The official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve
Elkhorn Slough Tidal Wetland Project Restoration Projects: Parsons Slough

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the Tidal Wetland Project.

Important information about the construction in the slough.

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  • Detailed Reports
  • Related Research

Elkhorn Slough Restoration Project Completed

  • Photographs of construction progress – Photographs taken between November 2010 and March 2011 at the construction site. Download PDF (1.2MB) or PPTX (1.6MB).

  • Video of the Parsons Slough Sill under construction.

  • Video footage of flow conditions at the Parsons Slough Sill are available on request. Please

After four years of work and input from more than one hundred scientists, specialists, and lawmakers, the Parsons Slough Project is complete.  This project, funded through the American Recovery and Reinvestment Act and managed by the Tidal Wetland Project—a joint effort between the Elkhorn Slough National Estuarine Research Reserve (ESNERR), was the most efficient and lowest risk approach to reducing erosion and wetland loss in Elkhorn Slough.

The construction of an underwater sill – 200 feet wide, 10 to 15 feet tall and five feet under water – started on November 10, 2010 and was completed on time in February of this year.  The sill acts as an underwater barrier to slow the flow of the tide and reduce erosion.  The finishing touches – repaving the staging area at Kirby Park and leaving behind a dock for public use – were completed in early May.

Early monitoring of the sill indicates the project is a success. The sill is expected to significantly reduce the erosive tides in Elkhorn Slough and prevent thousands of cubic yards of sediment from washing into the bay each year.  The cost to replace that sediment by other means would have cost hundreds of thousands of dollars annually.  The project is anticipated to restore an additional seven acres of tidal marsh around the perimeter of the Parsons Slough Complex.

Construction monitoring wrapped up in late March, and the data indicates that the plant, bird, and other animal life that inhabit this unique environment have adapted well to the project.   Monitors have already sighted as many as five otter moms and pups resting in the area by the sill, and witnessed another otter being born very near the construction site this April.  Harbor seals with pups are also using the area extensively. Long term monitoring of the wildlife and habitats in the area will continue for years to maximize the opportunity to learn about the project.

The Parsons Slough project not only improved habitat and reduced a major ecological concern in the slough, it has created or saved approximately 107 jobs through contracts and direct hires.  In Monterey County, where the unemployment rate exceeded 17% this past winter, this was a huge boon to the economy.  Over $1.5 million of the $4.5 million grant was spent regionally on the purchase of equipment and supplies (such as steel sheet piling and rock riprap) further stretching the stimulus dollars.

Now that it is complete, this underwater retaining wall is working to slow the ebbing flow of the slough’s waters for the first time in more than sixty years—a feat that will reduce erosion and increase rare marsh habitat.  The engineering, permitting, and construction of this structure were all conducted under rigorous scrutiny and with input from the local community, and environmental monitoring ensured not only that that wildlife was unharmed, but that others interested in such a restoration project can learn from how it was done in the Elkhorn Slough. 

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Elkhorn Slough otter raft

General Information
This information will give you an overview of the proposed project without taking up a lot of your time.

Images of the construction are available here.

PRESS RELEASE: Kirby Park Set as Staging Area for Elkhorn Slough Construction( 38KB, docx)
NEWS VIDEO: Restoration Project Addresses Erosion At Elkhorn Slough, KSBW via YouTube.
NEWS: Elkhorn Slough dam project will slow erosion, SF Chronicle
More press...

Project Objectives
The primary objective of the Parsons Slough Project is to reduce the tidal prism in Elkhorn Slough to minimize tidal marsh loss and habitat degradation as a result of tidal erosion and flooding, while maintaining sufficient tidal exchange and flushing to provide acceptable water quality. A secondary objective is to increase habitat diversity in Parsons Slough such that it better represents historic conditions.

Fact Sheet: Tidal Wetland Project and the Proposed Parsons Slough Restoration Project (pdf, 1.25MB)

Fact Sheet: Why Restore Elkhorn Slough? (pdf, 159KB)

Background Information

Frequently Asked Questions - a thorough  list of your questions about the proposed project and our answers.  Read this for answers to general questions.

Engineering Designs and Design Criteria - an overview of the specific project objectives.

Preliminary Project Description - a brief overview of the proposed project.

Supplemental Materials, November 2009 (.pdf 1.09MB) The material found here includes the goals, objectives, maps and other information associateed with the Preliminary Project Description.

Glossary of Terms - find definitions to commonly used words on our website and in our reports.

History and map of Parsons Slough- coming soon!


Elkhorn Slough Reserve

Detailed Reports (and their Executive Summaries)
These four reports are full of information, and because of that they are also very large.  Choose the one that interests you the most, or read them all!

The Final Initial Study/ Mitigated Negative Declaration for the Parsons Slough Sill Project is now available.
Final Initial Study/ Mitigated negative Declaration - High Resolution, pdf, 18.6MB
Final Initial Study/ Mitigated negative Declaration - Compressed version, pdf, 6.9MB

Targeted Supplement Environmental Assessment (TSEA) - The National Environmental Policy Act (NEPA) requires federal agencies to integrate environmental values into their decision making processes by considering the environmental impacts of their proposed actions and reasonable alternatives to those actions. To meet NEPA requirements federal agencies prepare a detailed statement known as an Environmental Impact Statement (EIS). For the Parsons Project there was a Programmatic Environmental Assessment done at the program level. Download the Targeted Supplement Environmental Assessment (TSEA) for this project (6.11MB, pdf).

Final Initial Study/ Mitigated negative Declaration for the Parsons Slough Sill Project - an in-depth assessment of the potential positive and negative effects the proposed project could have on the Elkhorn Slough. It is written with the public in mind rather than for a scientific audience, and is one of the best ways to learn about the proposed project.
Final Initial Study/ Mitigated negative Declaration - High Resolution, pdf, 18.6MB
Final Initial Study/ Mitigated negative Declaration - Compressed version, pdf, 6.9MB
Draft still available - High Resolution, pdf, 17.5MB
Draft still available - Low Resolution, pdf, 6.5MB

Elkhorn Slough Tidal Wetland Project Hydrodynamic Modeling and Morphologic Projections of Large-Scale Restoration Actions FINAL REPORT (2008) - The final Philip Williams and Associates report on the projected effects of major actions on Elkhorn Slough hydrodynamics, geomorphology and habitats is available for download.  It describes the four different restoration alternatives that were considered for fixing the problems in Elkhorn Slough. 

Elkhorn Slough Tidal Wetland Strategic Plan (2007) - This document summarizes the results of many technical discussions, scientific evaluations, and resource management decisions made over the past few years by participants in the Elkhorn Slough Tidal Wetland Project.  It is a guide for a variety of restoration projects for many years to come. 

Parsons Slough Wetland Restoration Plan Final (2010) - This detailed report examines the opportunities for ecological restoration of approximately 450 acres of intertidal habitats, including Parsons Slough, South Marsh, the Rookery Lagoon and other areas of the Elkhorn Slough National Estuarine Research Reserve.

Computer Model of the proposed project (2009) by Moffatt and Nichol - Check out this memo for a quick overview of the numerical modeling performed to simulate the proposed project's possible impacts on the slough.

View a detailed map (available to download as a PDF in either  414KB or 246KB) with this Excel map legend (106KB .xls) to get descriptions of the many water control structures in Elkhorn Slough.


Elkhorn Slough wetlands

Related Research
This information will give you a comprehensive understanding of the Elkhorn Slough's current condition and how it has changed over the years.  It is a great background for why the proposed project is needed. 

Browse the hundreds of research papers that have been written about the Elkhorn Slough by searching ESNERR's comprehensive bibliography, which includes key research findings from ESNERR's Technical Report Series. You can also purchase our compilation of 80 years of research at our bookstore for a summary of the research done at the Elkhorn Slough over the past eight decades.

Management Plans for the Elkhorn slough can be found in our Key Documents web page.


Aerial of Elkhorn Slough


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