San Juan Creek Stabilization / Jet Grouting

Southern Orange County, CA

PACE provided a preliminary engineering analysis, final design services, and services during construction for stream bank protection on the reach of San Juan Creek from approximately 2,000 feet downstream of the Ortega Highway Bridge to 5,500 feet upstream of the Antonio Parkway Bridge. The primary objective was to develop a comprehensive system of recommended bank protection measures that would provide flood protection and channel stabilization, preserve the natural resources of the existing floodplain, and provide enhanced opportunities for the community.

The project had several challenges that made traditional bank protection alternatives impractical. High groundwater, sensitive habitat, preservation of the natural character of the floodplain, flood protection and channel stabilization were primary considerations in the selected design approach. To effectively address site challenges, a soil cement stream bank protection solution was placed in 8-foot wide, 6-inch thick lifts, laid back at 0.5:1 and 1:1 (H:V) slopes. The soil cement structure was buried beneath native backfill so that vegetation could be planted along the slope, providing enhanced aesthetics. In areas where high groundwater conditions exist, dewatering is cost-prohibitive, so PACE applied jet grouting techniques for protection against potential erosion.

Jet grouting is a soil stabilization method that combines cement injected into the ground at high pressures with in-situ soil to create cemented formations known as soilcrete. The use of the jet grouting method to stabilize soil eliminates the need for trench excavation and dewatering operations. The jet grouting operation parameters include air, water, grout flow, and pressure, together with the monitor (operating head) rotation and withdrawal speed. The cement content is increased in the jet grouting method to make up for the reduced compacted effort that is possible compared to standard soil cement construction.

Key Features:

• Flood protection
• Sediment transport/scour analysis
• Conceptual planning alternative analysis
• Jet grouting for erosion protection
• Creative channel stabilization solution
• Plans, specifications, and estimates