Lansdale Project Fish-Ready
by Sandy Guldman
From late June until mid-October 2012, in-creek work, managed by Stetson Engineers and Friends of Corte Madera Creek, was carried out on the Lansdale Fish Passage Improvement Project, thanks to funding from the California Department of Fish and Game’s Fishery Restoration Grant Program. The project includes shallow resting pools inside the long culverts under Center Boulevard, and a pool-and-drop fishway at the downstream end. In addition, a new wall under the upstream end of the culverts reduces the amount of water flowing under the culvert; a low wall across one culvert diverts low flows into the culvert with baffles (the walls creating the resting pools inside the culvert); and a center wall keeps low flow in the resting pools.
The first job was to install fish screens to keep fish out of the work area. At the end of June, Ross Taylor and Associates relocated 105 rainbow trout/steelhead, 452 prickly sculpin, 317 California roach, and 6 stickleback from the work area into downstream pools. The contractor, Glissman Excavating, filled sandbags and built two temporary dams between the fish screens to limit the amount of water in the work area. Between the two dams, water flowed through a diversion pipe around the work area. The biggest challenge was dewatering. Thick gravels in the streambed and abundant groundwater allowed water to keep flowing into the work area. To remove it, a continuously running submersible pump was installed upstream of the culverts. Downstream, the contractor drilled a 20-ft deep sump and excavated a shallower sump, both with continuously running pumps. When active construction muddied water in the work area, another pump was used to direct the muddy water into two 20,000-gallon tanks parked near the Lansdale Station Playground. After the mud settled, relatively clear water was released from the tanks onto the blackberry-covered slope beside the parking lot, where it soaked into the ground. In July, Glissman installed baffles to form pools that steelhead will use when moving through one side of the culverts. To ensure that an existing retaining wall beside the new fishway would not sink or tilt when the hole for the fishway was excavated, micro-piles were drilled at its base and tie-backs anchor it into the hillside. After those were in place, a grade-control weir was constructed downstream using 2-ton rocks; it serves two purposes: to prevent undercutting of the new fishway and to provide a pool at the base of the fishway. After the weir was installed, a large hole was dug so that the drillers could install the concrete piers that support the fishway.
Completion of the drilling was a major milestone; finally work on the fishway could begin. First, the base of the fishway was poured, and then the walls to form the pool-and-drop structure. After removal of the forms in late September, the fishway structure was in place. The next step was to place rocks, sand, and gravel downstream of the fishway and rocks along both sides of it. Along the left side of the fishway, large rocks form a relatively flat surface all the way to the downstream end, where they slope steeply into the terminal pool. This configuration ensures that flows that attract spawning fish will be coming from the fishway, not from the left side where there are no resting pools. Right now there is limited fine sediment in the interstices between the large rocks; however, each storm big enough to allow flow through the left side of the culvert carries sand and fine gravel into the rocks. Eventually, there will be a mostly gravel surface to the left of the fishway. The last step before removing the temporary dams was to install stage gauges to enable the measurement of water surface elevations in the fishway very accurately.
After the pumps and sandbag dams were removed on October 9, water began filling the upstream creekbed; after a few hours it overflowed into the baffles. Each baffle took about an hour to fill, so after about 14 hours the flow reached the pool-and-drop fishway.
Post-construction work includes: surveys to document the hydraulics of the as-built structures and the shapes of the channel upstream and downstream of the structures, preparation of an operations and maintenance manual, planting in areas disturbed during construction, and monitoring flow.
Friends planned and will be maintaining the planting. A Conservation Corps North Bay (CCNB) crew worked for 4 days in late October to plant over 400 plants, including trees (buckeye, arroyo willow, grey willow, red willow, yellow willow, big-leaf maple), shrubs and vines (creek dogwood, box elder, coyote brush, California rose, California blackberry, elderberry, ocean spray, ninebark, sticky monkeyflower), and grasses and forbs (rush, sedge,, western sword fern,). The CCNB crew also laid out the drip irrigation system, which will be used to water the plants during the dry season for three years.
One part of monitoring is to take photos using two time-lapse cameras. One camera is fastened to a tree downstream of the fishway. During daylight hours, it takes one 10-second video each hour. A second camera is on the bank above the fishway. It takes a high-resolution still photo once every 10 minutes. These photos will be used by the design team to evaluate flows in the fishway. On the cameras we hope to capture spawning steelhead this winter, jumping up the new fishway on their way to now more accessible upper reaches of San Anselmo Creek.
Flood Management and the Ross Valley Watershed Program
The Department of Water Resources has awarded $7.66 million to the Marin County Flood Control District’s Ross Valley Watershed Flood Protection Program for the Phoenix Lake Retrofit Project. The total project cost is $15.6 million. The heart of the project is retrofitting and seismically up-grading the dam at Phoenix Lake, allowing the lake to be operated for flood management, drinking water supply, water quality improvements in Phoenix Lake and Ross Creek, ecosystem restoration, and public recreation improvements. The project will be developed in partnership with Marin Municipal Water District.
FEMA Flood Insurance Rate Maps (FIRMs)
FEMA has released revised FIRMs for the Ross Valley. Visit the FEMA Map Service Center web site to find the map of your neighborhood. Check with the jurisdiction where you live for more details.
Corte Madera Creek Flood Control Project
Congress continues to seriously underfund work by the US Army Corps of Engineers on completing work on the Unit 3 and Unit 4 components of this project.
Friends’ Active Contracts
1. Invasive Spartina Project, funded by the California Coastal Conservancy
$123,929 provided by the Coastal Conservancy for the 2011-13 treatment season.
Scope: Friends is the local sponsor of the Coastal Conservancy’s Invasive Spartina Project, an effort to eradicate invasive cordgrasses through the Bay. Our participation began in 2002; we expect several more years of work before the project can be declared a success. Even then, we will continue monitoring to find and remove plants that persist in some locations.
2. Replacement of Culvert at Hal Brown Park at Creekside, funded as part of the settlement of an enforcement action by the Regional Water Quality Control Board against the Ross Valley Sanitary District
Approximately $400,000 Total Budget, $249,370 provided by RVSD
Scope: Design, obtain permits, and construct:
• new culvert with approximately twice the cross-sectional area of the existing culvert, and
• plant some currently bare areas in the marsh.
3. Planting at Hal Brown Park at Creekside to enhance habitat, funded by the City of Larkspur to compensate for the unavoidable impacts to tidal marsh during the planned replacement of the Bon Air Bridge
$52,000 provided by City of Larkspur
Scope: Plant 0.529 acres of tidal marsh and upland refugia and monitor for three years
Friends Leads Coastal Clean-up Day on Corte Madera Creek