NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Assets (Details) - USD ($)	12 Months Ended
Dec. 28, 2019	Dec. 29, 2018
Amortizable intangible assets
Goodwill impairment charges recognized	$ 0	$ 0
Other long-term assets	654,000	$ 448,000
Aggregate property near Colorado Springs [Member]
Amortizable intangible assets
Other long-term assets	2,500,000
Mining permit refund receivable	$ 325,000

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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