Rusty Russell MAS 2019
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Presentation for the 2019 Massachusetts Sustainable Communities and Campuses Conference on March 29, 2019 in Cambridge, MA
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Rusty Russell MAS 2019
- 2. What Is a “Watershed?” Defining our terms: “Watershed”
- 4. Clean Water Act of 1972 – Results Are Hard to Miss! 1960s 2010s Nashua River, a major tributary
- 8. IN MASSACHUSETTS, IMPERVIOUS COVER IS INCREASING Source: Mass Audubon, Losing Ground—Planning for Resilience (June 2014), p. 3
- 9. AND SO IS (EXTREME) PRECIPITATION Climate Science Special Report: Fourth National Climate Assessment, Volume 1, U.S. Global Change Research Program (2017), p. 212 Four measures of increasing rainfall over past 115 and 58 years (in each, the greatest spike is in Northeast, with rate increasing over time) 92% increase 74% increase 55% increase 27% increase
- 10. THE RESULT: MORE STORMWATER POLLUTION How does it happen? ▪ Impervious cover prevents water from infiltrating (or percolating) into the soil ▪ This changes the water cycle from 10% surface runoff and 50% infiltration to just 15% infiltration and 55% surface runoff ▪ Runoff picks up all kinds of contaminants ▪ Polluted stormwater runs untreated into the river Increased surface runoff from the built environment is called STORMWATER POLLUTION
- 12. NEW EPA STORMWATER PERMIT PROGRAM: EFFECTIVE JULY 1, 2017 MS4: “MUNICIPAL SEPARATE STORM SEWER SYSTEM” ▪ MS4 is part of the federal Clean Water Act ▪ Nearly all of eastern Massachusetts is a “small MS4” area and must develop a stormwater management plan to reduce polluted stormwater runoff by: • Educating residents, businesses, and developers • Testing for leaking sewage from stormwater pipes • Controlling construction-site discharge • Retaining or treating runoff from development • Ensuring that streets and catch basins are clean
- 13. MS4 – Phase 2 communities: ▪ MA = 260 ▪ CT = 221 ▪ NH = 37 ▪ RI = 34 US Total = 6695 MS4 Ph. 2 Coverage: ▪ 4% US land area ▪ > 80% of US population
- 15. OR, USE “GREEN INFRASTRUCTURE” (GI) ▪ Water infiltrates soil and groundwater ▪ Water flow slows down, reducing flooding and erosion ▪ Plants and soil filter pollutants ▪ Sediments and trash are captured, then removed ▪ Native plants create habitat e.g., a bioretention cell
- 17. HOW (AND WHERE) DO I BUILD ONE? Choosing the Site ▪ Natural runoff spot ▪ Residential – generally 100-300 ft2 (10-20 feet in diameter) ▪ Often filtering runoff from roof or driveway ▪ Usually 5-7% of area that drains to the rain garden ▪ Slope < 20% ▪ 6-9 inches ponding depth treats 0.5-1 inch of runoff ▪ Groundwater layer is at least 6 feet deep Choosing the Materials ▪ Four layers: • Gravel at bottom • Then pea stone • Then bioretention soil ✓ 40-65% sand ✓ 20-30% topsoil ✓ 15-40% compost • Mulch at top ▪ Total depth: 24-48 inches ▪ Should drain in less than 72 hours
- 18. ▪ Native species ▪ Herbaceous perennials and shrubs ▪ Plants that tolerate: • Frequent ponding • Saline conditions • Extended dry periods ▪ Species should vary based on proximity to center (lowest point) ▪ Many on-line lists; try: University of New Hampshire Cooperative Extension and New Hampshire Department of Environmental Services, Native Plants for New England Rain Gardens, 2016, at: https://extension.unh.edu/resources/ files/Resource005899_Rep8265.pdf WHAT CAN YOU GROW THERE?
- 19. HOW MUCH WILL IT COST? HOW MUCH MAINTENANCE IS NEEDED? Cost… ▪ Self-install: $2-$5 per ft2 ▪ Contractor installation: $8-$12 per ft2 ▪ For 150 ft2 rain garden: • $300-$750 if DIY • $1200-$1800 if contracted Maintenance… ▪ Prune back dead leaves and branches in spring ▪ Replant as needed ▪ Weed, especially during first few months ▪ Mulch every 2-3 years to maintain 3-inch depth ▪ Remove excess sediment once or twice a year
- 20. HOW DOES IT WORK? WHAT DOES IT DO? The How… ▪ Sedimentation ▪ Filtration ▪ Adsorption (adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface, creating a film) ▪ Absorption (fluid is dissolved by or permeates a liquid or solid, respectively) ▪ Cation Exchange Capacity ▪ Polar / Non-polar Sorption ▪ Microbial Action (aerobic / anaerobic) (decomposition / nitrification /denitrification) ▪ Plant Uptake ▪ Cycling Nutrients / Carbon / Metals ▪ Biomass Retention (Microbes / Plant) ▪ Evaporation / Volatilization The What… (pollutant reductions) ▪ Total suspended solids (TSS) – with filter strip – 90% ▪ Nutrients • Total N – 30-50% • Total P – 30-90% ▪ Metals – 40-90% • Lead • Zinc • Cadmium • Copper ▪ Ammonia – 90% ▪ Bacteria – uncertain, but possible (90% in box experiment) ▪ Oil and Grease – 95% in box experiment
- 28. POLLUTED STORMWATER CONTROL— CHALLENGES AHEAD ▪ Multiple impacts, complex and incremental: • Physical structure of streams • Ecological health and aquatic habitat • Water quality and quantity • Local economy ▪ Impacts less visible/perceptible ▪ Impacts skew towards ecosystem health ▪ Difficult group action problem ▪ Large number of sources/avenues ▪ May be seen by some as effort to limit development and private property “rights” ▪ Local equity issues may be significant ▪ May be re-cast as “unfunded mandate” ▪ Political climate unfavorable
- 29. THE NEXT SET OF CHALLENGES: ▪ What % of polluted stormwater can GI/LID remove? ▪ How will total costs compare with “engineered” solutions? ▪ Can the public and its officials successfully transition to a more low- tech approach that: • Requires more frequent (but simple) maintenance? • Calls for new knowledge? • Is localized and highly diffuse? • May call for more cooperation than has been customary? ▪ How can GI/LID be woven into a strict system of private property? ▪ How can co-benefits be incorporated into the calculation? ▪ What economic drivers will make this happen? (think “stormwater utility”)