Maryland Oyster Restoration FAQs

 The below questions and answers pertain only to oyster restoration in Maryland. For more information on restoration efforts within the Corps Norfolk District’s jurisdiction in Virginia, visit


Why is oyster restoration important?

Oyster restoration is important because oysters provide a number of environmental benefits, including reef habitat that is significant to the Chesapeake Bay ecosystem for animals like blue crabs and fish. Additionally, oysters are filter feeders that improve water quality - a single adult oyster can filter up to 50 gallons of water in 24 hours. Other benefits also include nutrient cycling, reduced sedimentation, long-term carbon storage to help mitigate global warming, and oyster production that extends beyond the defined sanctuaries for restoration.

Oyster populations in the Chesapeake Bay have declined considerably in the last century, largely due to parasitic diseases, overharvesting, declining water quality, and loss of habitat. Less than one percent of historic oyster populations remains.


What guides oyster restoration in Maryland?

There are two important documents that guide how oyster restoration actions are conducted in the Maryland portion of the Chesapeake Bay. The U.S. Army Corps of Engineers (Corps) long-term, large-scale Native Oyster Restoration Master Plan (2012) guides projects funded for Corps construction as part of the Maryland and Virginia bay-wide oyster restoration program. The State of Maryland’s restoration actions in Maryland waters only are conducted in accordance with Maryland’s 10-Point Oyster Restoration Plan (Maryland Department of Natural Resources, (DNR), 2010). 

The initial purpose of Chesapeake Bay Oyster Restoration projects was to restore oyster habitat and populations in 20 tributaries of the Chesapeake Bay by 2025, as established in Executive Order 13508. The 2014 Chesapeake Bay Agreement later adapted this goal to 10 tributaries by 2025.


Who is involved with oyster restoration in Maryland, and what do they do?

The Corps, National Oceanic and Atmospheric Administration (NOAA), Maryland Department of Natural Resources (DNR), and Oyster Recovery Partnership (ORP), partner to conduct oyster restoration in Maryland’s tidal waters. This Maryland Interagency Workgroup facilitates oyster restoration by working together and consulting with scientific, academic and oyster restoration experts to ensure environmentally-sound and cost-effective efforts.

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 like DNR, the Corps evaluates the impact of the discharge of dredged or fill material into all Waters of the United States under Section 404 of the Clean Water Act, and any structures/work proposed in navigable waters under Section 10 of the Rivers and Harbors Act through a permitting process managed by the Corps Regulatory Program.

For Civil Works oyster restoration projects in Maryland, the Corps Baltimore District is the lead federal agency, and DNR is the non-federal sponsor.

The Corps restores reef structure to re-establish oyster habitat where it previously existed.

DNR is responsible for maintaining the network of oyster sanctuaries established in 2010 after extensive scientific study and public outreach. A key aspect of ensuring the success of sanctuaries is protecting them through the Natural Resource Police. In addition, DNR conducts initial sonar surveys of every sanctuary, monitors water quality, and funds and coordinates reef construction. DNR also provides funding for spat on shell oyster production as well as purchasing, aging and delivering the oyster shells necessary for the hatchery to operate. Moreover, DNR conducts annual bay-wide surveys of oyster bars to track disease pressure, relative oyster abundance and distribution.

NOAA maps the available, restorable water bottom using sonar in conjunction with various ground‐truthing methods to identify potential habitat. NOAA’s financial support is used to address infrastructure needs such as shell handling and hatchery production of seed oysters, as well as planting. They also aid in planting and conducting monitoring of restored reefs to evaluate success.

ORP is a non-profit that plants seed oysters grown at the University of Maryland Horn Point Hatchery on restoration sites.


Where is oyster habitat restored in Maryland?

The Maryland Interagency Workgroup, in consultation with other restoration partners, selects tributaries within pre-existing sanctuaries established by DNR for large-scale habitat restoration based on consideration of salinity levels, available restorable bottom, protection from harvest, historical spat set, and other criteria. Harris Creek was the first tributary selected, followed by the Little Choptank River and then the Tred Avon River.  

The type of restoration each site receives (reef restoration and placing seed/oyster spat; or placing seed/oyster spat only) is based on specific criteria and includes factors such as water-bottom type and presence of oyster and/or shell material.

In accordance with the Oyster Restoration Master Plan, federal funding for the oyster restoration program construction is used for sites that cannot be harvested, or sanctuaries. The federal government does not make the determination to designate specific tributaries as sanctuaries; this effort is led by the state. Though sanctuaries are closed to harvest, there is modeling that shows baby oysters settling not only within the oyster sanctuary, but also on public shellfish fishery areas outside of the sanctuaries. 

Oyster reefs are not constructed within any federal navigation or natural navigation channels. As a step in the Corps planning process, the team identifies a buffer of 150 feet from federally-maintained navigation channels and restricts site selection to outside this buffer. This means that no reefs are planned for restoration within the navigation channel or within the buffer.

There is also a 250-foot buffer around any navigational markers, natural channels, marinas, and residential docks.

Deeper waters typically experience low dissolved oxygen conditions that are not suitable for oysters or the reef community. Shallower waters can conflict with other uses of the waterway, such as navigation. Therefore, restoration activities are aimed at water depths between 6 and 20 feet.

Surveys are completed prior to site design to ensure that new sites are not placed on currently thriving reefs and that new sites will be constructed on hard-surface bottoms.


What is used to restore reefs?

There is not sufficient natural shell available to restore oyster habitat in the Bay, although it is used to the fullest extent when possible. Therefore, artificial reefs have been constructed at restoration locations throughout the Bay. Reefs may be constructed using oyster shell, clam shell, or alternate substrate such as crushed concrete, rock or granite (or in combination).

There is an insufficient amount of native shell due to overharvesting, disease, and being broken down by natural processes.

In 2009, the Corps completed an environmental assessment focused on use of clean substrates for reef restoration.

Most restored reefs are made of one of the following: rock only; combination of rock and mixed shell; or mixed shell only.  The shell comes from processing plants in the mid-Atlantic region and is permitted to be imported and placed in the river. The rock is quarried in Havre de Grace, Maryland.

The first large-scale reef construction at Harris Creek began in 2012. In 2016, the initial phase of Harris Creek restoration was completed on the final 165 acres of oyster reefs. The site is thriving, rich with oyster beds that continue to grow and reproduce. A 2016 Oyster Restoration Monitoring Report, released in 2017, conducted in Harris Creek shows that the average oyster density on reefs that were constructed using rock or stone as their base was roughly four times higher than on shell-base reefs.

The use of alternate substrate is important to meeting restoration goals. For instance, stone is readily available, cost-effective, is performing well at restored sites and allows for the conservation of natural shell resources. 


When will oyster restoration be completed in the Maryland portion of the Chesapeake Bay?

There is no hard date yet for restoration completion. The Chesapeake Bay Watershed Agreement goal is to restore native oyster habitat and populations in 10 tributaries by 2025. The timeline is dependent upon funding. Congress determines if the Corps is in the budget for oyster restoration and how much funding it will receive.


Is oyster restoration working in Maryland?

Through the interagency partnership, more than a billion oysters have been planted in the Harris Creek Sanctuary since 2011. The 2017 Oyster Reef Monitoring Report provides data and analysis that show that 100 percent of reefs constructed in the Harris Creek Oyster Sanctuary in 2014 and monitored in 2017 meet the requirements for oyster density (at least 15 oysters per square meter) and biomass.

Monitoring of the Virginia sites restored by the Corps Norfolk District and partners has shown that many of the Great Wicomico and Lynnhaven River sanctuary oyster reefs are exceeding the accepted target for successful oyster restoration.

Monitoring is part of the plan to document progress. Restored reefs are monitored at three years and again at six years. 


How is the environment considered for restoration actions?

It is mandated under the National Environmental Policy Act (NEPA) that before federal agencies make decisions, they must consider the effects of their actions on the quality of the human environment. The federal agency is required to inform the public about the work they are proposing to do. The federal actions for oyster restoration are supported by NEPA documents, such as environmental assessments or environmental impact statements, which have been completed to date. Supplemental NEPA documents would be needed for restoration actions not covered under existing documents. Each of the NEPA documents includes a section on public involvement and agency coordination, describing how public input is considered for federal action. The Corps must consider a suite of existing statutory and regulatory requirements on the impacts to water resources, water quality, and bay health prior to issuing a permit for work done by others.

The DNR plan is a policy document that guides state action. As such, it does not constitute a major federal action that would trigger NEPA.

All NOAA-funded Chesapeake Bay oyster restoration activities are reviewed for compliance with NEPA. The NOAA funds provided to DNR and Chesapeake Bay Foundation for production and planting of oyster seed in Harris Creek and the Little Choptank River were similarly reviewed, and are covered within the scope of NOAA’s Programmatic and Supplemental Programmatic Environmental Assessment for the Community-based Restoration Program.


How do you work with the public, including watermen?

The interagency efforts to restore the Chesapeake Bay’s oyster population are the result of scientifically-based, public processes that have transpired over several years. These processes have been conducted in compliance with federal and state law. Stakeholder engagement is a critical aspect of restoration, and the partnering agencies remain committed to transparency with interested parties.

To engage stakeholders and the public, beyond NEPA requirements, the Corps, DNR and NOAA held a series of public open houses to seek input on large-scale oyster restoration. These were held March 21, 2012, in St. Michaels, Maryland (for proposed Harris Creek work); November 7, 2013, in Oxford, Maryland (for proposed Tred Avon work); and February 27, 2014, in Cambridge, Maryland (for proposed Little Choptank River work.) Input received at these events was reviewed and incorporated into restoration plans where appropriate. Several public meetings have been held since. 

Each of the environmental assessments for restoration actions includes a section on public involvement and agency coordination, describing how public input is considered for federal action.

Throughout the public coordination process for the Tred Avon River, the Corps has worked to provide information to the public, including the residents that live adjacent to and boat recreationally within the river, so that they are able to fully understand the proposed oyster restoration work and where it will be located. The Corps is working with the public to ensure that restoration work will not impede navigation on the river.

The Corps works closely with the Maryland Watermen Association, as well as sits on the Oyster Advisory Commission that provides an opportunity to discuss project progress and concerns throughout oyster restoration efforts. Due to these interactions, the interagency team had amended plans in the past to use more shell and less rock for reef construction at certain sites in the Tred Avon River. 


How do you ensure reefs that are built too tall will not happen again?

The Corps takes any impediments to navigation seriously and has developed a process to more efficiently conduct post-construction surveys before the spat-on-shell is placed, and is also tightening quality-control procedures with contractors for future work to ensure reefs are built to the planned heights and that six feet of navigational clearance is maintained. Efforts include ensuring contractors use a consistent bucket size for reef material deployment and marking the depth on the bucket cable as an additional visual cue. Efforts will continue to notify boaters of changes in bathymetry resulting from the project through the Coast Pilot, Notice to Mariners, and other similar methods.