CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 2,135,000	$ 34,740,000
Restricted cash	487,000	487,000
Accounts receivable	27,691,000	23,377,000
Unbilled receivables	206,000	1,192,000
Inventories	5,272,000	9,092,000
Prepaid expenses and other current assets	4,992,000	3,849,000
Total current assets	40,783,000	72,737,000
Property, plant and equipment, net	210,037,000	172,202,000
Deferred financing costs, net	400,000	892,000
Other assets	3,414,000	971,000
Total assets	254,634,000	246,802,000
Current liabilities:
Accounts payable	12,243,000	26,123,000
Accrued and other expenses	11,819,000	7,576,000
Deferred revenue	872,000	0
Current portion of equipment financing obligations	502,000	572,000
Current portion of notes payable	288,000	288,000
Total current liabilities	25,724,000	34,559,000
Revolving credit facility, net	15,624,000	0
Deferred tax liabilities, long-term, net	13,546,000	13,239,000
Asset retirement obligation	8,117,000	8,982,000
Total liabilities	63,011,000	56,780,000
Commitments and contingencies (Note 18)
Stockholders’ equity
Common stock, $0.001 par value, 350,000,000 shares authorized; 40,580,437 issued and 40,490,563 outstanding at March 31, 2018; 40,474,085 issued and 40,393,033 outstanding at December 31, 2017	40,000	40,000
Treasury stock, at cost, 89,874 and 81,052 shares at March 31, 2018 and December 31, 2017, respectively	(720,000)	(666,000)
Additional paid-in capital	159,739,000	159,059,000
Retained earnings	32,564,000	31,589,000
Total stockholders’ equity	191,623,000	190,022,000
Total liabilities and stockholders’ equity	$ 254,634,000	$ 246,802,000

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.