Class location code in 192.5 states:
- 192.5 Class locations.
(a) This section classifies pipeline locations for purposes of this part. The following criteria apply to classifications under this section.
(1) A “class location unit” is an onshore area that extends 220 yards (200 meters) on either side of the centerline of any continuous 1- mile (1.6 kilometers) length of pipeline.
(2) Each separate dwelling unit in a multiple dwelling unit building is counted as a separate building intended for human occupancy.
(b) Except as provided in paragraph (c) of this section, pipeline locations are classified as follows:
(1) A Class 1 location is:
(i) An offshore area; or
(ii) Any class location unit that has 10 or fewer buildings intended for human occupancy.
(2) A Class 2 location is any class location unit that has more than 10 but fewer than 46 buildings intended for human occupancy.
(3) A Class 3 location is:
(i) Any class location unit that has 46 or more buildings intended for human occupancy; or
(ii) An area where the pipeline lies within 100 yards (91 meters) of either a building or a small, well-defined outside area (such as a playground, recreation area, outdoor theater, or other place of public assembly) that is occupied by 20 or more persons on at least 5 days a week for 10 weeks in any 12-month period. (The days and weeks need not be consecutive.)
(4) A Class 4 location is any class location unit where buildings with four or more stories above ground are prevalent.
(c) The length of Class locations 2, 3, and 4 may be adjusted as follows:
(1) A Class 4 location ends 220 yards (200 meters) from the nearest building with four or more stories above ground.
(2) When a cluster of buildings intended for human occupancy requires a Class 2 or 3 location, the class location ends 220 yards (200 meters) from the nearest building in the cluster.
(d) An operator must have records that document the current class location of each gas transmission pipeline segment and that demonstrate how the operator determined each current class location in accordance with this section.
What is not stated in 192.5©(2) is the allowable calculation methods of determining endpoint from a cluster. Although not in code it is specified in a formal interpretation that PHMSA did and includes:
PI-95-0100
April 13, 1995
Mr. Donald R. Linger
Vice President, Transmission
Algonquin Gas Transmission Company
1284 Soldiers Field Road
Boston, MA 02135
Dear Mr. Linger:
This responds to your letter of April 13, 1995, which expresses Algonquin’s views on two methods for determining boundary adjustments for class locations under 49 CFR § 192.5(f). Your letter also provides information from a poll of nineteen interstate gas pipeline operators pertaining to their understanding of § 192.5.
You agree that the “perpendicular/parallel method” described in my letter to you of January 30, 1995, complies with the requirements for determining location end points for clusters. But, you also believe that the “arc method,” not considered in my letter, also complies with the language and intent of § 192.5(f).
To illustrate the validity of the “arc method” (using an arc intercept), your letter includes a sketch showing a “hypothetical scenario” of the two methods as they apply to two groups of 46 buildings located on one side of a gas pipeline. The group containing Building “A” is identified as a cluster. For your information, I have enclosed a copy of that sketch (with handwritten revisions) to illustrate the following observations:
- Under the “arc method” an operator would install 36 feet of Class 3 pipe and 623 feet (659-36 = 623 feet) of the thinner wall Class 2 pipe. However, under the “perpendicular/parallel method” an operator would install 659 feet of the thicker wall Class 3 pipe. Nevertheless, with expanding urbanization, the cluster with Building “A” would probably be closer to the pipeline than the hypothetical scenario in your sketch. Such a scenario has been added to the sketch to illustrate that the length of Class 3 pipe, determined by the “arc method,” would approach the length determined by the “perpendicular/parallel method.”
- (2) Since § 192.5 applies only to buildings that are wholly or partially inside the class location unit corridor, there is no need for a minimum distance between the extremities of Building “A” and Building “B,” because the 661 foot distance to Building “B” excludes, by one foot, Building “B” and other buildings in that group.
We have looked into your statement on the extent of use of the “arc method” and find that it has been used for many years by a large number of interstate gas operators. Consequently, we have reconsidered our interpretation in my letter of January 30, 1995, and find both the “arc method” and the “perpendicular/parallel method” to be acceptable for determining the 220 yard boundary for the cluster of buildings in § 192.5(f).
The attached PowerPoint excerpt illustrates the two methods.
In summary, interpretations like this serve to clarify code. When in doubt about code clarity, you can:
- search interpretations on the PHMSA website: PHMSA Guidance | PHMSA (dot.gov)
- Read FAQs for different code section on the PHMSA websites: Pipeline Risk Management Information System (PRIMIS) (dot.gov) FAQs are not code enforceable but offer guidance
- Search PHMSA enforcement guidance available from the PHSMA FOIA reading room: FOIA Library/Electronic Reading room | PHMSA (dot.gov)
- Search PHMSA enforcement history: Enforcement Data | PHMSA (dot.gov)
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