SOIL STABILIZATION/GROUND IMPROVEMENT
SANTA ANA RIVER LEVEE IMPROVEMENT
SANTA ANA, CALIFORNIA
- 650 lf of Sheet Pile Coffer Dam in Santa Ana River
- Work at active plant amidst overhead and underground utilities
- 9,000 cy of In Situ Stabilization (ISS) in rocky subgrade conditions
- 700 ISS columns at 13 cy each
- 5,000 cy of Jet Grouting
- 699 Compaction Grout at 21 ft bgs
- Installation of a 1,200 gpm de-watering system
- 5,000 cy of spoils disposal
- 5,000 cy of imported fill
The Orange County Sanitation District is the fifth largest wastewater management agency in the country. Recent upgrades and improvements allow it to treat to secondary treatment standards. More than one-third of the secondary treated water is recycled by Orange County Water District, with the remainder discharged through the Pacific Ocean outfall.
This Phase 2 project was designed to complete repairs of the east and west Santa Ana River levees that were damaged during the original project and to install a pipeline between an existing pump station and the Huntington Beach Wastewater Treatment Plant in order to improve the reliability of the Sanitation District’s force main system in the City of Newport Beach. A portion of that work included tunneling under the Santa Ana River. Post-construction monitoring indicated the soil above the tunneled section of the pipeline settled more than anticipated necessitating stabilization efforts including compression grouting, jet grouting, and In Situ stabilization (ISS) on the plant site and on both Santa Ana River levees.
Prior to stabilization of the east and west levees, a 650 lf sheet pile coffer dam was constructed to facilitate sufficient dewatering to allow construction of a suitable working surface. Cofferdam sheet piles were installed to within one foot of the micro tunnel. Upon completion of the cofferdam installation, a dewatering system and treatment system capable of pumping and treating 1,200 gpm was installed. Discharge water from the dewatering operation was treated to a Total Dissolved Solids (TDS) limit of less than 20% above background. Once sufficient dewatering of the coffer dam enclosure was completed, Great Lakes E&I imported and placed 5,000 cy of fill material to create a stable working platform for jet grouting operations required in the Santa Ana River.
Great Lakes E&I performed the In Situ Deep Soil Mixing (DSM) using an ABI 18/22 drill rig with a 6 foot auger, a fully automated MPS 510 grout plant, a 50 ton low profile silo, a 150-ton reagent guppy, and an intricate computerized monitoring system to complete the scope of work. Our management used modern drafting and GPS technology to precisely layout the columns achieving 100% effective treatment. The computerized monitoring system, combined with GPS technology, allowed treatment of areas to within 1 foot of live utilities as well as real time quality control monitoring of pressure, verticality, flow, and auger speed (revolutions per minute). Upon completion of daily activities, data from the batch plant and the ABI rig were downloaded and utilized to generate required quality control (QC) reports.
The ISS specifications required a minimum of 250 psi unconfined compressive strength (UCS) at 28 days. Great Lakes E&I developed a mix design that achieved this requirement with a minimum 85% core recovery. The In Situ stabilization effort was performed using a two-step process that began with the addition of 4% bentonite slurry on the initial pass to enhance cohesion between native soil and the cement solidification reagent and was followed by the addition of 18% cement by dry weight of soil during the second pass for each column. In several cases, the presence of rip-rap and other debris ranging between 12 and 33 inches in diameter at depths of up to 18 foot below grade, required pre-drilling or excavator removal prior to commencement of the ISS effort. Great Lakes E&I utilized specialty 6 foot mixing augers with a unique “egg beater” design that better facilitated mixing in this rocky subgrade. In total, 700 columns consisting of 9,000 cy of contaminated soil was completed using In Situ solidification.
Compaction Grouting was performed within the active wastewater treatment plant on a 10 foot grid pattern. In total, this effort required the construction of 699 holes up to 40 feet deep totaling 15,000 lf. Prior to installation of the compaction grout holes, the top 7 feet of the subgrade was surveyed and cleared for utilities and other obstructions using ground penetrating radar (GPR) and air knifing. During grouting operations, ground pressure, ground movement, and heave were monitored to ensure there was no damage to multiple utility corridors that were present in the work area.
Jet Grouting was performed to complete the tie-in of Phase 1 sections along the east and west levees adjacent to the micro tunnel and in areas where there were overhead utilities. A YBM GL-50CII grout machine was used for this activity, with jet grouting columns ranging from 10 to 50 ft below grade and totaling 5,000+ cy. Jet grouting specifications required a minimum of 250 psi unconfined compressive strengths at 28 days.