Page 335 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

14/312Absolute Risk Estimates
Table 14.34 Sample "distance of concern" for natural gas pipelines Table 14.36 Summary of setback requirements in codes. standards,
and other guides
Characteristic Distance u?
Code, standard, Setback requirement
Population class 3 or4 660 guide for tankporn public (jii Yariables
Hard-to-evacuate facilities (schools, day cares, 800
prisons, elder care, rehabilitation clinics, etc.) IFC 2000 (adopted 5-175 Tank size and type
Hard-to-evacuate facilities, pipe diameter 30 in., 1000 in Alaska and of adjacent use
and pressures > 1000 psig proposed in
Areas ofpublic assembly 660 municipality
Areas of public assembly, pipe diameter > 30 in., 1000 ofhchorage
and pressures > 1000 psig UFC 2000 5-175 Tank size and type
@re-2001 in of adjacent
Alaska)
UFC 1997 50-75 Type ofadjacent use
APA Performance standard Site specific and
In cases of HVL pipeline modeling, default distances of process driven
1000 to 1500 ft are commonly seen, depending on pipeline HUD Buildings: 130-155 Product and tank
diameter, pressure, and product characteristics. HVL releases People: 650-775 size
cases are very sensitive to weather conditions and carry the USCG (open-water 150-> 10,000 Diameter of spill
potential for unconfined vapor cloud explosions, each of which fire)
can greatly extend impact zones to more than a mile. (See also
the discussion on land-use issues in a following section for Source: Golder and Associates, "Report on Hazard Study for the Bulk
thoughts on setback distances that are logically related to haz- POL Facilities in the POA Area," prepared for Municipality of
Anchorage POL Task Force, August 9,2002.
ard zones.) Notes: APA. American Planning Association; USCG. US. Coast Guard
A draft Michigan regulatory document suggests setback dis- (USCG); HUD, Department of Housing and Urban Development
tances for buried high-pressure gas pipelines based on the HUD (HUD). The National Fire Protection Association (NFPA) publishes
guideline thermal radiation criteria. The proposed setback dis- NFPA Code 30, Flammable and Combustible Liquids Code, 2000
tances are tabularized for pipeline diameters (from 4 to 26 in.) Edition. The lnternational Code Council publishes the lnternational
and pressures (from 400 to 1800 psig in 100-psig increments). Fife Code 2000 (IFC). The Western Fire Chiefs Association publishes
The end points of the various tables are shown inTabIe 14.35. It the Unifofm Fife Code 2000 Edition (UFC).
is not known ifthese distances will be codified into regulations.
In some cases, the larger distances might cause repercussions
regarding alternative land uses for existing pipelines. Land use
regulations can have significant social, political, and economic
ramifications, as are discussed in Chapter 15. Any time default hazard zone distances replace situation-
The U.S. Coast Guard (USCG) provides pdance on the safe specific calculations, the defaults should be validated by actual
distance for people and wooden buildings from the edge of a calculations to ensure that they encompass most, ifnot all, pos-
burning spill in their Hazard Assessment Handbook, sible release scenarios for the pipeline systems being evaluated.
Commandant Instruction Manual M 16465.13 . Safe distances
range widely depending on the size of the burning area, which
is assumed to be on open water. For people, the distances vary XI. Case studies
from 150 to 10,100 ft, whereas for buildings the distances vary
from 32 to 1900 ft for the same size spill. The spill radii for The following case stumes illustrate some techmques that are
these distances range between 10 and 2000 ft [35]. more numerically rigorous in producing absolute risk esti-
A summary of setback distances was published in a consult- mates. These are all extracted from public domain documents
ant report and is shown in Table 14.36. readily obtained from Internet sources and/or proceedings from
regulatory approval processes. Company names and locations
have been changed since the focus here is solely on illustrating
Table 14.35 Sample proposed setback distances the technique. Other minor modifications to the extracted
materials include the changing of table, figure, and reference
Minimum setback Ifr, numbering to correspond to the sequencing in this book.
4-in. pipeline 26-in.pipeline Case Study A: natural gas
Facility a1400psig at 1800psig
Quantitative risk calculations for XYZpipeline
Multifamily developments
(10,000 Btu/hr-A2 criteria) 40 318 The following case study illustrates the estimation ofrisk using
Elderly and handicapped units 67 772 calculated hazard zones and frequency-based failure frequen-
Unprotected areas of
congregation cies for a natural gas pipeline. Portions of this discussion were
(450 Btuihr-A2 criteria) 147 3164 extracted or are based on Ref. [18], in which a proposed high-
Primary egress 40 1489 pressure gas pipeline, having both onshore and offshore com-
ponents, was being evaluated. For this example, the proposed