Noise Reduction in Los Angeles County
LA Metro’s soundwall program was developed to improve the quality of life for residents near major freeways by providing quieter communities in Los Angeles County that have heavy traffic impacts. The Soundwall Package 11 was a key part of the soundwall program. This project minimizes sound impacts to the community by constructing masonry block walls to lower freeway noise in adjacent residential neighborhoods. This project also utilized available recycled water to irrigate highway landscaping, reducing potable water use and providing a more sustainable irrigation source. Trees and roadside landscaping were planted to improve the appeal behind the soundwalls, and further reduce greenhouse emissions thereby improving air quality in the community.
The Sound Walls
Sound Wall 11 is broken into two locations: Route 170 from Route 101 Separation to Sherman Way, and Route 405 from 0.2 miles North of Saticoy Street to 0.6 miles South of Roscoe Blvd. The soundwalls consist of ten to 17-foot-tall masonry block walls supported on Cas in Place Drilled Hole (CIDH) piles. The project also widened the freeway bridge and included adding precast concrete girders, concrete deck slab placement, and paving. Other improvements include drainage systems, elevated signage poles, lighting poles, retaining walls, utility relocations, landscaping, earthwork, paving, and traffic controls.
Full Services Construction Management Support
Ghirardelli provided construction management, structural/civil inspections, and contract administration during the construction of Soundwall 11. Ghirardelli’s personnel were responsible for scheduling, change orders, source inspection of structural materials in accordance with the Source Inspection Guidelines for Local Agencies, and resolution of complex issues. Ghirardelli worked closely with Caltrans Oversight, local city employees, and homeowners as the first point of contact to keep them informed about the project. Ghirardelli’s team also reviewed schedules, material testing, and quality assurance, as well as coordinated the work with local utilities, water districts, and sewer districts where the sound walls are being constructed.
Challenging Soils Conditions
Because of the existing soil conditions, traditional construction methods were not feasible to build the walls and could have caused settlement, damaging new and existing infrastructure. To address these issues, the project used a special engineering technique to inject permeation grouting to stabilize the soil. The initial soil studies indicated that drilling 6-foot diameter CIDH piles 70 ft deep for bridge widening would risk further settlement of the existing structures. Permeation grouting allowed us to inject grout into the soil at specified depths where soil conditions were most vulnerable to caving. This process is not commonly used in bridge construction and required a lot of coordination between the agency, consultants, and designers alike. Ultimately, the permeation grouting proved to be successful having all 29 piles drilled and installed without caving or settlement of existing structures.