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Nutrient Criteria for New Hampshire’s Estuaries

Nutrient Criteria for New Hampshire’s Estuaries. Background Information. Phil Trowbridge NH DES / NHEP September 30, 2005. Existing “Nutrient Criteria” for NH. Dissolved oxygen: 5 mg/L (instantaneous) 75% sat (24 hr average) RSA 485-A:8

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Nutrient Criteria for New Hampshire’s Estuaries

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  1. Nutrient Criteria for New Hampshire’s Estuaries Background Information Phil Trowbridge NH DES / NHEP September 30, 2005

  2. Existing “Nutrient Criteria” for NH • Dissolved oxygen: 5 mg/L (instantaneous) 75% sat (24 hr average) RSA 485-A:8 • Nutrients: “Class B waters shall contain no phosphorus or nitrogen in such concentrations that would impair any existing or designated uses, unless naturally occurring.” Admin Rule: Env-Ws 1703.14 • Chlorophyll-a: 20 ug/L (>10% of samples) DES-WMB Policy # 009

  3. Goal for the Nutrient Criteria Process • To improve these criteria and/or add other criteria so that DES can accurately assess cultural eutrophication in NH’s estuaries.

  4. Regulatory Implications • Assessments: Criteria will be used to determine violations of water quality standards (“impairments”). • TMDLs: For most impairments, a Total Maximum Daily Load study will be done. • Regulations: Results of TMDLs become discharge limits in point source NPDES permits and other sources. • This process has already begun using the existing criteria.

  5. 2004 Dissolved Oxygen or Chlorophyll-a Impairments in 2004

  6. Nutrients in NH’s Estuaries • Long-Term Water Quality Trends in Great Bay • Current Conditions from 2004 Probabilistic Survey • NH nutrient concentrations relative to other systems in the Northeast

  7. Current Conditions in NH’s estuaries

  8. Nitrogen in Northeast Estuaries

  9. Phosphorus in Northeast Estuaries

  10. Summary • New Hampshire’s existing nutrient criteria are minimal and not specific to estuarine environments. • Impairments for DO and chlorophyll-a criteria already exist. • Winter DIN concentrations have increased in Great Bay. • Average TN and TP concentrations are similar to RI and Long Island Sound.

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