2017-05-22-minutes-public-works-study-session

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KITTITAS COUNTY DEPARTMENT OF PUBLIC WORKS PUBLIC WORKS — BOARD OF COUNTY CONfMIISSIONERS STUDY SESSION STAFF REPORT STUDY SESSION DATE: May 18, 2017 TOPIC: Public Works Gravel Road Grading Business Practices ACTION REQUESTED: Informational LEAD STAFF. Mark R. Cook RECOMMENDATION: None are being sought at this time. BREWING SUMMARY: Public Works (PW) conducts two distinct grading practices: with base stabilization and without stabilization. Tb= are approximately 63 miles of gravel roadway in the PW grading system. Gravel roads that are base stabilized • Approximately 20 miles of gravel roads are base stabilized • Sprung grading includes the application of approximately 3,500 gallon of magnesium chloride per mile With roller compaction • A second round of grading occurs in fall for roads with average daily traffic greater than 70 cars per day • Spring timing is driven by roadway moisture and the ability of the road to support construction equipment. Ambient air moisture is also a consideration when applying magnesium chloride to limit the potential of "splashing" onto vehicles during a three day cure period. Gravel roads that are not base stabilized • Spring grade and roller compaction • Spot gravel application in areas not supporting the establishment of road crown minimum 2% from roadway centerline • Every seven (7) years, the road is re -rocked with approximately two (2) inches of crushed surfacing top course. • No dust control is provided. • Spring timing is driven by roadway moisture and the ability of the road to support construction equipment BACKGROUND: For the past several years, PW has been applying magnesium chloride to various county roads as a means of burdening gravel roadbed. The chloride significantly reduces Page 1 of 3 PUBLIC WORKS BOARD OF COUNTY COMMISSIONERS WORK SESSION STAFF REPORT