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Tred Avon River and Harris Creek Oyster Reef Restoration

NEW: Link to the 2014 Maryland oyster restoration update: Click HERE to view updated stats and implementation progress, including number of acres restored, number of acres constructed, number of oyster seeds planted, funds spent to date, and an outlook for future work for Maryland's restoration sites.

Click HERE to view a report the University of Maryland's Paynter Lab published regarding the 2014 monitoring of Cook Point, which is a site used to evaluate how well reefs made of various alternate materials are performing for oyster restoration. Our interagency partners and we take research and monitoring seriously because we want to ensure our oyster restoration efforts are working. Overall, this study found that reefs made of alternate substrate at the Cook Point Sanctuary are supporting dense, healthy oysters and reef habitat. The report seems to show that rock and rock/shell provide suitable habitat for oyster restoration. It supports that 1 foot is suitable in reef height for restoration efforts. The report also indicates that incorporating shell into the reef improves restoration performance. This report supports the reef design work the Corps has done and will most likely continue to pursue in the future.

The U.S. Army Corps of Engineers and partners completed 370 acres of restoration at Harris Creek in summer 2015. It is the first restored sanctuary. Through the interagency partnership, the State has planted more than a billion oysters in the Harris Creek Sanctuary since 2011. Since restoration efforts started, areas with less than one oyster per square meter now have upward of 25 oysters per square meter. The site now contains oyster beds that continue to grow and reproduce. The Harris Creek sanctuary will work to improve water quality and enhance fish habitat.

This effort is part of the Maryland and Virginia statewide oyster restoration program, as laid out by the Corps’ Native Oyster Restoration Master Plan that identifies the most suitable tributaries throughout the Chesapeake Bay for large-scale oyster restoration based on physical and biological conditions.

View a map of the restoration sites in Harris Creek by clicking here.*

Similar work in the Tred Avon River began in April 2015 and wrapped up for the season in July 2015. Work is anticipated to resume in winter 2015. In the Tred Avon, 24 acres of reef will be placed in water 9 to 20 feet deep (MLLW). View a map of the completed and proposed restoration work in the Tred Avon River by clicking here.* Work includes constructing 1-foot reefs using mixed-shell materials and rock. The shell comes from coastal processing plants and is permitted to be imported and placed in the river. The rock is quarried in Havre de Grace, Maryland.

* The Corps and its partners have engaged with the Maryland's Watermen Association to discuss a path forward for working more closely together throughout the process. Following a series of meetings and visits to the restoration sites with the watermen, the interagency team limited the use of rock planned during spring/summer 2015 restoration to three sites in the Tred Avon River. The remaining reef sites planned will be made of mixed shell. This change affects the following sites identified on the Tred Avon map: 39, 40, 43, 44, 60, and 61. These sites had originally been planned to be either 12 inches of rock or 6 inches of rock with a 6-inch mixed shell cap. They will now be constructed completely of mixed shell. This change was made to minimize impacts to trotlining by crabbers in the Tred Avon River. In Harris Creek, the following sites will now be constructed completely with rock: 43B, 53, 55, and 58. Extensive reef construction using rock has been completed prior to this work in Harris Creek. Restoration plans are subject to funding and the availability of material.

Comment on a public notice closed July 24, 2015. The content of this notice involved expanding the scope of the supplemental environmental assessment for Tred Avon River oyster restoration initiated in 2013 to include planting of disease-free spat-on-shell, or oyster seed, from state-owned hatcheries, on new oyster reefs in waters between 6 and 9 feet in depth, and on existing reefs/natural oyster bars in waters between 4 and 20 feet. This is in addition to the assessment of reef construction on 60 acres in shallow water depths between 6 and 9 feet that was the initial focus of the supplemental environmental assessment. Planting of spat-on-shell will add minimal change to the existing height of the natural oyster reefs, approximately 3 inches, and will increase the proposed project area by an additional 71 acres for a total of 131 acres.



Oyster populations in the Chesapeake Bay have declined dramatically in the last century, largely due to parasitic diseases, overharvesting, declining water quality, and a loss of habitat. Less than one percent of historic oyster populations remains. Oyster restoration is important because oysters provide a number of environmental benefits, including reef habitat that is significant to the Bay ecosystem for animals like blue crabs and fish. Additionally, oysters are filter feeders that improve water quality.

The Native Oyster Restoration Master Plan is the Corps' plan for large-scale, sanctuary-based (through Maryland Department of Natural Resources) oyster restoration throughout the Chesapeake Bay and its tributaries. The master plan examines and evaluates the problems and opportunities related to oyster restoration, and formulates plans for implementing large-scale, Bay-wide restoration.

Project elements include: (1) disease-free spat (oyster seeds) from state-owned hatcheries; (2) creation of new oyster habitat; (3) rehabilitation of existing non-productive oyster habitat; (4) construction of seed bars for production and collection of spat; (5) planting spat on the new and rehabilitated bars; and (6) monitoring of project performance.

The Maryland Department of Natural Resources (MDNR) is the non-federal sponsor for Corps’ oyster restoration activities in Maryland. Additional project partners include the National Oceanic and Atmospheric Administration (NOAA) and the Oyster Recovery Partnership (ORP). NOAA maps available restorable water bottom using sonar in conjunction with various ground‐truthing methods and funds the production and planting of seed oysters. The Corps constructs reef structure where none currently exists. ORP plants oyster spat (baby oysters) grown at the University of Maryland Horn Point Hatchery on restoration sites.

Restoration only takes place in pre-existing sanctuaries, as established by MDNR. Sanctuaries are areas that are closed to harvest; however, oysters within sanctuaries are expected to increase the abundance of adult oysters whose larvae are expected to settle not only within the sanctuary, but also on public shellfish fishery areas in the vicinity of the sanctuaries.

Typically, there are two barges used for constructing the reef: one barge holds the substrate, the other holds a crane with a bucket to move the substrate.  The bucket picks up the substrate from the barge, then, with a sweeping motion, releases it into the water.  GPS locaters are used to make sure the reefs are constructed in the selected sites. Oyster seed, which are technically referred to as spat on shell, are brought from hatcheries and placed or “planted” on the constructed reefs in hopes of restoring the oyster population in these areas.  Once planted, the oyster reefs will be monitored to assess the restoration progress.

The Corps is involved in oyster restoration in two ways. Through an authority under Section 704(b) of the Water Resources Development Act (WRDA) of 1986, as amended, the Corps provides construction assistance for certain oyster restoration projects through its Civil Works program. For work undertaken by others, the Corps evaluates the impact of dredged or fill material into Waters of the United States under Section 404 of the Clean Water Act and Section 10 of the Rivers and Harbors Act, through a permitting process managed by the Corps Regulatory Program.

The Maryland project cooperation agreement was executed in February 1997, with an amendment in July 2002.  Placement locations in Maryland include Kedges Strait, Eastern Bay; and the Chester, Choptank, Magothy, Patuxent, and Severn rivers (and soon to be Tred Avon) - a total of approximately 600 acres of new oyster bars. Some of the oyster bars were left for natural recruitment; others received hatchery-raised spat. The Virginia project cooperation agreement was executed in September 2001, with amendments in July 2004 and June 2007. The Corps' Norfolk and Baltimore districts support activities in Maryland and Virginia, respectively. In Virginia, activities include oyster bar creation in Tangier Sound, Pocomoke Sound, the Great Wicomico River, and the Lynnhaven River - a total of approximately 400 acres of new oyster bars.

Prior to the 2009 restoration activities, the Corps oyster restoration program did not focus on large-scale tributary restoration in Maryland, as it does now.  From 1997 to 2006, the Baltimore District received relatively small funding allocations for a number of small sites, scattered throughout the Maryland portion of the Chesapeake Bay.  An assessment of the sanctuary sites constructed during this period was prepared and can be found in the September 2011 report, 2008 Sanctuary Assessment.

Larval Transport Model

This video shows a model of the movement of oyster larvae in Harris Creek. As you can see, the benefits of restoration extends beyond the sanctuary boundaries and into areas that can be harvested.

Additional Information

Authorization: Section 704(b) of the Water Resources Development Act of 1986, as amended.

Type of Project: Aquatic Ecosystem Restoration

Contribution to the Chesapeake Bay: Directly contributes to Executive Order 13508 goals to restore clean water, recover habitat, and sustain fish and wildlife.

Project Phase: Construction

Non-Federal Sponsor: Maryland Department of National Resources, Virginia Marine Resources Commission

Congressional Interest:  Senators Mikulski and Cardin (MD), Warner and Kaine (VA); Representatives Harris (MD-01), Sarbanes (MD-03), Hoyer (MD-05), Wittman (VA-01), Rigell (VA-02), and Scott (VA-03).


The FY 2014 Maryland contract was awarded August 2014.  For this contract, mixed shell and a granite-like material will be placed as substrate on 57 acres of shallow water in Harris Creek and 24 acres of deepwater in the Tred Avon River.  The work is anticipated to start fall 2014 and end spring 2015.  Monitoring of the Virginia sites has shown that many of the Great Wicomico and Lynnhaven River sanctuary oyster reefs are exceeding the accepted target for successful oyster restoration. 



Total Estimated Cost (MD+VA)


Federal Cost Estimate


Non-Federal Cost Estimate 


Federal Funds Data  
Allocation thru FY 2013


Allocation for FY 2014


President Budget FY 20152


Allocation for FY 20152


Balance to Complete


1 Estimate based on the current Federal authorization for this program. The long-term master plan has identified a need of $2-6 billion.

2 The President typically sends the budget to Congress in February each year. Upon release, budget amounts for the USACE Civil Works programs and specified projects are posted online at the USACE website in a program budget press book at http://www.usace.army.mil/Missions/CivilWorks/Budget.apsx

3 The final FY 2015 allocation of funds to projects will be available upon enactment of the Energy and Water Appropriations Act or the public release of an approved FY 2015 work plan, given continuing authority for the full year.  The FY 2015 funds will be distributed between Baltimore and Norfolk districts.



FY 2014 Completed Work (Baltimore District): Construction of the 2013 substrate sites, 23.3 acres in Harris Creek, was completed April 2014.  In August 2014, a contract was awarded to Argo Systems, LLC, for substrate construction in Harris Creek and the Tred Avon. Project monitoring continued at all sites.  

FY 2015 Scheduled Work: Construction of the 2014 substrate sites in Harris Creek and Tred Avon. With anticipated FY 2015 Federal funding, design and award construction for additional acreage in the Tred Avon. Continue project monitoring.     

COMPLETION: TBD.  With optimal funding and an increase in WRDA cost authority, oyster restoration activities would continue toward achieving the oyster restoration outcome guided by the implementation strategy associated with the Chesapeake Bay Protection and Restoration Executive Order (E.O. 13508) and the Chesapeake Bay Watershed Agreement to restore native oyster habitat and populations in 10 tributaries by 2025.

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