A crew from Lewis Tree Service Inc. was at Hemming Plaza on Monday trimming dead branches from the live oaks in the park. Small areas in the park will be closed temporarily to ensure the safety of visitors and to allow access to most of the one square block plaza adjacent to City Hall, the Main Library, the Museum of Contemporary Art and the Hemming Plaza Skyway Station. The project is expected to last through Friday, depending on weather. Lewis Tree Service has a $124,000 one-year contract with the city to provide “hazard tree services” for parks.