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Broad decision making has been led by the Strategic Planning Team, a group of twenty leaders with expertise in natural resource management or local issues. The Tidal Wetland Project team has also sought out advice of over eighty well-respected scientists and specialists in the form of a Science Panel to get an unbiased perspective on restoration options available to the Elkhorn Slough.
Finally, the proposed project's Adaptive Management Plan is being informed by Working Groups. Working Groups are formed by specialists in a given scientific field who have offered their time to ensure that the restoration's impacts on their area of expertise will be considered, from changes in water quality to effects on shorebirds. The input from these experts will be used to establish acceptable changes in the watershed that might result from the project as part of the proposed adaptive management plan.
Click here for a visual representation of the parties involved in this project.
The Elkhorn Slough Tidal Wetland Project (TWP) is more than just the Parsons Slough Sill Project.
TWP is a collaborative effort to develop and implement strategies to conserve and restore estuarine habitats in the Elkhorn Slough watershed. It involves over one hundred coastal resource managers, representatives from key regulatory and jurisdictional entities, leaders of conservation organizations, scientific experts and community members.
The main goals of the Tidal Wetland Project are to:
(1) conserve existing high quality estuarine habitats
(2) restore and enhance degraded estuarine habitats
(3) restore the physical processes that support and sustain estuarine habitats.
Particular emphasis has been placed on the first goal in the restoration planning process, which aims to stop the ongoing marsh loss and estuarine habitat erosion in Elkhorn Slough.
The Tidal Wetland Project team members are the people making sure that the goals of the Tidal Wetland Project are being met. The team is comprised of:
Tidal Wetland Project Director: Bryan Largay
Tidal Wetland Project Manager: Monique Fountain
Assistant Tidal Wetland Project Manager: Nathan Chaney
Tidal Wetland Project Specialist: Erin McCarthy
Tidal Wetland Project Adaptive Management Lead: Nina D'Amore
Tidal Wetland Project Communications Assistant: Quinn Labadie
For more information on these individuals and their roles, click here.
It's a restoration project designed to conserve healthy habitat in Elkhorn Slough. The project involves constructing an underwater wall called a sill to maintain a healthy slough ecosystem and correct the problem of tidal scour.
Tidal scour is the erosion of soft muddy sediment in the slough due to the velocity of the water as it moves in and out with the tide. Historically the slough was more shallow and less prone to scour, but past management decisions have caused the slough channel to deepen. The sill is designed to slow the tide coming out of the Parsons Slough and reduce erosion in Elkhorn Slough from Parsons Slough to Monterey Bay. This should help to maintain the diverse range of habitats that can be found here.
Although Parsons Slough makes up only about 15% of the slough's surface area, it comprises roughly 30% of its volume. When the land in Parsons Slough was drained for agriculture in the mid 1900s, the ground gradually dropped by up to five feet through a process called subsidence. That volume, which used to be occupied by salt marsh, now fills and drains with each tidal cycle. All that extra water scours the main channel of Elkhorn Slough. This process carries the mud out of the estuary that would otherwise provides habitat to clams and other animals, and which provides the soil that sustains the salt marshes that fringe the slough.
Adaptive management is an approach to improve the management of complex systems. The idea behind it is that it is not always possible to know exactly how the ecosystem will respond to your carefully thought-out project once it is put into action, and if you are paying close attention you will see things happening that you hadn't anticipated. By carefully assessing the performance of your project you can learn what things might need to be done differently. Adaptive management is not simply a ‘wait and see’ approach—it's a process guided by specific questions that are addressed by targeted monitoring.
Adaptive management allows for a structured approach to management with responses planned in advance, but provides more freedom to react to changes in the managed system than traditional management approaches. The biggest difference in adaptive management from other types of project management is that you aren't tied to rigid outlines; if you see a problem, you can react and fix it. It is a great way to minimize unintended consequences.
The structure at Parsons Slough will influence the ecosystem in Parsons Slough and the rest of Elkhorn Slough in many ways. We are using the knowledge we have gained from years of research to make predictions of how the project will affect key natural resources, such as shorebirds, benthic invertebrates, sharks and other fishes, but our knowledge is still limited.
We are using adaptive management to ensure that the management plan we are creating for the sill at Parsons Slough will be a "living" document that outlines what changes caused by the sill are expected and permissible, and what changes are warning signs that we should "adapt" the management process.
For questions about adaptive management, please .
The National Oceanic Atmospheric Administration issued a $3.95 million grant to the Elkhorn Slough Foundation to build a water control structure at the mouth of Parsons Slough to reduce habitat loss throughout Elkhorn Slough, and later issued an additional $562,880.
Elkhorn Slough is one of nine California restoration projects to receive a grant as part of the American Recovery and Reinvestment Act that President Barack Obama signed into law February 17, 2009. The agency awarded $167 million to fund 50 coastal habitat restoration projects nationwide.
The Parsons Slough Sill Project is expected to use the entire grant. Additional funding from the David and Lucille Packard Foundation, the Resources Legacy Fund Foundation, the Environmental Protection Agency, and the California Coastal Conservancy supported the planning process preceding this award, for a total expected investment of nearly $6 million.
The Parsons Slough Sill Project is expected to create or save over 100 jobs! Some jobs will be created directly through the hiring of new staff and through subcontracts, while others will be created by the money spent on construction and materials. Over 55 people have worked on the project to date.
Job creation is one benefit to the community from the proposed project, but the grant was awarded for reasons beyond job creation. The proposed project is designed to benefit the unique habitats of Elkhorn Slough, a national treasure. The proposed project has the goal of preserving and restoring the vital salt marsh and soft mud habitats of Elkhorn Slough by reducing tidal scour. This is to be accomplished while minimizing impacts to fish and wildlife and existing high quality habitats.
The Parsons Slough Sill Project was a planning process conducted between 2007and 2010 with several goals:
Goal 1: Restore and enhance intertidal marsh habitats and functions within the Parsons Slough tidal wetland complex while addressing the needs of special-status species, estuarine-dependent species, and ongoing human uses.
Goal 2: Support the ecological recovery of the larger Elkhorn Slough system to the extent possible while meeting Goal 1.
Goal 3: Conserve high quality subtidal and intertidal estuarine habitats and functions within the Parsons Slough tidal wetland complex.
During that process it became clear that achieving Goal 1, by restoring extensive salt marsh to Parsons Slough, would require much more planning. Goals 2 and 3, however, could be advanced by the Parsons Slough Sill project. The Parsons Slough Sill was advanced to the implementation phase.
The Tidal Wetland Project team is working to secure funding to plan future salt marsh restoration projects that also conserve existing high quality mudflat and subtidal habitats for shorebirds and large fish.
A "sill" is a structure like an underwater wall or weir. In some ways it is a speed bump to the flow of water. The intent of putting a sill near the Parsons Slough opening is to slow the speed of the current and in doing so reduce the erosion that is degrading Elkhorn Slough. The Parsons Slough channel where the sill is to be located used to be much shallower, and the sill in some ways replicates that geometry. The existing narrows at the Parsons Slough bridge makes it a feasible construction site.
Tidal scour has been eroding the soft slough mud, washing away mud flat and tidal marsh habitat for about 60 years, ever since the construction of Moss Landing Harbor. The sill will slow the speed of the currents as they flow out of Parsons Slough on the falling tide. These currents erode the channel of Elkhorn Slough from Parsons Slough to Monterey Bay.
The sill will slow down the outgoing tides, particularly during spring tides and near low tide. During neap tides and at high tide, water will flow in and out of Parsons Slough largely unaffected by the sill. During spring tides a slightly smaller total volume of water will flow in and out of Parsons Slough and Elkhorn Slough as a result. The sill will slow the velocity of water moving through the portion of the Elkhorn Slough south of Parsons Slough, and is expected to reduce scour in the main channel by as much as 10%.
TWP has considered a range of options, including:
Preliminary estimates indicated that the cost to restore fully tidal salt marsh in Parsons Slough by sediment addition would be substantial at $80,000 per acre or more. Building a sill at the harbor mouth could increase the risk of water quality problems. A sill at Parsons Slough was settled on as the best project because it is cost-effective, low risk, and yet substantial enough to have a significant positive impact on the slough.
TWP is looking at the overall health of the slough and is definitely not picking any favorites. While some components of the project will benefit specific species more than others, it is not TWP's intention to harm any species or habitat.
Elkhorn Slough is changing from a more estuarine to a more marine ecosystem as a result of past management, specifically the opening of the Harbor Mouth. This project aims to slow the rate of change.
To ensure that the project does not adversely impact existing species (such as large fish), water quality—particularly dissolved oxygen—will be monitored closely. If unacceptable conditions are observed, plans are in place to lower the sill to increase the exchange of water and recover pre-project water quality conditions. However, the project has been carefully designed to minimize the chance that that will be necessary.
TWP has consulted with North Salinas Valley Mosquito Abatement District and determined that it is not likely the sill will increase mosquito populations, and therefore West Nile Virus is not expected to be a concern.
The sill is designed to accommodate increasing rates of sea level rise associated with climate change such that it will remain effective with a sea level rise of 1.6 feet, which is a median forecast of sea level for the year 2060. The sill is also designed to support additional weight, if, because of sea level rise, a future decision is made to make it higher. Such an action is not planned at this time and would require approval from regulatory agencies.
The project design has been lead by Ducks Unlimited.They anticipate that construction will be done from barges with a 90 ton crane, vibratory hammers, impact hammers, loaders, push boats, material barges, loading cranes, barge mounted cranes, and highway dumps. There will be a staging area for the equipment at Kirby Park.
Construction of the sill is expected to last approximately four months and is anticipated to begin in October of 2010. Actual construction days will be dependent on the tide.
Two main panels have been intimately involved with the decisions regarding the restoration of the Elkhorn Slough: a Science Advisory Panel and a Strategic Planning Panel. These more than one hundred panel members are all experts in their fields, which include wetland science, biology, hydrology, geomorphology, and more. Many of these experts have extensive experience working in and around the Elkhorn Slough area. In addition to these two panels, the Elkhorn Slough National Estuarine Research Reserve (ESNERR) team have been conducting research in the Elkhorn Slough since 1989 with a volunteer water quality monitoring program, which later became more robust in 1995, they have helped guide the decision-making process with their knowledge and insight on the slough.
Some research has been conducted in the Elkhorn Slough since the 1920s, and ESNERR has amassed a collection of hundreds of research papers for studies in the slough. While no one can predict the future, the ESNERR Staff have been on the ground floor of the proposed project since its inception and have been dedicated champions of the slough throughout the entire decision-making process.
The potential impacts of the project were examined in the Initial Study, a document that is part of the regulatory compliance process for undertaking new development projects on public land. It was determined that there would be no significant negative impacts from the project that could not be mitigated in some way. Therefore, TWP predicts that no negative impacts will result from the construction of the project. Additionally, post-construction monitoring will be undertaken to watch for any unforeseen negative impacts on marine mammals, sharks and fish, birds, invertebrates and marsh habitat. If any negative impacts are discovered in the future TWP will take corrective measures.
No. There is no expectation that groundwater will be impacted by the project.
The disappearance of the dock at Kirby Park actually has nothing to do with the Tidal Wetland Project! It was damaged and has not yet been replaced by the Moss Landing Harbor District. This project will use part of Kirby Park for staging equipment, and we are working with the Harbor District to ensure the area is left in good condition afterwards.
Unknowns exist in every project because no one can see into the future, and TWP acknowledges that we are no exception. We can't say with 100% certainty what every impact of the proposed project will be, but we do have a lot of data on expected outcomes.
Traditionally, tidal restriction projects have relied on culverts and flap gates, which are commonly associated with negative effects to aquatic species related to reduced circulation, poor water quality, and barriers to animal movement. The Parsons Slough Sill Project proposes a different approach, using an open channel to maximize connectivity and reduce the likelihood of encountering the negative impacts associated with restoration. However, it is a novel design with few examples to use as a guide.
Because this approach has not been widely used, there is not a great deal of data to draw on from similar projects, and so we are relying on our extensive knowledge of the Elkhorn Slough to anticipate the responses to the sill. Our scientists have been working in Elkhorn Slough for decades, and we are drawing on this data, as well as data from our engineering consultants' project models, to implement the project with best management practices (BMPs).
Currently the slough is eroding at an alarming rate. This project is a relatively inexpensive way to slow down this process. Because of uncertainty in our predictions, this project may have more benefit than expected. Following the tenet of “First – do no harm”, this project conservatively and incrementally addresses the tidal scour problem. If nothing else, it buys time to understand the ecosystem better to clarify the risks and benefits of more intensive management actions.
The hydraulic modeling was performed by URS Corporation using the United States Army Corps of Engineers (USACE) software, HEC-RAS version 4.0.0. This software was used to perform one dimensional river hydraulic calculations using unsteady flow. Predictions for tidal scour were developed using a geomorphic analysis tool developed by Philip Williams and Associates, which is based on the Delft3D modeling software. More information on project analysis, modeling and predictions can be found in the on our website.
Restoring fully tidal salt marsh in the Parsons Slough is likely to be costly and to require substantial additional technical analyses. TWP found that a simpler project that prioritizes the preservation of existing high quality habitat in both Elkhorn Slough and the Parsons Slough could be implemented at a small fraction of the cost of a project that restored extensive tidal marsh. The proposed Parsons Slough Sill could preserve disappearing habitat until a later time when additional funding might become available to enact a more sweeping restoration project, and would be compatible with possible future projects without being dependent on them. Likewise the success of possible future projects would not be dependent on the sill project.
The mud in Elkhorn Slough near the project site is approximately 80 feet deep, and there is little solid ground in any direction. During the design process it became clear that, because of geotechnical issues, making the sill as high as originally planned would have required a more expensive and more visually obtrusive structure than we were prepared to build. As we discussed changing the design to the low sill, which is much simpler, less obtrusive and has no moving parts, many stakeholders strongly supported the change. Operations and maintenance costs will also be lower.
The low sill could serve as the foundation for an adjustable sill in the future. But that is not presently planned, and a new regulatory compliance process would be required for such a project to proceed.
The latest information for events, recent reports, meeting notes and updates on the Parsons Slough Sill Project will always be on the this website, but you can also sign up to receive the TWP newsletter for information on project developments and upcoming events. If you prefer to speak with a real person, you are always welcome to contact the TWP Communications Assistant by or call (831) 728-2822, extension 325.
It is our hope that anyone who wants to express their delight or concern with this project will do so! We have multiple forums to facilitate your feedback, including: