AROs are legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development or normal operation of such assets. Our AROs are primarily associated with phosphogypsum stack systems and mine reclamation in Florida.

The changes in our AROs from December 31, 2011 to March 31, 2012 are summarized below:

	(in millions)

Obligation at December 31, 2011	$	131.6
Accretion expense		2.4
Liabilities incurred		0.4
Expenditures		(2.0	)

Obligation at March 31, 2012	$	132.4

Our phosphate operations in Florida are subject to regulations governing the construction, operation, closure and long-term maintenance of phosphogypsum stack systems and regulations concerning site reclamation for phosphate rock mines. Our liability for phosphogypsum stack costs includes the cost of stack closure at our Plant City, Florida phosphate fertilizer complex and the costs of cooling pond closure, post-closure monitoring, and ongoing water treatment at both Bartow and Plant City. The actual amounts to be spent will depend on factors such as the timing of activities, refinements in scope, technological developments, cost inflation and changes in regulations. It is possible that these factors could change at any time and impact the estimates. In addition to reclamation AROs arising from normal mining activity, AROs may increase in the future upon expansion of the Plant City phosphogypsum stack.

AROs are reported in accrued expenses and other noncurrent liabilities on our consolidated balance sheets, as follows:

	March 31, 2012		December 31, 2011

	(in millions)
Current portion	$	16.2	$	13.8
Noncurrent portion		116.2		117.8

	$	132.4	$	131.6

In addition to various operational and environmental regulations related to our phosphate segment, we are also subject to financial assurance requirements related to the closure and maintenance of our phosphogypsum stack systems at both our Plant City, Florida phosphate fertilizer complex and our closed Bartow, Florida phosphate fertilizer complex. The financial assurance requirements pertaining to our operations are outlined in two separate regulations. First, in 2010, we entered into a consent decree with the U.S. Environmental Protection Agency (EPA) and the Florida Department of Environmental Protection (FDEP) with respect to our compliance with the Resource Conservation and Recovery Act (RCRA) at our Plant City, Florida complex (the Plant City Consent Decree). Second, the State of Florida financial assurance regulations (Florida Financial Assurance) apply to both our Plant City and Bartow complexes. Both of these regulations allow the use of a funding mechanism as a means of complying with the financial assurance requirements associated with the closure, long-term maintenance, and monitoring costs for the phosphogypsum stacks, as well as costs incurred to manage the water contained in the stack system upon closure. We have established a trust account for the benefit of the EPA and FDEP and an escrow account for the benefit of the FDEP to meet these financial assurance requirements. On our consolidated balance sheet, these are collectively referred to as "Asset retirement obligation funds" (ARO funds). We expect to deposit approximately $50.0 million in 2012 which will fully fund the trust account for the Plant City Consent Decree and we expect to fund the remaining $2.0 million in the State of Florida Financial Assurance escrow account by 2016. Both financial assurance funding obligations require estimates of future expenditures that could be impacted by the timing of activities, refinements in scope, technological developments, cost inflation, discount rates and change in regulations. Additional funding will be required in the future if increases in cost estimates exceed investment earnings in the trust or escrow accounts. At March 31, 2012 and December 31, 2011, the balance in the ARO funds was $147.6 million and $145.4 million, respectively.