Monitoring Wastewater Overflows and Bypasses
Temporary Bypass Location
A new Main Pumping Station is currently under construction at the Woodward Wastewater Treatment Plant. As part of the final stages of construction, the capacity at the wastewater treatment plant will be temporarily reduced between October 21 and December 24, 2021. During this time, if a significant wet weather event occurs which results in the wastewater treatment plant receiving more than 1000 Megaliters per day (1 Megaliter equals 1 Million Liters) of combined wastewater, the City of Hamilton will be required to initiate a Plant Bypass, which would result in untreated wastewater being discharged into the Red Hill Creek and Hamilton Harbour. The approval letter has been received from the Ministry of the Environment, Conservation & Parks that is required for this work and the temporary reduction in wastewater treatment plant capacity. Should a Plant Bypass occur, information about the bypass will be posted below.
Live map is updated every 15 minutes providing current information for each outfall location. If you remain on this page for an extended period of time you will need to refresh the page to update the map data points.
Map Legend
No overflow within last 48 hours
Sewer currently overflowing
Overflow occurred within last 48 hours
Monitoring temporarily out of service
No live data available
Combined Sewer Area
Community Boundaries
City Boundary
Historical Wastewater Treatment Plant Bypass Log
Updated weekly
| Initiation | Completion | Wastewater Treatment Plant | Type of Bypass | Duration | Volume |
|---|---|---|---|---|---|
| December 11, 2021 5:40 am |
December 11, 2021 2:03 pm |
Woodward WWTP | Secondary Bypass | 8.38 hrs | 65.643 million litres |
| December 5, 2021 10:38 pm |
December 6, 2021 5:12 am |
Woodward WWTP |
Secondary Bypass |
6.56 hrs |
55.288 million litres |
|
October 29, 2021 |
October 31, 2021 |
Woodward WWTP |
Secondary Bypass |
31.59 hrs |
346.886 million litres |
|
October 25, 2021 |
October 27, 2021 |
Woodward WWTP |
Secondary Bypass |
39.61 hrs |
453.663 million litres |
|
October 15, 2021 |
October 16, 2021 |
Woodward WWTP |
Secondary Bypass |
15.40 hrs |
114.737 million litres |
|
October 9, 2021 |
October 10, 2021 |
Woodward WWTP |
Secondary Bypass |
18.08 hrs |
156.669 million litres |
|
October 4, 2021 |
October 4, 2021 |
Woodward WWTP |
Headworks Bypass |
4.12 hrs |
40.108 million litres |
|
October 3, 2021 |
October 4, 2021 |
Woodward WWTP |
Plant Bypass |
5.81 hrs |
48.434 million litres |
|
October 3, 2021 |
October 4, 2021 |
Woodward WWTP |
Secondary Bypass |
23.40 hrs |
265.084 million litres |
|
September 22, 2021 |
September 23, 2021 |
Woodward |
Secondary Bypass |
23.78 hrs |
272.260 million litres |
|
September 22, 2021 |
September 23, 2021 |
Woodward |
Headworks Bypass |
3.70 hrs |
39.140 million litres |
| September 13, 2021 11:36 pm |
September 14, 2021 |
Woodward | Secondary Bypass | 3.05 hrs | 24.033 million litres |
| September 7, 2021 10:12 pm |
September 8, 2021 4:24 pm |
Woodward | Secondary Bypass | 18.19 hrs | 213.360 million litres |
| August 26, 2021 7:40 pm |
August 26, 2021 11:51 pm |
Woodward | Secondary Bypass | 4.18 hrs | 65.926 million litres |
| August 7, 2021 4:26 pm |
August 7, 2021 6:47 pm |
Woodward | Secondary Bypass | 2.35 hrs | 16.689 million litres |
| July 8, 2021 12:43 pm |
July 8, 2021 5:15 pm |
Woodward | Secondary Bypass | 4.53 hrs | 19.350 million litres |
| July 2, 2021 7:02 pm |
July 2, 2021 8:45 pm |
Woodward | Secondary Bypass | 1.72 hrs | 15.607 million litres |
| June 26, 2021 1:42 am |
June 26, 2021 10:29 am |
Woodward | Secondary Bypass | 5.88 hrs | 35.636 million litres |
| May 28, 2021 4:20 pm |
May 28, 2021 7:32 pm |
Woodward | Secondary Bypass | 3.20 hrs | 18.663 million litres |
| April 11, 2021 9:03 am |
April 11, 2021 12:07 pm |
Woodward | Secondary Bypass | 3.07 hrs | 7.092 million litres |
| March 26, 2021 4:45 am |
March 26, 2021 11:46 am |
Woodward | Secondary Bypass | 7.02 hrs | 41.994 million litres |
| February 27, 2021 8:36 am |
February 27, 2021 12:52 pm |
Woodward | Secondary Bypass | 4.25 hrs | 36.996 million litres |
| January 2, 2021 1:48 am |
January 2, 2021 8:37 pm |
Woodward | Secondary Bypass |
15.13 hrs |
50.877 million litres |
| Table data is not official record. | |||||
Historical Combined Sewer Overflow Log
Updated weekly
January 1, 2020 through June 24, 2020 the Overflow Log shows CSO tank overflow events. Starting June 25, 2020 the Overflow Log will show all monitored overflow location events.
| Initiation | Completion | CSO Outfall | Duration | Volume | |
|---|---|---|---|---|---|
|
December 25, 2021 |
December 25, 2021 |
Wentworth CSO Outfall |
1.08 hrs |
No flow metering present at this location |
|
| December 11, 2021 5:24 am |
December 11, 2021 6:04 am |
Pleasant/Sunrise Pump Station |
0.67 hrs | 37.59 thousand litres | |
| December 11, 2021 5:17 am |
December 11, 2021 6:42 am |
Pleasant/Edenbridge Pump Station | 1.42 hrs | 106.32 thousand litres | |
| December 11, 2021 4:30 am |
December 11, 2021 6:10 am |
Wellington CSO Outfall | 1.68 hrs | No flow metering present at this location | |
| December 11, 2021 1:54 am |
December 11, 2021 6:25 am |
Wentworth CSO Outfall | 2.68 hrs | No flow metering present at this location | |
|
December 5, 2021 |
December 5, 2021 |
Wentworth CSO Outfall |
0.74 hrs |
No flow metering present at this location |
|
|
December 5, 2021 |
December 6, 2021 |
Wentworth CSO Outfall |
4.03 hrs |
No flow metering present at this location |
|
|
November 12, 2021 |
November 12, 2021 |
Wentworth CSO Outfall |
0.72 hrs |
No flow metering present at this location |
|
|
October 30, 2021 |
October 30, 2021 |
Wentworth CSO Outfall |
0.20 hrs |
No flow metering present at this location |
|
|
October 30, 2021 |
October 30, 2021 |
Royal CSO Tank |
8.16 hrs |
0.666 million litres |
|
|
October 30, 2021 |
October 31, 2021 |
Main/King CSO Tank |
32.32 hrs |
68.835 million litres |
|
|
October 30, 2021 |
October 31, 2021 |
Greenhill CSO Tank |
29.26 hrs |
211.499 million litres |
|
|
October 29, 2021 |
October 29, 2021 |
Wellington CSO Outfall |
1.74 hrs |
No flow metering present at this location |
|
|
October 29, 2021 |
October 30, 2021 |
Wentworth CSO Outfall |
10.89 hrs |
No flow metering present at this location |
|
|
October 26, 2021 |
October 27, 2021 |
Eastwood CSO Tank |
19.95 hrs |
46.132 million litres |
|
|
October 26, 2021 |
October 27, 2021 |
Main/King CSO Tank |
20.67 hrs |
40.147 million litres |
|
|
October 25, 2021 |
October 27, 2021 |
Greenhill CSO Tank |
37.07 hrs |
279.499 million litres |
|
|
October 25, 2021 |
October 26, 2021 |
Wentworth CSO Outfall |
14.42 hrs |
No flow metering present at this location |
|
| October 21, 2021 7:39 pm |
October 21, 2021 8:10 pm |
Wentworth CSO Outfall | 0.50 hrs | No flow metering present at this location | |
|
October 15, 2021 |
October 15, 2021 |
Parkdale Pump Station |
0.78 hrs |
1.653 million litres |
|
|
October 15, 2021 |
October 15, 2021 |
Wellington CSO Outfall |
1.13 hrs |
No flow metering present at this location |
|
|
October 15, 2021 |
October 15, 2021 |
Wentworth CSO Outfall |
2.52 hrs |
No flow metering present at this location |
|
|
October 9, 2021 |
October 10, 2021 |
Greenhill CSO Tank |
14.32 hrs |
59.654 million litres |
|
|
October 9, 2021 |
October 9, 2021 |
Parkdale Pump Station |
4.70 hrs |
3.586 million litres |
|
|
October 9, 2021 |
October 9, 2021 |
Wellington CSO Outfall |
2.29 hrs |
No flow metering present at this location |
|
|
October 9, 2021 |
October 9, 2021 |
Wentworth CSO Outfall |
5.73 hrs |
No flow metering present at this location |
|
|
October 3, 2021 |
October 5, 2021 |
Greenhill CSO Tank |
29.07 hrs |
228.682 million litres |
|
|
October 3, 2021 |
October 4, 2021 |
Red Hill CSO Outfall |
5.11 hrs |
8.750 million litres |
|
|
October 3, 2021 |
October 4, 2021 |
Royal CSO Tank |
22.55 hrs |
4.434 million litres |
|
|
October 3, 2021 |
October 4, 2021 |
Strathearne CSO Outfall |
5.85 hrs |
No flow metering present at this location |
|
|
October 3, 2021 |
October 4, 2021 |
Main/King CSO Tank |
24.20 hrs |
104.529 million litres |
|
|
October 3, 2021 |
October 4, 2021 |
Pleasant/Edenbridge Pump Station |
0.29 hrs |
38.74 thousand litres |
|
|
October 3, 2021 |
October 4, 2021 |
Wellington CSO Outfall |
6.11 hrs |
No flow metering present at this location |
|
|
October 3, 2021 |
October 4, 2021 |
Wentworth CSO Outfall |
12.48 hrs |
No flow metering present at this location |
|
|
September 25, 2021 |
September 25, 2021 |
Wentworth CSO Outfall |
0.33 hrs |
No flow metering present at this location |
|
|
September 23, 2021 |
September 23, 2021 |
Red Hill CSO Outfall |
1.03 hrs |
123.36 thousand litres |
|
|
September 22, 2021 |
September 23, 2021 |
Strathearne CSO Outfall |
3.69 hrs |
No flow metering present at this location |
|
|
September 22, 2021 |
September 23, 2021 |
Royal CSO Tank |
14.05 hrs |
2.092 million litres |
|
|
September 22, 2021 |
September 23, 2021 |
Eastwood CSO Tank |
21.03 hrs |
82.099 million litres |
|
|
September 22, 2021 |
September 22, 2021 |
Pleasant/Sunrise Pump Station |
1.58 hrs |
44.020 thousand litres |
|
|
September 22, 2021 |
September 23, 2021 |
Parkdale Pump Station |
5.13 hrs |
4.095 million litres |
|
|
September 22, 2021 |
September 23, 2021 |
Greenhill CSO Tank |
22.99 hrs |
148.260 million litres |
|
|
September 22, 2021 |
September 23, 2021 |
Pleasant/Edenbridge Pump Station |
3.87 hrs |
265.260 thousand litres |
|
|
September 22, 2021 |
September 24, 2021 7:08 am |
Main King CSO Tank |
39.71 hrs |
164.034 million litres |
|
|
September 22, 2021 |
September 22, 2021 |
Wellington CSO Outfall |
4.02 hrs |
No flow metering present at this location |
|
|
September 22, 2021 |
September 23, 2021 3:40 am |
Wentworth CSO Outfall |
15.05 hrs |
No flow metering present at this location |
|
|
September 15, 2021 |
September 15, 2021 |
Wellington CSO Outfall |
0.66 hrs |
No flow metering present at this location |
|
|
September 15, 2021 |
September 15, 2021 |
Wentworth CSO Outfall |
0.84 hrs |
No flow metering present at this location |
|
|
September 13, 2021 |
September 13, 2021 |
Wellington CSO Outfall |
1.07 hrs |
No flow metering present at this location |
|
|
September 13, 2021 |
September 13, 2021 |
Wentworth CSO Outfall |
1.53 hrs |
No flow metering present at this location |
|
|
September 12, 2021 |
September 13, 2021 |
Wellington CSO Outfall |
0.63 hrs |
No flow metering present at this location |
|
|
September 12, 2021 |
September 13, 2021 |
Wentworth CSO Outfall | 1.81hrs | No flow metering present at this location | |
|
September 9, 2021 |
September 9, 2021 |
Wentworth CSO Outfall |
0.38 hrs |
No flow metering present at this location |
|
|
September 8, 2021 |
September 8, 2021 |
Royal CSO Tank |
4.14 hrs |
2.120 thousand litres |
|
|
September 8, 2021 |
September 8, 2021 |
Greenhill CSO Tank |
11.62 hrs |
73.655 million litres |
|
|
September 8, 2021 |
September 8, 2021 |
Red Hill CSO Outfall |
2.49 hrs |
4.211 million litres |
|
|
September 7, 2021 |
September 8, 2021 |
Main/King CSO Tank |
16.36 hrs |
54.750 million litres |
|
|
September 7, 2021 |
September 8, 2021 |
Strathearne CSO Outfall |
3.23 hrs |
No flow metering present at this location | |
| September 7, 2021 10:47 pm |
September 8, 2021 12:32 am |
Parkdale Pump Station | 1.75 hrs | 3.755 million litres | |
| September 7, 2021 7:50 pm |
September 8, 2021 4:53 am |
Wellington CSO Outfall | 4.77 hrs | No flow metering present at this location | |
| September 7, 2021 7:38 pm |
September 8, 2021 5:09 am |
Wentworth CSO Outfall | 6.33 hrs | No flow metering present at this location | |
| September 5, 2021 2:58 am |
September 5, 2021 3:37 am |
Wellington CSO Outfall | 0.65 hrs | No flow metering present at this location | |
| September 5, 2021 12:36 am |
September 5, 2021 3:38 am |
Wentworth CSO Outfall | 1.37 hrs | No flow metering present at this location | |
| August 29, 2021 2:01 pm |
August 29, 2021 |
Wellington CSO Outfall | 0.76 hrs | No flow metering present at this location | |
| August 29, 2021 1:56 pm |
August 29, 2021 11:42 pm |
Wentworth CSO Outfall | 1.18 hrs | No flow metering present at this location | |
| August 26, 2021 8:49 pm |
August 27, 2021 12:22 am |
Red Hill CSO Outfall | 3.55 hrs | 2.695 million litres | |
| August 26, 2021 8:06 pm |
August 26, 2021 8:29 pm |
Parkdale Pump Station | 0.38 hrs | 0.940 million litres | |
| August 26, 2021 7:11 pm |
August 26, 2021 8:44 pm |
Wellington CSO Outfall | 1.54 hrs | No flow metering present at this location | |
| August 26, 2021 7:01 pm |
August 26, 2021 8:35 pm |
Wentworth CSO Outfall | 1.57 hrs | No flow metering present at this location | |
| August 17, 2021 1:27 pm |
August 17, 2021 2:08 pm |
Wellington CSO Outfall | 0.68 hrs | No flow metering present at this location | |
| August 17, 2021 1:24 pm |
August 17, 2021 2:12 pm |
Wentworth CSO Outfall | 0.80 hrs | No flow metering present at this location | |
| August 11, 2021 5:19 am |
August 11, 2021 6:04 am |
Wellington CSO Outfall | 0.76 hrs | No flow metering present at this location | |
| August 11, 2021 5:13 am |
August 11, 2021 7:21 am |
Wentworth CSO Outfall | 1.16 hrs | No flow metering present at this location | |
| August 7, 2021 2:54 pm |
August 7, 2021 4:17 pm |
Wentworth CSO Outfall | 1.38 hrs | No flow metering present at this location | |
| August 7, 2021 2:54 pm |
August 7, 2021 3:01 pm |
Pleasant/Edenbridge Pump Station | 0.08 hrs | 6.33 thousand litres | |
| August 7, 2021 2:57 pm |
August 7, 2021 4:28 pm |
Wellington CSO Outfall | 1.51 hrs | 6.33 thousand litres | |
| August 7, 2021 2:58 pm |
August 7, 2021 7:35 pm |
Pleasant/Sunrise Pump Station | 0.04 hrs | 0.11 thousand litres | |
| August 7, 2021 3:22 pm |
August 7, 2021 3:35 pm |
James St CSO Tank | 0.22 hrs | 0.101 million litres | |
| August 7, 2021 4:11 pm |
August 7, 2021 6:30 pm |
McMaster CSO Tank | 2.31 hrs | 0.053 million litres | |
| August 1, 2021 5:17 pm |
August 1, 2021 5:38 pm |
Pleasant/Edenbridge Pump Station | 0.11 hrs | 3.44 thousand litres | |
| July 29, 2021 8:23 am |
July 29, 2021 9:31 am |
Wellington CSO Outfall | 1.12 hrs | No flow metering present at this location | |
| July 29, 2021 8:03 am |
July 29, 2021 9:53 am |
Wentworth CSO Outfall | 1.83 hrs | No flow metering present at this location | |
| July 27, 2021 11:10 am |
July 27m 2921 11:32 am |
Wentworth CSO Outfall | 0.37 hrs | No flow metering present at this location | |
| July 24, 2021 3:34 pm |
July 25, 2021 12:25 am |
Wentworth CSO Outfall | 1.12 hrs | No flow metering present at this location | |
| July 8, 2021 12:05 pm |
July 8, 2021 2:45 pm |
Wellington CSO Outfall | 0.91 hrs | No flow metering present at this location | |
| July 8, 2021 11:00 am |
July 8, 2021 3:20 pm |
Wentworth CSO Outfall | 3.14 hrs | No flow metering present at this location | |
| July 7, 2021 8:39 pm |
July 7, 2021 8:55 pm |
Wentworth CSO Outfall | 0.28 hrs | No flow metering present at this location | |
| July 2, 2021 5:37 pm |
July 2, 2021 6:43 pm |
Parkdale CSO | 1.1 hrs | 1.567 million litres | |
| July 2, 2021 4:08 pm |
July 2, 2021 7:05 pm |
Wellington CSO Outfall | 2.77 hrs | No flow metering present at this location | |
| July 2, 2021 4:05 pm |
July 2, 2021 7:13 pm |
Wentworth CSO Outfall | 3.15 hrs | No flow metering present at this location | |
| July 1, 2021 6:46 pm |
July 1, 2021 7:37 pm |
Wellington CSO Outfall | 0.86 hrs | No flow metering present at this location | |
| July 1, 2021 5:04 pm |
July 1, 2021 7:39 pm |
Wentworth CSO Outfall | 1.29 hrs | No flow metering present at this location | |
| June 29, 2021 6:19 pm |
June 29, 2021 7:03 pm |
Wellington CSO Outfall | 0.74 hrs | No flow metering present at this location | |
| June 29, 2021 6:06 pm |
June 29, 2021 6:56 pm |
Wentworth CSO Outfall | 0.83 hrs | No flow metering present at this location | |
| June 26, 2021 10:50 am |
June 26, 2021 12:50 pm |
Greenhill CSO Tank | 2.00 hrs | 1.945 million litres | |
| June 26, 2021 8:17 am |
June 26, 2021 3:51 pm |
Main/King CSO Tank | 7.56 hrs | 7.592 million litres | |
| June 26, 2021 12:06 am |
June 26, 2021 7:17 am |
Wellington CSO Outfall | 3.13 hrs | No flow metering preset at this location | |
| June 25, 2021 10:09 pm |
June 26, 2021 9:05 am |
Wentworth CSO Outfall | 7.05 hrs | No flow metering preset at this location | |
| June 21, 2021 2:25 am |
June 21, 021 3:15 am |
Wentworth CSO Outfall | 0.83 hrs | No flow metering preset at this location | |
| June 18, 2021 12:55 pm |
June 18, 2021 1:01 pm |
Wentworth CSO Outfall | 0.09 hrs | No flow metering present at this location | |
| June 14 6:39 pm |
June 14 7:03 pm |
Wellington CSO Outfall | 0.40 hrs | No flow metering present at this location | |
| June 14 9:02 am |
June 14 7:11 pm |
Wentworth CSO Outfall | 1.00 hrs | No flow metering present at this location | |
| June 8, 2021 5:32 am |
June 8, 2021 5:27 pm |
Wellington CSO Outfall | 1.34 hrs | No flow metering present at this location. | |
| June 8, 2021 5:17 am |
June 8, 2021 5:33 pm |
Wentworth CSO Outfall | 1.77 hrs | No flow metering present at this location. | |
| June 3 2021 4:46 am |
June 3, 2021 5:20 am |
Wentworth CSO Outfall | 0.56 hrs | No flow metering present at this location. | |
| May 28, 2021 12:01 pm |
May 28, 2021 5:01 pm |
Wentworth CSO Outfall | 5 hrs | No flow metering present at this location. | |
| May 26, 2021 7:15 pm |
May 26, 2021 7:33 pm |
Wellington CSO Outfall | 0.29 hrs | No flow metering present at this location. | |
| May 26, 2021 7:01 pm |
May 26, 2021 7:34 pm |
Wentworth CSO Outfall | 0.56 hrs | No flow metering present at this location. | |
| May 8, 2021 1:43 pm |
May 8, 2021 2:07 pm |
Wentworth CSO Outfall | 0.40 hrs | No flow metering present at this location. | |
| April 29, 2021 6:36 pm |
April 29, 2021 7:30 pm |
Wentworth CSO Outfall | 0.82 hrs | No flow metering present at this location. | |
| April 18, 2021 3:49 pm |
April 18, 2021 4:54 pm |
Wentworth CSO Outfall | 1.08 hrs | No flow metering present at this location. | |
| April 11, 2021 5:51 am |
April 11, 2021 10:43 am |
Wentworth CSO Outfall | 4.27 hrs | No flow metering present at this location. | |
| April 11, 2021 7:49 am |
April 11,2021 8:46 am |
Wellington CSO Outfall | 0.96 hrs | No flow metering present at this location. | |
| April 5, 2021 5:28 pm |
April 5, 2021 6:12 pm |
Wentworth CSO Outfall | 0.72 hrs | No flow metering present at this location. | |
| March 28, 2021 10:35 am |
March 28, 2021 2:08 pm |
Wentworth CSO Outfall | 3.30 hrs | No flow metering present at this location. | |
| March, 26, 2021 10:32 am |
March, 26, 2021 9:16 pm |
Greenhill CSO Tank |
10.73 hrs | 33.235 million litres | |
| March, 26, 2021 9:09 am |
March, 26, 2021 1:48 pm |
Main/King CSO Tank |
4.65 hrs |
11.934 million litres |
|
| March, 26, 2021 7:29 am |
March, 26, 2021 10:55 am |
Strathearne CSO Outfall |
.3.45 hrs | No flow metering present at this location. | |
| March, 26, 2021 3:55 an |
March, 26, 2021 7:30 am |
Wellington CSO Outfall | 2.89 hrs | No flow metering present at this location. | |
| March, 26, 2021 3:14 am |
March, 26, 2021 9:59 am |
Wentworth CSO Outfall | 6.41 hrs | No flow metering present at this location. | |
| March 11, 2021 7:09 pm |
March 11, 2021 7:38 pm |
Wentworth CSO Outfall | 0.48 hrs | No flow metering present at this location. | |
| February 28, 2021 12:46 pm |
February 28, 2021 1:03 pm |
Wentworth CSO Outfall | 0.28 hrs | No flow metering present at this location. | |
| February 27, 2021 7:34 am |
February 27, 2021 9:13 am |
Wellington CSO Outfall | 0.69 hrs | No flow metering present at this location. | |
| February 27, 2021 6:46 am |
February 27, 2021 9:46 am |
Wentworth CSO Outfall | 3.00 hrs | No flow metering present at this location | |
| January 2, 2021 1:06 am |
January 2, 2021 2:20 am |
Wellington CSO Outfall | 1.23 hrs | No flow metering present at this location | |
| January 2, 2021 12:17 am |
January 2, 2021 4:37 am |
Wentworth CSO Outfall | 3.86 hrs | No flow metering present at this location | |
| Table data is not official record. | |||||
Historical CSO Overflow and Wastewater Bypass Logs
- View the 2020 Report (PDF, 270 KB)
- View the 2019 Report (PDF, 124 KB)
Why do wastewater bypasses and combined sewer overflow events occur?
The City of Hamilton has a large complex wastewater collection network consisting of both separated sewer and combined sewer systems. Modern areas of the City have separated sewer systems, which consist of sanitary sewers that carry wastewater from toilets and household drains in one sewer system, and storm sewers which carry surface water such as rainwater or snowmelt in another separated system. In older areas of the City a combined sewer system collects both storm water (rainwater or melt water), and wastewater in the same pipe. During periods of heavy rainfall or snowmelt, combined sewers are inundated with large volumes of storm water that can exceed the capacity of the pipes.
Bypasses and CSO events are a necessary operating condition to prevent rainwater and wastewater from backing up and causing basement flooding, surface flooding of our roads and potential damage to the Wastewater Treatment Plants. Flooding from large volumes of storm water at the treatment plants can cause significant damage to mechanical and electrical equipment as well as ‘wash out’ the microscopic organisms needed for secondary wastewater treatment, which can affect the wastewater treatment plant’s ability to function for several days or weeks.
Wastewater Treatment Plant Operations staff monitor incoming flows and system/plant levels and make operational adjustments to the treatment processes as required.
Types of Bypasses and Overflows
Wastewater Treatment Plant Bypasses
The Wastewater Treatment Plant (WWTP) operations staff can bypass the WWTP at four locations, a total plant bypass, headworks bypass, primary bypass, and secondary bypass.
Plant Bypass
A plant bypass sends untreated sewage from the main pumping station (MPS) wet-well directly to the natural environment. This type of bypass would only be initiated if there was danger of flooding the MPS, or if there was significant maintenance or other works taking place for downstream WWTP processes.
Headworks Bypass
A headworks bypass sends partially treated sewage to the natural environment, bypassing the majority of the WWTP processes. In the event of a headworks bypass, large solids and heavy grit have been removed from the sewage, and chemicals have been added for phosphorous removal. This type of bypass would be initiated if the maximum primary and secondary bypass capacity was reached and flows continue to increase.
Primary Bypass
A primary bypass sends partially treated sewage to the natural environment, bypassing the majority of the WWTP processes. In the event of a primary bypass, large solids and heavy grit have been removed from the sewage, and chemicals have been added for phosphorous removal. Between May 15th and October 15th each year, primary bypasses will also be disinfected with chlorine, and then the chlorine will be removed. This type of bypass would only be initiated if there was danger of flooding or damage to the primary treatment processes, or if there was significant maintenance or other works taking place for downstream WWTP processes.
Secondary Bypass
A secondary bypass is the most common type of bypass event at a WWTP. A secondary bypass sends partially treated sewage to the natural environment, bypassing the WWTP’s secondary treatment processes (biological treatment and final clarification). In the event of a secondary bypass, large solids and heavy grit have been removed from the sewage, chemicals have been added for phosphorous removal, and the majority of settleable solids and floatable materials have also been removed. Between May 15th and October 15th each year, secondary bypasses will also be disinfected with chlorine, and then the chlorine will be removed. This type of bypass is initiated when WWTP flows exceed the WWTP capacity risking non-compliance of the Environmental Compliance Approval (ECA) for the WWTP and ‘wash-out’ of the WWTP’s biological treatment processes (which would result in partially treated sewage being discharged from the WWTP continuously for days or weeks until the biological processes can be restored), or if there was significant maintenance or other works taking place for downstream WWTP processes.
Combined Sewer Overflow (CSO) Tank Events
Hamilton has nine CSO tanks at eight locations that were built from the 1980’s through 2010 to help add capacity to the combined sewer system The nine large storage tanks hold more than 314,000 cubic metres of diluted wastewater. During rain events the combined sewer overflow tanks will fill and store the excess water. If the storm continues the combined sewer system - now being full and at capacity, will then overflow into the environment.
When the storm stops, and the sewer system and treatment plant have capacity for the volume of wastewater inside the combined sewer overflow tanks, the water is then put back into the sewer system to head to the treatment plant for cleaning.
If the combined sewer system didn’t have the designed overflow option to release wastewater to the harbour, large areas of Hamilton would experience flooding - which would impact homes, business, roadways, public spaces and public health. Watch a video on how CSO tanks function.
Combined Sewer Overflow (CSO) Outfalls
Hamilton has CSO outfalls from each CSO tank location as well as other unmonitored combined sewer overflow structures within the sewer system that outfall to the environment. These unmonitored structures are primarily passive weir structures that only overflow when the volume within the upstream pipe exceeds the height of the weir wall. These structures provide sewer system relief to minimize flooding impacts to the community when sewer pipes have reached their capacity.
Sanitary Sewer Overflow Pump Station (SSOPS)
Sanitary sewer overflow pump stations are in limited areas and function when the sanitary sewer system is at capacity and there is risk to flood local homes. These pump stations engage and will send the wastewater to the storm sewer which will then be released into the environment.
Additional Wastewater Treatment Plant Bypass/CSO Information
Swimming after heavy rain falls
Public Health services monitors beaches in accordance with the Ministry of Health and Long-Term Care’s Operational Approaches for Recreational Water Guideline 2018 and the Recreational Water Protocol 2018 under the Ontario Public Health Standards. As outlined in the above protocols, beach samples are collected and tested for E. coli bacteria at least once per week during the swimming season.
Beach sampling results cannot be guaranteed accurate as conditions can change quickly depending on the weather. You should not swim at the beach during and after storms, floods or heavy rainfall. Cloudy water may indicate high levels of bacteria.
For more information on ways to stay safe at the beach, visit the Canadian Red Cross’s website.
Eating fish caught during a Bypass Event in Hamilton Harbour
The Government of Ontario provides fish consumption advisories for Ontario’s lakes and rivers which are available in the Guide to Eating Ontario Fish. You can use this guide and the interactive map to help you identify the types and amounts of fish that are safe to eat from more than 2,400 fishing locations.
Drinking Water Quality
Wastewater treatment plant bypass or CSO storage tank overflow events do not have an impact on the quality of the City’s drinking water.
Wastewater Treatment Plants in Hamilton
There are 2 Wastewater Treatment Plants in Hamilton:
Woodward Wastewater Treatment Plant
700 Woodward Ave. Hamilton
Dundas Wastewater Treatment Plant
135 King St. E. Dundas
Notification Protocol for Wastewater Bypass and CSO Events
All bypasses are promptly reported to the Ministry of Environment, Conservation and Parks (MECP) Spills Action Centre and to Public Health Services as required by the WWTP’s ECA.
Signage at CSO Outfalls
Signage has been added at each outfall location to identify the CSO structure to anyone visiting those areas. The sign includes the name of the individual outfall, a health message, a link to the monitoring webpage and contact information.
Why do some CSO outfall locations not have monitoring?
The combined sewer system was installed well before any monitoring technology existed and it was not until the addition of CSO tanks and real time control gates which started in the 1990’s, that locations then had monitoring instrumentation installed. For many of the remaining outfall locations that are unmonitored there are potentially limiting factors to adding instrumentation which include:
- infrastructure on private property (e.g. active shipping piers),
- no hydro or communications infrastructure at CSO locations,
- many of the outfalls are partially or completely submerged underwater where waves and changing water levels impact the function of overflow monitoring instrumentation.
In 2020, the City will be conducting a study to determine the options available to monitor each location and the costs associated for each. Once the study is complete the details will be presented to the Public Works Committee for consideration.
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