NPDES ID0021504 · Clean Water Act
CALDWELL, CITY OF - CALDWELL WWTP, Caldwell, ID: NPDES ID0021504 discharge permit, effluent exceedances, inspections, penalties
CALDWELL, CITY OF - CALDWELL WWTP, Caldwell, Idaho: Individual permit ID0021504, held by CALDWELL, CITY OF; Publicly owned treatment works; Administratively continued; issued December 29, 1998, term to February 2, 2004, by U.S. EPA, REGION 10; discharges to BOISE RIVER & INDIAN CREEK; Sewage Treatment Facilities.
- Nitrogen, ammonia total [as N]: 12 limits, 47 violations of any kind, 35 effluent exceedances, latest June 30, 2019, largest 4,627% over the limit.
- Solids, total suspended: 8 limits, 67 violations of any kind, 6 effluent exceedances, latest June 30, 2019, largest 52% over the limit.
- Coliform, fecal MF, MFC broth, 44.5 C: 6 limits, 30 violations of any kind, 5 effluent exceedances, latest May 31, 2014, largest 600% over the limit.
- Oxygen, dissolved [DO]: 1 limit, 17 violations of any kind, 5 effluent exceedances, latest May 31, 2007, largest 23% over the limit.
- E. coli, MTEC-MF: 1 limit, 12 violations of any kind, 4 effluent exceedances, latest November 30, 2025, largest 99,999% over the limit.
- pH: 2 limits, 23 violations of any kind, 1 effluent exceedance, latest October 31, 2001.
- Chlorine, total residual: 14 limits, 17 violations of any kind, 1 effluent exceedance, latest March 31, 1999, largest 6% over the limit.
- Solids, suspended percent removal: 1 limit, 8 violations of any kind, 1 effluent exceedance, latest January 31, 2013, largest 967% over the limit.
- BOD, 5-day, percent removal: 1 limit, 7 violations of any kind, 1 effluent exceedance, latest August 31, 1999, largest 13% over the limit.
- Floating solids, waste or visible foam-visual: 0 limits, 1 violation of any kind, 1 effluent exceedance, latest March 31, 2019.
- BOD, 5-day, 20 deg. C: 8 limits, 60 violations of any kind.
- Temperature, water deg. centigrade: 3 limits, 41 violations of any kind.
- Phosphorus, total [as P]: 2 limits, 24 violations of any kind.
- Nitrogen, nitrate total [as N]: 2 limits, 16 violations of any kind.
- Nitrogen, Kjeldahl, total [as N]: 2 limits, 16 violations of any kind.
- Phosphate, ortho [as PO4]: 2 limits, 16 violations of any kind.
- Chromium, total dry weight [as Cr]: 0 limits, 12 violations of any kind.
- Lead, total dry weight [as Pb]: 0 limits, 12 violations of any kind.
- Selenium, sludge, total, dry weight [as Se]: 0 limits, 12 violations of any kind.
- Arsenic total, dry weight, sludge: 0 limits, 12 violations of any kind.
- Molybdenum, sludge, total, dry weight [as Mo]: 0 limits, 12 violations of any kind.
- Zinc, sludge, total, dry weight [as Zn]: 0 limits, 12 violations of any kind.
- Nickel, sludge, total, dry weight [as Ni]: 0 limits, 12 violations of any kind.
- Mercury, sludge, total, dry weight [as Hg]: 0 limits, 12 violations of any kind.
- Copper, sludge, total, dry weight [as Cu]: 0 limits, 12 violations of any kind.
- Cadmium, sludge, total, dry weight [as Cd]: 0 limits, 12 violations of any kind.
- Flow, in conduit or thru treatment plant: 1 limit, 11 violations of any kind.
- Mercury, total [as Hg]: 1 limit, 10 violations of any kind.
- Turbidity, lab, NTU: 2 limits, 8 violations of any kind.
- Hardness, total [as CaCO3]: 1 limit, 8 violations of any kind.
- Toxicity [chronic], Ceriodaphnia dubia: 1 limit, 7 violations of any kind.
- Toxicity [chronic], Pimephales promelas [Fathead Minnow]: 1 limit, 7 violations of any kind.
- Copper, total recoverable: 1 limit, 6 violations of any kind.
- Carbon, dissolved organic [as C]: 0 limits, 6 violations of any kind.
- Arsenic, dissolved [as As]: 0 limits, 6 violations of any kind.
- Copper, dissolved [as Cu]: 0 limits, 6 violations of any kind.
- Lead, dissolved [as Pb]: 0 limits, 6 violations of any kind.
- Zinc, dissolved [as Zn]: 0 limits, 6 violations of any kind.
- Cadmium, dissolved [as Cd]: 0 limits, 5 violations of any kind.
- Chromium, dissolved [as Cr]: 0 limits, 5 violations of any kind.
- Nickel, dissolved [as Ni]: 0 limits, 5 violations of any kind.
- Arsenic, total recoverable: 1 limit, 4 violations of any kind.
- Nickel, total recoverable: 1 limit, 4 violations of any kind.
- Silver total recoverable: 1 limit, 4 violations of any kind.
- Zinc, total recoverable: 1 limit, 4 violations of any kind.
- Cadmium, total recoverable: 1 limit, 4 violations of any kind.
- Lead, total recoverable: 1 limit, 4 violations of any kind.
- Chromium, total recoverable: 1 limit, 4 violations of any kind.
- Phosphate, ortho, dissolved [as P]: 0 limits, 2 violations of any kind.
- Silver, dissolved [as Ag]: 0 limits, 2 violations of any kind.
- Conductivity: 0 limits, 1 violation of any kind.
- June 27, 2026: WW SSO - Overflow to Dry Land or Building Backup (ST6).
- May 27, 2026: Evaluation (S).
- March 16, 2026: No Further Action (State).
- March 13, 2026: No Further Action (State).
- March 13, 2026: No Further Action (State).
- February 11, 2026: Evaluation (S).
- January 22, 2026: WW SSO - Narrative effluent violation (ST6).
- January 21, 2026: WW SSO - Overflow to Dry Land or Building Backup (ST6).
Idaho holds 110 Publicly owned treatment works coverages of this permit type in EPA’s file; 1 were issued before ID0021504.
Coverages issued nearest ID0021504
- 1975-09-25: CITY OF SANDPOINT - SAND CREEK WTP, Sandpoint: ID0024350, held by SANDPOINT, CITY OF
- 1998-12-29: NAMPA, CITY OF - NAMPA WWTP, Nampa: ID0022063, held by NAMPA, CITY OF
- 1999-03-12: MOSCOW, CITY OF - MOSCOW WWTP, Moscow: ID0021491, held by MOSCOW, CITY OF
- 1999-07-29: FILER, CITY OF - FILER WWTP, Filer: ID0020061, held by FILER, CITY OF
- 1999-07-29: JEROME, CITY OF - JEROME WWTP, Jerome: ID0020168, held by JEROME, CITY OF
- 1999-07-29: BUHL, CITY OF - BUHL WWTP, Buhl: ID0020664, held by CITY OF BUHL
CALDWELL, CITY OF - CALDWELL WWTP among its neighbors
197 discharge permits are in the Mill Slough-Boise River subwatershed (HUC 170501140410); ID0021504 is one. Its county: 377, 2 major; ID0021504 is major permit.
Other permits in the Mill Slough-Boise River subwatershed (HUC 170501140410)
- 1ST STREET TOWNHOMES SUBDIVISION, Star: IDR10C20H, minor, term to 2027-02-09
- 2684 BEACON LIGHT IMPROVEMENT PROJECT, Eagle: IDR10C1O0, minor, term to 2027-02-09
- 9335 SH-44 4 ACRE LOT, Middleton: IDR1002ZU
- ACHD LINDRE: SH44 TO FLOATING FEATHER, Eagle: IDR10C1TT, minor, term to 2027-02-09
- AMBERLY RANCH SUBDIVISION, Eagle: IDR10L0FX
- AMERICAN STAR SUBDIVISION NO. 2, Star: IDR1002TO, minor, term to 2022-02-15
- AMERICAN STAR SUBDIVISION NO. 3, Star: IDR10C05M, minor, term to 2022-02-16
- ARTESIAN SPRINGS SUBDIVISION, Middleton: IDR10C1JY, minor, term to 2027-02-09
- ARVORY CREST SUBDIVISION PHASE 4, Star: IDR10C1YC, minor, term to 2027-02-09
- BALD EAGLE POINTE SUBDIVISION NO. 1, Eagle: IDR1002PH, minor, term to 2022-02-15
Identity
| Facility | CALDWELL, CITY OF - CALDWELL WWTP |
|---|---|
| Permittee | CALDWELL, CITY OF |
| NPDES ID | ID0021504 |
| Status | Administratively continued |
| Type | Individual permit |
| Class | Major |
| Facility type | Publicly owned treatment works |
| Program | Publicly owned treatment works |
| Issued | December 29, 1998 |
| Expires | February 2, 2004 |
| Agency | U.S. EPA, REGION 10 |
| Address | Caldwell, ID 83605 |
| Receiving water | BOISE RIVER & INDIAN CREEK |
| Receiving water impaired | 303(D) Listed |
| Subwatershed | Mill Slough-Boise River (HUC 170501140410) |
| Program components on file | Biosolids, POTW, Pretreatment |
| NAICS | 221320 – Sewage Treatment Facilities |
| SIC | 4952 – Sewerage Systems |
NPDES ID0021504: effluent limits and exceedances
CALDWELL, CITY OF - CALDWELL WWTP (NPDES ID0021504): 51 pollutants on file, 29 limited; 51 with a violation of any kind, 10 with an exceedance.
| Pollutant | Limits | Violations | Exceedances | Latest | Largest, as filed |
|---|---|---|---|---|---|
| Nitrogen, ammonia total [as N] | 12 | 47 | 35 | June 30, 2019 | 4,627% over the limit |
| Solids, total suspended | 8 | 67 | 6 | June 30, 2019 | 52% over the limit |
| Coliform, fecal MF, MFC broth, 44.5 C | 6 | 30 | 5 | May 31, 2014 | 600% over the limit |
| Oxygen, dissolved [DO] | 1 | 17 | 5 | May 31, 2007 | 23% over the limit |
| E. coli, MTEC-MF | 1 | 12 | 4 | November 30, 2025 | 99,999% over the limit |
| pH | 2 | 23 | 1 | October 31, 2001 | |
| Chlorine, total residual | 14 | 17 | 1 | March 31, 1999 | 6% over the limit |
| Solids, suspended percent removal | 1 | 8 | 1 | January 31, 2013 | 967% over the limit |
| BOD, 5-day, percent removal | 1 | 7 | 1 | August 31, 1999 | 13% over the limit |
| Floating solids, waste or visible foam-visual | 0 | 1 | 1 | March 31, 2019 | |
| BOD, 5-day, 20 deg. C | 8 | 60 | 0 | ||
| Temperature, water deg. centigrade | 3 | 41 | 0 | ||
| Phosphorus, total [as P] | 2 | 24 | 0 | ||
| Nitrogen, nitrate total [as N] | 2 | 16 | 0 | ||
| Nitrogen, Kjeldahl, total [as N] | 2 | 16 | 0 | ||
| Phosphate, ortho [as PO4] | 2 | 16 | 0 | ||
| Chromium, total dry weight [as Cr] | 0 | 12 | 0 | ||
| Lead, total dry weight [as Pb] | 0 | 12 | 0 | ||
| Selenium, sludge, total, dry weight [as Se] | 0 | 12 | 0 | ||
| Arsenic total, dry weight, sludge | 0 | 12 | 0 | ||
| Molybdenum, sludge, total, dry weight [as Mo] | 0 | 12 | 0 | ||
| Zinc, sludge, total, dry weight [as Zn] | 0 | 12 | 0 | ||
| Nickel, sludge, total, dry weight [as Ni] | 0 | 12 | 0 | ||
| Mercury, sludge, total, dry weight [as Hg] | 0 | 12 | 0 | ||
| Copper, sludge, total, dry weight [as Cu] | 0 | 12 | 0 | ||
| Cadmium, sludge, total, dry weight [as Cd] | 0 | 12 | 0 | ||
| Flow, in conduit or thru treatment plant | 1 | 11 | 0 | ||
| Mercury, total [as Hg] | 1 | 10 | 0 | ||
| Turbidity, lab, NTU | 2 | 8 | 0 | ||
| Hardness, total [as CaCO3] | 1 | 8 | 0 | ||
| Toxicity [chronic], Ceriodaphnia dubia | 1 | 7 | 0 | ||
| Toxicity [chronic], Pimephales promelas [Fathead Minnow] | 1 | 7 | 0 | ||
| Copper, total recoverable | 1 | 6 | 0 | ||
| Carbon, dissolved organic [as C] | 0 | 6 | 0 | ||
| Arsenic, dissolved [as As] | 0 | 6 | 0 | ||
| Copper, dissolved [as Cu] | 0 | 6 | 0 | ||
| Lead, dissolved [as Pb] | 0 | 6 | 0 | ||
| Zinc, dissolved [as Zn] | 0 | 6 | 0 | ||
| Cadmium, dissolved [as Cd] | 0 | 5 | 0 | ||
| Chromium, dissolved [as Cr] | 0 | 5 | 0 | ||
| Nickel, dissolved [as Ni] | 0 | 5 | 0 | ||
| Arsenic, total recoverable | 1 | 4 | 0 | ||
| Nickel, total recoverable | 1 | 4 | 0 | ||
| Silver total recoverable | 1 | 4 | 0 | ||
| Zinc, total recoverable | 1 | 4 | 0 | ||
| Cadmium, total recoverable | 1 | 4 | 0 | ||
| Lead, total recoverable | 1 | 4 | 0 | ||
| Chromium, total recoverable | 1 | 4 | 0 | ||
| Phosphate, ortho, dissolved [as P] | 0 | 2 | 0 | ||
| Silver, dissolved [as Ag] | 0 | 2 | 0 | ||
| Conductivity | 0 | 1 | 0 |
NPDES ID0021504: inspections, violations and enforcement
NPDES ID0021504: 3 single-event violations
| Date | What EPA recorded | Agency |
|---|---|---|
| June 27, 2026 | WW SSO - Overflow to Dry Land or Building Backup | ST6 |
| January 22, 2026 | WW SSO - Narrative effluent violation | ST6 |
| January 21, 2026 | WW SSO - Overflow to Dry Land or Building Backup | ST6 |
NPDES ID0021504: 2 inspections
| Date | What EPA recorded | Agency |
|---|---|---|
| May 27, 2026 | Evaluation | S |
| February 11, 2026 | Evaluation | S |
NPDES ID0021504: 3 informal enforcement actions
| Date | What EPA recorded | Agency |
|---|---|---|
| March 16, 2026 | No Further Action | State |
| March 13, 2026 | No Further Action | State |
| March 13, 2026 | No Further Action | State |
NPDES ID0021504 (CALDWELL, CITY OF - CALDWELL WWTP): no formal enforcement action on file.
Watch NPDES ID0021504
NPDES ID0021504: one email when its EPA record changes — $99/month.
Permits near NPDES ID0021504
NPDES ID0021504: 51 pollutant rows, 8 dated events; ICIS-NPDES download, loaded October 14, 2026.