INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Federal:
Current	$ (387,000)	$ 988,000
Deferred	(1,454,000)	27,000
State:
Current	1,000	32,000
Deferred	(345,000)	(26,000)
Total	$ (2,185,000)	$ 1,021,000
Difference between tax rate for continuing operations on income or loss for financial statement purposes and federal statutory tax rate
Statutory tax rate (as a percent)	21.00%	34.00%
Statutory tax rate (as a percent)	(21.00%)
Remeasurement of deferred tax liability, provisional benefit		$ 27,000
Percentage depletion	(0.90%)	(4.70%)
Non-deductible expenses (as a percent)	0.40%	1.70%
Valuation allowance for tax assets (as a percent)	1.20%	2.50%
State income taxes, net of federal benefit (as a percent)	(4.50%)	2.00%
Domestic production deduction		(0.30%)
Revaluation of deferred items for new Tax Act		(1.00%)
Other (as a percent)	(2.40%)	1.80%
Total (as a percent)	(27.20%)	36.00%
Current statutory federal and states tax rates (as a percent)	25.74%
Deferred tax assets
Reserves for self-insured losses	$ 466,000	$ 328,000
Accrued reclamation	1,445,000	1,386,000
Unfunded supplemental profit sharing plan liability	263,000	275,000
Asset valuation reserves	685,000	293,000
Future state tax credits	833,000	863,000
Net state operating loss carryforwards	226,000	126,000
Federal AMT carryforward	387,000	620,000
Federal NOL carryforward	468,000
Other	700,000	701,000
Total deferred tax assets	5,473,000	4,592,000
Deferred tax liabilities
Depreciation	1,200,000	859,000
Deferred development	116,000	1,298,000
Prepaid royalties		161,000
Other	443,000	458,000
Total deferred tax liabilities	1,759,000	2,776,000
Net deferred tax asset before valuation allowance	3,714,000	1,816,000
Beginning balance	(200,000)	(130,000)
(Increase) decrease during the period	100,000	70,000
Ending Balance	(300,000)	(200,000)
Net deferred tax asset	$ 3,414,000	$ 1,616,000