If you’ve stopped by the farmer’s market you’ve seen the plans for the dredging project to widen the lower flood plain in Alhambra Creek. The plan is to remove all vegetation (100 foot width) from the east side of the bank from the Marina Vista bridge to the train bridge with the exception of a two foot border where a silt fence will be installed during the work. Our position all along has been that we support the widening as good for the health of the creek but have asked for the city to leave a 10% strip for the beavers to feed. (10 feet instead of 2). We have not yet been assured that this will happen, although there has been a committment to replant willows that are removed. Work starts monday and it would be good if you could come check in so that the contractors are reminded that there are lots of concerned eyes on this project.
Today’s guest blogger is city engineer Tim Tucker who describes the project:
City of Martinez’s
2008 Silt Removal Project
Guest Blogger: City Engineer Tim Tucker
In the late 1990’s and early 2000’s the City of Martinez widened Alhambra Creek, created a flood terrace and constructed a new train bridge and pedestrian bridge for approximately $3.2 million dollars at the new Amtrak Station (Intermodal) site. These improvements increased the capacity of Alhambra Creek, north of Marina Vista, to a 100-year flood level. The New Years Eve flood of 2005 deposited large amounts of silt on City streets from Highway 4 to the downtown railroad tracks. This storm also deposited approximately two to three feet of silt on the flood terrace. The raised elevation of the flood terrace not only reduced flood capacity but also changed the dynamics of the plant and animal habitat. The area no longer experienced the environmental benefit associated with occasional inundation from very high tides. Invasive weeds and non-native grasses can better sustain themselves in this higher, drier zone.
In July the City Council awarded a construction contract for the silt removal. As part of the contract award the Council directed staff to evaluate the possibility of preserving vegetation and still meet the objectives of the project. Several volunteer willows are in the removal area.
Removal of the silt from the flood terrace is scheduled to begin on September 15th. City staff walked the site to evaluate vegetation preservation. The plans called for vegetation from the waters edge to two feet beyond the top of bank to be preserved. This will provide an approximate 8-10 foot swath of vegetation in the area with the highest density of cattails. In addition staff concluded that several of the willows can be easily saved. Preserving the willows will not affect the function of the flood terrace. As the contractor’s excavator encounters a willow tree to be saved the tree will be scooped up and replanted to an adjacent area already graded. Willows are very hardy plants and will quickly take root this time of year. Trees planted as part of the original project will also be saved. Lastly the City has hired a biologist to supplement oversight of the vegetation removal and construction oversight.
This is the sentence that most confuses me; “for vegetation from the waters edge to two feet beyond the top of bank to be preserved. This will provide an approximate 8-10 foot swath of vegetation in the area with the highest density of cattails” and for which I have asked for clarification without success. Since the area is a steep (not sloped) bank, it sounds to me like 2 feet of vegetation will mean 2 feet of vegation, period. Here’s hoping I’m reading something wrong.
At any rate, work starts monday, so expect to see bulldozers and heavy equipment camped out. If you’re down in the morning you can help by making sure our beavers have cleared the area before work begins. Remember they still have lots on the west bank to feed on, including blackberry, cottonwood and poplar.
