Water Quality Standards And Classifications

Water Quality Standards and Criteria

Water Quality Standards are the basis for programs to protect the state waters. Standards set forth the maximum allowable levels of chemical pollutants and are used as the regulatory targets for permitting, compliance, enforcement, and monitoring and assessment of the quality of the state's waters. Waters are classified for their best uses (fishing, source of drinking water, etc.) and standards (and guidance values) are set to protect those uses.

The water quality standards program is a state program with federal (U.S. EPA) oversight. New York's longstanding water quality standards program predates the federal Clean Water Act and protects both surface waters and groundwaters.

U.S. EPA defines a water quality standard to include the criteria, the designated (best) uses of the water, and an antidegradation policy.

Information regarding the New York State Water Quality Standards Program can be found in state regulation, specifically New York Codes, Rules and Regulations Title 6 (6 NYCRR) and guidance documents found in the Division of Water Technical and Operational Guidance Series (TOGS). Contact Jason Fagel at [email protected], Chief, Standards and Analytical Support Section.

Standards and Criteria 

DEC establishes water quality standards and other criteria for many specific substances. These standards can be either narrative (e.g., "none in amounts that will impair ...") or numeric (e.g., "0.001 µg/L") and are found in NYS regulation 6 NYCRR Part 703. In the absence of established water quality standards, numeric guidance values are derived and compiled in Division of Water guidance (TOGS 1.1.1 [PDF]). Ambient standards and guidance values are supported by technical documents called "Fact Sheets" that are also available upon request.

Water Classifications and Reclassification 

All waters in New York State are assigned a letter classification that denotes their "best uses" (e.g., fishing, swimming, source of drinking water). Letter classes such as A, B, C, and D are assigned to fresh surface waters, and SA, SB, SC, I, and SD to saline (marine) surface waters. Best uses include: source of drinking water, primary contact recreation (i.e., swimming), secondary contact recreation (i.e., boating), fishing, and shellfishing. The letter classifications and their best uses are described in regulation 6 NYCRR Part 701. The classification of individual bodies of surface water is in regulation 6 NYCRR Chapter X (Parts 800 - 941).

Surface waters of the State are reclassified through the formal rule making process. Requests for reclassification can be made by submitting a completed Water Reclassification Request Form.

All fresh groundwater in New York State is Class GA. The best use of Class GA groundwater and Class A, A-Special, AA, and AA-Special surface waters is a source of potable water supply. Standards and guidance values of the Health (Water Source) Type are established for these waters to protect this use. Separate standards for drinking water are promulgated by the New York State Department of Health (NYS DOH).

Antidegradation 

New York has a statewide antidegradation policy as set forth in the September 9, 1985 Organization and Delegation Memorandum Number 85-40 (PDF). For the Great Lakes System, this statewide policy is supplemented by implementation guidance in TOGS 1.3.9 (PDF)

Other Resources

Standards and guidance values of other Types, including Health (Fish Consumption), Aquatic (Chronic), Aquatic (Acute), Wildlife, and Aesthetic are also established. Further information is provided in the Introduction to TOGS 1.1.1 (PDF).

Water quality standards and standard-setting procedures are in 6 NYCRR Chapter X, Parts 700-706.

Several Technical and Operational Guidance Series (TOGS) are relevant to water quality standards:

• TOGS 1.1.3 (PDF) - Procedures for derivation of site-specific standards and guidance values for protection of aquatic life.
• TOGS 1.1.4 (PDF) - Procedures for derivation of bioaccumulation factors.
• TOGS 1.1.5 (PDF) - Procedures for deriving ambient water quality standards and guidance values for the protection of wildlife.
• TOGS 1.1.6 (PDF)- Interpretation Guidance for Marine Dissolved Oxygen (DO) Standard.

Recreational Criteria Upgrades and Classification Updates for Saline Waters

 Starting in July 2022, with the Advanced Notice of Proposed Rule Making (ANPRM), New York State Department of Environmental Conservation (NYSDEC) has engaged in a comprehensive, multi-year effort to increase attainment of the Clean Water Act’s (CWA) fishable and swimmable goals in the saline waters of the State. This includes NYSDEC’s October 2023 adoption of regulatory updates to protect the shellfishing best use in Class SA waters; protect the primary contact recreation best use in Class SA and SB waters; maintain water quality suitable for primary contact recreation in Class SC waters; protect the secondary contact recreation best use in Class I waters; and add a wet weather (WW) limited use designation for waters impacted by combined sewer overflow discharges. 

Currently, NYSDEC has proposed a Notice of Proposed Rule Making to amend Parts 701, 703, 864, 890, 891, 920, and 935 of 6 NYCRR. The proposed regulatory updates modify how the wet weather (WW) limited use designation can be applied, amend water quality standards (WQS) to protect off-season secondary contact recreation best uses in saline waters, and amend classifications of 30 formerly Class I or SD waterbody segments to Class SB, SB(WW), or SC. Additional information on all saline rule making activities, including public hearing information, can be found on the Saline Water Quality Standards and Reclassification webpage. 

Water Quality Guidance Values to Regulate PFOA, PFOS, and 1, 4-Dioxane

The finalized guidance values (GVs) are shown in the table below. The Department of Health (DOH) maximum contaminated levels (MCL) for finished drinking water are displayed for informational purposes.

The GVs were derived by procedures established in Title 6 of the New York Codes, Rules, and Regulations (NYCRR) Part 702. Learn more about these Emerging Contaminants.

Nutrient Criteria

On December 20, 2024, NYSDEC released new water quality guidance values that will advance the State’s regulation of the nutrient phosphorus in ambient freshwaters. This announcement was formalized in NYSDEC’s Environmental Notice Bulletin (ENB) on December 24, 2024, and the public comment period closed on March 11, 2025. More details on the guidance values and NYSDEC’s implementation of them can be found here.

Nutrients: The Problem

Nutrients (phosphorus and nitrogen) are a natural part of healthy lakes, rivers, streams, and estuary ecosystems. However, excessive nutrients can cause water quality problems that negatively affect water supplies, recreational uses, and aquatic life.

High levels of nitrogen and phosphorus in waters can produce nuisance algal blooms and increase aquatic weed growth.

Excessive algal and weed growth reduces:

• water clarity;
• recreational value of a waterbody;
• oxygen in the water; and
• can produce "dead zones" where dissolved oxygen levels drop so low that aquatic life cannot survive.

Point and nonpoint sources of nutrient enrichment and eutrophication to streams, lakes, and estuaries:

• Agricultural activities that result in animal waste and sediments washing into waterbodies.
• Urban runoff from impervious surfaces (parking lots, lawns, rooftops, roads).
• Inadequate onsite septic system.
• Municipal wastewater treatment plant discharges.
• Atmospheric deposition.

Current Standards

Nutrients are regulated in New York State Waters by a narrative water quality standard rather than a numeric standard. A numeric standard provides a specific numeric threshold (e.g., mercury not more than 0.0007 ug/L), and a narrative standard lays out a descriptive condition that needs to be met.

The narrative standard for phosphorus and nitrogen is: None in amounts that result in the growths of algae, weeds, and slimes that will impair the waters for their best usages.

Challenges

Developing specific numeric criteria for nutrients is complicated by a number of factors:

• Nutrients are naturally occurring and everywhere in our environment, so more stringent criteria are expected to affect many activities, stakeholders, and regulatory programs.
• Some level of nutrients is necessary for a healthy ecosystem and appropriate levels of nutrients vary from waterbody to waterbody, depending on a variety of characteristics (for example, depth, streamflow, water temperature, etc).
• Elevated nutrient levels by themselves do not normally cause direct impairment (except at extremely high levels), but rather they can produce conditions, such as reduced clarity, weed/algal growth, and low dissolved oxygen, that can impair aquatic life, water supplies and recreational uses.

Because of these complicating factors and the impact numeric nutrient criteria are likely to have across the state, New York is taking an intentionally deliberate approach to developing these criteria. DEC will evaluate and communicate the implications, to insure that the final plan will be effectively and successfully implemented.

Current Nutrient Reduction Efforts

The Numeric Nutrient Criteria will build on work that New York has already taken to reduce nutrients in lake, rivers, streams, and estuaries:

• Total Maximum Daily Load (TMDL) plans are watershed-based pollutant reduction strategies that have been established for many high-profile nutrient-impacted watersheds, such as Lake Champlain, Susquehanna (Chesapeake Bay), and Long Island Sound.
• Municipal Separate Storm Sewer Systems (MS4) program requires practices to reduce nutrients and other pollutants from stormwater discharges and impervious surface runoff.
• Concentrated Animal Feeding Operations (CAFO) program requires best management practices to limit nutrient runoff from agricultural activity.
• The State Pollutant Discharge Elimination System (SPDES) regulates all discharges of wastewater to lakes, rivers and streams and requires all dischargers to meet standard treatment levels.
• Water Quality Based Effluent Limits (WQBELs) can require dischargers to reduce nutrients beyond standard treatment levels where necessary to protect water quality and recreational uses.
• Numeric guidance for total phosphorus, a value of 20 ug/L, is already in place for most lakes and reservoirs in the state.
• Dishwasher Detergent and Nutrient Runoff Law are in place banning phosphorus-based detergents and lawn fertilizers statewide.

Milestones for Nutrient Criteria

Most of the actions from NYSDEC’s former Table of Milestones for Nutrient Criteria have been addressed through the proposed Addendum to TOGS 1.1.1 and proposed Update to TOGS 1.3.6. . The public comment period for both TOGS will be open for 60 days, and NYSDEC expects to finalize both TOGS a few months after comments close. More details on the public comment process can be found here.

One item from the Table of Milestones for Nutrient Criteria not addressed by the recent TOGS is numeric nitrogen criteria for saline and estuary waters. NYSDEC continues to examine numeric nitrogen criteria for these waters , including USEPA criteria recommendations and the implementation and effectiveness of current control strategies outside of the water quality standards program. These control strategies include, but are not limited to the Long Island Nitrogen Action Plan (LINAP), the Long Island Sound TMDL, and the Chesapeake Bay TMDL. 

Reclassification of St. Lawrence River Drainage Basin

The Division of Water expects to propose upgrades to the classifications of certain surface waters in 6 NYCRR Part 910 (St. Lawrence River drainage basin). These reclassifications are necessary to meet federal Clean Water Act (CWA) goals for water quality and, if adopted, would result in higher classifications (and thus more stringent water quality standards) for some waters in this drainage basin.

Numerous Class D surface waters, which only provide protection for fish survival, would be proposed to be upgraded to higher classifications (Class C or higher), which are protective of both fish survival and fish propagation, and are fully consistent with the "fishable" goal of the CWA. When a water is upgraded from Class D to C (or higher), an additional set of water quality standards would apply to protect the water quality for fish propagation. These are more stringent than the standards for fish survival that apply to Class D waters. Certain waters would also receive protection for trout or trout spawning.

When the rule is proposed, DEC anticipates having one or more public information meetings within the St. Lawrence River drainage basin, along with a public hearing. Notification of the formal public process will be made via both the New York State Register and the Environmental Notice Bulletin.