Source Water Protection

A source water protection ordinance using a watershed overlay district is a zoning tool designed to safeguard surface drinking water supplies, such as lakes, reservoirs, and their tributary streams. Unlike conventional zoning which assigns a single set of regulations to a parcel, an overlay district imposes an additional layer of standards on top of the existing, or underlying, zoning. This approach allows a municipality to apply specific, targeted protections to sensitive watershed lands without completely rezoning large areas.

The fundamental premise is that land use activities within a watershed directly impact the quality of the water that drains into a public supply. By regulating development intensity, prohibiting high-risk land uses, and requiring performance standards like vegetated buffers and stormwater controls, these ordinances aim to prevent nonpoint source pollution at its origin. This proactive strategy can reduce the need for costly water treatment and protect public health. The overlay district boundaries are typically delineated based on hydrological studies of the watershed, defining the land area that drains to the water supply intake.

Models for this approach often establish different tiers of protection based on proximity and sensitivity. For example, a “critical area” may be designated immediately adjacent to a reservoir, with the most stringent rules, while a “general watershed area” covers the remaining drainage basin with slightly less restrictive standards. This tiered approach, seen in ordinances from jurisdictions like Greensboro, North Carolina, and York County, Virginia, focuses the highest level of protection on the most vulnerable areas. These ordinances provide a framework for managing development in a way that is compatible with the primary goal of protecting a vital public resource. Similar watershed protection strategies are used for major water supplies, as seen in the Croton Watershed Protection regulations for New York City.

Key provisions

Source water protection ordinances based on an overlay district model share several common regulatory components, though the specific standards vary based on local hydrology, state regulations, and policy goals.

Applicability and Boundaries

The ordinance first defines the geographic area to which the overlay rules apply. This is a critical step, grounded in watershed science.

• Delineation: Boundaries are established on an official zoning map, which is incorporated into the ordinance by reference. These boundaries are based on the topographic drainage area of the public water supply reservoir and its tributaries.
• Subdistricts: The overlay district is often divided into subdistricts to provide varying levels of protection. The Greensboro, NC, ordinance establishes a Watershed Critical Area (WCA) extending at least one-half mile from the normal pool elevation of the reservoir, and a General Watershed Area (GWA) covering the rest of the watershed. This allows for more stringent controls closer to the water supply.
• Inter-jurisdictional Cooperation: When a watershed crosses municipal lines, the ordinance may include provisions for cooperation. The Town of Skaneateles, NY, ordinance for the Skaneateles and Owasco Lake watersheds explicitly incorporates and enforces the watershed rules and regulations of the downstream water purveyors, the City of Syracuse and the City of Auburn, respectively.

Prohibited Uses

To prevent contamination from high-risk activities, these ordinances typically prohibit certain land uses within the overlay district. The list of prohibited uses is tailored to address the most significant local threats.

• Hazardous Materials: A common feature is the prohibition of uses that involve the large-scale production, storage, use, or disposal of hazardous materials. This includes junkyards, truck terminals, and certain industrial processes.
• Waste Disposal: Sanitary landfills, land application of industrial or septic sludge, and similar waste disposal activities are generally prohibited.
• High-Risk Commercial Uses: Automobile service stations, petroleum pipelines, and dry-cleaning businesses may be prohibited or subject to strict performance standards to ensure containment of potential contaminants.
• Location-Specific Prohibitions: Some ordinances, like that of York County, VA, prohibit specific uses like septic systems, feed lots, and bulk fuel storage within a certain distance (e.g., 500 feet) of a required stream buffer.

Performance Standards

Beyond prohibiting certain uses, overlay ordinances establish performance standards that all new development must meet. These standards focus on controlling stormwater runoff and limiting development intensity.

Impervious Cover and Density Limits

To minimize the volume of stormwater runoff, ordinances set limits on the amount of impervious surface or the overall development density. The Greensboro ordinance provides a detailed example, offering developers a choice between a “low density option” with less built-upon area and fewer structural stormwater controls, and a “high density option” that allows more impervious cover but requires engineered stormwater controls.

Stream Buffers

Maintaining vegetated buffers along streams is a core requirement for filtering pollutants, reducing erosion, and protecting aquatic habitat. These standards are a key component of many water quality protection efforts, including standalone Stream Buffers ordinances.

• Buffer Width: Widths vary based on the type of stream (perennial or intermittent) and the management zone. York County, VA, requires a 200-foot buffer, which may be reduced to 50 feet if an impact study demonstrates equivalent water quality protection. Greensboro, NC, requires buffers of 30 to 100 feet depending on the development density option chosen.
• Buffer Zones: Some ordinances divide buffers into zones with different allowable uses. The Greensboro ordinance for the Randleman Lake watershed establishes an inner “Zone 1” (0-30 feet) intended as an undisturbed vegetated area, and an outer “Zone 2” (30-50 feet) where activities like selective cutting and stormwater facilities may be permitted.
• Allowed Encroachments: Ordinances typically specify conditions under which infrastructure like roads or utility lines may cross a buffer, requiring that the crossing be minimized and use best management practices.

Permitting and Review Procedures

Development within a watershed overlay district is subject to a specific review and approval process to ensure compliance with the ordinance’s standards.

• Watershed Development Plan: Applicants are typically required to submit a detailed site plan or watershed development plan showing proposed impervious areas, stormwater controls, buffer boundaries, and other relevant features.
• Impact Study: For larger projects or those seeking modifications to standards (such as a buffer reduction), a detailed impact study may be required. The York County, VA, ordinance requires a study certified by a professional engineer that analyzes pre- and post-development runoff characteristics and demonstrates how water quality will be protected.
• Specialized Review: Plans are often reviewed by a designated body, such as a Technical Review Committee or the zoning administrator, with expertise in stormwater management. As seen in Skaneateles, NY, the downstream water utility may also be granted status as an involved agency in the review process.
• Maintenance and Enforcement: To ensure long-term function, ordinances require a mechanism for the maintenance of stormwater controls. This often involves establishing a homeowners’ association or other responsible party and granting the municipality authority to inspect facilities and perform necessary maintenance at the owner’s expense if they fail to do so.

Selected provisions, annotated

A two hundred foot (200′) wide buffer strip shall be maintained along the edge of any tributary stream or reservoir. … The zoning administrator may authorize a reduction in the two hundred foot (200′) wide buffer down to an absolute minimum of fifty feet (50′) upon presentation of an impact study … which provides documentation and justification … that even with the reduction, the same or a greater degree of water quality protection would be afforded…

County of York, VA, Watershed Management and Protection Area Overlay District

This provision establishes a significant default buffer width but builds in flexibility. It allows for site-specific engineering solutions through an impact study, shifting the ordinance from a purely prescriptive standard to one that incorporates performance-based criteria.

Two overlay districts cover designated water supply watersheds. They are the Watershed Critical Area (WCA) and the General Watershed Area (GWA). The WCA covers the area adjacent to a water supply intake or reservoir where risk associated with pollution is greater than from the remaining portions of the watershed. … The GWA covers the rest of the watershed draining to the reservoir or intake.

Greensboro, NC, Water Supply Watershed District Overlay

This section clearly defines the tiered approach common to watershed overlay districts. By creating zones based on risk, the ordinance can apply the most stringent and costly regulations where they are most needed, balancing development goals with water quality protection across the entire watershed.

Within the entire LW District, the current City of Syracuse Watershed Rules and Regulations shall apply and be enforceable by the town… A copy of any application … occurring partly or wholly within the Skaneateles Lake watershed, Shall be submitted simultaneously with its submission to the town, to the city of Syracuse pursuant to the City’s watershed Regulations.

Town of Skaneateles, NY, Lake Watershed Overlay District

This language demonstrates a practical solution for inter-jurisdictional watershed management. The Town of Skaneateles, an upstream community, adopts and enforces the regulations of the downstream water provider, Syracuse. This ensures consistent protection across political boundaries, which rarely align with watershed boundaries.

What makes it a useful model

The watershed overlay district model offers a robust and adaptable framework for protecting surface drinking water supplies. Its primary strength lies in its ability to add targeted environmental protections to an existing zoning code without requiring a complete and potentially contentious overhaul of the underlying land use plan. This makes it a politically and administratively feasible tool for many communities.

The model is effective because it is based on scientifically defensible watershed boundaries and integrates multiple protection strategies. It combines prescriptive standards (prohibited uses, buffer widths) with performance-based requirements (density limits, pollutant loading targets), creating a comprehensive, defense-in-depth system. This multi-barrier approach is more resilient than relying on a single regulatory tool. It addresses not only the type and location of development but also its intensity and its direct hydrological impacts, which is essential for managing nonpoint source pollution.

Furthermore, the examples demonstrate significant flexibility. The framework can be tailored to local conditions, from the specifics of a single lake watershed like in Skaneateles to a complex, multi-reservoir system like in Greensboro. Provisions for impact studies, density options, and inter-jurisdictional review allow the regulations to adapt to different site conditions and political landscapes. This combination of a strong scientific basis, comprehensive regulatory tools, and inherent adaptability makes the watershed overlay district a valuable model for any municipality seeking to protect its drinking water sources. It is one of several important tools in a library of model ordinances for water resource protection, complementing regulations for Groundwater Protection.

Adaptation checklist for municipalities

Before adopting a source water protection overlay ordinance, a municipality should customize the model language to fit local legal, administrative, and environmental contexts. The following steps are essential for this process:

• Delineate and formally map the boundaries of all public water supply watersheds within the jurisdiction.
• If using a tiered approach, define the boundaries for the Watershed Critical Area (WCA) and General Watershed Area (GWA) based on proximity to intakes, reservoirs, and major tributaries.
• Acquire or develop accurate GIS data and maps for all perennial and intermittent streams to serve as the basis for buffer requirements.
• Establish specific buffer widths for different stream types and zones. Determine the rules governing activities and encroachments within the buffer.
• Define clear, quantitative limits for impervious cover or development density for each overlay district or sub-district.
• Compile a list of prohibited land uses based on an assessment of local risks from existing and potential future commercial and industrial activities.
• Define the required contents of a watershed development plan or impact study, including necessary engineering calculations and certifications.
• Designate a specific municipal officer or board (e.g., Zoning Administrator, Planning Board, Technical Review Committee) responsible for reviewing applications and enforcing the ordinance.
• If the watershed is shared, establish formal procedures for notifying and involving adjacent or downstream municipalities and water authorities in the review process.
• Develop clear standards for the design of required stormwater controls, often by referencing a local or state Design Manual.
• Establish legally sound mechanisms to ensure the long-term inspection and maintenance of all private stormwater management facilities.
• Define a clear set of penalties for violations and procedures for enforcement actions, consistent with state enabling statutes.