Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Cash Flows from Operating Activities:
Net income (loss)	$ 207	$ (738)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Income from discontinued operations, net of tax		(284)
Loss on disposal of discontinued operations, net of tax		378
Gain on sale of property and equipment	(153)	(389)
Depreciation and amortization	32,396	30,866
Depletion of landfill operating lease obligations	6,198	5,491
Interest accretion on landfill and environmental remediation liabilities	1,752	2,068
Amortization of discount on senior subordinated notes	129	119
Loss from equity method investments		887
Loss (gain) on derivative instruments	293	(25)
Stock-based compensation	1,209	1,209
Excess tax benefit on the vesting of share based awards	(12)
Deferred income taxes	379	504
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(6,700)	(5,782)
Accounts payable	(4,412)	(2,432)
Prepaid expenses, inventories and other assets	(3,017)	(2,997)
Accrued expenses and other liabilities	(5,435)	(756)
Net cash provided by operating activities	22,834	28,119
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(314)	(2,822)
Additions to property, plant and equipment	(35,548)	(26,059)
Payments on landfill operating lease contracts	(2,454)	(3,471)
Payments related to investments		(2,148)
Proceeds from sale of property and equipment	342	929
Net cash provided by (used in) investing activities	(38,019)	(34,936)
Cash Flows from Financing Activities:
Proceeds from long-term borrowings	80,700	83,190
Principal payments on long-term debt	(65,070)	(72,586)
Payments of financing costs	(506)	(388)
Proceeds from the exercise of share based awards	143
Excess tax benefit on the vesting of share based awards	12
Net cash provided by (used in) financing activities	15,279	10,216
Discontinued Operations:
Net cash used in operating activities		(201)
Net cash provided by investing activities	176
Net cash provided by (used in) discontinued operations	176	(201)
Net increase in cash and cash equivalents	270	3,198
Cash and cash equivalents, beginning of period	2,464	1,755
Cash and cash equivalents, end of period	2,734	4,953
Cash paid during the period for:
Interest	17,439	17,577
Income taxes, net of refunds	75	622
Supplemental Disclosures of Non-Cash Investing and Financing Activities:
Receivable due from noncontrolling interest holder	152
Property, plant and equipment acquired through lease obligations		2,301
Acquisition [Member]
Cash Flows from Investing Activities:
Additions to property, plant and equipment	$ (45)	$ (1,365)