Balance Sheet Items (Tables)

9 Months Ended

Sep. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Changes in the Allowance for Doubtful Accounts

The following table presents the changes in the allowance for doubtful accounts:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Balance, beginning of period	$	249	$	—	$	146	$	—
Add: provision	5		—		124		—
Less: deduction and other adjustments	(2)		—		(18)		—
Balance, end of period	$	252	$	—	$	252	$	—

Schedule of Property and Equipment, Net

The following table shows the components of property and equipment, net:

	September 30, 2020		December 31, 2019
Plant, machinery and equipment	$	79,781	$	75,578
Structural fill site improvements	55,760		55,760
Vehicles	18,396		19,163
Office equipment	2,847		2,741
Buildings and leasehold improvements	262		262
Structural fill sites	432		7,110
Construction in progress	7,474		12,324
Total property and equipment	$	164,952	$	172,938
Less: accumulated depreciation	(100,183)		(87,644)
Property and equipment, net	$	64,769	$	85,294

Schedule of Bargain Purchase Liability

The following table reflects activity related to the bargain purchase liability:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Balance, beginning of period	$	7,110	$	7,110	$	7,110	$	10,017
Amortization expense	(7,110)		—		(7,110)		(2,907)
Balance, end of period	$	—	$	7,110	$	—	$	7,110

Schedule of Accrued Liabilities

The following table shows the components of accrued liabilities:

	September 30, 2020		December 31, 2019
Accrued expenses	$	19,309	$	20,456
Accrued payroll and bonuses	24,014		13,273
Accrued dividends	877		—
Accrued interest	823		1,761
Accrued liabilities	$	45,023	$	35,490

Schedule of Asset Retirement Obligations

The following table reflects the activity for the asset retirement obligation:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Balance, beginning of period	$	10,948	$	20,945	$	15,131	$	26,065
Liabilities incurred	—		—		—		1,017
Liabilities settled	(2,009)		(3,440)		(6,542)		(10,222)
Change in estimated cash flows	(2,127)		—		(2,127)		—
Accretion	135		262		485		907
Balance, end of period	6,947		17,767		6,947		17,767
Less: current portion	(2,921)		(13,738)		(2,921)		(13,738)
Non-current portion	$	4,026	$	4,029	$	4,026	$	4,029