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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES - Inventories of Materials and Supplies (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Sep. 30, 2017
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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RISKS AND UNCERTAINTIES |  |
Inventory reserve percentage | 5.90% | 6.30%
Reserves for excess and obsolete inventory | $ 9.9 | $ 9.2

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