Nutrient Criteria for New Hampshires Estuaries

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Nutrient Criteria for New Hampshires Estuaries

• Background Information

Phil Trowbridge NH DES / NHEP September 30, 2005
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Existing Nutrient Criteria for NH

• Dissolved oxygen 5 mg/L (instantaneous) 75
  sat (24 hr average) RSA 485-A8
• 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 (gt10 of
  samples) DES-WMB Policy 009

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Goal for the Nutrient Criteria Process

• To improve these criteria and/or add other
  criteria so that DES can accurately assess
  cultural eutrophication in NHs estuaries.

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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.

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2004 Dissolved Oxygen or Chlorophyll-a
Impairments in 2004
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Nutrients in NHs 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

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Current Conditions in NHs estuaries
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Nitrogen in Northeast Estuaries
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Phosphorus in Northeast Estuaries
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Summary

• New Hampshires 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.