NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - (Details)	3 Months Ended				12 Months Ended
	Dec. 28, 2019 USD ($)	Sep. 28, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 28, 2019 USD ($) item	Dec. 29, 2018 USD ($) item	Dec. 30, 2017 USD ($)
RETIREMENT PLANS
Unfunded liabilities related to the Supplemental Profit Sharing Plan	$ 1,250,000				$ 1,250,000	$ 1,001,000
RESERVE FOR SELF-INSURED AND INSURED LOSSES
Reserve for reclamation activities	911,000				911,000	874,000
RECLAMATION
Reclamation liabilities	20,217,000				20,217,000	6,269,000
Current portion of reserve for reclamation	4,200,000				4,200,000	1,017,000
Changes in the aggregated product warranty liability
Beginning balance				$ 132,000	104,000	132,000
Warranty related expenditures					(148,000)	(148,000)
Warranty expense accrued					120,000	120,000
Ending balance	76,000				76,000	104,000
Cost in excess of billings	420,000				420,000
Retainage on contracts	345,000				345,000
IMPAIRMENT OF LONG-LIVED ASSETS
ARO liabilities	27,913,000				27,913,000	6,269,000	$ 6,166,000
Charges related to write off of deferred development						$ 6,840,000
Impairment charge on other long-lived assets			$ 6,840,000	6,840,000	$ 2,230,000
Increase in ARO	45,000
Fiscal year end
Length of fiscal year					364 days	364 days
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Changes in the aggregated product warranty liability
Number of customers accounted for 10% or more of total sales | item					0	0
Heating and Cooling [Member] | Customer Concentration Risk [Member]
Changes in the aggregated product warranty liability
Number of customers accounted for 10% or more of account receivable | item					1
Heating and Cooling [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Changes in the aggregated product warranty liability
Concentration Risk, Percentage					15.90%	16.10%
Minimum
REVENUE RECOGNITION
Payment Terms Number Of Days					30 days
Maximum
REVENUE RECOGNITION
Payment Terms Number Of Days					90 days
Aggregate property near Colorado Springs [Member]
IMPAIRMENT OF LONG-LIVED ASSETS
ARO liabilities		$ 20,715,000
ARO offsetting asset		20,715,000
Impairment charge on other long-lived assets		$ 20,217,000
Pueblo Colorado gravel operations
IMPAIRMENT OF LONG-LIVED ASSETS
ARO liabilities	6,660,000				$ 6,660,000
Charges related to write off of deferred development			$ 6,840,000	$ 6,840,000
ARO offsetting asset	$ 6,660,000				6,660,000
Impairment charge on other long-lived assets					$ 2,230,000