The aging railroad bridge over the San Dieguito River will be retrofitted as part of the San Dieguito Lagoon Restoration Project later this fall.
The last stage of the restoration project, dredging 80,000 cubic yards of sand from the lagoon inlet, is going to expose and take away some support from the bridge pylons. To ensure the bridge remains safe, the pylons will be wrapped with heavy duty plastic and grout and the bridge will be braced.
Since the reinforcement is partly required because of lagoon restoration activities, Southern California Edison has agreed to cover 80 percent of the estimated $1.5 million retrofit. The utility is paying for the $86 million restoration project as mitigation for environmental damage caused by its San Onofre Nuclear Generation Station.
North County Transit District (NCTD), which owns the bridge, will fund the remainder of the retrofit.
The project will have to be closely coordinated with the lagoon inlet dredging because the sand cannot be completely removed before the bridge has been reinforced, said Tom Lichterman, operations director for NCTD.
That means the dredging, scheduled to take place in September, may have to be pushed back a little later into the fall.
The dredging will help ensure tidal flow remains open between the river, lagoon and ocean. However, the large salt marsh habitat east of Interstate 5 will not always be filled with water. The large basin is shallower and at a higher elevation, so mud flats will be exposed at low tides, said coastal engineer Hany Elwany. The sand from the dredging will be placed on Del Mar's beach.