Once part of a natural wetland habitat, this 1.25 acre area of land was bought to become a real estate parcel. Even though it was later abandoned due to the site’s government protection, the ecosystem was severely degraded from its original state. Caltrans acquired this site and began their Supplemental Environmental Project (SEP) designed to restore and protect the Napolitano site.
Goal:
To establish a functional, long term, self-sustaining habitat that can support the native plants and animals found in local salt-marsh communities, as well as provide needed habitat for the light-footed clapper rail.
Description:
Alteration 1:
To create physical conditions similar to those of a local salt marsh habitat, a tidal channel was created to distribute flow throughout the low marsh. Also, debris was removed and storm drain water diverted to prevent sedimentation.
First, a meandering tidal channel was created to distribute tidal flow to the low marsh. To compensate for sedimentation and side slumping, the channel depth was graded to be .75 m, around 0.3-0.5 m below the mean of the low water level in order to support tidal flow during seasonal fluctuations. In the marsh transition zone, the slope ratio was graded to a ration of 1:1. and outcroppings of asphalt, concrete, brick debris at the eastern boundary of the site were removed. To minimize soil compaction, earth-moving equipment followed a systematic north-to-south track with a buffer strip across the lower marsh.
An earthen trench was dug next to the northern grate of the storm drain system for a reduction in sedimentation around the site and prevent future damage to plants.
The over-excavated soil of the marsh was replaced with a 2:1 ration of topsoil and dried kelp for soil nutrient replenishment.
Alteration 2:
Vegetation was replanted in order to re-establish local marsh habitat. All planted seeds and cuttings were taken from the Tijuana Estuary, basing species composition on a reference site south of the restoration area.
In low marsh habitats, the dominant plants of the ecosystem, pickleweed and Pacific cordgrass, were planted clusters around 1 meter wide. The sub-dominants, saltwort, alkali heath, sea lavender, and jaumea, were planted in clusters dispersed around the dominant plant clusters. Around 2,700 of each of the dominants and 205 each of the sub-dominants were planted.
The transition zone of marsh was planted with clusters including 201 of the dominant plant Distichlis spicata, 18 Salicornia subterminalis, and 8 lyium brevipes, some being onsite salvages.
Timeline:
Preliminary soil borings taken during initial site investigation (Oct 16-17, 1997)
Draft Removal and Restoration Plan completed (March 1998)
Excavation begins (December 1998)
Excavation completed (January 1999)
Planting begins (February 1999)
Present Activity:
-Monitoring: Caltrans 3 year monitoring program following planting completion
Bibliography/Sources:
Brown and Caldwell and Tierra Environmental Services “Tijuana Estuary Wetlands Restoration Project: Draft Removal and Restoration Plan- California Department of Transportation District 11, San Diego” March 1998
“Caltrans Rescues a Hunk of Marshland.” California Transportation Journal November-December 2002: 40-43