Geotechnical Engineering Design for Deep Soil Excavation Program
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In its effort to expand and renew its campus facilities and related infrastructure, the Los Angeles Unified School District (LAUSD) evaluates numerous candidate sites including properties that may have been impacted by contaminants. All properties being considered for a new school are subject to a rigorous Environmental Assessment and Remedial Investigation process. At one site testing indicated that shallow soils were impacted with lead and deep soils were impacted with petroleum hydrocarbons and volatile organic compounds to such a degree that remediation was required.

Geosyntec's Scope of Services

Geosyntec developed a Remedial Action Plan that called for excavation of soils to 35 feet and offsite disposal of impacted materials. Site conditions required a design that allowed deep excavation yet limited the amount of materials destined for offsite disposal to that deemed to be impacted above threshold levels in order to minimize disposal costs. Geosyntec prepared a grading plan for site soil removal and designed excavation shoring for the 35-foot deep portion of the excavation. The grading plan was designed for shallow excavations for lead-impacted soils. The shoring design specified a 35-foot deep excavation, soldier beams installed in predrilled 24-in. diameter holes, 50 to 100-kip bar anchors (1 to 1-3/4 in. diameter) [10 percent of anchors tested to 200% of Design Load (for production anchors); all others to 150% of Design Load], and three rows of tiebacks with tie back removal within 20 ft. below grade.

Because of the site's location, shoring permits were required from both the County of Los Angeles Department of Public Works (LACDPW) and the City of Los Angeles Bureau of Engineering (LABOE). Geosyntec successfully obtained permit approvals from both agencies quickly, allowing the overall site redevelopment schedule to remain on track.

Notable Accomplishments

Geosyntec's early recognition that the project's success, i.e., the design, construction, and opening of a new school, depended upon not just the ability to assess and remove impacted soils. Geosyntec applied its expertise in geotechnical engineering design, particularly excavation shoring systems, to secure permits from local agencies quickly without potentially delaying review/response cycles. Through our geotechnical engineering design, Geosyntec was able to minimize the volume of soil excavated and tested for expensive offsite disposal.

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Project Summary

  • Location: Los Angeles, California, USA
  • Client: Los Angeles Unified School District
  • Project Practice Areas: Contaminated Sites, Geotechnical
  • Type of Facility: Brownfield Site
  • Services Provided: Remedial Design; Grading and Excavation Plan for Soil Removal; Geotechnical Excavation Shoring Design
  • Type of Work: Shoring Design
  • Governing Regulation: State Regulations