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Intent To Prepare a Joint Environmental Impact Statement/Environmental Impact Report for the Corte Madera Creek Flood Control Project, Marin County, CA

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Department of the Army, U.S. Army Corps of Engineers, DoD.


Notice of intent.


The U.S. Army Corps of Engineers (Corps) authorized through the Flood Control Act of 1962, Public Law No. 87-4, 87th Congress, 2nd Session, approved October 23, 1962, and amended by Section 204 of Pub. L. No. 89-789, the Flood Control Act of 1966, and the Water Resources Start Printed Page 38423Development Act of 1986, will address channel modification opportunities to Unit 4 of Corte Madera Creek, Marin County, CA. The purpose of the Corte Madera Creek Flood Control Project is to provide flood risk management for Corte Madera Creek, from the upstream end of the existing Unit 3 concrete channel to Sir Francis Drake Boulevard at the border of Ross and San Anselmo. Although Units 1, 2, and 3 channel modifications were completed in 1971, public concerns led to a delay in the planned actions for Unit 4. In 1996, Marin County requested the completion of Unit 4 by the Corps, and damages incurred by the December 2005 flood have also renewed public interest in finding solutions to minimize the risk of future floods. Since 1971, additional technical studies were conducted that provide another opportunity to formulate and review new alternatives in order to complete the project. This is a notice of intent to prepare a joint Environmental Impact Statement/Environmental Impact Report (EIS/EIR) to consider all reasonable alternatives and to evaluate potential impacts associated with the proposed actions. The U.S. Army Corps of Engineers is the lead agency for this project under the National Environmental Policy Act (NEPA) and Marin County Flood Control and Water Conservation District Zone 9 is the lead agency under the California Environmental Quality Act (CEQA).


A public scoping meeting will be held on July 23, 2008, from 7 p.m. to 9 p.m. Written comments from all interested parties must be received by August 6, 2008.


The scoping meeting will be held at the Drakes Landing Community Room, 300 Drakes Landing, Greenbrae, CA 94904.

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Questions and comments regarding the proposed action and NEPA aspects of the study can be addressed to Ms. Nancy Ferris at (415) 503-6865, U.S. Army Corps of Engineers, San Francisco District, 1455 Market Street, San Francisco, CA 94103. For questions concerning the CEQA aspects of the study, contact Jack Curley at (415) 499-3051, County of Marin, P.O. Box 4186, San Rafael, CA 94913. All written comments can also be faxed to (415) 503-6692 or sent electronically to Further information is also available on the project Web site at​cortemaderacreek/​index.html.

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The following section will address the study area, recent development of technical studies, and some of the alternatives that will be addressed in this study.

1. Background. Corte Madera Creek drains an area of approximately 28 square miles in Marin County, CA, and discharges into the San Francisco Bay just nine miles north of the Golden Gate Bridge. Units 1, 2, and 3 extend from San Francisco Bay through the communities of Corte Madera, Larkspur, Kentfield, and Ross. Unit 4 extends from the Lagunitas Road Bridge, near the upstream terminus of Unit 3, to the Sir Francis Drake Boulevard Bridge right before the Ross/San Anselmo town line. The project was originally authorized in 1962 and construction for Units 1, 2, and 3 were completed by 1971. Unit 4 of the original project was not started due to a series of design changes, transfer of district ownership, property litigation, and lack of public support. Unit 3 was built so that it could be modified with the future design plans of Unit 4, such that changes to the Unit 3 channel would also be evaluated if implementation of project construction in Unit 4 caused flooding downstream.

The Corps has conducted additional studies focused on evaluating the design performance of Units 3 and 4 since 1971. These studies have identified the unsmooth transition between Units 3 and 4 created by the existing Denil fish ladder, the narrow channel condition on the east and west bank, and the Lagunitas Road Bridge as constrictions to flood flow. The replacement of Lagunitas Road Bridge is an option that is being evaluated by the Town of Ross and is not currently part of this federal project.

The following proposed action seeks to address the issues associated with the current channel capacity of Unit 4.

2. Proposed Action. The U.S. Army Corps of Engineers and the Marin County Flood Control and Water Conservation District propose to manage flood risk along Corte Madera Creek, downstream of Sir Francis Drake Boulevard. The proposed action may include changes to the existing design of Unit 3 to ensure a total project design capacity. The alternatives evaluated will be developed in consideration of fish passage for threatened and endangered fish species that migrate through the project area.

3. Project Alternatives. The following represent a minimum of the alternatives that will be evaluated in the EIS/EIR regarding the proposed project to increase flood flow capacity, in addition to considering the improvement of fish passage and bank stability in Corte Madera Creek. The possibility of hybrid alternatives representing a combination of measures will also be evaluated:

a. No action. Under this alternative, the current conditions would be retained at Units 3 and 4, and flood capacity would remain unchanged at approximately 3,200 cfs (cubic feet per second). Under these existing conditions, excess flood flows would pass outside the channel onto a residential floodplain. The no action alternative would be considered as a baseline in evaluating other alternatives.

b. Minimum action. This alternative addresses the existing Denil fish ladder which exacerbates flooding in the Unit 4 channel and is inadequate for fish passage. The existing ladder would be replaced with a concrete pool-and-chute fish ladder, with a proposed location within the upstream length of the Unit 3 concrete channel. Other design considerations include meeting current fish passage criteria as established by NOAA's National Marine Fisheries Services (NMFS) restrictions on the height of vertical leaps. The estimated flood flow capacity of Unit 4 would depend on the design of the replacement fish ladder.

c. Unit 4 structural design alternative. In addition to the minimum action, flood risk management measures proposed for Unit 4 include (1) Installing vertical wall configurations that would widen the channel and increase the maximum flood flow capacity to approximately 5,100-5,400 cfs, depending on the specific design; (2) constructing a bypass culvert adjacent to Lagunitas Bridge that would convey high flows from the bridge to the beginning of the concrete channel, with capacity ranging from 300-1,300 cfs depending on the type of culvert structure; (3) installing temporary or permanent low floodwalls or landscape berms; (4) enlarging the sediment basin immediately downstream of Lagunitas Bridge, which would decrease the water surface profile downstream and increase flood flow capacity; (5) creating a natural channel bottom with natural grade protection that would accommodate a flow rate of approximately 5,400 cfs; and (6) implementing grade control in order to stabilize the stream bottom.

d. Unit 3-4 structural design alternative. Measures that are proposed to modify the junction between Unit 3 and 4 include (1) Replacing the existing fish ladder with a natural grade roughened rock channel between the Unit 3 and 4 transition, which would allow for fish passage while increasing flood flow capacity to 4,900 cfs and improving conveyance into the existing concrete channel; (2) bank regrading Start Printed Page 38424and use of biotechnical bank stabilization techniques involving such natural materials as native vegetation, logs, and woody debris; and (3) installing concrete wing walls to facilitate flood flows into the stream channel.

e. Non-structural alternative. The non-structural plan would include expanding the existing floodplain by moving residential property through real estate acquisitions.

4. Environmental Considerations. In all cases, pursuant to NEPA and CEQA guidelines, environmental considerations will include human health, riparian habitat, improving fish passage and fish habitat, geophysical impacts, air quality, hazards, noise, utilities and service systems, transportation, land use and planning, historic and cultural resources, aesthetics, recreation, social and economic effects, as well as other potential environmental issues of concern.

5. Scoping Process. The Corps and the Marin County Flood Control and Water Conservation District is seeking participation of all interested federal, state, and local agencies, Native American groups, and other interested private organizations or individuals through this public notice. The public scoping meeting will be held in Greenbrae, CA (see DATES). Any changes to the date, time, or location will be published in the local newspaper or provided by mail to those requesting information. The purpose of this meeting is to solicit comments and questions regarding the potential impacts, environmental issues, and the alternatives that should be discussed in the EIS/EIR. Public participation will help define the scope of the environmental analysis, identify other significant issues, provide other relevant information, and recommend mitigation measures, where possible. The public comment period closes on August 6, 2008.

6. Availability of EIS. The public will have an additional opportunity to comment on the proposed alternatives after the draft EIS/EIR is released.

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Craig W. Kiley,

Lieutenant Colonel, U.S. Army, Commanding.

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[FR Doc. E8-15329 Filed 7-3-08; 8:45 am]