The Pennichuck Brook Watershed Watershed Protection & Recharge - PowerPoint PPT Presentation

The Pennichuck Brook Watershed

Watershed Protection & Recharge – What’s In It For Me?  Compliance with EPA stormwater permit  Save money & help protect your citizens o Opportunity to combine efforts & materials o Less stormwater runoff – spend less on treatment o Less erosion – less need for stabilizing banks o Less flooding & infrastructure repair  Protect & improve water resources  Protect drinking water supply – public & private

Background  17,000 acre urbanizing/urbanized watershed to outlet of Harris Pond  Occupies land in five towns – Nashua, Merrimack, Amherst, Milford, Hollis  10 subwatersheds of roughly 1,200 ‐ 3,200 acres each

Changes to the Water Balance & Its Impact on Water Quality

Source: Center for Watershed Protection “Impacts of Urbanization” Impervious area increases stormwater runoff & • Clean cool baseflow • reduces baseflow Minimal stormwater (surface) runoff • Runoff picks up pollution – nutrients, sediments, • oil & grease – and causes streambank erosion

Watershed Restoration Goals  Reduce pollutant loads  Promote groundwater recharge & baseflow  Reduce infill of ponds

Past Efforts (1998 ‐ 2008)

Past Efforts (2008 ‐ present)  Community Based Social Marketing (CBSM)  Watershed Website ( www.pennichuck.com)  Identification of Top 10 BMP Retrofits  Tinker Road Detention Basin Retrofit  Sediment Study of Ponds  Harris Pond Aeration  Long ‐ Term Monitoring Program  Updated Watershed Restoration Plan

www.pennichuck.com

www.pennichuck.com/watershed_interactive_map.php

2012 Watershed Restoration Plan  Goals Reduce pollutant loads o Promote groundwater recharge & baseflow o Reduce infill o  Biggest “bang for buck” Public education o Regulations o Private property maintenance o

Restoration Approach – Next Few Years  Develop school education program on watershed protection  Work with watershed communities to coordinate stormwater permit compliance with watershed protection efforts o Adoption of State of NH Alteration of Terrain (AoT) Requirements o Roof leader disconnection program  Investigate methods to increase maintenance on private properties

Restoration & Stormwater Permit – Common Goals  Protect & improve water resources  Control stormwater runoff from new & redevelopment projects  Maximize recharge

What Does Stormwater Permit Require?  For construction projects that disturb >1 acre o Ordinances  erosion & sediment control during construction – must reference BMP Standards  control runoff from new & re ‐ development projects  2013 draft stormwater permit – ordinance to require compliance with the design criteria set forth in the most recent version of the New Hampshire Stormwater Manual (based on AoT)  Recharge & infiltration where feasible – encouraged to adopt State of NH AoT requirements  Annually report increase or decrease in impervious area (IA) & directly connected impervious area (DCIA)

What Does AoT Require? 1. Erosion & sediment control during construction 2. Attenuation Channel Protection (2 yr) 1. Flood Protection (10 & 50 2. yr) 3. Treatment of Stormwater 4. Groundwater Recharge

When Does AoT Apply?  Projects that disturb… o 100,000 sf (2.3 ac) or more of earth o 50,000 sf or more of earth, if ANY of the disturbance is within the Protected Shoreland o Any area of earth, if ANY of the disturbance is within 50’ of a surface water AND on a steep slope (>25%)  Versus <1 acre required under stormwater permit  Adopting AoT Standards at the lower 1 acre threshold complies with stormwater permit & provides better watershed protection

Roof Leader Disconnection Program  Ordinances address stormwater runoff from new & re ‐ development projects o New subdivisions o New site plan reviews o Redevelopment of existing commercial & industrial properties  Existing residential development not addressed through regulations

Roof Leader Disconnection Program Benefits  Meets stormwater permit – more recharge, disconnect impervious area  Cooler, cleaner baseflow  Saves $$ o Reduced pollutant loads – less $ on stormwater treatment o Reduced erosion & sedimentation – less $ on bank stabilization o Reduced flooding & infrastructure damage – less $ on repairs

Quantitative Benefits – Recharge Volumes Water Supply for 2050 people Water Supply for 1460 people Water Supply for 630 people

Quantitative Benefits – Phosphorus Reduction

Quantitative Benefits – Disconnection of Impervious Area

Approaches to Roof Leader Disconnection  Public education to encourage disconnection  Monetary incentives for DIY projects  Work with organization to disconnect  Community staff disconnects or hires contractor to disconnect  Require disconnection through ordinance

Outreach Tools  Step ‐ by ‐ step instructions to install do ‐ it ‐ yourself stormwater treatment practices  Soak up the Rain NH – encourage widespread adoption of stormwater BMPs http://des.nh.gov/organization/divisions/water/stormwater/stormwate rmgmt ‐ homeowners.htm

Tools to Quantify Benefits (for stormwater permit tracking) NHDES Residential Loading Model  Inputs o Annual precipitation o Impervious area o Existing stormwater best management practices (BMPs) o Proposed do ‐ it ‐ yourself stormwater BMPs  Outputs o Existing annual runoff volume o Existing annual phosphorus load o Post ‐ BMP runoff volume & phosphorus load

Summary  Watershed Restoration & Stormwater Permit Have Same Goals – Improve Water Quality  AoT at local level addresses new development & redevelopment  Roof leader disconnection addresses existing residential development & can be applied to new development