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ACCRUED CAPPING, CLOSURE AND POST CLOSURE (Tables) | 9 Months Ended
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Jan. 31, 2013
Changes to Accrued Capping, Closure and Post-Closure Liabilities | The changes to accrued capping, closure and post-closure liabilities for the nine months ended January 31, 2013 and 2012 are as follows:
|  | Nine Months Ended January 31, |
|  | 2013 |  |  | 2012 |
Beginning balance |  | $ | 39,629 |  |  | $ | 36,407 |
Obligations incurred |  |  | 2,606 |  |  |  | 2,350 |
Accretion expense |  |  | 2,653 |  |  |  | 2,510 |
Payments |  |  | (2,304 | ) |  |  | (1,298 | )
Ending balance |  | $ | 42,584 |  |  | $ | 39,969 |

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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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