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SEGMENT AND GEOGRAPHICAL INFORMATION - Concentration Risk (Details) | 12 Months Ended
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Dec. 29, 2023 | Dec. 30, 2022 | Dec. 31, 2021
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Top Ten Customers |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) | 52.70% | 54.60% | 49.20%
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Los Angeles Department of Water and Power |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) |  | 12.00% | 10.80%
Revenue from Contract with Customer Benchmark | Geographic Concentration Risk | California |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) | 45.10% | 41.70% | 36.80%
Revenue from Contract with Customer Benchmark | Geographic Concentration Risk | New York |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) | 24.70% | 22.80% | 21.00%
Revenue from Contract with Customer, Segment Benchmark | Customer Concentration Risk | Los Angeles Department of Water and Power | Energy |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) |  | 14.40% |
Revenue from Contract with Customer, Segment Benchmark | Customer Concentration Risk | Los Angeles Department of Water and Power, Duke Energy, and Consolidated Edison of New York | Engineering and Consulting |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) |  |  | 34.50%
Revenue from Contract with Customer, Segment Benchmark | Customer Concentration Risk | Los Angeles Department of Water and Power, and The Dormitory Authority State of New York | Energy |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) | 22.70% |  |
Revenue from Contract with Customer, Segment Benchmark | Customer Concentration Risk | City of Elk Grove | Engineering and Consulting |  |  |
Concentration Risk |  |  |
Concentration risk (as a percent) |  |  | 10.30%

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