CITIES & COUNTIES

Several slope failures occurred on the slopes of Diamond Bar Center during the rainy season of 2004-2005. Diamond Bar Center is a Community Center built in 2002. It is located near the high point of Grand Avenue. Diamond Bar Center building and surrounding parking lots were developed on top of a natural hillside. Relatively shallow side hill fill slopes, and deep buttress fills to enhance slope stability, were constructed over the natural hillsides along most of the facility perimeter. Therefore, slopes below the Diamond Bar Center are generally side hill fills or deep buttress fills placed over native slopes. The fill slopes range in design inclination from 2H:1V to 1.5H:1V.

Surficial slope failures occurred at three locations within the Diamond Bar Center site, due to heavy rainfall, saturation of surface soils, and slope parallel seepage. The failures were up to 4 feet deep, and resulted in down slope movement of soils into the mid-slope v-ditch. Group Delta, an NV5 Company, performed geotechnical investigation and developed detailed recommendations, plans, and specifications to provide the necessary factors of safety for slope parallel seepage conditions. The repair involved excavation of a keyway, placing layers of geogrid reinforcement at 3 foot vertical spacing, installation of geocomposite drains and gravel drain blankets, benching into the hillside, and reconstructing the slope with on-site and imported fills. Our team also provided engineering support and full-time observation and compaction testing services during construction.

Added Value

• Targeted Slope Failure Response: Our team conducted a detailed geotechnical investigation following multiple surficial slope failures, identifying causes such as heavy rainfall, soil saturation, and slope-parallel seepage.
• Engineered, Long-Term Slope Stabilization: Our team developed and implemented a robust repair design including keyway excavation, geogrid reinforcement, geocomposite and gravel drainage systems, and strategic slope reconstruction using on-site and imported fill.
• Comprehensive Construction Support: Our team provided full-time engineering oversight, observation, and compaction testing during construction to ensure quality control and long-term slope stability.