive stormwater flow |
April 2 – 3 |
24.0419 |
1,211,680 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2025)
Humber Treatment Plant Bypasses (2025)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
March 5 |
1.4 |
8,195 |
Excessive stormwater flow |
March 16 |
8.5 |
49,016 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2024)
Ashbridges Bay Treatment Plant Bypasses (2024)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 9 – 10 |
9.766 |
415,000 |
Excessive stormwater flow |
January 13 |
6.583 |
135,410 |
Excessive stormwater flow |
January 26 |
9.767 |
346,000 |
Excessive stormwater flow |
February 27 – 28 |
7.5833 |
290,330 |
Excessive stormwater flow |
March 9 |
6.9166 |
128,940 |
Excessive stormwater flow |
March 14 – 15 |
4.5 |
178,910 |
Excessive stormwater flow |
April 3 – 4 |
37 |
1,605,810 |
Excessive stormwater flow |
April 12 – 13 |
17.7833 |
473,700 |
Excessive stormwater flow |
April 14 |
5.1 |
88,680 |
Excessive stormwater flow |
April 18 |
2.5833 |
107,530 |
Excessive stormwater flow |
May 27 |
12.7119 |
468,040 |
Excessive stormwater flow |
June 7 |
2 |
61,140 |
Excessive stormwater flow |
June 20 |
3.6166 |
90,000 |
Excessive stormwater flow |
June 29 |
4.4333 |
170,720 |
Excessive stormwater flow |
July 10 |
10.4333 |
477,960 |
Excessive stormwater flow |
July 15 |
5.2 |
222,510 |
Excessive stormwater flow |
July 16 |
11.7666 |
859,900 |
Excessive stormwater flow |
July 24 |
3.2166 |
135,880 |
Excessive stormwater flow |
August 5 |
6.25 |
266,000 |
Excessive stormwater flow |
August 17 – 18 |
6.65 |
239,320 |
Excessive stormwater flow |
September 10 |
0.7833 |
50 |
Planned maintenance |
September 23 |
4.9 |
200,080 |
Excessive stormwater flow |
September 25 |
2.3666 |
55,740 |
Excessive stormwater flow |
November 20 – 21 |
4.4175 |
196,930 |
Excessive stormwater flow |
December 16 – 17 |
2.7722 |
71,100 |
Excessive stormwater flow |
December 29 |
7.1317 |
270,290 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2024)
Humber Treatment Plant Bypasses (2024)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 9 |
5.8 |
23,006 |
Excessive stormwater flow |
January 26 |
4.5 |
16,455 |
Excessive stormwater flow |
April 3 |
15.8 |
117,032 |
Excessive stormwater flow |
April 11 |
23.8 |
80,517 |
Excessive stormwater flow |
May 27 |
3 |
32,028 |
Excessive stormwater flow |
July 10 |
17.2 |
28,562 |
Excessive stormwater flow |
July 15 |
2.8 |
16,981 |
Excessive stormwater flow |
July 16 |
16 |
381,514 |
Excessive stormwater flow |
August 17 |
10 |
255,411 |
Excessive stormwater flow |
September 23 |
4.7 |
45,568 |
Excessive stormwater flow |
December 29 |
10.6 |
82,381 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2023)
Ashbridges Bay Treatment Plant Bypasses (2023)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 4 |
5.3416 |
267,090 |
Excessive stormwater flow |
February 9 to 10 |
14.5566 |
745,270 |
Excessive stormwater flow |
March 25 |
8.95 |
427,060 |
Excessive stormwater flow |
April 1 |
6.866 |
351,060 |
Excessive stormwater flow |
April 5 |
9.575 |
453,980 |
Excessive stormwater flow |
April 22 |
8.85 |
248,820 |
Excessive stormwater flow |
May 20 |
6.6833 |
208,350 |
Excessive stormwater flow |
June 12 |
12.6 |
758,740 |
Excessive stormwater flow |
July 13 |
5.516 |
183,610 |
Excessive stormwater flow |
July 27 |
3.092 |
128,310 |
Excessive stormwater flow |
July 29 |
3.325 |
105,660 |
Excessive stormwater flow |
August 25 |
1.4833 |
35,740 |
Excessive stormwater flow |
September 14 |
0.65 |
50 |
Annual planned maintenance |
November 8 to 9 |
4.48333 |
90,660 |
Excessive stormwater flow |
November 21 |
3.95 |
102,040 |
Excessive stormwater flow |
December 17 |
5.233 |
92,510 |
Excessive stormwater flow |
December 27 |
6.683 |
395,720 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2023)
Humber Treatment Plant Bypasses (2023)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 4 |
6.0 |
72,890 |
Excessive stormwater flow |
February 17 |
13.4 |
65,174 |
Excessive stormwater flow |
March 17 |
11.1 |
67,795 |
Excessive stormwater flow |
March 25 |
11.7 |
112,948 |
Excessive stormwater flow |
April 1 |
11.1 |
41,006 |
Excessive stormwater flow |
April 05 |
12.4 |
101,625 |
Excessive stormwater flow |
April 22 |
2.6 |
12,894 |
Excessive stormwater flow |
April 30 |
4.8 |
28,012 |
Excessive stormwater flow |
May 5 |
3.5 |
37,390 |
Excessive stormwater flow |
June 12 |
9.8 |
235,572 |
Excessive stormwater flow |
June 26 |
0.1 |
312 |
Excessive stormwater flow |
June 27 |
2.4 |
13,241 |
Excessive stormwater flow |
July 13 |
3.8 |
15,249 |
Excessive stormwater flow |
July 23 |
1.4 |
3.462 |
Excessive stormwater flow |
July 27 |
2.6 |
19,203 |
Excessive stormwater flow |
July 29 |
3.3 |
19,604 |
Excessive stormwater flow |
September 7 |
0.8 |
1,926 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2022)
Ashbridges Bay Treatment Plant Bypasses (2022)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
February 2 |
2.9166 |
50,140 |
Excessive stormwater flow |
February 17 |
12.7666 |
591,830 |
Excessive stormwater flow |
February 22 |
3.6166 |
111,810 |
Excessive stormwater flow |
June 7 |
7.6333 |
291,650 |
Excessive stormwater flow |
July 18 |
5.1666 |
208,520 |
Excessive stormwater flow |
August 22 |
7.2 |
199,610 |
Excessive stormwater flow |
October 13 |
1.42 |
27,660 |
Excessive stormwater flow |
November 8 |
1.683 |
41 |
Annual planned maintenance |
November 11 |
4.133 |
52,150 |
Excessive stormwater flow |
November 30 |
7.649 |
220,430 |
Excessive stormwater flow |
December 15 to 16 |
22.2666 |
636,910 |
Excessive stormwater flow |
December 23 |
8.4964 |
232,650 |
Excessive stormwater flow |
December 31 |
9.2333 |
235,370 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2022)
Humber Treatment Plant Bypasses (2022)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
February 17 |
15.183 |
191,452 |
Excessive stormwater flow |
February 22 |
4.033 |
12,433 |
Excessive stormwater flow |
March 23 |
3.25 |
35,586 |
Excessive stormwater flow |
July 24 |
0.65 |
4,127 |
Excessive stormwater flow |
December 31 |
1.1 |
1,153 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2021)
Ashbridges Bay Treatment Plant Bypasses (2021)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
March 26 |
6.7433 |
305,870 |
Excessive stormwater flow |
June 29 |
0.43 |
6,800 |
Excessive stormwater flow |
July 8 |
3.82 |
216,480 |
Excessive stormwater flow |
August 24 |
2.26 |
31 |
Annual planned maintenance |
September 8 |
3.5 |
153,320 |
Excessive stormwater flow |
September 22 to 23 |
7.56 |
245,240 |
Excessive stormwater flow |
October 30 |
5.59 |
224,660 |
Excessive stormwater flow |
December 5 |
3.4833 |
122,220 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2021)
Humber Treatment Plant Bypasses (2021)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
March 26 |
3.0 |
31,663 |
Excessive stormwater flow |
May 2 |
0.33 |
1,390 |
Power/Equipment Failure |
June 29 |
2.3 |
27,465 |
Excessive stormwater flow |
July 8 |
3.75 |
26,563 |
Excessive stormwater flow |
August 28 |
1.5 |
7,058 |
Excessive stormwater flow |
September 7 |
2.5 |
6,750 |
Excessive stormwater flow |
September 8 |
2.9 |
36,141 |
Excessive stormwater flow |
September 15 |
1.8 |
13,060 |
Excessive stormwater flow |
September 22 |
0.8 |
579 |
Excessive stormwater flow |
September 22 |
7.0 |
128,486 |
Excessive stormwater flow |
October 15 |
1.7 |
15,870 |
Excessive stormwater flow |
December 5 |
3.0 |
34,811 |
Excessive stormwater flow |
December 11 |
2.8 |
17,547 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2020)
Ashbridges Bay Treatment Plant Bypasses (2020)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 11 to 12 |
21.55 |
807,000 |
Excessive stormwater flow |
January 24 to 25 |
23.35 |
1,088,140 |
Excessive stormwater flow |
March 3 |
4.37 |
158,890 |
Excessive stormwater flow |
August 2 |
2.38 |
86,500 |
Excessive stormwater flow |
November 30 |
9.217 |
289,550 |
Excessive stormwater flow |
December 12 |
2.8 |
86,510 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2020)
Humber Treatment Plant Bypasses (2020)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 11 |
35.8 |
818,105 |
Excessive stormwater flow |
January 24 |
9.6 |
138,795 |
Excessive stormwater flow |
March 3 |
1.5 |
29,099 |
Excessive stormwater flow |
July 8 |
2.7 |
28,667 |
Excessive stormwater flow |
July 11 |
1.0 |
4,664 |
Excessive stormwater flow |
August 2 |
1.9 |
14,440 |
Excessive stormwater flow |
August 3 |
2.1 |
29,135 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2019)
Ashbridges Bay Treatment Plant Bypasses (2019)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
February 4 to 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 to 15 |
2.6 |
40,120 |
Excessive stormwater flow |
April 14 to 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 to 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 |
August 17 |
3.2 |
51,300 |
Excessive stormwater flow |
August 27 |
0.41 |
23,160 |
Excessive stormwater flow |
October 21 |
6.01 |
221,400 |
Excessive stormwater flow |
October 27 |
9.05 |
342,380 |
Excessive stormwater flow |
October 30 to November 1 |
16.75 |
592,510 |
Excessive stormwater flow |
December 9 |
7.15 |
256,720 |
Excessive stormwater flow |
December 14 |
10 |
526,270 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2019)
*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. |
Humber Treatment Plant Bypasses (2019)
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 |
June 20 |
3.7 |
35,985 |
Excessive stormwater flow |
July 17 |
7.1 |
69,573 |
Excessive stormwater flow |
August 17 |
1.4 |
8,332 |
Excessive stormwater flow |
October 16 |
1.1 |
2,920 |
Excessive stormwater flow |
October 27 |
4.4 |
42,424 |
Excessive stormwater flow |
October 31 |
6.25 |
95,650 |
Excessive stormwater flow |
December 14 |
2.25 |
14,228 |
Excessive stormwater flow |
Ashbridges Bay Treatment Plant Bypasses (2018)
Ashbridges Bay Treatment Plant Bypasses (2018)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 12 |
4.25 |
90,709 |
Excessive stormwater flow |
April 16 to 17 |
16.95 |
729,819 |
Excessive stormwater flow |
June 24 |
4.10 |
99,410 |
Excessive stormwater flow |
August 7 to 8 |
3.72 |
127,350 |
Excessive stormwater flow |
November 1 to 2 |
7.55 |
244,510 |
Excessive stormwater flow |
November 26 |
9.86 |
264,440 |
Excessive stormwater flow |
Humber Treatment Plant Bypasses (2018)
*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. |
Humber Treatment Plant Bypasses (2018)
Date |
Duration (hrs) |
Volume (m3) |
Reason |
January 11 to 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 to 4 |
6.5 |
31,962 |
Excessive stormwater flow |
April 16 to 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 to 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 to 2 |
8.75 |
43,713 |
Excessive stormwater flow |
November 26 |
2.5 |
13,736 |
Excessive stormwater flow |
Bypass information can also be found in the Ashbridges Bay and Humber Treatment Plant Annual Reports.