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Crocker Restoration

As part of its Fisheries Enhancement Project, the Agency sponsors and conducts riparian and aquatic habitat restoration projects within the Russian River watershed. Through restoration projects such as the Crocker Creek Dam Removal Project, the Agency strives to improve habitat for fish and other aquatic species and restore runs of salmonid species that have been negatively impacted by current and historic watershed uses.

Historic information relevant to the construction and use of the Crocker Creek Dam is limited. Long time residents believe that the dam was constructed to impound water for recreational use by the original landowners. The exact year of construction is unknown, however field investigations by Agency engineers estimate the initial construction to have occurred in the early 1900s. The dam appears to have been raised and widened at least three times. The final configuration of the Crocker Creek Dam was a concrete buttress, flashboard dam approximately 30 feet high and 100 feet wide with two concrete spillways (one used and one abandoned), each approximately 150 feet long. At no point in the dam's history were any attempts made to facilitate fish passage.

The current property owner acquired the property on which the dam is located in 1993. The dam began to show signs of impending structural failure as early as 1974, however, major structural failure did not occur until 1995. In 1995, the entire northern side of the dam, with the exception of the original base, collapsed. Further failure occurred in 1997. The impact to Crocker Creek as a result of the failures has been significant. The creek downstream of the dam was inundated with the sediment that had been trapped behind the structure. The creek upstream of the dam has experienced major erosion and collapsing of banks as a result of the acute loss of the major grade control structure. Currently, all that remains of the Crocker Creek Dam are the north and south abutments, both spillways, the original base, and a large pile of concrete and other structural debris directly below the base of the dam. While the elevation of the base is significantly lower than the previous top of the dam, the structure and associated debris pile remains a potential barrier to anadromous salmonids.

Project Description

There are three primary goals for this project:

  1. provide upstream and downstream passage for anadromous salmonids
  2. remove the remains of the failed dam
  3. prevent further bank erosion/re-establish riparian vegetation

The proposed project would consist of several restoration activities; including demolishing and removing the remaining structures and debris, bank recontouring, biotechnical channel adjustments, and revegetation.

Restoration activities would occur at three locations within the project site. Areas 1 and 2 comprised of the remnants of the dam, the spillways, and the adjacent north and south banks. Area 3 is located approximately 150 feet upstream of Area 1 on the north bank. This site is an erosional scarp approximately 21 feet high and 170 feet long. Area 4 is approximately 400 feet upstream of Area 3 on the north bank and encompasses an area that contains a previous bank stabilization project that has failed.

At Areas 1 and 2, the remains of the north and south bank abutments and the two concrete spillways would be demolished. As a result of the dam failure, the north abutment has become unstable and is subject to collapse. Stabilizing the abutment would require removing the soil material and recontouring the bank to a 2:1 slope at the north abutment and upstream and downstream for approximately 150 feet to match existing grades. The upstream extent of the recontoured north bank would terminate at the base of a culvert that is failing. A down drain would be installed on the culvert and rock would be placed at the base to dissipate stream energy. Recontouring of the bank would require removal of an abandoned powerline and associated power poles, two transformers, and a concrete pad.

The south abutment and concrete spillways (Area 2) are only partially supported in the streambanks. There are signs of significant erosion and undercutting of the banks around these structures. The abutment and spillways would be demolished and removed. Concrete rubble from the failed dam would also be removed from the stream channel. Soil removed from the abutments would be used to recontour eroded portions of the spillway along the existing slope.

The eroding bank at Area 3 would be recontoured to a 2:1 slope. The slopes would be protected with stabilization fabric to reduce erosion and planted with native vegetation. An approximately 1,500 cubic yard bench would be created at the base of the slope to reduce stream velocity along the bank and to move the creek back to its original low flow channel. Two redwood log spurs would be installed at the top and bottom of the constructed bench to deflect stream energy away from the bench.

Recontoured slopes at Areas 1, 2, and 3 would be planted with native vegetation based upon surveys of riparian habitat upstream and downstream of the project site. Planting of vegetation would help stabilize existing soil to reduce erosion and improve aquatic habitat quality by providing shade over the creek. An irrigation system would be installed to water the vegetation at all three sites until it is well established.

At Area 4, concrete blocks installed during a previous attempt to stabilize the north bank would be removed. The bank would then be recontoured to a 2:1 slope and the toe of the bank would be reinforced with a willow revetment and four redwood log spurs.

The access road leading to the staging area and construction site crosses an ephemeral stream. The stream would be surveyed at the crossing and clean drain rock and a culvert would be installed to provide access to the construction site. The fill and culvert would be removed and the pre-existing grade would be re-established upon completion of the project.

Container plants will be contract grown using a local source of propagules. Container plants will be planted in late fall/early winter 2002. Willow sprigging will be conducted when willow trees are dormant (November- January of 2002/2003). All planting materials have been collected from areas in or near the Project Site.