Third, Fourth, and I Avenue Storm Drain Rehabilitation Project (CP2015-05)

Third, Fourth, and I Avenue Storm Drain Rehabilitation Project (CP2015-05)

The project proposes replacement of an existing 24-in storm drain outfall with a new 48-in storm drain outfall at the same location. The new outfall would carry both the drainage from the existing outfall as well as drainage from a new storm system along "I" Avenue intended to mitigate the existing flooding problems at the Fourth Ave/Alameda Blvd intersection. Inlets would be installed on the north and south side of Fourth Ave, on the east side of its intersection with "I" Ave. The new storm drain would run the length of "I" Ave from Fourth St to the San Diego Bay and would intercept the existing 24-in storm drain conveying flows from First St just prior to the existing point of discharge of the 24-in pipe. To handle the expanded peak flow capacity, the outlet to the Bay would be upsized from 24 in to 48 in. A low flow diverter would be installed within the storm drain system that would divert low-flows to the sanitary sewer system and not out the storm drain outfall. Additionally, energy dissipation is proposed at the outlet of the pipe to reduce potential displacement of sands into existing eelgrass beds. This would result in an additional 134 sf of riprap beyond the limit of the existing revetment slope. Placement of the dissipater apron would be matched to a similar area of removal of existing non-functioning rubble revetment to the north of the pipe outlet to ensure a no net expansion of rock placed on the beach. The rubble to be removed would be from the area adjacent to the Bay to provide a potential area for future eelgrass habitat.

Coronado

San Diego