Editing Pipeline (section)

==Exposure==
[[File:Keystone jan08 DSC 0173.jpg|thumb|Protest against the [[Keystone Pipeline]]]]
Previous work<ref name="stansbury">{{cite web|last=Stansbury|first=John|title=Analysis of Frequency, Magnitude and Consequence of Worst-Case Spills From the Proposed Keystone XL Pipeline|url=http://watercenter.unl.edu/downloads/2011-Worst-case-Keystone-spills-report.pdf|url-status=dead|archive-url=https://web.archive.org/web/20150117101558/http://watercenter.unl.edu/downloads/2011-Worst-case-Keystone-spills-report.pdf|archive-date=2015-01-17}}</ref> has shown that a 'worst-case exposure scenario' can be limited to a specific set of conditions. Based on the advanced detection methods and pipeline shut-off [[standard operating procedure|SOP]] developed by TransCanada, the risk of a substantive or large release over a short period of time contaminating groundwater with benzene is unlikely.<ref name="potential">{{cite web|last=US State Dept|title=Potential Releases From Project Construction and Operation and Environmental Consequence Analysis|url=http://www.keystonepipeline-xl.state.gov/clientsite/keystonexl.nsf/19_KXL_FEIS_Sec_3.13_Potential_Releases.pdf?OpenFileResource|archive-url=https://web.archive.org/web/20230909100930/https://www.keystonepipeline-xl.state.gov/clientsite/keystonexl.nsf/19_KXL_FEIS_Sec_3.13_Potential_Releases.pdf?OpenFileResource|url-status=dead|archive-date=September 9, 2023|access-date=2 November 2011}}</ref> Detection, shutoff, and remediation procedures would limit the dissolution and transport of benzene. Therefore, the exposure of benzene would be limited to leaks that are below the [[detection limit|limit of detection]] and go unnoticed for extended periods of time.<ref name=stansbury/> Leak detection is monitored through a [[SCADA]] system that assesses pressure and volume flow every 5 seconds. A pinhole leak that releases small quantities that cannot be detected by the SCADA system (<1.5% flow) could accumulate into a substantive spill.<ref name=potential/> Detection of pinhole leaks would come from a visual or [[olfactory]] inspection, aerial surveying, or mass-balance inconsistencies.<ref name=potential/> It is assumed that pinhole leaks are discovered within the 14-day inspection interval, however snow cover and location (e.g. remote, deep) could delay detection. Benzene typically makes up 0.1 – 1.0% of oil and will have varying degrees of [[volatility (chemistry)|volatility]] and dissolution based on environmental factors.

Even with pipeline leak volumes within SCADA detection limits, sometimes pipeline leaks are misinterpreted by pipeline operators to be pump malfunctions, or other problems. The [[Enbridge]] Line 6B [[Kalamazoo River oil spill|crude oil pipeline failure]] in [[Marshall, Michigan]], on July 25, 2010, was thought by operators in Edmonton to be from column separation of the [[dilbit]] in that pipeline. The leak in wetlands along the [[Kalamazoo River]] was only confirmed 17 hours after it happened by a local gas company employee.

===Spill frequency-volume===
Although the [[Pipeline and Hazardous Materials Safety Administration]] (PHMSA) has standard baseline incident frequencies to estimate the number of spills, TransCanada altered these assumptions based on improved pipeline design, operation, and safety.<ref name="potential"/> Whether these adjustments are justified is debatable as these assumptions resulted in a nearly 10-fold decrease in spill estimates.<ref name="stansbury"/> Given that the pipeline crosses 247 miles of the Ogallala Aquifer,<ref>{{cite web|last=US State Dept|title=Environmental Analysis: Water Resources|url=http://www.keystonepipeline-xl.state.gov/clientsite/keystonexl.nsf/09_KXL_FEIS_Sec_3.3_Water_Resources.pdf?OpenFileResource|archive-url=https://web.archive.org/web/20230909100929/https://www.keystonepipeline-xl.state.gov/clientsite/keystonexl.nsf/09_KXL_FEIS_Sec_3.3_Water_Resources.pdf?OpenFileResource|url-status=dead|archive-date=September 9, 2023|access-date=2 November 2011}}</ref> or 14.5% of the entire pipeline length, and the 50-year life of the entire pipeline is expected to have between 11 – 91 spills,<ref name="stansbury"/> approximately 1.6 – 13.2 spills can be expected to occur over the aquifer. An estimate of 13.2 spills over the aquifer, each lasting 14 days, results in 184 days of potential exposure over the 50 year lifetime of the pipeline.
In the reduced-scope worst-case exposure scenario, the volume of a pinhole leak at 1.5% of max flow-rate for 14 days has been estimated at 189,000 barrels or 7.9 million gallons of oil.<ref name="stansbury"/> According to PHMSA's incident database,<ref>{{cite web|last=PHMSA|title=Incident Statistics|url=http://www.phmsa.dot.gov/hazmat/library/data-stats/incidents|access-date=2 November 2011}}</ref> only 0.5% of all spills in the last 10 years were >10,000 barrels.

===Benzene fate and transport===
[[File:Benzene Transport to Groundwater from Oil Spill.pdf|thumb|300px|Scenario for benzene leaching to groundwater]]

Benzene is considered a light [[aromatic hydrocarbon]] with high solubility and high volatility.{{Clarify|reason = Benzene has a solubility of 1.79 g/L in water at 15 °C. Is this considered high?|date = August 2014}} It is unclear how temperature and depth would impact the volatility of benzene, so assumptions have been made that benzene in oil (1% weight by volume) would not volatilize before equilibrating with water.<ref name="stansbury"/>

Using the [[octanol-water partition coefficient]] and a 100-year precipitation event for the area, a worst-case estimate of 75&nbsp;mg/L of benzene is anticipated to flow toward the aquifer.<ref name="stansbury" /> The actual movement of the [[plume (hydrodynamics)|plume]] through [[groundwater]] systems is not well described, although one estimate is that up to 4.9 billion gallons of water in the Ogallala Aquifer could become contaminated with benzene at concentrations above the MCL.<ref name="stansbury" /> The Final Environmental Impact Statement from the State Department does not include a quantitative analysis because it assumed that most benzene will volatilize.<ref name="potential" />

===Previous dilbit spill remediation difficulties===
One of the major concerns over [[dilbit]] is the difficulty in cleaning it up.<ref>[http://www.loe.org/shows/segments.html?programID=12-P13-00027&segmentID=1 "Kalamazoo River Spill Yields Record Fine"], ''[[Living on Earth]]'', July 6, 2012. Lisa Song, a reporter for Inside Climate News, interviewed by Bruce Gellerman. Retrieved 2013-01-01.</ref> When the aforementioned Enbridge Line 6B crude oil pipeline ruptured in Marshall, Michigan in 2010, at least 843,000 gallons of dilbit were spilled.<ref>[https://www.ntsb.gov/doclib/reports/2012/PAR1201.pdf] {{webarchive|url=https://web.archive.org/web/20140928113319/https://www.ntsb.gov/doclib/reports/2012/PAR1201.pdf|date=September 28, 2014}}</ref> After detection of the leak, [[Telescopic handler|booms]] and [[vacuum truck]]s were deployed. Heavy rains caused the river to [[overtop]] existing dams, and carried dilbit 30 miles downstream before the spill was contained. Remediation work collected over 1.1 million gallons of oil and almost 200,000 cubic yards of oil-contaminated sediment and debris from the Kalamazoo River system. However, oil was still being found in affected waters in October 2012.<ref>[http://www.epa.gov/enbridgespill/ "More Work Needed to Clean up Enbridge Oil Spill in Kalamazoo River"], US EPA, October 3, 2012.</ref>