Under an on-call contract with Alameda County Flood Control and Water Conservation District (District), CE&G has provided geotechnical investigation, analysis, and design (complete PS&E) services during bidding and construction for flood capacity improvements to about 2000 lf of the District’s Zone 6, Line E (Laguna Creek) flood control channel. The project provides additional capacity by widening the channel from I-880 to SF Bay at the low flow elevation and constructing concrete floodwalls along the right of way. The project design also required extensive modification to existing City storm drain outfalls/penetrations, new in-channel, erosion-resistant access maintenance roads using articulated concrete block, and three prefabricated railcar bridges supported on geosynthetic reinforced soil – integrated bridge system (GRS-IBS) abutments for access across existing ditches. CE&G initially completed a geotechnical study for the project (which was originally to be designed by the District) and was then tasked with taking over the all civil and structural design of the project while incorporating the District’s design work. Challenges included designing the project to address regulatory concerns related to water pollution control and diversion of flows in the tidally-influenced channel, design of floodwalls with limited right-of-way and virtually no available temporary construction easements, and design with two other projects directly upstream that were also be jointly designed by CE&G and the District. The successful bidder was approximately 10% below the engineer’s estimate. Construction is taking place over two seasons and is near completion.
Challenges included designing the project to address regulatory concerns related to water pollution control and diversion of flows in the tidally-influenced channel, design of floodwalls with limited right-of-way and virtually no available temporary construction easements, and design with two other projects directly upstream that were also be jointly designed by CE&G and the District. The successful bidder was approximately 10% below the engineer’s estimate. Construction took place over two seasons and is near completion with limited change orders.
