Geologists began drilling holes and collecting soil samples Tuesday in downtown Fresno in preparation for the first stages of construction on California's proposed high-speed train project.
The first soil borings by Earth Mechanics Inc. took place along H Street, under the Stanislaus Street overpass that spans H Street, the Union Pacific Railroad tracks and G Street. It's the first of more than two dozen locations between the northeast edge of Madera and the south end of Fresno where the company will test the subsurface soil conditions.
The tests offer a mole's-eye view to geologists, and the results will help engineers determine what kind of foundations will be required for new overpasses and other structures needed for the first 29-mile stretch of high-speed rail construction, said Michael Hoshiyama, a staff geologist with Orange County-based EMI.
"Different soil conditions can yield different types of foundations or footings for the bridges," Hoshiyama said. For example, he said, sandy soils react differently to vibrations or earthquakes than clay, while a shallow water table creates a different set of circumstances for engineers to analyze.
A boring rig set up on the west side of H Street bored 100 feet deep into the earth, allowing geologists to take samples every five feet to understand the soil profile. At a table set up just a few feet from the hole, geologist Jody Castle was taking quick preliminary notes as she studied the samples.
"Even to the untrained eye, different colors pop out, different textures are obvious," Castle said. "There's fine grain, coarse grain, sand, clay, silt."
Each layer is the result of different geological conditions on the floor of the San Joaquin Valley over thousands of years. "What you're seeing is history," Castle said. "Each environment gives you different types of sediments."
Just across H Street, technicians with Middle Earth Geo Testing Inc. sat in a truck laden with computerized testing gear, while a metal probe mounted under the truck was driven into the ground. The probe, called a cone penetrometer, provides geologists with continuous readings of soil density and conditions to a depth of up to 100 feet.
EMI and Middle Earth Geo Testing are subcontractors on the Madera-Fresno section of the rail route -- the stretch targeted as the first construction portion of the 520-mile, $68.4 billion project that, if built, would link San Francisco and Los Angeles with electric trains capable of traveling at up to 220 mph.
The prime contractor for the Madera-Fresno section is a consortium of construction companies -- Tutor Perini Corp. of Sylmar, Zachry Construction of Texas and Pasadena-based Parsons Corp. The consortium was awarded the $985 million contract earlier this year by the California High-Speed Rail Authority.
While the soil testing and other preliminary work will set the stage for construction, there remains no firm date for the start of major work on the railroad route or related structures like bridges, tunnels or overpasses. The Tutor Perini/Zachry/Parsons contract was awarded as a design-build contract, which requires the companies to complete the engineering and design of the project, and then build what they've designed.
While that engineering work continues, the rail authority is trying to acquire the right of way it needs before construction can begin. As of last week, the agency reported that it had closed escrow on only five of the 380 parcels it needs between Avenue 17, northeast of Madera, to American Avenue at the south edge of Fresno.
Hoshiyama said his company is testing where road overpasses or underpasses are planned to span the railroad, including at Stanislaus and H streets, where a new bridge is being designed to replace the existing Stanislaus Street bridge. Another subcontractor will be doing similar soil testing where longer bridges or viaducts are needed to carry the actual high-speed tracks, including across the San Joaquin River north of Fresno and above Highway 99 at the south end of the city.