Excerpts from the SCC Accident Investigation Report

FCFD has closed its investigation and concluded that the explosion and subsequent fire at 4303 Lees Corner Road was accidental and created by the release of natural gas. The Fire Department’s report further concludes that the probable ignition source was the open flame water heater located in the first floor utility room. The FCFD’s report did not indicate the source of the natural gas. A copy of the FCFD’s report is presented an Attachment No. 10 to this report.

Based upon its investigation, Staff notes the following findings:

1. Just prior to the incident, a resident reported a smell of gas in the road in front of Brookfield Elementary School, approximately 250 yards from the incident site;
2. The homeowner at 4304 Willoughby Court, located immediately behind 4303 Lees Corner Road, noticed a strong smell of gas at the intersection of Pennsboro Drive and Lees Corner Road. This homeowner was the person who called 911 and reported the strong odor of gas;
3. Another resident noticed a strong smell of gas between the curb and sidewalk across the street from 4303 Lees Corner Road;
4. The Fire Department reported "bubbling" at the curb in front of 4303 Lees Corner Road;
5. Soon after arrival to the scene, the Fire Department measured five percent and eight percent of the LEL of natural gas in the homes located at 4300 and 4302 Lees Corner Road respectively. These levels dropped to zero percent by 2:00 a.m. December 20, 2010 after the leak on the service line to 4303 Lees Corner Road was repaired;
6. The natural gas was odorized such that it was readily detectable by a person with a normal sense of smell at approximately 0.17% gas in air;
7. WGL did not document the initial combustible gas readings taken upon their arrival to the site. The only documented readings taken occurred after the leak on the service line to 4303 Lees Corner Road had been repaired;
8. Based on the information from several residents in the area, and the Fire Department, gas was migrating from the leak on the service line. The Company did not fully identify the gas migration area. The barholes and testing performed as a result of this incident by WGL crews was to find the leak. The extent of the gas migration or its path was never determined;
9. WGL did not perform any barhole testing past the curb at 4303 Lees Corner Road. According to the Company, barhole testing was not conducted because the Fire Department had restricted access to the area. However, Staff's discussions with the Fire Department indicated that permission to perform such testing up to the front of the structure would have been granted upon request;
10. Severe corrosion created a number of holes in the natural gas service line serving 4303 Lees Corner Road at the connection to the service tee on the steel main. The piping had been weakened to the extent that a portion of the service line broke off when it was removed from the ground. Natural gas would have been escaping from these holes at 55 psig;
11. WGL did not take any readings of combustible gas in the soil prior to beginning to aspirate to remove residual natural gas in the ground;
12. An open ended section of customer owned natural gas fuel line terminating on the second floor of the home was found. Testing of the threads on the open end did not identify any constituents of thread sealant that may have been placed on the pipe if a cap was installed. As the interior fuel lines operate at approximately 0.25 psig, gas would have been escaping from this opening at that pressure until the service regulator ceased to function properly as a result of damage from the incident;
13. The homeowner built two additions to the home and gave notice of the construction to Virginia's notification center on April 1, 2008. WGL marked the service line to 4303 Lees Corner Road on April 3, 2008. The homeowner or his contractor did not request the Company to move the gas service line so it would not have been in conflict with the home addition;
14. The addition built in 2008 on the left side of the house was built on a concrete slab poured directly over WGL's gas service line;
15. WGL received notice of the proposed construction for the additions to the home via the notification center on April 1, 2008 and marked the gas service line on April 3, 2008. The Company did not identify that the addition was being constructed over its gas service line and that the gas service line should be moved;
16. WGL performed a leak survey of its facilities in this area on June 1, 2009. No record was provided that demonstrated the service line to 4303 Lees Corner Road was surveyed for leaks under the house;
17. The Fire Department concluded that the incident was caused by the accidental release of natural gas. The origin of the natural gas was not determined by the Fire Department; and
18. WGL concluded that two potential sources of the natural gas existed. As a result, the Company states that the "... root cause of this incident remains undetermined." WGL neither collected nor documented important information and, therefore, certain necessary facts are unknown such as the extent of the gas migration and the combustible gas readings in the soil taken prior to the service line repair and aspiration of the soil. The testing of the open ended section of the customer owned fuel line terminating on the second floor of the home did not conclusively show this pipe was capped. Accordingly, the Division of Utility and Railroad Safety cannot determine the source of the natural gas that caused the December 19, 2010, accident at 4303 Lees Corner Road in Chantilly, Virginia.

Below is a list of "probable violations" of the Commission's Standards that the Division of Utility and Railroad Safety has noted as a result of its investigation of this incident. The Division's enforcement process provides WGL an opportunity to review this report and respond to the "probable violations", before an enforcement action is recommended to the Commission.

1. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Operations and Maintenance Standard, Section 3020, by not recording test readings of natural gas discovered on Company's Maintenance Field Orders on December 19, 2010 after the incident that occurred at 4303 Lees Corner Road, Chantilly, Virginia;
2. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Emergency Plan Standard, Section 1070, by not documenting specific leakage test readings and locations of natural gas discovered as part of the Company's on-site investigation on December 19, 2010 at the incident that occurred at 4303 Lees Corner Road, Chantilly, Virginia;
3. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Operations and Maintenance Standard, Section 4050, which was developed to comply with 49 C.F.R. § 192.721, by not observing a condition that may affect the safety and operations of a pipeline. Specifically the service line that was located under a concrete foundation at 4303 Lees Corner Road, Chantilly, Virginia was not identified as a condition that impacted WGL's facilities;
4. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Operations and Maintenance Standard, Section 4010, by not performing a complete leak survey on June 1, 2009 of a residential service line as a result of the service line being located under a concrete foundation at 4303 Lees Corner Road, Chantilly, Virginia;
5. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Operations and Maintenance Standard, Section 4010, by not identifying and recording a "service violation" of the service line that was located under a concrete foundation at 4303 Lees Corner Road, Chantilly, Virginia during the June 1, 2009 leak survey;
6. 49 C.F.R. § 192.605 (a) - Failing to follow the Company's Operations and Maintenance Standard, Section 3019, by not documenting the natural gas migration on December 19, 2010 after the incident that occurred at 4303 Lees Corner Road, Chantilly, Virginia;
7. 49 C.F.R. § 192.605 (b)(1) - Failing to have a procedure for the temporary abandonment of copper service lines.
8. 49 C.F.R. § 192.605 (b)(1) - Failing to have a procedure for reuse of the polymer isolation sleeve on copper service lines.
9. 49 C.F.R. § 192.467 (d) – Failing to make inspections and tests to assure that the electrical isolation of the copper service line from the cathodically protected steel main was adequate.
10. 49 C.F.R. § 192.614 (a) – Failing to monitor excavations over Company facilities as required by Company's Operations and Maintenance Standard 4099, Damage Prevention Monitoring, developed to comply with § 192.614 (c)(6).
11. Failure to comply with the Commission Order of Settlement in Case No. URS-2007- 002384 by not prominently displaying Virginia's damage prevention educational messages on the outside of the incident command trailer.