# ALGONQUIN GAS TRANSMISSION, L.L.C. (SPECTRA ENERGY PARTNERS, LP) — Gas transmission and gathering — incident on 2018-05-05

**Citation:** PHMSA Report 20180057  
**Type / status:** incident / historical  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2018-05-05  
**Published:** 2018-06-04

Gas transmission and gathering incident in CROMWELL, MIDDLESEX County, CT. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 5805 NATURAL GAS released, $1,000 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings. PHMSA trend classification: not significant, not serious.

## Document text

Gas transmission and gathering incident in CROMWELL, MIDDLESEX County, CT. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 5805 NATURAL GAS released, $1,000 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20180057.

Operator ID: 288.

Reported incident date: 5/5/2018 1:30.

Location detail: CROMWELL CS

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: A RELIEF VALVE AT THE CROMWELL COMPRESSOR STATION ON THE ALGONQUIN GAS TRANSMISSION PIPELINE SYSTEM RELEASED NATURAL GAS TO ATMOSPHERE AT 1:30 AM ON MAY 5, 2018 WHILE PIPELINE SYSTEM WAS OPERATING BELOW THE RELIEF VALVE'S SET POINT. THE AMOUNT OF NATURAL GAS RELEASED EXCEEDED 5 MILLION CUBIC FEET BEFORE THE RELIEF VALVE WAS ISOLATED. THE APPARENT CAUSE OF THE INADVERTENT OPERATION OF THE RELIEF VALVE WAS ITS CONTROL PILOT DRIFTING OFF SET POINT.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — MALFUNCTION OF CONTROL/RELIEF EQUIPMENT.

PHMSA indexed costs: $18,415 reported total cost, $16,739.923 in 1984 dollars, $21,143.954 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.

## Provenance

- Official: Yes
- Source: <https://data.transportation.gov/api/views/27nc-rsge/files/2b05c2d8-d14a-4c56-ac1c-7d23a4bc31c8?download=true&filename=Gas%20Transmission%20%26%20Gathering%20Incident%20Data%20-%20January%202010%20to%20present.zip>
- Source ID: `phmsa-pipeline-incidents`
- SHA-256: `cc5f14e42b1f4732ae81c1bef2ffc55f93c91a723e59f384848d609a0d9b1b11`
- Retrieved: 2026-08-20T03:30:32.010Z
- Exported: 2026-08-24T09:47:38.141Z
- Document slug: `phmsa-incident-2e2ed5f6065127880e406058`

### Source metadata

```json
{
  "recordKind": "pipeline_incident",
  "datasetType": "gas_transmission_gathering",
  "datasetLabel": "Gas transmission and gathering",
  "datasetPeriod": "January 2010 to present",
  "report": {
    "number": "20180057",
    "supplementalNumber": "30997",
    "type": "SUPPLEMENTAL FINAL",
    "receivedDate": "2018-06-04",
    "receivedDateRaw": "6/4/2018"
  },
  "operator": {
    "id": "288",
    "name": "ALGONQUIN GAS TRANSMISSION, L.L.C. (SPECTRA ENERGY PARTNERS, LP)"
  },
  "incident": {
    "date": "2018-05-05",
    "dateRaw": "5/5/2018 1:30"
  },
  "location": {
    "city": "CROMWELL",
    "county": "MIDDLESEX",
    "state": "CT",
    "postalCode": "06416",
    "latitude": 41.6320605,
    "longitude": -72.6727214,
    "type": "OPERATOR-CONTROLLED PROPERTY",
    "details": {
      "DESIGNATED_NAME": "CROMWELL CS"
    },
    "facilityName": "CROMWELL COMPRESSOR STATION"
  },
  "cause": {
    "category": "EQUIPMENT FAILURE",
    "details": {
      "CAUSE_DETAILS": "MALFUNCTION OF CONTROL/RELIEF EQUIPMENT",
      "NARRATIVE": "A RELIEF VALVE AT THE CROMWELL COMPRESSOR STATION ON THE ALGONQUIN GAS TRANSMISSION PIPELINE SYSTEM RELEASED NATURAL GAS TO ATMOSPHERE AT 1:30 AM ON MAY 5, 2018 WHILE PIPELINE SYSTEM WAS OPERATING BELOW THE RELIEF VALVE'S SET POINT. THE AMOUNT OF NATURAL GAS RELEASED EXCEEDED 5 MILLION CUBIC FEET BEFORE THE RELIEF VALVE WAS ISOLATED. THE APPARENT CAUSE OF THE INADVERTENT OPERATION OF THE RELIEF VALVE WAS ITS CONTROL PILOT DRIFTING OFF SET POINT."
    }
  },
  "consequences": {
    "fatalities": 0,
    "injuries": 0,
    "commodity": "NATURAL GAS",
    "release": "5805",
    "propertyDamage": 1000,
    "estimatedOperatorCost": 0,
    "estimatedEmergencyCost": 0,
    "estimatedEnvironmentalCost": null,
    "ignition": "NO",
    "explosion": "NO",
    "evacuated": 0,
    "raw": {
      "FATAL": "0",
      "INJURE": "0",
      "UNINTENTIONAL_RELEASE": "5805",
      "EST_COST_PROP_DAMAGE": "1000",
      "PRPTY": "18415"
    }
  },
  "provenance": {
    "viewId": "27nc-rsge",
    "viewUrl": "https://data.transportation.gov/api/views/27nc-rsge",
    "assetId": "2b05c2d8-d14a-4c56-ac1c-7d23a4bc31c8",
    "archiveFilename": "Gas Transmission & Gathering Incident Data - January 2010 to present.zip",
    "archiveSha256": "fe0b136ca4b00ac987a8bc2e195098accf910d97512c5fc3b59e62d9da5f674e",
    "memberPath": "incident_gas_transmission_gathering_jan2010_present.txt",
    "memberSha256": "b435f2a25718cf54c54e00294e6788c4f9c6860e02fb86355e75d294c243c4dd",
    "rowNumber": 976,
    "rowSha256": "5efe879e93e034542c8a6e21d423918cf42034182744ab9aec6db8f6b957d9ef"
  },
  "caveat": "Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.",
  "operatorReported": true,
  "finalAgencyFinding": false,
  "flaggedAnalysis": {
    "dataAsOf": "2026-07-31",
    "flags": {
      "fireFirst": null,
      "significant": false,
      "serious": false
    },
    "standardizedCause": {
      "sevenCategory": "MATERIAL/WELD/EQUIP FAILURE",
      "sevenSubcategory": "MALFUNCTION OF CONTROL/RELIEF EQUIPMENT",
      "eightCategory": "EQUIPMENT FAILURE",
      "eightSubcategory": "MALFUNCTION OF CONTROL/RELIEF EQUIPMENT"
    },
    "costs": {
      "reported": 18415,
      "in1984Dollars": 16739.92314104766,
      "currentYearDollars": 21143.954424937576
    },
    "caveat": "PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.",
    "provenance": {
      "sourceUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/data_statistics/pipeline/PHMSA_Pipeline_Safety_Flagged_Incidents.zip",
      "landingPageUrl": "https://www.phmsa.dot.gov/data-and-statistics/pipeline/pipeline-incident-flagged-files",
      "catalogUrl": "https://data.transportation.gov/Pipelines-and-Hazmat/Pipeline-Incident-Flagged-Files/qdme-9bbm",
      "retrievalMode": "official_live",
      "archivedAt": null,
      "archiveSha256": "317e6a3e16d60b9b677efe391dc40258b5dd7ead83fb8bea74cb553cedfbbdec",
      "workbook": "gtggungs2010toPresent.xlsx",
      "sheet": "gtggungs2010toPresent",
      "rowNumber": 1021,
      "rowSha256": "195c7d5f0d259e7456909292544a9853220c1181c02effef408589a39011a7a4"
    }
  },
  "jurisdiction": "US",
  "operatorName": "ALGONQUIN GAS TRANSMISSION, L.L.C. (SPECTRA ENERGY PARTNERS, LP)"
}
```