Accountability

Sewage Spill Rankings

The utilities and states responsible for the most reported sewer overflows, and the largest single spills on record — from EPA ECHO and state reporting programs. Reporting completeness varies by state, so these reflect reported events.

Repeat-offender utilities

Most events Most volume Reached waterways

#	Facility	State	Events	Volume	Reached water
1	Sacramento Area Sewer District (merged)	CA	18,588	6.9M gal	651
2	Cumberland WWTP	MD	6,631	18.0M gal	0
3	City of Baltimore Department of Public Works	MD	4,175	—	0
4	Kenmore (V) POSS	NY	2,817	160 gal	2,817
5	Stockton City MUD	CA	2,297	3.1M gal	67
6	Los Angeles City Bureau of Sanitation	CA	2,167	15.4M gal	150
7	Oakland City DPW	CA	2,157	6.3M gal	487
8	Palo Alto City	CA	2,134	164K gal	20
9	WSSC	MD	1,884	980 gal	0
10	San Jose City	CA	1,805	2.2M gal	207
11	Patapsco WWTP	MD	1,608	641.2M gal	0
12	Back River WWTP	MD	1,358	183.4M gal	0
13	Cheektowaga Sanitary Sewer	NY	1,020	220.5M gal	1,020
14	Metropolitan Syracuse WWTP	NY	978	85K gal	949
15	Napa Sanitation District	CA	977	1.0M gal	100
16	San Diego City Metropolitan Wastewater Dept (Public Utilities)	CA	905	53.8M gal	191
17	Cambridge WWTP	MD	766	—	0
18	City of Baltimore	MD	757	—	0
19	Central Contra Costa Sanitary District	CA	701	795K gal	87
20	Sacramento City	CA	687	296K gal	13
21	West Seneca (T) Sanitary ORF	NY	657	2K gal	655
22	Frostburg Combined Sewer Overflows	MD	643	—	0
23	Richmond City	CA	588	58.3M gal	302
24	City of Fairfield	CA	587	438K gal	15
25	Antioch City	CA	562	745K gal	10
26	Patapsco WWTP Collection System - Baltimore City	MD	543	35.8M gal	0
27	Niagara Falls (C) WWTP	NY	542	5.8B gal	540
28	San Mateo City	CA	514	12.6M gal	208
29	Modesto City	CA	505	1.4M gal	26
30	Ross Valley SD	CA	491	4.5M gal	148
31	Roseville City	CA	488	651K gal	13
32	WASHINGTON SUBURBAN SANITARY COMMISSION	MD	481	—	0
33	John J. DiFonzo Water Reclamation Facility	MD	472	—	0
34	San Rafael Sanitation District	CA	466	340K gal	64
35	Kingston (C) WWTP	NY	455	645.9M gal	179
36	Watertown (C) WPCP	NY	453	268.5M gal	453
37	Burlingame City PWD	CA	450	3.1M gal	28
38	CUMBERLAND, CITY OF	MD	446	—	0
39	Mill Valley City	CA	443	86K gal	37
40	San Carlos City	CA	435	197K gal	47
41	Los Angeles Cnty DPW	CA	432	700K gal	258
42	City Of Long Beach	CA	420	275K gal	39
43	Ogdensburg WWTP	NY	404	150.8M gal	404
44	Pittsburg City	CA	385	65K gal	8
45	Vallejo Flood & Wastewater District (formerly Vallejo San & Flood Control District)	CA	377	2.2M gal	39
46	Back River WWTP Collection System - Baltimore City	MD	363	38.2M gal	0
47	John J. DiFonzo WRF	MD	354	—	0
48	City Cleanout	CA	353	21K gal	2
49	1914 Truxtun Avenue	CA	349	813K gal	20
50	Cumberland	MD	348	—	0

Biggest single spills on record

12.8B galAberdeen, City of SSCSSD · Mar 23, 2026 2772.2M galJohn J. DiFonzo (Cumberland) WRF & Collection SystemMD · May 13, 2025 3747.8M galBELLEVILLE STP #1, CITY OF SSCSIL · Apr 19, 2025 4321.0M galNiagara Falls (C) WWTPNY · Feb 16, 2022 5313.1M galNiagara Falls (C) WWTPNY · Feb 16, 2022 6313.1M galNiagara Falls (C) WWTPNY · Feb 16, 2022 7310.6M galNiagara Falls (C) WWTPNY · Feb 16, 2022 8302.7M galNiagara Falls (C) WWTPNY · Feb 16, 2022 9280.0M galBlue Plains WWTP Collection System - Potomac InterceptorMD · Jan 19, 2026 10262.2M galBELLEVILLE STP #1, CITY OF SSCSIL · Mar 4, 2026 11257.5M galPatapsco WWTPMD · Mar 2, 2024 12250.0M galBuffalo Sewer Authority -Bird IslandNY · Aug 30, 2022 13242.0M galD.C. WASA Sanitary Sewer SystemDC · Jan 19, 2026 14241.3M galBELLEVILLE STP #1, CITY OF SSCSIL · Jan 1, 2025 15222.2M galBELLEVILLE STP #1, CITY OF SSCSIL · Mar 23, 2025

States with the most reported overflows

1California72,702

2Maryland30,714

3New York14,394

4North Carolina3,210

5Illinois1,356

6Georgia908

7Puerto Rico646

8Arizona264

9Mississippi239

10Rhode Island212

11South Dakota177

12New Hampshire169

13Nebraska133

14District of Columbia126

15NN46

Data: EPA ECHO + California CIWQS, Maryland MDE, New York DEC, North Carolina DWR. Rankings reflect reported events; states with weaker reporting are undercounted.