Nassau County seeks watershed master plan for two major river basins

Nassau County is taking bids for a watershed master plan that will cover two of the county's major river systems, a foundational planning document that will guide stormwater management, development approvals, and flood-mitigation efforts as the county absorbs one of the fastest growth rates in Northeast Florida.

The county's procurement office will open proposals for solicitation NC26-015-RFP on October 7, 2026, at 10:00 a. m. at the Robert M. Foster Justice Center in Yulee. The request for proposals seeks a comprehensive watershed master plan for both the Nassau River Basin and the St. Mary's River Basin, the two dominant drainage systems in the county.

What's happening

Nassau County issued the request for proposals under solicitation number NC26-015-RFP for a watershed master plan covering the Nassau River Basin and St. Mary's River Basin. The bid opening is scheduled for October 7, 2026, at 10:00 a. m. in Suite 456 on the second floor of the Robert M. Foster Justice Center, 76347 Veterans Way, Yulee.

The solicitation process is being conducted under Florida Statutes Section 255. 0518 and Section 286. 011, which govern public construction procurement and open-meeting requirements. The Nassau County Board of County Commissioners has delegated authority to the county's procurement manager to conduct the public opening. Bids will be opened at the meeting, but no award decision will be made that day. The public is invited to attend and be heard.

Alyson R. McCullough chairs the Nassau County Board of County Commissioners, and Mitch L. Keiter serves as ex-officio clerk. Questions about the solicitation or public-participation accommodations should be directed to the county manager's office at 96135 Nassau Place, Suite 1, Yulee, or by calling 904-530-6010.

Why watershed planning matters for growth and flooding

Watershed master plans are the technical blueprints that determine how stormwater moves across a landscape, where flooding risks concentrate, and what drainage infrastructure is needed to handle development. In a county adding residential subdivisions and industrial sites at Nassau County's pace, the plan will inform where growth can safely occur and what mitigation measures developers must build.

The Nassau River drains much of the central and western portions of the county, flowing northeast into Nassau Sound near Fernandina Beach. The St. Mary's River forms the county's northern boundary with Georgia and drains the northwestern corner of the county. Together, the two basins cover virtually all of Nassau County's land area, meaning the master plan will touch every corner of the jurisdiction.

Watershed plans typically model existing drainage capacity, identify choke points and flood-prone areas, project how future land use will change runoff volumes, and recommend capital projects—culvert upgrades, retention ponds, channel improvements—to keep the system functioning. They also set the technical standards developers must meet for stormwater detention and treatment, which directly affects project costs and site design.

For Nassau County, the plan arrives as growth accelerates along the SR 200 and A1A corridor in the south, around Wildlight and the Yulee area in the center, and in previously rural areas now seeing rezoning applications. Each new subdivision replaces pervious land with rooftops and pavement, increasing the volume and speed of stormwater runoff into rivers, creeks, and wetlands. Without updated drainage infrastructure and standards, that intensification can worsen downstream flooding and degrade water quality in the river systems and the coastal estuaries they feed.

Flood risk and property owners

Homeowners and prospective buyers in Nassau County have a direct stake in how the watershed plan addresses flood risk. Properties in the 100-year floodplain face federal flood-insurance requirements, and FEMA flood maps—which hinge on watershed hydrology—determine insurance premiums and resale values.

A comprehensive watershed study can identify areas where localized flooding occurs even outside mapped floodplains, often because of undersized culverts, inadequate road drainage, or cumulative upstream development. The resulting capital-improvement recommendations, if funded and built, can reduce nuisance flooding that damages homes and closes roads during heavy rain events.

The plan may also influence county decisions on septic-to-sewer conversions and utility extensions. Areas with high water tables, poor drainage, or dense development often struggle with septic-system performance, and connecting them to central sewer can be contingent on stormwater improvements that prevent inflow and infiltration into sewer lines during wet weather.

For neighborhoods near the Nassau River, Lofton Creek, or tributaries of the St. Mary's, the study's water-quality component will matter. Stormwater runoff carries nutrients, sediment, and pollutants into these waterways, affecting fish habitat, drinking-water sources, and the health of downstream marshes that buffer the Intracoastal Waterway and Atlantic coast. Improved stormwater treatment standards that flow from the plan can slow that degradation.

Development and permitting implications

Developers and engineers will watch the master plan closely, because its technical standards will become the basis for stormwater permit reviews. Projects that require county site-plan approval or rezoning must demonstrate adequate stormwater management, typically by modeling post-development runoff and designing retention or detention systems to keep peak flows at or below pre-development levels.

A new watershed plan often updates the rainfall data, soil infiltration rates, and modeling methods that engineers must use, which can change required pond sizes, pipe diameters, and treatment features. In some cases, a basin-wide plan identifies regional stormwater facilities—large ponds or wetland treatment areas—that can serve multiple developments, allowing developers to pay into a shared system rather than building on-site ponds. That approach can unlock sites with challenging topography or tight lot yields.

The plan may also designate priority areas for capital investment, such as outfall improvements or tidal-gate replacements, that would relieve drainage bottlenecks and make upstream development feasible. Conversely, it may flag basins that are at or near capacity, signaling that new development there will face stricter standards or require off-site mitigation.

For large master-planned communities like Wildlight, which span hundreds or thousands of acres and build out over many years, the watershed plan provides the regional context for phased infrastructure. It can show whether a project's internal drainage system will function as downstream public improvements come online, or whether the developer must oversize early-phase systems to handle future flows.

Environmental and regulatory context

Both the Nassau River and St. Mary's River systems include extensive wetlands and floodplain forests that provide natural flood storage, filter pollutants, and support fish and wildlife. Development that affects wetlands typically requires permits from the St. Johns River Water Management District and, for larger impacts, the U. S. Army Corps of Engineers.

A watershed master plan helps coordinate local, district, and federal reviews by establishing a common set of hydrologic data and impact thresholds. It can also identify wetlands and stream corridors that the county wants to preserve or acquire for conservation and flood storage, guiding land-use decisions and green-infrastructure investments.

The St. Mary's River is an Outstanding Florida Water, a state designation that imposes stricter water-quality standards and makes permitting more rigorous for activities that could degrade the river. The Nassau River flows into the Nassau Sound and the Atlantic Intracoastal Waterway, both of which are vital to the county's commercial fishing, recreation, and tourism economy. Managing stormwater to protect those receiving waters is a recurring theme in environmental permit reviews.

Nassau County's growth also intersects with habitat for species such as gopher tortoises, which are common on sandy uplands that are prime targets for development, and wading birds that depend on coastal wetlands. Stormwater systems that maintain more natural hydroperiods—the seasonal rhythm of wet and dry—can help sustain those habitats even as surrounding land is developed.

What happens next

The bid opening on October 7 at 10:00 a. m. is a public meeting where submitted proposals will be opened and read aloud, but the county will not make an award decision that day. Procurement staff and a selection committee will evaluate the proposals, often scoring them on technical approach, team qualifications, past performance, and cost.

Once the county selects a consultant, the firm will typically spend months gathering field data, running hydrologic and hydraulic models, meeting with county staff and stakeholders, and drafting the plan. Public workshops are common midway through the process to present preliminary findings and gather input from residents, especially on flooding hot spots and drainage complaints.

The final master plan, once adopted by the Board of County Commissioners, becomes a guiding document for the county's engineering, planning, and environmental-management staff. It feeds into the county's comprehensive plan, capital-improvement program, and development code. Updates to stormwater ordinances and design standards often follow within months of plan adoption.

Residents who want to follow the process can monitor the county procurement page for award announcements and later watch for public notices of workshops once the consultant begins work. Those with property-specific drainage concerns may have opportunities to submit comments or data during the study phase.

The watershed master plan for the Nassau River and St. Mary's basins will join a growing list of infrastructure-planning efforts across Northeast Florida aimed at managing the pressures of rapid growth. As Nassau County continues to attract new residents drawn by its coastal location, relative affordability, and proximity to Jacksonville, the technical decisions embedded in this plan—how much stormwater a basin can handle, where capital dollars should go, what standards developers must meet—will shape the county's landscape and livability for decades to come.