Representative Projects: Marine Structures :

Threemile Slough Tidal Gate (Franks Tract Project) - The Department of Water Resources (DWR) and U.S. Department of the Interior, Bureau of Reclamation (BuRec) propose to install operable gates to improve water quality and fisheries conditions in the Sacramento-San Joaquin Delta. The gate structure would be located on Threemile Slough, near the Highway 160 Bridge.  The tidal gates would be operated seasonally to reduce sea water intrusion, positively influencing movement of fish species of concern. By protecting fish resources, the project will improve operational reliability of the State Water Project and Central Valley Project by reducing pumping restrictions. 

One gate foundation scheme consists of excavating soft and loose materials, placing a gravel base and setting gravity gate structure on a screeded gravel subgrade.  Densifying existing subgrade with vibratory probes is also under consideration.  HTE has proposed abutment improvements that include in situ densification of loose sands, tied-back sheetpile bulkheads and buttressing the Sherman Island levee at the abutment.  HTE is evaluating a potential seepage collection system that incorporates properly graded “stone” columns (used to densify loose foundation sands beneath the buttress). The stone columns would drain up a drainage blanket beneath the new stability/seepage berm.