Combined Sewer Overflow (CSO) Reporting

State regulations (314 CMR 16.00) require the City of Cambridge to notify the public when certain events occur that result in untreated wastewater being released into surface water--a river or stream. Notifications are posted below and also sent out via email. All Data are preliminary and subject to change.

Subscribe to Cambridge's Combined Sewer Overflow (CSO) Alerts.

Public Health Warning: Public health officials recommend avoiding contact with water bodies during rainstorms and for 48 hours afterwards, as there may be increased health risks due to bacteria or other pollutants associated with urban stormwater runoff and CSO discharges.

CSO Discharge Table

Note: The CSO discharge table below provides details of recent discharges. Data for CSOs is preliminary and subject to change. Discharge duration and volume are estimates and are subject to calculation limitations, including meter data reliability, unmonitored downstream conditions such as river level, and MWRA system operations. See the following links for information on past CSO annual reporting and yearly CSO discharge summaries. Annual reporting data for each calendar year will be published by April 30 of the following year. Updated/revised data is indicated by ( ).

2025 CSO Activation Table

Event Date	CSO Number	Outfall Location	Potentially Affected Area	Start Time	Stop Time	Duration	Volume (million gallons)	Event Rainfall (inches)	Notice
10.22.2025 (under reporting threshold)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	8:54 am (8:45 am)	10:03 am (8:50 am)	69 minutes (5 minutes)	0.75 MG (estimated average of last three years) (<0.01>	0.54	Alert 1
10.20.2025 (retracted - no activation)	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	11:17 am (N/A)	11:37 am (N/A)	20 minutes (N/A)	0.12 MG (estimated average of last three years) (N/A)	0.65
10.20.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	11:15 am (11:20 am)	11:50 am (11:40 am)	35 minutes (20 minutes)	0.75 MG (estimated average of last three years) (0.21 MG)	0.76	Alert 1
10.08.2025	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	9:05 am (9:15 am)	10:10 am (10:00 am)	65 minutes (45 minutes)	0.32 MG (estimated average of last three years) (0.03 MG)	1.1	Alert1
10.08.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	9:00 am (9:15 am)	9.46 am (9:30 am)	46 minutes (15 minutes)	0.12 MG (estimated average of last three years) 0.83	0.83	Alert1 Alert 2
10.08.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	8:45 am	10:10 am (9:30 am)	85 minutes (45 minutes)	0.75 MG (estimated average of last three years) (2.14 MG)	1.1	Alert1 Alert 2
09.18.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	3:00 am (3:15 am)	3:45 am (3:45 am)	45 minutes (30 minutes)	0.75 MG (estimated average of last three years) (0.01 MG)	0.24	Alert1 Alert 2
09.06.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	5:30 pm (5:45 pm)	7:00 pm (7:15 pm)	90 minutes (90 minutes)	0.75 MG (estimated average of last three years) (1.96 MG)	1.88	None
09.06.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	6:20 pm (6:15 pm)	6:39 pm (6:45 pm)	19 minutes (30 minutes)	0.12 MG (estimated average of last three years) (0.09 MG)	1.49	Alert 1
09.06.2025	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	6:15 pm (6:30 pm)	6:40 pm (6:45 pm)	25 minutes (15 minutes)	0.32 MG (estimated average of last three years) (0.01 MG)	1.88	Alert 1
08.29.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	2:45 pm (3:00 pm)	3:20 pm (3:10 pm)	35 minutes (10 min)	0.75 MG (estimated average of last three years) (0.34 MG)	0.53	Alert 1
08.14.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	6:50 pm (6:45 pm)	7:05 pm (7:15 pm)	15 minutes (30 min)	0.12 MG (estimated average of last three years) (1.22 MG)	0.76	Alert 1
08.14.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	6:40 pm (6:30 pm)	7:05 pm (6:55 pm)	25 minutes (25 minutes)	0.75 MG (estimated average of last three years) (1.27 MG)	0.76	Alert 1
07.31.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	(9:00 pm)	(9:15 pm)	15 minutes	0.75 MG (estimated average of last three years) (0.04 MG)	1.65	Alert 1
07.25.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	3:10 pm (3:00 pm)	3:15 pm (3:10 pm)	5 minutes (10 minutes)	0.75 MG (estimated average of last three years) (0.05 MG)	0.41	Alert 1
07.25.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	3:05 pm (3:00 pm)	3:20 pm (3:15 pm)	15 minutes (15 minutes)	0.12 MG (estimated average of last three years) (0.07 MG)	0.41	Alert 1
07.20.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	7:59 pm (7:45 pm)	8:10 pm (8:15 pm)	11 minutes (30 minutes)	0.12 MG (estimated average of last three years) (0.17 MG)	0.42	Alert 1
07.20.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	7:52 pm (7:45 pm)	7:59 pm (8:00 pm)	7 minutes (15 minutes)	0.75 MG (estimated average of last three years) (0.08 MG)	0.42	Alert 1
07.08.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of Rt. 2 Bridge	11:24 pm (11:15 pm)	11:34 pm (11:20 pm)	10 minutes (5 minutes)	0.75 MG (estimated average of last three years) 0.01 MG)	0.96	Alert 1 Alert 2
06.07.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	5:23 pm (5:30 pm)	6:03 pm (6 pm)	40 minutes (30 minutes)	0.75 MG (estimated average of last three years) (0.33 MG)	1.01	Alert 1
05.22.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	6:38 pm (7:00 pm)	1:08 am on 05.23.2025 (1:15 am)	3.25 hours	0.75 MG (estimated average of last three years) (1.35 MG)	3.14	Alert 1 Alert 2
05.06.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	6:13 pm (6:15 pm)	6:33 pm (6:30 pm)	20 minutes (15 minutes)	0.75 MG (estimated average of last three years) (0.16 MG)	1.37	Alert 1
04.01.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	12:38 am (12:45 am)	1:03 am (1:15 am)	23 minutes (30 minutes)	0.75 MG (estimated average of last three years) (0.35 MG)	0.68	Alert 1 Alert 2
03.17.2025	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	4:13 am (4:30 am)	4:30 am (4:45 am)	17 minutes (15 minutes)	0.12 MG (estimated average of last three years) (0.01 MG)	1.37	Alert 1 Alert 2
03.17.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	3:53 am (4:00 am)	4:53 am (4:45 am)	60 minutes (45 minutes)	0.75 MG (estimated average of last three years) (1.02 MG)	1.37	Alert 1 Alert 2
03.06.2025	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	3:22 am and 3:57 am (4:14 am)	3:28 am and 4:38 am (4:45 am)	47 minutes (30 minutes)	0.75 MG (estimated average of last three years) (0.10 MG)	1.04	Alert1 Alert2
01.01.2025 (Revised)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	3:07 am (3:15 am)	3:42 am (3:30 am)	35 minutes (15 minutes)	0.89 MG (estimated average of last three years) (0.04 MG)	0.74	Alert

Prior CSO Activations

Event Date	CSO Number	Outfall Location	Potentially Affected Area	Start Time	Stop Time	Duration	Volume (million gallons)	Event Rainfall (inches)	Notice
12.30.2024	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	8:27 am (8:30 am)	8:37 am (8:45 am)	10 minutes (15 minutes)	0.89 MG (estimated average of last three years) (0.01 MG)	0.50"	Alert
12.11.2024	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	2:37 pm (2:45 pm) 4:37 pm (4:45 pm) 6:25 pm (6:30 pm)	2:42 pm (3:00 pm) 5:02 pm (5:15 pm) 7:07 pm (7:15 pm)	72 minutes (1 hour, 30 minutes)	0.89 MG (estimated average of last three years) (0.56 MG)	2.19"	Alert 1 Alert 2
08.18.2024 (Revised)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	7:52 am (8:18 am)	8:18 am (8:28 am)	26 minutes (10 minutes)	0.89 MG (estimated average of last three years) (<0.01>	0.30"	Alert
08.15.2024 (Revised)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	4:38 pm (4:45 pm)	4:56 pm (5:15 pm)	18 minutes (30 Minutes)	0.89 MG (estimated average of last three years) (0.02 MG)	0.21"	Alert
08.04.2024 (Revised)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	5:08 pm (5:15 pm)	5:23 pm (5:45 pm)	15 minutes (30 minutes)	0.89 MG (estimated average of last three years) (0.15 MG)	0.62"	Alert 1 Alert 2
07.31.2024 (Revised)	CAM401A	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	11:57 am (12:00 pm)	12:22 pm (12:30 pm)	25 minutes (30 minutes)	0.89 MG (estimated average of last three years) (0.83 MG)	0.53"	Alert
07.31.2024 (Revised)	CAM005	Charles River	Downstream of thee Elliot Bridge across from mount Auburn Hospital	11:53 am (11:45 am) <12:15 pm="">	12:13 pm (12:15 pm) <12:30 pm="">	20 minutes (30 minutes) <15 minutes="">	0.21 MG (estimated average of last three years) (0.01 MG) <0.03 mg="">	0.53"	Alert
06.27.2024	CAM005 (Revised)	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	12:22 am (12:30 am) <12:30 am="">	12:30 am (2:00 am) <12:45 am="">	8 minutes (1 hour, 30 Minutes) <15 minutes="">	0.21 MG (estimated average of last three years) (0.02 MG) <0.01 mg="">	0.78"	Alert 1 Alert 2
06.27.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	12:12 am (12:15 am)	12:42 am (12:45 am)	30 minutes	0.89 MG (estimated average of last three years) (0.78 MG)	0.78"	Alert 1 Alert 2
06.20.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with Little River and upstream of the Route 2 Bridge	9:42 pm (9:40 pm)	9:55 pm (10:19 pm)	13 minutes (39 minutes)	0.89 MG (estimated average of last three years) (0.16 MG)	0.6" (0.56")	Alert 1 Alert 2
05.30.2024	CAM401B (Revised) (Revised)	Alewife Brook	Upstream of the Massachusetts Ave Bridge	9:17 am (9:30 am)	10:34 am (10:30 am)	1 hour, 17 minutes (1 hour)	0.32 MG (estimated average of last three years) (0.15 MG)	1.51"	Alert
05.30.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	8:27 am (8:30 am)	10:57 am (10:45 am)	2 hours, 30 minutes (2 hours, 15 minutes)	0.66 MG (estimated average of last three years) (2.18 MG)	1.51"	Alert 1 Alert 2
05.27.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	11:22 pm (NA)	11:32 pm (NA)	10 minutes (NA)	0.66 MG (estimated average of last three years) (0.00)	0.38"	Alert 1 Alert 2 No Activation
05.08.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	11:37 am (11:34 am)	12:02 pm (11:54 am)	25 minutes (20 minutes)	0.66 MG (estimated average of last three years) (0.06 MG)	0.80"	Alert
04.12.2024	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	8:22 pm	9:18 pm	56 minutes	0.10 MG	1.79"	City’s SCADA system had not indicated a spill previously but a spill was identified during review of the final year end data
03.23.2024	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	9:03 am	9:23 am	20 minutes	0.02 MG	0.78"	City’s SCADA system had not indicated a spill previously but a spill was identified during review of the final year end data
03.07.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	1:05 am (2:27 am)	2:36 am (2:37 am)	1 hour, 31 minutes (10 minutes)	0.66 MG (estimated average of last three years) (<0.01>	1.33"	Alert 1 Alert 2
03.02.2024	CAM005 (Revised)	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	11:21 pm (11:30 pm) <11:30 pm="">	11:51 pm (1:30 am) <11:45 pm="">	30 minutes (2 hours) <15 minutes="">	0.28 MG (estimated average of last three years) (<0.01>	1.45"	Alert 1 Alert 2
03.02.2024 (03.03.2024)	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	11:05 pm (12:00 am)	12:22 am (12:20 am)	1 hour, 17minutes (20 minutes)	0.66 MG (estimated average of last three years) (0.05 MG)	1.45"	Alert 1 Alert 2
01.13.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	5:06 am (5:15 am) <5:15> and 7:30 am>	8:46 am (6:00 am) <5:45> and 8:45 am>	3 hours, 40 minutes (45 minutes) <1 hour,="" 45="" minutes="">	0.66 MG (estimated average of last three years) (0.02 MG) <0.70 mg="">	1.23"	Alert 1 Alert 2
01.10.2024	CAM007 (Revised)	Charles River	Downstream of Eliot Bridge across from Hathorne Street	4.05 am (4:15 am)	4:45 am (5:00 am)	40 minutes (45 minutes)	1.04 MG (estimated average of last three years) (0.13 MG)	2.42"	Alert 1 Alert 2
01.10.2024	CAM017 (Revised)	Charles River	Downstream of the Longfellow Bridge across from Front Park	3:55 am	5:29 am (5:20 am)	1 hour, 34 minutes (1 hour, 25 minutes)	1.90 MG (estimated average of last three years) (1.04 MG)	2.42"	Alert 1 Alert 2
01.10.2024	CAM005 (Revised)	Charles River	Downstream o the Eliot Bridge across from Mount Auburn Hospital	3:51 am (4:00 am)	5:11 am (5:15 am)	1 hour, 20 minutes (1 hour, 15 minutes)	0.28 MG (estimated average of last three years) ((0.16 MG) <0.94>	2.42"	Alert 1 Alert 2
01.10.2024	CAM001 (Revised)	Alewife Brook	Downstream of Massachusetts Ave Bridge across from Murray Hill Road	3:50 am (NA)	4:41 am (NA)	51 minutes (NA)	0.05 MG (estimated average of last three years) (0.00)	2.26"	Alert 1 Alert 2 (No Activation)
01.10.2024	CAM401B (Revised)	Alewife Brook	Upstream of the Massachusetts Ave Bridge	3:36 am (3:45 am)	7:29 am (7:15 am)	3 hours, 53 minutes 3 hours, 30 minutes)	0.32 MG (estimated average of last three years) (0.90 MG)	2.26"	Alert 1 Alert 2
01.10.2024	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	12:46 am (2:30 am)	6:11 am (6:00 am)	5 hours, 25 minutes (3 hours, 30 minutes)	0.66 MG (estimated average of last three years) (7.81 MG)	2.26"	Alert 1 Alert 2
12.18.2023 (Revised)	CAM005 (Revised0	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	12:41 pm (12:40 pm)	12:54 pm (1:06 pm)	13 minutes (20 minutes)	0.28 MG (estimated average of last three years) (0.06 MG)	2.50"	Alert
12.18.2023 (Revised)	CAM017 9revised)	Charles River	Downstream of the Longfellow Bridge across from Front Park	12:36 pm (12:35 pm)	12:54 pm (12:50 pm)	18 minutes (15 minutes)	1.9 MG (estimated average of last three years) (0.03 MG)	2.50"	Alert
12.18.2023 (Revised)	CAM401B (Revised)	Alewife Brook	Upstream of the Massachusetts Ave Bridge	12:30 pm (12:45 pm)	1:07 pm (1:15 pm)	37 minutes (30 minutes)	0.32 MG (estimated average of last three years) (0.04 MG)	2.50"	Alert
12.18.2023 (Revised)	CAM401A (Revised)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	12:21 pm (12:30 pm)	1:16 pm (1:45 pm)	55 minutes (1 hour, 15 minutes)	0.66 MG (estimated average of last three years) (1.62 MG)	2.50"	Alert
12.11.2023 (Revised)	CAM017	Charles River	Downstream of the Longfellow Bridge across from front Park	3:20 am (NA)	3:30 am (NA)	10 minutes (NA)	1.9 MG (estimated average of last three years) (0.00)	2.46"	Alert (No Activation)
12.11.2023 (Revised)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	3:06 am (3:15 am)	4:13 am (3:45 am)	1 hour, 17 minutes (30 minutes)	0.28 MG (estimated average of last three years) (0.01 MG)	2.46"	Alert
12.11.2023 (Revised)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	3:06 am (3:15 am)	3:42 am (3:45 am)	36 minutes (30 minutes)	0.32 MG (estimated average of last three years) (0.02 MG)	2.46"	Alert
12.11.2023 (Revised)	CAAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	2:41 am (2:45 am)	5:36 am (5:45 am)	2 hours, 55 minutes (3 hours)	0.66 MG (estimated average of last three years) (2.56 MG)	2.46"	Alert
09.18.2023 (Rev)	CAM401A (Reactivation)	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	10:50 pm (11:00 pm)	11:05 pm (11:15 pm)	15 minutes [Total CSO spill time 1 hour, 45 minutes including reactivation. Reactivations that occur within 12 hours of initial activation are considered the same event. This event will be reported as a 3 hour event to DEP: beginning of first activation (8:15 pm) and ending time of reactivation (11:15 pm)]	0.66 MG (estimated average of last three years) (0.57 MG for both activations)	2.77"	Alert
09.18.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	8:36 pm (8:45 pm)	9:13 pm (9:15 pm)	37 minutes (30 minutes)	0.32 MG (estimated average of last three years) (0.03 MG)	2.77"	Alert
09.18.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	8:20 pm (8:30 pm)	9:03 pm (9:15 pm)	43 minutes (45 minutes)	0.28 MG (estimated average of last three years) (0.01 MG)	2.77"	Alert
09.18.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	8:10 pm (8:15 pm)	9:30 pm (9:45 pm)	1 hour, 20 minutes (1 hour, 30 minutes)	0.66 MG (estimated average of last three years) (see reactivation summary)	2.77"	Alert
09.13.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	1:35 pm (1:45 pm)	2:00 pm (2:15 pm)	25 minutes (30 minutes)	0.66 MG (estimated average of last three years) (0.14 MG)	1.52"	Alert
08.30.2023 (rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	9:35 am (9:45 am)	9:55 am (10:15 am)	20 minutes (30 minutes)	0.66 MG (estimated average of last three years) (0.09 MG)	0.71"	Alert
08.25.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	9:56 am (10:00 am)	10:20 am (10:30 am)	24 minutes (30 minutes)	0.28 MG (estimated average of last three years) (<0.01>	2.46"	Alert
08.25.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	9:05 am (9:00 am)	11:33 am (10:15 am)	2 hours, 28 minutes (1 hour, 15 minutes)	0,28 MG (estimated average of last three years) (0.01 MG)	2.46"	Alert
08.25.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	8:50 am (9:00 am)	1:10 pm (11:00 am)	4 hours, 20 minutes (2 hours)	0,66 MG (estimated average of last three years) (0.58 MG)	2.46"	Alert
08.21.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	8:40 pm (8:45 pm)	8:50 pm (9:00 pm)	10 minutes (15 minutes)	0.66 MG (estimated average of last three years) (0.03 MG)	0.43"	Alert
08.18.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	4:20 pm (4:30 pm)	4:30 pm (4:45 pm)	10 minutes (15 minutes)	0.66 MG (estimated average of last three years) (0.02 MG)	0.62"	Alert
08.08.2023 (rev)	CAM007	Charles River	Downstream of the Eliot Bridge across from Hawthorne Street	11:05 am (11:15 am)	12:21 pm (1:00 pm)	1 hour, 16 minutes (1 hour, 45 minutes)	1.04 (estimated average of last three years) (0.92 MG)	2.53"	Alert
08.08.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	10:51 am (11:00 am)	12:20 pm (11:53 am)	1 hour, 29 minutes (53 minutes)	0.28 MG (estimated average of last three years) (0.63 MG)	2.53"	Alert
08.08.2023 (Rev)	CAM001	Alewife Brook	Downstream of Massachusetts Ave Bridge across from Murry Hill Road	11:05 am (11:15 am)	11:41 am (11:45 am)	36 minutes (30 minutes)	0.05 MG (estimated average of last three years) (<0.01>	2.53"	Alert
08.08.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	10:51 am (11:00 am)	12:27 pm (12:30 pm)	1 hour, 36 minutes (1 hour, 30 minutes)	0.32 MG (estimated average of last three years) (0.53 MG)	2.53"	Alert
08.08.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	10:36 am (10:45 am)	12:34 pm (12:45 pm)	1 hour, 58 minutes (2 hours)	0.66 MG (estimated average of last three years) (3.55 MG)	2.53"	Alert
07.29.2023	CAM017	Charles River	Downstream of the Longfellow Bridge across from front Park	5:10 pm	5:40 pm	30 minutes	0.35 MG (estimated average of last three years)	2.37"	Not issued
07.29.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	6:19 pm (NA)	8:53 pm (NA)	2 hours, 34 minutes (NA)	0.28 MG (estimated average of last three years) (NA)	2.37"	Alert (Retraction)
07.29.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	6:09 pm (5:30 pm)	9:14 pm (9:15 pm)	3 hours, 5 minutes (3 hours, 45 minutes)	0.66 MG (estimated average of last three years) (2.0 MG)	2.37"	Alert
07.25.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	3:30 pm	3:40 pm (3:45 pm)	10 minutes (15 minutes)	0.66 MG (estimated average of last three years) ((0.31 MG)	0.42"	Alert
07.21.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	9:25 pm (9:30 pm)	10:01 pm (10:00 pm)	36 minutes (30 minutes)	0.32 MG (estimated average of last three years) (0.08 MG)	1.68"	Alert
07.21.2023 (Rev)	CAM007	Charles River	Downstream of the Eliot Bridge across from Hawthorne Street	9:20 pm (9:30 pm)	10:05 pm (10:15 pm)	45 minutes	1.05 MG (estimated average of last three years) (0.33 MG)	1.68"	Alert
07.21.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	9:20 pm (9:30 pm)	11:00 pm (11:15 pm)	1 hour, 40 minutes (1 hour, 45 minutes)	0.66 MG (estimated average of last three years) (3.05 MG)	1.68"	Alert
07.21.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	9:20 pm (9:13 pm)	10:40 pm (9:58 pm)	1 hour, 20 minutes (45 minutes)	0.28 MG (estimated average of last three years) (0.60 MG)	1.68"	Alert
07.21.2023 (Rev)	CAM017	Charles River	Downstream of the Longfellow Bridge across from Front Park	8:25 pm (8:30 pm)	10:10 pm	1 hour, 45 minutes (1 hour, 40 minutes)	1.90 MG (estimated average of last three years) (1.38 MG)	1.68"	Alert
07.16.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	12:10 pm (12:15 pm)	12:20 pm (12:30 pm)	10 minutes (15 minutes)	0.66 MG (estimated average of last three years) (0.04 MG)	1.97"	Alert
07.10.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	2:30 pm (2:45 pm)	3:00 pm	30 minutes (15 minutes)	0.32 MG (estimated average of last three years) (0.02 MG)	1.06"	Alert
07.10.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence of the Little River and upstream of the Route 2 Bridge	2:10 pm (2:15 pm)	3:11 pm (3:00 pm)	61minutes (45 minutes)	0.66 MG (estimated average of last three years) (0.67 MG)	1.06"	Alert
07.10.2023 (Rev)	CAM005	Charles River	Downstream of the Elliot Bridge across from Mount Auburn Hospital	2:20 pm	2:50 pm (2:30 pm)	30 minutes (10 minutes)	0.28 MG (estimated average of last three years) (0.01)	1.06"	Alert
07.03.2023 (Rev)	CAM401B	Alewife brook	Upstream of the Massachusetts Ave Bridge	2:01 am (2:15 am)	2:23 am (2:30 am	22 minutes (15 minutes)	0.32 MG (estimated average of last three years) (<0.01>	1.28"	Alert
07.03.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from mount Auburn hospital	1:50 am (1:45 am)	2:12 am (1:55 am)	22 minutes (10 minutes)	0.28 MG (estimated average of last three years) (0.04 MG)	1.28"	Alert
07.03.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence of the Little River and upstream of the Route 2 bridge	1:36 am (1:45 am)	3:01 am (3:00 am)	1 hour, 25 minutes (1 hour, 15 minutes)	0.66 MG (estimated average of last three years) (0.69 MG)	1.28"	Alert
05.20.2023 (Rev)	CAM001	Alewife Brook	Downstream of Massachusetts Ave Bridge across from Murry Hill Road	11:50 pm (NA)	1:58 am (NA)	2 hours, 8 minutes (NA)	0.05 MG (estimated average of last three years) (0.00)	2.27	Alert (No activation)
05.20.2023 (Rev)	CAM401B	Alewife Brook	Upstream of the Massachusetts Ave Bridge	11:37 pm (11:45 pm)	1:32 am (1:30 am)	1 hour, 55 minutes (1 hour, 45 minutes)	0.32 MG (estimated average of last three years) (0.27 MG)	2.27	Alert
05.20.2023 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge across from Mount Auburn Hospital	11:36 pm (11:45 pm)	12:51 am (1:45 am)	1 hour, 15 minutes (2 hours)	0.28 MG (estimated average of last three years) (0.04 MG)	2.27	Alert
05.20.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little river and upstream of the Route 2 Bridge	11:20 pm (11:33 pm)	1:47 am (2:10 am)	2 hours, 27 minutes (2 hours, 37 minutes)	0.66 MG (estimated average of last three years) (1.77 MG - modeled)	2.27	Alert
05.01.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and Upstream of the Route 2 Bridge	12:51 am (1:00 am)	1:15 am (1:30 am)	24 minutes (30 minutes)	0.66 MG (estimates average of last three years) (0.05 MG)	1.52"	Alert
03.14.2023 (Rev)	CAM401A	Alewife brook	Upstream of the confluence with the Little River and Upstream of the route 2 Bridge	7:11 am (9:00 am)	12:46 pm (12:30 pm)	5 hours, 35 minutes 3 hours, 30 minutes)	0.66 MG (estimated average of last three years) (0.42 MG)	2.5"	Alert
03.14.2023	CAM007	Charles River	Downstream of the Eliot Bridge across from Hawthorne Street	NA	NA	NA	NA	2.5"	Retraction Alert
03.02.2023	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	NA	NA	NA	NA	0.70"	Retraction Alert
01.26.2023 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	2:05 am (2:15 am)	4:15 am	2 hours, 10 minutes (2 hours)	0.78 MG (estimated average of last three years) (0.09 MG)	1.08"	Alert
12.23.2022 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	12:55 am (12:59 am)	1:36 am (1:19 am)	41 minutes (20 minutes)	0.78 MG (estimated average of last three years) (< 0.01="" />	1.85" (1.73")	Alert
11.30.2022 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	7:20 pm (7:19 pm)	7:36 pm (7:39 pm)	16 minutes (20 minutes)	0.78 MG (estimated average of last three years) (0.09MG)	0.73 (0.82")	Alert
11.16.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	(7:11 am)	(7:41 am)	30 minutes	(<0.01>	(0.94")	Not issued
10.18.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	(2:25 am)	(2:35 am)	(10 minutes)	(<0.01>	(0.35")	Not issued
10.14.2022 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge, across from Munt Auburn Hospital	9:10 am (9:15 am)	10:55 am (9:30 am)	105 minutes (15 minutes)	0.40 MG (estimated average of last three years) (0.03 MG)	1.83"	Alert
10.14.2022 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	9:05 am (9:22 am)	10:05 am (9:52 am)	60 minutes (30 minutes)	0.78 (estimated average of last three years) (0.19 MG)	1.83" (1.70")	Alert
09.19.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	(9:35 pm)	(9:45 pm)	(10 minutes)	(0.01 MG)	(0.29")	Not issued
08.26.2022 (Rev)	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	4:40 pm (4:37 pm)	4:55 pm (4:57 pm)	15 minutes (20 minutes)	0.78 (estimated average of last three years) (0.12 MG)	0.50"	Alert
08.26.2022 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	(4:45 pm)	(5:00 pm)	(15 minutes)	(0.01 MG)	0.50"	Not issued
08.05.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	(4:44 pm)	(4:54 pm)	(10 minutes)	(<0.01>	(0.10")	Not issued
06.27.2022 (Rev)	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	2:05 pm (2:00 pm)	2:15 pm	15 minutes	0.01	0.79"	Alert
04.19.2022	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	4:35 am (4:00 am rev)	6:00 am	120 minutes	0.11	1.02"
02.04.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	(7:23 am)	(7:33 am)	10 minutes)	(< />	(1.33")
01.17.2022	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	7:40 am - No activation (7:49 am)	No Spill (7:59 am)	No Spill (10 minutes)	No Spill (< />	0.98"
11.12.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	4:05 pm	4:50 pm	45 minutes	0.06	1.07"
10.30.2021	CAM401B	Alewife Brook	Upstream of the Mass Ave Bridge	7:24 pm	7:39 pm	15 minutes	< />	1.63"
10.30.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	7:20 pm	7:50 pm	30 minutes	0.02	1.63"
10.30.2021	CAM001	Alewife Brook	Downstream of the Massachusetts Ave Bridge across from Murray Hill Road	7:17 pm	7:22 pm	5 minutes	< />	1.63"
10.30.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	7:05 pm	8:20 pm	75 minutes	0.23	1.63"
10.26.2021	CAM401B	Alewife Brook	Upstream of the Mass Ave Bridge	7:09 am	7:39 am	30 minutes	0.27	1.43"
10.26.2021	CAM001	Alewife Brook	Downstream of the Massachusetts Ave Bridge across from Murray Hill Road	7:02 am	7:17 am	15 minutes	0.01	1.43"
10.26.2021	CAM017	Charles River	Downstream of the Longfellow Bridge, across from Front Park	6:05 am	6:35 am	30 minutes	0.54	1.43"
10.26.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	6:35 am	8:05 am	90 minutes	0.70	1.43"
10.05.2021	CAM001	Alewife Brook	Downstream of the Massachusetts Ave Bridge across from Murry Hill Road	2:45 am - No Activation	No Spill	No Spill	No Spill	1.64"
10.05.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	12:50 am - No Activation	No Spill	No Spill	No Spill	1.64"
09.28.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	11:40 am (11:45 am)	8:00 pm	495 minutes	0.28	1.60"
09.28.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	10:35 am	8:00 pm	565 minutes	1.10	1.60"
09.10.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	1:16 am - No Activation	No Spill	No Spill	No Spill	0,96"
09.10.2021	CAM401A	Alewife Brook	Upstream of the confluence of the Little River and upstream of the Route 2 Bridge	1:04 am	3:29 am	145 minutes	0.10	0.96"
09.02.2021	CAM007	Charles River	Downstream of the Eliot Bridge, across from Hawthorne Street	3:05 am	5:15 am	130 minutes	0.47	4.25"
09.02.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	2:45 am	5:45 am	180 minutes	0.06	4.25"
09.02.2021	CAM017	Charles River	Downstream of the Longfellow Bridge, across from Front Park	1:35 am	5:15 am	220 minutes	4.43	4.25"
09.02.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	12:07 am	6:00 am	353 minutes	0.29	4.25"
09.02.2021	CAM401B	Alewife Brook	Upstream of the Mass Ave Bridge	12:15 am	7:30 am	435 minutes	0.18	4.25"
09.01.2021	CAM401A	Alewife Brook	Upstream of the confluence of the Little River and upstream of the Route 2 Bridge	7:00 pm	6:45 am	705 minutes	2.95	4.25"
09.01.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	11:26 pm - no activation	see 09.02.2021	see 09.02.2021	see 09.02.2021"	4.25"
08.22.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	9:25 am	9:40 am	15 minutes	0.02	0.89"
08.22.2021	CAM401B	Alewife Brook	Upstream of the Mass Ave Bridge	9:20 am	9:45 am	15 minutes	0.004	0.89"
08.22.2021	CAM401A	Alewife Brook	Upstream of the confluence of the Little River and upstream of the Route 2 Bridge	9:05 am	9:45 am	40 minutes	0.29	0.89"
08.19.2021	CAM007	Charles River	Downstream of Eliot Bridge, across from Hawthorne Street	12:35 pm	1:15 pm	40 minutes	0.20	1.72"
08.19.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	12:05 pm	12:50 pm	45 minutes	0.43	1.72"
08.19.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	12:00 pm	1:15 pm	75 minutes	0.10	1.72"
08.19.2021	CAM401B	Alewife Brook	Upstream of the Mass Ave Bridge	11:45 am	1:30 pm	135 minutes	0.55	1.72"
08.19.2021	CAM401A	Alewife Brook	Upstream of the confluence with the Little River and upstream of the Route 2 Bridge	11:00 am	1:30 pm	150 minutes	1.13	1.72"
08.19.2021	CAM017	Charles River	Downstream of the Longfellow Bridge, across from Front Park	11:00 am	12:30 pm	90 minutes	2.43	1.72"
07.27.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	No Spill	No Spill	No Spill	No Spill	0.74"
07.27.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	7:50 pm	8:20 pm	30 minutes	0.04	0.74"
07.27.2021	CAM401B	Alewife Brook	Upstream of Mass Ave Bridge	7:51 pm	8:20 pm	30 minutes	0.08	0.74"
07.27.2021	CAM401A	Alewife Brook	Confluence of Little River, upstream of Mass Ave Bridge	7:45 pm	8:15 pm	30 minutes	0.24	0.74"
07.18.2021	CAM005	Charles River	Downstream of the Eliot Bridge, across from Mount Auburn Hospital	5:15 am	5:30 am	15 minutes	0.02	0.34"
07.18.2021	CAM401A	Alewife Brook	Confluence of Little River, upstream of Mass Ave Bridge	5:11 am	5:45 am	34 minutes	0.75	0.34"
07.18.2021	CAM007	Charles River	Downstream of the Eliot Bridge, across from Hawthorne Street	5:00 am	5:30 am	30 minutes	0.24	0.34"
07.12.2021	CAM005	Charles River	Downstream of Eliot Bridge, across from Mount Auburn Hospital	8:30 am	9:00 am	30 minutes	0.02	1.05"
07.12.2021	CAM401A	Alewife Brook	Confluence of Little River, upstream of Mass Ave Bridge	7:45 am	10:45 am	3 hours	1.72	1.05"
07.09.2021	CAM401A	Alewife Brook	Confluence of Little River, upstream of Mass Ave Bridge	12:45 pm	2:13 pm	1.5 hours	0.44	2.53"
07.09.2021	CAM007	Charles River	Downstream of Eliot Bridge across from Hawthorne Street	12:10 pm	1:20 pm	1.2 hours	0.68	2.53"
07.09.2021	CAM005	Charles River	Downstream of Eliot Bridge across from Mount Auburn Hospital	11:30 am	1215 pm	0,75 hours	0.18	2.53"
07.09.2021	CAM017	Charles River	Downstream of Longfellow Bridge, across from Front Park	10:15 am	1:30 pm	3.25 hours	3.31	2.53"
07.09.2021	CAM401B	Alewife Brook	Upstream of Mass Ave Bridge	11:30 am	2:50 pm	3.33 hours	0.57	2.53"
07.03.2021	CAM401A	Alewife Brook	Confluence of Little River, upstream of Mass Ave Bridge	9:37 pm	9:42 pm	5 minutes	0.07	1.39"
07.03.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	Data Unavailable	Data Unavailable	Data Unavailable	Data Unavailable	1.39"
07.02.2021	CAM401B	Alewife Brook	Upstream of Mass Ave Bridge	2:00 am	3:30 am	1.5 hours	0.473	2..23"
07.02.2021	CAM007	Charles River	Downstream of Eliot Bridge	2:08 am	3:20 am	1.2 hours	0.038	2.23"
07.02.2021	CAM401A	Alewife Brook	Confluence of Little River, Upstream of Mass Ave Bridge	1:29 am	3:30 am	2.0 hours	0.81	2.23"
07.02.2021	CAM001	Alewife Brook	Downstream of Mass Ave Bridge, across from Murry Hill Road	Data Unavailable	Data Unavailable	Data Unavailable	Data Unavailable	2.23"
07.02.2021	CAM005	Charles River	Downstream of Elliot Bridge, across from Mount Auburn Hospital	2:15 am	3:52 am	1.62 hours	2.27	2.23"
07.02.2021	CAM017	Charles River	Downstream of Longfellow Bridge, across from Front Park	12:30 am	2:30 am	2.0 hours	2.91	2.23"

City of Cambridge Public Notification Plan

On June 16, 2023, the Massachusetts Department of Environmental Protection (MassDEP) approved the City’s Public Notification Plan describing how it will comply with the requirements of An Act Promoting Awareness of Sewage in Public Waters, signed into law in 2021. Anyone signed up to receive CSO Discharge Notifications will receive an email notification When a CSO occurs at a Cambridge-owned outfall.

The Massachusetts Water Resource Authority (MWRA) and the cities of Boston, Chelsea and Somerville manage their own combined sewer outfalls, including CSO reporting. These communities must be contacted directly for information regarding their CSO discharges.

Subscribe to Cambridge's Combined Sewer Overflow (CSO) Alerts.

CSO Discharge Table

2025 CSO Activation Table

Prior CSO Activations

City of Cambridge Public Notification Plan

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