Representative Projects: Municipal :

Delta Road Bridge, Contra Costa County, CA – Located in the San Joaquin River Delta of Central California, the bridge span on Rock Slough between Veale Tract on the south and Holland Tract on the north.  The project consists of replacing an existing one lane Bailey-bridge with a new two lane bridge constructed adjacent to the existing bridge.  Site conditions included a thin layer of peat over very loose sand that could liquefy under large seismic excitation.  Hultgren-Tillis Engineers developed criteria for densifying the loose sand in place to permit safe installation of the bridge pile foundations and wing walls. Their evaluation of the stability of the abutment fill over thin lenses of peat foundation materials lead to criteria for overexcavation of the peat where the fill footprint was being enlarged.  Hultgren-Tillis Engineers also presented conceptual schemes for using geogrid reinforced fill with a segmented block facing for wingwalls with the walls extending into the tidal zone.  Criteria for foundation piles were also developed.