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Geotechnical

Feasibility Evaluation of a Subaqueous Cap for Disposed Dredged Material, Palos Verdes Peninsula, California

2026-04-02T15:50:53-06:00October 24th, 2009|Tags: , , |

U.S. EPA had proposed placing a subaqueous cap over a 37 square mile of sea floor seaward of a major wastewater ocean outfall along the Palos Verdes peninsula in Los Angeles County, California. The intent of the subaqueous cap was to contain DDT and PCB impacted ocean floor sediments and reduce exposure to the sediments by benthic organisms. The water depth in the area of the proposed cap ranges from about 130 to 170 feet. This area is also subject to significant ocean currents and is seismically active (Palos Verdes Fault Zone). The proposed cap was to be placed by dumping hydraulically dredged sand and/or crushed rock from hopper barges. Geosyntec was retained by a group of Potentially Responsible Parties (PRPs) to be a member of a multi-disciplinary team to evaluate the feasibility of U.S. EPA's proposed capping remedy. Our specific role was to evaluate the geotechnical feasibility of the proposed plan.

Comprehensive Remediation and Construction for LNAPL Plume Remediation

2026-04-02T15:50:52-06:00October 24th, 2009|

In 2002, the Federal Reserve Bank broke ground on a four-story, 280,000-square-foot facility on the former Jefferson Davis Memorial Hospital site in Houston, scheduled for completion in 2005. A gasoline plume from an off-site City of Houston vehicle maintenance facility threatened to disrupt construction, as previously installed recovery systems were still in place.

Geotechnical Investigation and Landslide Stabilization at Vandale Junkyard Superfund Site

2026-06-16T14:30:23-06:00October 23rd, 2009|Tags: |

The Vandale Junkyard NPL site was operated as a permitted junkyard for over 40 years, and was included on the NPL in 1986. After extensive site investigation activities conducted by others, U.S. EPA Region 5 issued the Record of Decision (ROD) in 1994 calling for a non-time critical remedy involving capping. During the junkyard's active life, waste in one area of the site was ignited at the top of a 150-ft high slope, which resulted in a solid waste residue (SWR) consisting of glass, metal debris, and ash mixed with soil. The SWR was pushed down the slope over the natural colluvium present over bedrock. The planned remedy developed by others for the site included placement of stockpiled waste from other areas of the site over the SWR and a final cover system installed over the placed waste materials. At the onset of remedy implementation, it was discovered that the hillside was geologically unstable and the surficial SWR and colluvial soil were actively creeping downslope. The EPA required the site PRP group to quickly investigate the cause of the geologic instability and to develop a revised site design to stabilize the slope and achieve the environmental remedial action objectives. The PRPs retained Geosyntec to undertake this scope of work.

Airport Improvements Subsurface Investigation and Geotechnical Recommendations

2026-04-02T15:49:48-06:00October 22nd, 2009|Tags: |

McClellan-Palomar Airport is a commercial airport located in Carlsbad, San Diego County, California, serving the general aviation community, corporate aircraft, and commercial services operated by the County of San Diego Department of Public Works. The county proposed numerous improvements to the airport including construction of a new terminal building to replace an existing building, upgrading Taxiway C, adding additional aircraft parking, re-routing the existing drive aisles for the new terminal building, and construction of an elevator and pedestrian bridge from the lower parking area to the upper terminal building.Because the airport was constructed over three unlined, inactive municipal solid waste landfills, ongoing settlement and the potential presence of methane present continuous challenges for expanding the airport's operations. As a result, the geotechnical analysis required for the proposed improvements required the careful characterization of the general nature and extent of existing fill and landfill waste deposits along the lower parking lot perimeter and their effects on geotechnical engineering design recommendations.

Levee Seepage Evaluation and Stability Assessment

2026-06-16T14:30:16-06:00October 22nd, 2009|

The City of Novato retained Geosyntec to evaluate the sources of seepage along the levee at Hamilton Field, a former military base that has undergone redevelopment. The levee was constructed over compressible soils in 1997, and was raised in 2007 to account for settlement since construction. The levee was originally constructed for flood control. However, there is a current U.S. Army Corps of Engineers (USACE) project in conjunction with the California Coastal Conservancy to develop wetlands along the outboard side of the levee, the Hamilton Wetland Restoration Project (HWRP). Two seeps were identified on the inboard side of the levee that separates the Hamilton Field residential/commercial area from the ongoing HWRP. The seeps were identified shortly after commencement of filling of Cell 2 of the HWRP in 2008. Two additional seeps were identified in 2009 during later filling stages.

Non-Urban Levee Evaluation Program

2026-06-16T14:30:20-06:00October 22nd, 2009|

The California Department of Water Resources (DWR) is leading a multifaceted initiative called FloodSAFE California to improve integrated flood management throughout the state, with an emphasis on improved flood risk management related to the state-federal flood protection system in the Central Valley. DWR is evaluating approximately 1,230 miles of non-urban levees.The Non-Urban Levee Evaluation (NULE) Program team is assessing the condition of non-urban State-federal project levees and associated non-project levees, to determine conformance with geotechnical criteria and, where needed, identify remedial measures, including cost estimates, necessary to meet those criteria. The information being developed through the NULE Program will be used within the Central Valley Flood Management Planning Program to inform development of two required documents: the Flood Control System Status Report and the Central Valley Flood Protection Plan.

Geotechnical Exploration and Engineering Analyses Supporting Redevelopment Design and Construction Activities

2026-04-02T15:49:47-06:00October 22nd, 2009|Tags: |

The Britannia Modular Laboratories 4 (BML4) project, located in South San Francisco, California, consists of three existing buildings that have been renovated for conversion to laboratory and office use. This project involves demolition or upgrade of the structures, including the addition of a new pile-supported second floor mezzanine inside one building; new canopy entrances for each building; a new service yard for heavy equipment related to laboratory infrastructure; and new site work (parking lot, walkways, etc.) - all with challenging ground conditions. Geosyntec was selected by the conversion team to develop geotechnical engineering recommendations for foundations and other site infrastructure.

Field Exploration and Laboratory Testing Program to Support Gabion Wall Stability Assessment

2026-04-06T13:19:19-06:00October 22nd, 2009|

A Fortune 100 company requested that Geosyntec provide a technical assessment and evaluation of a 2,200-foot long gabion-faced combination gravity and mechanically stabilized earth wall at one of its major distribution centers in the eastern United States. Other retaining structures on the project site experienced significant movements or collapse. Previous consultants expressed concern regarding the long-term stability and distress for this wall such that the owner would be required to initiate major rehabilitation activities to stabilize it. The owner was actively considering complete wall rehabilitation at an estimated cost of $2.5 million.

Design of Foundation and Structural Integrity Support System for Soil Removal Beneath an Operating Manufacturing Facility

2026-04-02T15:50:26-06:00October 22nd, 2009|Tags: |

The owners of an active aircraft hydraulics manufacturing and testing facility in southwest Michigan were charged by state regulators with the removal of a large quantity of soil and other materials from beneath an active processing area known as the EPD Room. The owners turned to Geosyntec to engineer a system that would allow soil removal without disturbing foundation elements while maintaining the structural integrity of the active facility.

Design and Construction of a Slurry Wall and Engineered Cap for Site Redevelopment

2026-04-02T15:50:27-06:00October 22nd, 2009|Tags: |

A portion of the privately owned former industrial manufacturing site known as the "Route 44" property was impaired by the presence of contaminants from past site uses. Geosyntec was selected to develop an engineered solution for the containment and isolation of residual contaminants and to render the property suitable for redevelopment as a Brownfields site.

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