Numeric Criteria Development

The information presented below gives a summary of state progress towards the development of numeric criteria. The information comes from EPA’s “State Adoption of Numeric Nutrient Standards (1998-2008)” report, current water quality standards, program activity measures, and nutrient criteria development plans. Links to the Delaware’s Nutrient Criteria Plan and state water quality standards are also provided.

• Existing Numeric Criteria
• Links to the Plan and Criteria
• Milestone Information

Existing Numeric Criteria

S = Statewide    W = For selected waterbody    N ⁄ A=Not Applicable

Note: See Statewide Criteria and Site-specific Criteria tabs for more information.

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Links to Numeric Nutrient Criteria Plan and Existing Nutrient Criteria

Plans:

• Nutrient Criteria Development Plan for the State of Delaware 2008
• Nutrient Criteria Development Plan for the State of Delaware 2004

WQS: Delaware Water Quality Standards
Delaware Department of Natural Resources and Environmental Control: Water Quality Standards Program Exit

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Milestone Information

Milestone information updated July 2012.

TN: Total Nitrogen; TP: Total Phosphorus

Statewide Criteria

The information on this tab shows EPA-approved nutrient criteria for Delaware’s waterbodies. The language presented below comes directly from state water quality standards and applies to all waterbodies within the state (unless a waterbody type or designated use is noted). Criteria applicable to specific waterbodies within the state can be found on the “Site-specific Criteria” tab. For more information, refer to the Delaware water quality standards.

The following information reflects Delaware’s water quality standards posted to the Water Quality Standards Repository as of November 2010 (EPA-approved March 2005).

Section 4: Criteria To Protect Designated Uses

4.1. All surface waters of the State (except as detailed in Sections 7 and 8) shall meet the following minimum criteria:

4.1.1. Waters shall be free from substances that are attributable to wastes of industrial, municipal, agricultural or other human-induced origin. Examples include but are not limited to the following:

4.1.1.3. Any pollutants, including those of a thermal, toxic, corrosive, bacteriological, radiological, or other nature, that may interfere with attainment and maintenance of designated uses of the water, may impart undesirable odors, tastes, or colors to the water or to aquatic life found therein, may endanger public health, or may result in dominance of nuisance species.

4.6.2. Nutrients
Nutrient over-enrichment is recognized as a significant problem in some surface waters of the State.

4.6.2.1. It shall be the policy of this Department to minimize nutrient input to surface waters from point and human induced non-point sources.

4.6.2.2. The types of, and need for, nutrient controls shall be established on a site-specific basis. Nutrient controls may include, but shall not be limited to, discharge limitations or institution of best management practices.

4.6.2.3. For lakes and ponds, controls shall be designed to eliminate over-enrichment.

4.6.3. Toxic Substances

4.6.3.3. Specific Numerical Criteria:

4.6.3.3.2. Human Health Criteria

Table 2 Water Quality Criteria for Protection of Human Health
(All Values Are Listed in Micrograms per Liter)

*The columns labeled "Fish and Water Ingestion" shall apply only to waters of the State designated Public Water Supply sources in these standards.
**Values shown with "(MCL)" under header "Fish and Water Ingestion" are Primary Maximum Contaminant Levels (MCLs) as given in the State of Delaware Regulations Governing Public Drinking Water Systems that became effective September 10, 2001
 

5.6. Criteria for Waters of Exceptional Recreational or Ecological Significance (ERES Waters)

5.6.2. General Provisions

5.6.2.2. All point, and human induced nonpoint sources subject to control through use of best management practices or otherwise, shall be required to remove nutrients to the extent necessary to prevent excessive growth of photosynthetic organisms.

Site-specific Criteria

The information on this tab shows EPA-approved site-specific nutrient criteria for Delaware’s waterbodies. Criteria on this page apply only to the waterbodies listed below. Criteria applicable to all waterbodies within the state are found on the “Statewide Criteria” tab. For more information, refer to the Delaware water quality standards.

The following information reflects Delaware’s water quality standards posted to the Water Quality Standards Repository as of November 2010 (EPA-approved March 2005).

Section 3: Stream Basins & Designated Uses

The designated uses applicable to the various stream basins represent the categories of beneficial use of waters of the state which must be maintained and protected through application of appropriate criteria.

p) The Nanticoke River from the upstream-most limits of the City of Seaford to the Maryland State Line and the Broad Creek from the upstream-most limits of the Town of Laurel to the confluence with the Nanticoke River have special criteria in Section 4.5 that are protective of open water fish and shellfish, shallow-water bay grass and migratory fish spawning and nursery designated uses consistent with the Maryland portion of the tidal Nanticoke River and as described in the U.S. Environmental Protection Agency document Ambient Water Quality Criteria for Dissolved 15 Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and its Tidal Tributaries (EPA 903-R-03-002). Attainment of the water quality criteria that apply to these waters will be determined following the guidelines documented within the same document and any future published addendums or modifications to that original publication.

4.5. The following criteria shall apply outside approved regulatory mixing zones unless otherwise specified:

4.5.2. Dissolved Oxygen, measured as milligrams per liter (mg/L)

4.5.2.4. The Nanticoke River from the upstream-most limits of the City of Seaford to the Maryland State Line and Broad Creek from the upstream-most limits of the Town of Laurel to the confluence with the Nanticoke River
At water temperatures greater than 84 degrees Fahrenheit, instantaneous minimum shall not be less than 4.3 mg/L

4.5.2.4.1. For the period February 1- May 31:

4.5.2.4.1.1. 7-Day mean shall not be less than 6.0 mg/L
4.5.2.4.1.2. Instantaneous minimum shall not be less than 5.0 mg/L

4.5.2.4.2. For June 1- January 31

4.5.2.4.2.1. 30 Day mean shall not be less than 5.5 mg/L
4.5.2.4.2.2. 7-Day mean shall not be less than 4.0 mg/L
4.5.2.4.2.3. Instantaneous minimum shall not be less than 3.2 mg/L

4.5.6. Water Clarity in the The Nanticoke River from the upstream-most limits of the City of Seaford to the Maryland State Line and Broad Creek from the upstream-most limits of the Town of Laurel to the confluence with the Nanticoke River
During the period of April 1 to October 31 the minimum seasonal averaged secchi depth shall be 1.0 m.

4.5.6.1. Chlorophyll-a criteria for the Nanticoke River from the upstream-most limits of the City of Seaford to the Maryland State Line and Broad Creek from the upstream-most limits of the Town of Laurel to the confluence with the Nanticoke River:
Concentrations of chlorophyll-a in free-floating microscopic aquatic plants (algae) shall not exceed levels that result in ecologically undesirable consequences – such as reduced water clarity, low dissolved oxygen, food supply imbalances, proliferation of species deemed potentially harmful to aquatic life or humans or aesthetically objectionable conditions or otherwise render tidal waters unsuitable for designated uses.

4.6.2. Nutrients
Nutrient over-enrichment is recognized as a significant problem in some surface waters of the State.

4.6.2.4. For tidal portions of the stream basins of Indian River, Rehoboth Bay, and Little Assawoman Bay, controls needed to attain submerged aquatic vegetation growth season (approximately March 1 to October 31) average levels for dissolved inorganic nitrogen of 0.14 mg/L as N, for dissolved inorganic phosphorus of 0.01 mg/L as P, and for total suspended solids of 20 mg/L shall be instituted.