The Pennichuck Brook Watershed

Transcription

1 The Pennichuck Brook Watershed

2 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

3 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

4

5 Changes to the Water Balance & Its Impact on Water Quality

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

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

8 Past Efforts ( )

9 Past Efforts (2008 present) Community Based Social Marketing (CBSM) Watershed Website ( 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

10

11

12 2012 Watershed Restoration Plan Goals o Reduce pollutant loads o Promote groundwater recharge & baseflow o Reduce infill Biggest bang for buck o Public education o Regulations o Private property maintenance

13 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

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

15 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)

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

17 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

18 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

19 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

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

21 Quantitative Benefits Phosphorus Reduction

22 Quantitative Benefits Disconnection of Impervious Area

23 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

24 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 rmgmt homeowners.htm

25

26 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

27 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