planning and developing achievable stormwater water ...€¦ · planning and developing achievable...
TRANSCRIPT
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Horsley Witten Group, Inc.
Planning and Developing Achievable Stormwater Water Quality Goals in
New Hampshire
NEWEA Annual MeetingJanuary 23, 2017
Renee L. Bourdeau, PEHorsley Witten Group, Inc.
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Horsley Witten Group, Inc.
Presentation Outline
• Regulatory Background
• Community Case Studies
• Conclusions
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Horsley Witten Group, Inc.
Great Bay
Background: Great Bay Watershed
• Home to 25% of NH’s population
• Intersects 39 NH and 9 ME communities (48 total)
• Previous studies have found:– Dissolved inorganic nitrogen up
42% over the last 5 years (PREP).– Eelgrass biomass in the estuary
declined by 64% between 1990 and 2008
– Adult oyster populations have decreased from 125,000 (1997) to 10,044 (2009).3
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Horsley Witten Group, Inc.
Background: Great Bay Watershed
• 2009 – NHDES established numericnutrient criterion for nitrogen in tidalwaters of Great Bay to protecteelgrass and dissolved oxygen
• 2009 - NHDES lists Great Bay and 11 ofthe 18 sub-estuaries as impaired fornitrogen
• 2010 - NHDES established existingloads and load reductions to meetwater quality criterion
• 2014 - NHDES estimates non-pointsource load from all watersheds andtowns within the Great Bay Watershed.
• 2014 – As result of a court approvedsettlement and peer review findings,NHDES will cease to use numericnutrient thresholds4
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Background: 2017 Final NH MS4 Permit • Discharges to Waters
Impaired by Nitrogen– Public Education & Outreach
– Amend/adopt regulations to include BMPs optimized for nitrogen removal
– Management of municipal land
– Nitrogen Source Identification Report
– Potential Structural BMPs
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Horsley Witten Group, Inc.
Background: WWTF Permits & AOC• Require tracking of all sources
which contribute nitrogen to the Great Bay
• Development of a Nitrogen Control Plan– 5-year schedule– Identify specific measures to be
installed to reduce non-point and point source stormwater
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Background: NH State Water Quality Standard
“Class B waters shall contain no nitrogen in such concentrations that would impair any existing or designated uses, unless
naturally occurring.”
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Horsley Witten Group, Inc.
Case Studies
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Horsley Witten Group, Inc.
Case Study 1: Exeter- Squamscott River
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• Freshwater & Tidal Tributary
• Portions of 19 Towns– 11 Regulated MS4s– 8 with MS4 waivers
Case Study 1: Exeter-Squamscott River
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• Town of Exeter – WWTF AOC– MS4 Community– Contributes
greatest stormwater load in watershed (21%)
Case Study 1: Exeter- Squamscott River
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Horsley Witten Group, Inc.
Case Study 1: Exeter- Squamscott River
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Horsley Witten Group, Inc.
Case Study 1: Exeter- Squamscott River
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Horsley Witten Group, Inc.
Case Study 1: Exeter- Squamscott River
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Horsley Witten Group, Inc.
Case Study 1: Exeter- Squamscott River
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• Challenges to Exeter– Investing significant $ to reduce nitrogen
loads at wastewater plant– NPS contributions in watershed will affect
their future investments in wastewater– Future development load reductions are
critical– Financial resources– Political buy-in– Septic System Regulations
Case Study 1: Exeter- Squamscott River
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*Developed load includes stormwater, groundwater and septic systems
Case Study 2: Current Loads
Numeric Nutrient Criteria
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*Developed load includes stormwater, groundwater and septic systems
Numeric Nutrient Criteria
Case Study 2: Future Loads
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Case Study 2: Example: Potential impacts of Zoning Changes
Future (2040) Stormwater Annual Nitrogen Load by Min. Lot Size19
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Horsley Witten Group, Inc.
Conclusions
• Need to understand the complete picture
• Put local regulations in place to reduce future impacts
• Incorporate reduction strategies on EVERY project
• EDUCATE
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