# NORTHERN NATURAL GAS CO — Warning Letter

**Citation:** CPF 320071010W  
**Type / status:** enforcement / historical  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** Not stated  
**Published:** 2007-05-21

CLOSED warning letter citing 191.7.

## Document text

Warning Letter involving NORTHERN NATURAL GAS CO. PHMSA's enforcement data identifies the cited regulation as 191.7. The case was opened on 2007-05-21 and is reported as closed as of 2007-05-21. Open the official case record for notices, responses, orders, and the latest status.

Official case documents:

320071010W_operator response to warning letter_06052007.pdf: https://primis.phmsa.dot.gov/enforcement-documents/320071010W/320071010W_operator%20response%20to%20warning%20letter_06052007.pdf

## Provenance

- Official: Yes
- Source: <https://primis.phmsa.dot.gov/enforcement-data/case/320071010W>
- Source ID: `phmsa-enforcement`
- SHA-256: `981d72aa7645859dae5baf2fa53045c90025db87393658485450168cb982bb4b`
- Retrieved: 2026-08-20T04:44:44.458Z
- Exported: 2026-08-23T00:54:44.684Z
- Document slug: `phmsa-enforcement-320071010w`

### Source metadata

```json
{
  "cpf": "320071010W",
  "operator": "NORTHERN NATURAL GAS CO",
  "region": "Central",
  "pipelineType": "GAS INTERSTATE ONSHORE",
  "caseStatus": "CLOSED",
  "citedSections": [
    "191.7"
  ],
  "dataAsOf": "08/04/2026 12PM",
  "caseDataAsOf": "2026-08-04",
  "attachmentCount": 1,
  "attachments": [
    {
      "name": "320071010W_operator response to warning letter_06052007.pdf",
      "url": "https://primis.phmsa.dot.gov/enforcement-documents/320071010W/320071010W_operator%20response%20to%20warning%20letter_06052007.pdf",
      "bytes": 37619,
      "category": "party_submission"
    }
  ],
  "extractedAgencyDocumentCount": 0,
  "attachmentPolicy": "Official attachment links are retained. Agency-issued documents may also include a verified local PDF and page-level text representation.",
  "jurisdiction": "US",
  "operatorName": "NORTHERN NATURAL GAS CO"
}
```