In early 2021, the United States Coast Guard (USCG) broke ground on their new 13,200-square-foot, 2-story search and rescue facility at the Vallejo Municipal Marina along the Napa River in Vallejo, California. For 25 years, Station Vallejo has been housed in temporary facilities. The people serving at USCG Station Vallejo will utilize a new boat bay for small-boat maintenance, berthing for 14 watchstanders, a gally, a command center, training room and fitness room. In 2020 alone, USCG Station Vallejo responded to 80 search and rescue calls which led to 76 lives saved or assisted.
Subsurface exploratory borings by CTE and AECOM revealed undocumented fill to depths of 5 to 24 feet consisting of loose to medium dense clayey gravel (GC), stiff sandy gravelly clay (CL), and clay with gravel (CL). Below the undocumented fill, native bay mud clay deposits were encountered and consisted of soft, highly plastic clay (CH) over stiff, medium plastic clay (CL/CH), which were characterized as younger and older bay mud deposits, respectively. The younger bay mud deposits are considered weak, compressible, and unconsolidated. The high groundwater level was assumed to be about 5-feet below working pad elevation due to the proximity to the Napa River and are expected to fluctuate due to tidal influence on the river.
Farrell’s low-vibration, Type 2 Drill Displacement Column™ (DDC) system was selected as the ground improvement solution to provide a higher allowable bearing capacity than the soft and compressible native soil. The DDC elements were installed into the stiffer underlying bearing layer, bringing foundation loads past the weak, unconsolidated, and compressible young bay mud layer. The Type 2 DDC elements included rebar for ductility and higher strength. Farrell successfully designed and installed over 200, 16-inch diameter, Type 2 DDCs to depths of 43-feet to control the building’s total settlement to less than a 1-inch after construction is completed.
Farrell’s project team is honored and supports the US Coast Guard Station Vallejo to Go Vertical with Confidence!®
Farrell Design-Build Inc. | Sacramento 530.621.4867 | Irvine 949.428.9596