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Sewage discharges in New Hampshire

17 waters tracked: 0 red, 1 yellow, 2 unresolved, 14 with no current report, as of Nov 2, 2026, 6:56 AM EST. 6 discharges reported in the last 30 days.

Source: DirtyWaterWatch statuses from the 0 feeds listed under Coverage below, as of 2026-11-02 11:56 UTC.

Source: water outlines from OpenBoatLaunch and OpenStreetMap contributors (ODbL); outfalls from EPA ECHO and the state outfall layers; modeled reaches computed by DirtyWaterWatch from USGS NLDI, NHDPlus and the nearest USGS gauge (Jobson 1996); basemap OpenFreeMap and OpenMapTiles.

Caution Caution: 1 water

Unresolved: no end reported Unresolved: no end reported: 2 waters

No current report No current report: 14 waters

Dischargers

Coverage

What the authority says about the period after a discharge

72 hours after the discharge ends. Basis: “RSA 485-A:8 III: CSO partial-use criteria apply during discharges "and up to 3 days following cessation"; EPA permits require 2-hour notice but state no public window”

Source: rules.json red.by_state.NH (research/nh-vt/report.md).

How long a water stays coloured, in every state

Feeds we read

No feed for New Hampshire in this build.

28 other sources considered for New Hampshire are listed on the sources page.

Discharges in New Hampshire over the years

  • Discharge events, last 12 months40Dec 2025 to Nov 2026
  • Days with a discharge, last 12 months34Dec 2025 to Nov 2026
  • Hours under advisory, last 12 months1,137Dec 2025 to Nov 2026; on at least one water in the state
  • 2026 season under advisory15%May to October; 659 h

Discharge events per month

276 events, Jan 2022 to Nov 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Bypass, blended or other

EPA ECHO sewer overflow records are sparse (only what permittees file with EPA). NH permittees publish on their own pages; each discharger's record begins on a different date. Some dischargers here report only monthly or yearly totals; those are shown under reported totals, not counted here.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2022-01-01 to 2026-11-02.

Show table
Discharge events per month
MonthCombined sewer overflowSanitary sewer overflowBypass, blended or otherTotalCounted fromCoverage
Jan 20225005Source records
Feb 20226006Source records
Mar 20221001Source records
Apr 20227007Source records
May 20221001Source records
Jun 20221001Source records
Jul 20225117Source records
Aug 20224105Source records
Sep 20223003Source records
Oct 20224004Source records
Nov 20222002Source records
Dec 20222024Source records
Jan 20232013Source records
Feb 20231001Source records
Mar 20230011Source records
Apr 20234116Source records
May 20232013Source records
Jun 2023130013Source records
Jul 2023352037Source records
Aug 20238008Source records
Sep 2023120012Source records
Oct 20234004Source records
Nov 20231102Source records
Dec 2023101112Source records
Jan 20240101Source records
Feb 20240000
Mar 20243003Source records
Apr 20240101Source records
May 20241001Source records
Jun 20240000
Jul 2024120012Source records
Aug 20247007Source records
Sep 20240000
Oct 20240000
Nov 20240000
Dec 20243003Source records
Jan 20253003Source records
Feb 20252103Source records
Mar 2025100111Source records
Apr 20250000
May 2025140014Source records
Jun 20251102Source records
Jul 20256107Source records
Aug 20257108Source records
Sep 20252103Source records
Oct 20254037Source records
Nov 20251102Source records
Dec 20250404Source records
Jan 20260000
Feb 20260000
Mar 20260101Source records
Apr 20262103Source records
May 20261102Source records
Jun 20260112Source records
Jul 20269009Source records
Aug 20268008Source records
Sep 20261315Source records
Oct 20266006Source records
Nov 20260000

Hours under advisory per month

Hours at least one water in the state was under an advisory, by the map's red rules.

  • Advisory in effect

771 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here. 1 events reported to last more than 31 days are counted to 31 days. Official beach and cyanobacteria advisories are counted on water pages only. EPA ECHO sewer overflow records are sparse (only what permittees file with EPA). NH permittees publish on their own pages; each discharger's record begins on a different date.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Hours under advisory per month
MonthHours under advisoryFrom discharge windowsHours in monthCoverage
Jan 202200744
Feb 202200672
Mar 202200744
Apr 202200720
May 202200744
Jun 202200720
Jul 202200744
Aug 20227474744
Sep 202200720
Oct 202200744
Nov 202200720
Dec 202200744
Jan 202300744
Feb 2023236236672
Mar 202300744
Apr 2023316316720
May 202300744
Jun 202300720
Jul 20239696744
Aug 202300744
Sep 202300720
Oct 202300744
Nov 2023491491720
Dec 2023438438744
Jan 20249696744
Feb 202400696
Mar 202400744
Apr 20247979720
May 202400744
Jun 202400720
Jul 202400744
Aug 202400744
Sep 202400720
Oct 202400744
Nov 202400720
Dec 202400744
Jan 202500744
Feb 20257272672
Mar 202500744
Apr 202500720
May 202500744
Jun 20257272720
Jul 20257373744
Aug 2025298298744
Sep 2025119119720
Oct 2025166166744
Nov 2025101101720
Dec 2025183183744
Jan 20264444744
Feb 202600672
Mar 20267272744
Apr 2026179179720
May 20267373744
Jun 2026145145720
Jul 202600744
Aug 202600744
Sep 2026243243720
Oct 2026197197744
Nov 20260032

Days with a discharge per month

A day counts when any counted discharge was under way on it (start to reported end, local time); an event with no end counts its start day.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2022-01-01 to 2026-11-02.

Show table
Days with a discharge per month
MonthDays with a dischargeCoverage
Jan 20221
Feb 20224
Mar 20221
Apr 20225
May 20221
Jun 20221
Jul 20222
Aug 20225
Sep 20223
Oct 20224
Nov 20222
Dec 20222
Jan 20233
Feb 20238
Mar 20231
Apr 202313
May 20233
Jun 20236
Jul 20239
Aug 20233
Sep 20235
Oct 20231
Nov 20232
Dec 20235
Jan 20241
Feb 20240
Mar 20242
Apr 20241
May 20241
Jun 20240
Jul 20246
Aug 20242
Sep 20240
Oct 20240
Nov 20240
Dec 20241
Jan 20251
Feb 20253
Mar 20254
Apr 20250
May 20256
Jun 20252
Jul 20254
Aug 202514
Sep 20254
Oct 20254
Nov 20253
Dec 20254
Jan 20260
Feb 20260
Mar 20261
Apr 20266
May 20262
Jun 20262
Jul 20264
Aug 20261
Sep 20265
Oct 20269
Nov 20260

Discharge events per year, 2013 to 2026

807 events, 2013 to 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Bypass, blended or other
  • Partly covered or sparse source

EPA ECHO sewer overflow records are sparse (only what permittees file with EPA). NH permittees publish on their own pages; each discharger's record begins on a different date.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Discharge events per year, 2013 to 2026
YearCombined sewer overflowSanitary sewer overflowBypass, blended or otherTotalCoverage
201311600116Partly covered or sparse source
2014520052
2015310031
2016282030
2017241025
2018752077
2019795286
2020362139
2021740175
2022412346
20239255102
2024262028
20255010464
2026277236

Reported volume per year

Gallons, summed from the 786 events that gave a number (21 did not).

  • Partly covered or sparse source

21 of 807 events gave no volume as a number (1 gave a range); only numbers are summed.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Reported volume per year
YearGallonsEvents with a numberEvents withoutCoverage
201341,568,0001124Partly covered or sparse source
201450,834,000520
20154,612,000310
201610,716,493291
201710,332,260250
201845,107,565770
201947,088,532842
202012,160,365381
202149,822,000750
20224,518,751442
202368,566,2851002
202411,036,821271
202538,229,225631
202623,470,313297

Hours under advisory per year

Hours under advisory each year; 2026 to date.

  • Advisory in effect
  • Partly covered or sparse source

771 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here. 1 events reported to last more than 31 days are counted to 31 days. Official beach and cyanobacteria advisories are counted on water pages only.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Hours under advisory per year
YearHours under advisoryShare of the yearCoverage
201300.0%Partly covered or sparse source
201400.0%
201500.0%
201600.0%
20171201.4%
201800.0%
20191201.4%
20201201.4%
202100.0%
2022740.8%
20231,57618.0%
20241752.0%
20251,08312.4%
202695413.0%

Share of the May to October season under advisory

Share of the hours from May 1 to October 31 with an advisory in effect.

  • Advisory in effect

771 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here. 1 events reported to last more than 31 days are counted to 31 days. Official beach and cyanobacteria advisories are counted on water pages only.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Share of the May to October season under advisory
SeasonShare under advisoryHours under advisoryHours coveredSeason hoursPartly covered
20130.0%04,4164,416
20140.0%04,4164,416
20150.0%04,4164,416
20160.0%04,4164,416
20170.0%04,4164,416
20180.0%04,4164,416
20190.0%04,4164,416
20200.0%04,4164,416
20210.0%04,4164,416
20221.7%744,4164,416
20232.2%964,4164,416
20240.0%04,4164,416
202516.5%7274,4164,416
202614.9%6594,4164,416

Discharge events by calendar month, all years

Every counted discharge event, by the calendar month it began.

Months are summed over every year a source covers; the table gives the number of years behind each month.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Discharge events by calendar month, all years
MonthEventsYears of records
Jan5614
Feb2414
Mar3414
Apr4714
May4114
Jun9114
Jul16114
Aug9514
Sep9714
Oct6814
Nov3914
Dec5413

Discharge events by outfall

The 10 outfalls with the most events of 26, all years.

EPA ECHO sewer overflow records are sparse (only what permittees file with EPA). NH permittees publish on their own pages; each discharger's record begins on a different date.

Sources: EPA ECHO sewer overflow events; NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2013-01-10 to 2026-11-02.

Show table
Discharge events by outfall
OutfallDischargerEvents
008 Broad St.City of Nashua Wastewater Department184
005 East Hollis St.City of Nashua Wastewater Department179
006 Nashua RiverCity of Nashua Wastewater Department91
004 Burke St.City of Nashua Wastewater Department90
014 Bridge St.City of Nashua Wastewater Department70
009 Lock St.City of Nashua Wastewater Department61
003 Farmington Rd.City of Nashua Wastewater Department46
001 WWTP outfall 001Town of Exeter WWTP14
003 Clemson Pond tide gate (CSO structures: Spring St, Water St)Town of Exeter DPW14
007 Tampa St.City of Nashua Wastewater Department8
Other outfalls (16)17
Outfall not stated33

Reported monthly totals: NH permittee notices (Nashua, Manchester, Portsmouth, Exeter)

Portsmouth publishes monthly CSO volumes per outfall, not events. Source: NH permittee notices (Nashua, Manchester, Portsmouth, Exeter). Covered 2010-01-01 to 2025-05-01.

Reported volume

Gallons per year (monthly figures summed by year).

Show table
Reported volume
YearReported volume
2010108,495,900 gal
201113,681,800 gal
201210,181,000 gal
20133,892,600 gal
201414,709,200 gal
20153,513,670 gal
20163,493,200 gal
20171,229,800 gal
20187,808,300 gal
20193,542,000 gal
2020916,000 gal
20211,940,000 gal
2022636,000 gal
202313,266,000 gal
202410,248,000 gal
202555,000 gal
How these charts are counted

Discharge events are counted once: where a source publishes both public notices and verified reports (MassDEP, Vermont DEC), a discharger's month with any verified report counts its verified reports only, and other months count notices. Revisions are folded into the record they revise, and EPA copies of a state report are not counted twice. Monthly and yearly totals (Maine DEP, EPA discharge monitoring reports, Portsmouth) are shown on their own and never added to the event counts. Hours under advisory follow the map's red rules. A muted band marks periods no source covers: a gap there is missing data, not a quiet month.

  • EPA ECHO sewer overflow events: 2022-05-03 to now (sparse)
  • NH permittee notices (Nashua, Manchester, Portsmouth, Exeter): 2013-01-10 to 2026-08-03
  • NH permittee notices (Nashua, Manchester, Portsmouth, Exeter): 2016-01-10 to 2025-09-30
  • NH permittee notices (Nashua, Manchester, Portsmouth, Exeter): 2019-04-25 to now
  • NH permittee notices (Nashua, Manchester, Portsmouth, Exeter): 2026-09-29 to now

Discharges in the last 30 days

Discharges in New Hampshire in the last 30 days, newest first
StartEnd Water Discharger OutfallTypeVolumeSourceLinks
not reported (reported Oct 18, 2026, 8:23 AM EDT) Oct 17, 2026, 8:23 PM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14033, reported Oct 18, 2026, 8:23 AM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 18, 2026, 8:23 AM EDT) · Map
not reported (reported Oct 14, 2026, 12:08 AM EDT) Oct 17, 2026, 8 PM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14026, reported Oct 14, 2026, 12:08 AM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 14, 2026, 12:08 AM EDT) · Map
not reported (reported Oct 12, 2026, 3:04 PM EDT) Oct 17, 2026, 8 PM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14024, reported Oct 12, 2026, 3:04 PM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 12, 2026, 3:04 PM EDT) · Map
not reported (reported Oct 12, 2026, 1:53 PM EDT) Oct 12, 2026, 1:53 AM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14023, reported Oct 12, 2026, 1:53 PM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 12, 2026, 1:53 PM EDT) · Map
not reported (reported Oct 7, 2026, 5:22 AM EDT) Oct 6, 2026, 5:22 PM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14013, reported Oct 7, 2026, 5:22 AM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 7, 2026, 5:22 AM EDT) · Map
not reported (reported Oct 3, 2026, 11:38 PM EDT) Oct 3, 2026, 11:38 AM EDT Merrimack River, NH, Piscataquog River, NH City of Manchester DPW Environmental Protection Division not stated Combined sewer overflow not reported City of Manchester EPD (CSO Discharge Notification page) via nh-permittees, record manchester:Item14011, reported Oct 3, 2026, 11:38 PM EDT, retrieved 2026-11-02 11:55 UTC · notice Event: Combined sewer overflow, City of Manchester DPW Environmental Protection Division, not reported (reported Oct 3, 2026, 11:38 PM EDT) · Map