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soil under the severely distressed area was replaced by light -weight cellular concrete material and approximately 1,200 square feet of less severely distressed area was repaired by a conventional base repair construction method. This project also included the replacement of 340 feet of existing concrete curb and gutter, 2,200 square feet of existing sidewalk, and two ADA curb ramps. In addition, this project also overlaid existing roadway surface with asphalt concrete within the project limits. In 2015, O'Grady Paving completed emergency repair work under the Annual Streets Resurfacing and Preventative Maintenance Project, CIP No. 145003, for $76,120 for areas adjacent to the 2013 repairs. The work included 21 locations along West Positas Boulevard between the DMV and Stoneridge Drive. Over 20,000 square feet of existing depressed pavement was milled and leveled with 1/2 -inch hot mix asphalt concrete and 1,200 square feet of distressed pavement was also repaired. The repairs near the DMV appear to be relatively stable. In 2018, Ranger Pipelines completed leveling and roadway repairs at the Tassajara Creek crossing as part of the recycled water pipeline installation traffic lane restoration work. The work included leveling work on and immediately adjacent to the segments repaired in 2013 and 2015. In the summer 2019, cracks and minor settlement began showing back up within repaired areas, including areas of the lightweight cellular concrete. By spring 2020, significant settlement had occurred in the street and Streets Maintenance Division installed signage and began working on temporary leveling and roadway repairs. The repairs became greater than the capacity of the streets department to efficiently handle. In order to address the urgent need of pavement restoration to provide a safe travel way to vehicular traffic, Engineering began working on scoping the project to be completed as a change order under one of the active paving contracts underway. DISCUSSION The roadway continues to experience differential settlement within the repair areas. Previous exploratory excavations have uncovered open cracks one-half inch wide in the soil to a depth of approximately 4 feet below the roadway surface. The soil is silty expansive clays and is heavily impacted by varying levels of moisture contained within the soil. Clay particles on a micro -scale are shaped like round plates. Clay can hold significant amounts of water within its random structure of plates, but as the clay soil dries the plates align as if stacking, and the material consolidates. This is further compounded by roadway traffic dynamically loading the soil pushing downward and causing further consolidation. When water is re -introduced some swelling of the clay soil will occur, but lacking a dynamic force opposite the traffic loading, the soil will remain relatively consolidated. The consolidation experienced is a near surface issue where water content can more readily change. This became evident during the drought when irrigation was restricted, and significant differential settlement occurred between the exposed soil in the median areas, and the soil more protected from water loss by the asphalt roadway surface. Page 3 of 6