The project involved the design of a high voltage 230/12.47 kV electrical gas-insulated substation with a maximum redundant capacity of 62.5 million volt-amperes (MVA) at 398 Quint Street, and the construction of several high voltage and medium voltage cables in approximately 9,000 feet ductbank, starting at Mission Rock Street and Terry Francois Boulevard, crossing Islais Creek and continuing to the new substation. The ductbanks were installed using open cut and various trenchless methods and involved crossing of Islais Creek.
Geotechnical and Environmental Engineering: AGS’ work involved conducting a geotechnical investigation, geophysical surveying, laboratory testing, and preparing a geotechnical study report, including conclusion and recommendations for the foundation design, open cut, and trenchless ductbank design and jet grouting according to SFPUC procedures, regulatory requirements, guidelines, and applicable codes. The high voltage electrical gas-insulated substation system included a transformer, switchyards, ductbank, and other related facility associated. AGS performed seismic hazard evaluation and conducted ground motion analyses to develop site-specific seismic design criteria for the design of the electrical substation. AGS performed environmental soil investigation, laboratory testing, and profiling, and prepared a report for the removal and hauling off the excavated soil materials. AGS collected soil samples for corrosion assessment and provided recommendations for corrosion potential at the site. AGS provided geotechnical and geological engineering services during the construction of the substation.
AGS developed geotechnical design criteria for trenchless and open-cut excavations and the construction of duct banks. The project also involved geotechnical evaluations for the duct bank crossing of Islais Creek and evaluation of Islais Creek stability under the design earthquake.
AGS developed design criteria for the Ground Improvements at Islais Creek. AGS finalized the geotechnical investigation and report and provided geotechnical engineering services during the design and construction for the soil improvements at Islais Creek. The ground improvement was an essential task for seismic mitigation of the existing electrical conduit crossing the Islais Creek which connects the new electrical ductbank at the north to the new electrical ductbank at the south of the Islais Creek.
Civil Engineering: AGS’ Civil Engineering team provided the design and construction documents for the site's civil elements – grading, paving, and site utilities (water, storm drain, fire service, and flexible utility connections for static and seismic settlement). AGS was also responsible for the public street improvements along the project frontage on Davidson Avenue (curb, gutter, sidewalk, grading, curb ramps, driveways, and paving) and new water mains, fire hydrants, and combined sewer facilities on Davidson Avenue and Rankin Street. Extensive coordination was required with the SFPUC, Public Works, the electrical consultants, and the Phase 2b team who was responsible for the design of the new electrical duct banks in the streets and into the substation.
Structural Engineering: Structural engineering services involved the design of the substation including wall piles and footing design, power factor correction, and GIS Vault Slab Modifications.