Incident details
Operator, cause, commodity and consequences with raw source fields.
GTG incident on 2025-08-06 — NE
Operator
Northern Natural Gas Co
Cause
Equipment Failure
Commodity
Natural Gas
Program
GTG
Damage and Injuries
0 fatalities
0 injuries
Property damage (nominal)
$0
Incident datetime
2025-08-06 14:05
Report number
Location
NE
Narrative
At 14:05 hours on august 6, 2025, a northern natural gas operations technician discovered a relief valve venting at the minneapolis, minnesota no. 1r (station no. 753160) in carver, minnesota. The operations team contacted the local fire department and sheriffs department to support with the closing of county road 40. The road was successfully closed at 14:24 hours until the operations team was able to divert flow through the station bypass and successfully stopped the relief valve venting at 14:28 hours. The county road was then reopened at 14:35 hours. During the onsite inspection of the relief valve the operations team, it was believed that the relief valve and relief pilot valve were damaged by debris preventing it from reseating and closing. The debris was suspected to have originated from recent nearby construction on the pipeline. When the regulator strainers were examined, they were found to have become dislodged, releasing any debris they held. The relief valve and relief valve pilot were rebuilt on-site and verified for proper operation. At 17:00 hours on august 7, 2025, the station was put back into normal operations. Following the incident, the relief valve pilot was sent to the vendor to be examined by a material specialist. The specialist found that the pilot disk had weakened causing the pilot to fail open damaging the relief valve boot due to the high velocity of gas venting through the relief valve. This style of pilot disk was known by specialist to weaken over time, and it is no longer being used by the vendor. Northern natural gas is looking at replacing all pilot disks of this style.
Detailed record list
Report Received Date
2025-09-02 00:00:00
Iyear
2025
Report Number
20250099
Supplemental Number
41523
Report Type
Supplemental Final
Operator Id
13750
Name
Northern Natural Gas Co
Operator Street Address
1111 South 103rd Street
Operator City Name
Omaha
Operator State Abbreviation
NE
Operator Postal Code
68124
Local Datetime
2025-08-06 14:05:00
Time Zone
Central
Daylight Savings Ind
Yes
Location Latitude
44.732578
Location Longitude
-93.668255
Nrc Rpt Num
1439074
Nrc Rpt Datetime
2025-08-06 15:15:00
Additional Nrc Report Numbers
1439260
Commodity Released Type
Natural Gas
Unintentional Release
5595
Intentional Release
0
Accompanying Liquid
0
Fatality Ind
No
Fatal
0
Injury Ind
No
Injure
0
Status When Identified
Normal Operation, Includes Pauses During Maintenance
Shutdown Due Accident Ind
No
Shutdown Explain
The Station By-Pass Piping Was Used To Maintain Delivery To The Customer.
Communication State Fed Ind
Yes
Party Initiated Communication
Operator
Initial Responder Com Datetime
2025-08-06 14:13:00
Ignite Ind
No
Num Pub Evacuated
0
Incident Identified Datetime
2025-08-06 14:05:00
On Site Datetime
2025-08-06 14:08:00
Confirmed Discovery Datetime
2025-08-06 14:45:00
On Off Shore
Onshore
Onshore State Abbreviation
Mn
Onshore Postal Code
55315
Onshore City Name
Not Within A Municipality
Onshore County Name
Carver
Designated Location
Not Applicable
Pipe Fac Name
Minneapolis Mn #1r Town Border Station
Segment Name
753160
Federal
No
Location Type
Operator-Controlled Property
Incident Area Type
Aboveground
Incident Area Subtype
Typical Aboveground Facility Piping Or Appurtenance
Crossing
No
Pipe Facility Type
Interstate
System Part Involved
Onshore Regulator/metering Station Equipment And Piping
Item Involved
Regulator/control Valve
Installation Year
2015
Manufactured Year
2014
Material Involved
Carbon Steel
Release Type
Other
Release Type Details
Relief Valve Went Off And Then Could Not Reseat Due To The Valve Boot Being Damaged.
Class Location Type
Class 1 Location
Could Be Hca
No
Pir Radius
185
Heat Damage Ind
No
Non Heat Damage Ind
No
Did Occur In Mca Ind
No
Est Cost Oper Paid
0
Est Cost Unintentional Release
15330
Est Cost Intentional Release
0
Est Cost Prop Damage
0
Est Cost Emergency
500
Est Cost Other
0
Gas Cost In Mcf
2.74
Prpty
15830
Num Persons Hosp Not Ovnght
0
Num Injured Treated By Emt
0
Num Resident Building Affctd
0
Num Business Building Affctd
0
Wildlife Impact Ind
No
Accident Psig
631
Gas Flow In Pipe In Mcf
314600
Mop Psig
1000
Mop Cfr Section
192.619(A)(2)
Maop Established Date
1982-10-01 00:00:00
Maop Reversal Flow Ind
No
Accident Pressure
Pressure Did Not Exceed Maop
Pressure Restriction Ind
No
Gas Required Odorized Ind
No
Pipeline Function
Transmission System
Scada In Place Ind
Yes
Scada Operating Ind
Yes
Scada Functional Ind
Yes
Scada Detection Ind
No
Scada Conf Ind
No
Accident Identifier
Local Operating Personnel, Including Contractors
Operator Type
Operator Employee
Investigation Status
No, the operator did not find that an investigation of the controller(s) actions or control room issues was necessary due to: (provide an explanation for why the operator did not investigate)
Investigation Status Details
The event was caused by a failure of the station relief valve due to damage to the relief valve internals which prevented the valve from reseating.
Employee Drug Test Ind
No
Contractor Drug Test Ind
No
Cause
Equipment Failure
Cause Details
Malfunction Of Control/relief Equipment
Eq Failure Type
Malfunction Of Control/relief Equipment
Relief Valve Ind
Yes
Eq Additional Other Ind
Yes
Eq Additional Other Details
Soft Goods Of The Relief Valve Got Damaged And The Valve Could Not Reseat.
Preparer Name
W**** C*****
Preparer Title
Sr Pipeline Integrity Engineer
Preparer Email
W***********@n****.com
Preparer Telephone
4026764066
Local Contact Name
W**** C*****
Local Contact Email
W***********@n****.com
Local Contact Telephone
4026764066
Authorizer Name
T** C******
Authorizer Title
Vp Pipeline Safety And Risk
Authorizer Telephone
4023987715
Authorizer Email
T*************@n****.com
Narrative
At 14:05 hours on august 6, 2025, a northern natural gas operations technician discovered a relief valve venting at the minneapolis, minnesota no. 1r (station no. 753160) in carver, minnesota. The operations team contacted the local fire department and sheriffs department to support with the closing of county road 40. The road was successfully closed at 14:24 hours until the operations team was able to divert flow through the station bypass and successfully stopped the relief valve venting at 14:28 hours. The county road was then reopened at 14:35 hours. During the onsite inspection of the relief valve the operations team, it was believed that the relief valve and relief pilot valve were damaged by debris preventing it from reseating and closing. The debris was suspected to have originated from recent nearby construction on the pipeline. When the regulator strainers were examined, they were found to have become dislodged, releasing any debris they held. The relief valve and relief valve pilot were rebuilt on-site and verified for proper operation. At 17:00 hours on august 7, 2025, the station was put back into normal operations. Following the incident, the relief valve pilot was sent to the vendor to be examined by a material specialist. The specialist found that the pilot disk had weakened causing the pilot to fail open damaging the relief valve boot due to the high velocity of gas venting through the relief valve. This style of pilot disk was known by specialist to weaken over time, and it is no longer being used by the vendor. Northern natural gas is looking at replacing all pilot disks of this style.
| Report Received Date | 2025-09-02 00:00:00 |
|---|---|
| Iyear | 2025 |
| Report Number | 20250099 |
| Supplemental Number | 41523 |
| Report Type | Supplemental Final |
| Operator Id | 13750 PHMSA Enforcement |
| Name | Northern Natural Gas Co |
| Operator Street Address | 1111 South 103rd Street |
| Operator City Name | Omaha |
| Operator State Abbreviation | NE |
| Operator Postal Code | 68124 |
| Local Datetime | 2025-08-06 14:05:00 |
| Time Zone | Central |
| Daylight Savings Ind | Yes |
| Location Latitude | 44.732578 Google Maps OpenStreetMap |
| Location Longitude | -93.668255 Google Maps OpenStreetMap |
| Nrc Rpt Num | 1439074 NRC Report How to search |
| Nrc Rpt Datetime | 2025-08-06 15:15:00 |
| Additional Nrc Report Numbers | 1439260 |
| Commodity Released Type | Natural Gas |
| Unintentional Release | 5595 |
| Intentional Release | 0 |
| Accompanying Liquid | 0 |
| Fatality Ind | No |
| Fatal | 0 |
| Injury Ind | No |
| Injure | 0 |
| Status When Identified | Normal Operation, Includes Pauses During Maintenance |
| Shutdown Due Accident Ind | No |
| Shutdown Explain | The Station By-Pass Piping Was Used To Maintain Delivery To The Customer. |
| Communication State Fed Ind | Yes |
| Party Initiated Communication | Operator |
| Initial Responder Com Datetime | 2025-08-06 14:13:00 |
| Ignite Ind | No |
| Num Pub Evacuated | 0 |
| Incident Identified Datetime | 2025-08-06 14:05:00 |
| On Site Datetime | 2025-08-06 14:08:00 |
| Confirmed Discovery Datetime | 2025-08-06 14:45:00 |
| On Off Shore | Onshore |
| Onshore State Abbreviation | Mn |
| Onshore Postal Code | 55315 |
| Onshore City Name | Not Within A Municipality |
| Onshore County Name | Carver |
| Designated Location | Not Applicable |
| Pipe Fac Name | Minneapolis Mn #1r Town Border Station |
| Segment Name | 753160 |
| Federal | No |
| Location Type | Operator-Controlled Property |
| Incident Area Type | Aboveground |
| Incident Area Subtype | Typical Aboveground Facility Piping Or Appurtenance |
| Crossing | No |
| Pipe Facility Type | Interstate |
| System Part Involved | Onshore Regulator/metering Station Equipment And Piping |
| Item Involved | Regulator/control Valve |
| Installation Year | 2015 |
| Manufactured Year | 2014 |
| Material Involved | Carbon Steel |
| Release Type | Other |
| Release Type Details | Relief Valve Went Off And Then Could Not Reseat Due To The Valve Boot Being Damaged. |
| Class Location Type | Class 1 Location |
| Could Be Hca | No |
| Pir Radius | 185 |
| Heat Damage Ind | No |
| Non Heat Damage Ind | No |
| Did Occur In Mca Ind | No |
| Est Cost Oper Paid | 0 |
| Est Cost Unintentional Release | 15330 |
| Est Cost Intentional Release | 0 |
| Est Cost Prop Damage | 0 |
| Est Cost Emergency | 500 |
| Est Cost Other | 0 |
| Gas Cost In Mcf | 2.74 |
| Prpty | 15830 |
| Num Persons Hosp Not Ovnght | 0 |
| Num Injured Treated By Emt | 0 |
| Num Resident Building Affctd | 0 |
| Num Business Building Affctd | 0 |
| Wildlife Impact Ind | No |
| Accident Psig | 631 |
| Gas Flow In Pipe In Mcf | 314600 |
| Mop Psig | 1000 |
| Mop Cfr Section | 192.619(A)(2) View CFR 49 §192 |
| Maop Established Date | 1982-10-01 00:00:00 |
| Maop Reversal Flow Ind | No |
| Accident Pressure | Pressure Did Not Exceed Maop |
| Pressure Restriction Ind | No |
| Gas Required Odorized Ind | No |
| Pipeline Function | Transmission System |
| Scada In Place Ind | Yes |
| Scada Operating Ind | Yes |
| Scada Functional Ind | Yes |
| Scada Detection Ind | No |
| Scada Conf Ind | No |
| Accident Identifier | Local Operating Personnel, Including Contractors |
| Operator Type | Operator Employee |
| Investigation Status | No, the operator did not find that an investigation of the controller(s) actions or control room issues was necessary due to: (provide an explanation for why the operator did not investigate) |
| Investigation Status Details | The event was caused by a failure of the station relief valve due to damage to the relief valve internals which prevented the valve from reseating. |
| Employee Drug Test Ind | No |
| Contractor Drug Test Ind | No |
| Cause | Equipment Failure |
| Cause Details | Malfunction Of Control/relief Equipment |
| Eq Failure Type | Malfunction Of Control/relief Equipment |
| Relief Valve Ind | Yes |
| Eq Additional Other Ind | Yes |
| Eq Additional Other Details | Soft Goods Of The Relief Valve Got Damaged And The Valve Could Not Reseat. |
| Preparer Name | W**** C***** |
| Preparer Title | Sr Pipeline Integrity Engineer |
| Preparer Email | W***********@n****.com |
| Preparer Telephone | 4026764066 |
| Local Contact Name | W**** C***** |
| Local Contact Email | W***********@n****.com |
| Local Contact Telephone | 4026764066 |
| Authorizer Name | T** C****** |
| Authorizer Title | Vp Pipeline Safety And Risk |
| Authorizer Telephone | 4023987715 |
| Authorizer Email | T*************@n****.com |
| Narrative | At 14:05 hours on august 6, 2025, a northern natural gas operations technician discovered a relief valve venting at the minneapolis, minnesota no. 1r (station no. 753160) in carver, minnesota. The operations team contacted the local fire department and sheriffs department to support with the closing of county road 40. The road was successfully closed at 14:24 hours until the operations team was able to divert flow through the station bypass and successfully stopped the relief valve venting at 14:28 hours. The county road was then reopened at 14:35 hours. During the onsite inspection of the relief valve the operations team, it was believed that the relief valve and relief pilot valve were damaged by debris preventing it from reseating and closing. The debris was suspected to have originated from recent nearby construction on the pipeline. When the regulator strainers were examined, they were found to have become dislodged, releasing any debris they held. The relief valve and relief valve pilot were rebuilt on-site and verified for proper operation. At 17:00 hours on august 7, 2025, the station was put back into normal operations. Following the incident, the relief valve pilot was sent to the vendor to be examined by a material specialist. The specialist found that the pilot disk had weakened causing the pilot to fail open damaging the relief valve boot due to the high velocity of gas venting through the relief valve. This style of pilot disk was known by specialist to weaken over time, and it is no longer being used by the vendor. Northern natural gas is looking at replacing all pilot disks of this style. |
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