Sorrento Valley Double Track Project


San Diego, California

Scope of Work:

  • Geotechnical Engineering
  • Hazardous Waste Initial
    Site Assessment
  • Data Analysis
  • Laboratory Testing
  • Written Report

Ninyo & Moore provided geotechnical design services for the reconstruction of the existing rail corridor through Sorrento Valley in northern San Diego. The Sorrento Valley Double Track project lies between the cities of Del Mar and San Diego along the Los Angeles-San Diego (LOSSAN) rail corridor, west of the Caltrans Interstate 5 (I-5) corridor near the I-5 and I-805 interchange. The project included construction of a second track extending the railroad double tracks from just south of the existing Sorrento Valley Station. Three existing single-track wooden trellis railroad bridges were to be replaced with double track concrete, double-cell box girder bridges as part of the project.

Project Challenge: A major project challenge was simply accessibility to most of the project area. The existing rail line is located along narrow fill embankments and most of the alignment passes through environmentally sensitive wetlands with little or no road access. In addition, a major part of the work was to evaluate the three existing wood-trellis bridges. Access to several embankment areas was possible using limited-access, track-mounted drill rigs. However, drive-up access to major portions of the railroad alignment and to the bridges was not possible for our drilling and Cone Penetrometer Soundings (CPT) equipment.

Innovative Solution: Due to lack of standard access, several of the borings and CPTs were performed directly from the rail bed using “low-railer” self-propelled flat-bed rail cars provided by NCTD. The rail cars were modified to carry our drill rigs, CPT trucks, and other equipment and supplies. The equipment and materials were loaded on the low railers at existing rail spurs in Sorrento Valley and near Miramar Road and then transported to the drill sites. The excavations were then drilled or sounded between railroad ties along the embankments or within holes manually drilled by NCTD personnel in the bridge decks. Borings performed through the bridge decks were cased to prevent drilling fluids and cuttings from entering waterways. Soil borings were drilled off the end of the low railer and the CPT probes were extended through holes cut in the center of the rail car deck. To accommodate regular train traffic, our on-rail exploration program was performed during periods when the railroad was shut down for construction or over weekend nights.

Services: Ninyo & Moore's subsurface exploration consisted of the drilling, logging, and sampling of exploratory borings and the advancement of CPTs. The borings and CPTs were advanced to depths ranging from approximately 40 to 125 feet below existing surface grades. Laboratory analyses including sieve analyses, Atterberg limits, consolidation, shear strength, and soil corrosivity were performed. Ninyo & Moore also performed a Hazardous Materials and Hazardous Waste Initial Site Assessment (ISA) for the Sorrento Valley Double Track Project. The purpose of the ISA was to document potential environmental concerns related to hazardous materials (including underground or aboveground tanks, etc.) and/or hazardous wastes including oil/water separators, waste oil, polychlorinated biphenyls (PCBs), asbestos containing material (ACM), lead-based paint (LBP), and aerially deposited lead (ADL), within or immediately adjacent to the construction area.

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