<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>2105100 - Disclosure - Asset Retirement Obligations</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>D2013Q2YTD</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0000751652</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="6 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_AssetRetirementObligationAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Asset Retirement Obligation [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_AssetRetirementObligationDisclosureTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;text-align:justify;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;Note 5 - Asset Retirement Obligations&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Questar records an asset retirement obligation (ARO) along with an increase to the carrying value of the related property, plant and equipment when there is a legal obligation associated with the retirement of a tangible long-lived asset. Questar's AROs apply primarily to abandonment costs associated with gas and oil wells, production facilities and certain other properties. The Company has not recorded AROs on a majority of its long-lived transportation and distribution assets because the Company does not have a legal obligation to restore the area surrounding abandoned assets. The fair value of retirement costs is estimated by Company personnel based on abandonment costs of similar properties available to field operations and depreciated over the life of the related assets. Revisions to estimates result from material changes in the expected timing or amount of cash flows associated with AROs. Income or expense resulting from the settlement of ARO liabilities is included in net gain (loss) from asset sales in the Consolidated Statements of Income. The ARO liability is adjusted to present value each period through an accretion calculation using a credit-adjusted risk-free interest rate. Changes in Questar's AROs from the Condensed Consolidated Balance Sheets were as follows:&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"&gt;&lt;table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"&gt;&lt;tr&gt;&lt;td colspan="8" rowspan="1"&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td width="73%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="1%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="11%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="1%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="1%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="1%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="11%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;td width="1%" rowspan="1" colspan="1"&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="7" style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:center;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;6 Months Ended&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="7" style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:center;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;June&amp;#160;30,&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:center;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;2013&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="3" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:center;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;2012&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="7" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:center;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;(in millions)&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;AROs at beginning of year&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;$&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;67.2&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;$&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;63.8&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Accretion&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;1.5&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;1.5&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Liabilities incurred&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;1.3&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;1.7&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Revisions in estimated cash flows&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;(6.8&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-right:2px;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;)&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;(1.2&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;padding-right:2px;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;)&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Liabilities settled&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;(0.8&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;)&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;" rowspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;(0.2&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;)&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;AROs at June 30,&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;$&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;62.4&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="overflow:hidden;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;$&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;padding-top:2px;padding-bottom:2px;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:right;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;65.6&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;td style="vertical-align:bottom;border-bottom:3px double #000000;border-top:1px solid #000000;" rowspan="1" colspan="1"&gt;&lt;div style="text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;&lt;/div&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;&lt;br clear="none"/&gt;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;text-align:left;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;Wexpro collects from Questar Gas and deposits in trust certain funds related to AROs. The funds are recorded as other noncurrent assets and used to satisfy retirement obligations as the properties are abandoned. The accounting treatment of reclamation activities associated with AROs for properties administered under the Wexpro Agreement is defined in a guideline letter between Wexpro and the Utah Division of Public Utilities and the staff of the Wyoming Public Service Commission (PSCW).&lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 410

 -SubTopic 20

 -Section 50

 -Paragraph 1

 -URI http://asc.fasb.org/extlink&amp;oid=6392692&amp;loc=d3e7535-110849



Reference 2: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Accounting Standards Codification

 -Topic 410

 -SubTopic 20

 -Section 50

 -Paragraph 2

 -URI http://asc.fasb.org/extlink&amp;oid=6392692&amp;loc=d3e7569-110849



Reference 3: http://www.xbrl.org/2003/role/presentationRef

 -Publisher FASB

 -Name Statement of Financial Accounting Standard (FAS)

 -Number 143

 -Paragraph 22

 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.  This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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