1. NATURE-BASED
WATERSHED SOLUTIONS:
TAKING THE
TECHNIQUES
BEYOND TALK
Rusty Russell,
Executive Director
Merrimack River
Watershed Council
Massachusetts Sustainable
Communities and Campuses
Cambridge, Mass.
Friday, March 29, 2019
2-2:55 p.m.

2. What Is a “Watershed?”
Defining our terms:
“Watershed”

3. Merrimack Watershed
consists of:
Merrimack “main stem”
and
Sub-watersheds:
• Beaver
• Cohas
• Concord
• Contoocook
• Nashua
• Pemigewasset
• Piscataquag
• Powwow
• Salmon
• Shawsheen
• Soucook
• Souhegan
• Spicket
• Stony Brook
• Suncook
• Winnipesaukee

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

11. WHAT’S WRONG WITH MORE RUNOFF?
▪ It’s polluted – by trash, chemicals,
bacteria, sediments
▪ It can lead to more flooding
▪ It can intensify droughts
▪ It triggers combined sewer overflows
▪ It’s a lost resource….

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

14. HOW CAN WE DEAL WITH RUNOFF?
Reduce pollutants—
Keep streets clean, scoop up,
use fewer yard chemicals
Capture/treat runoff—
Take advantage of “gray
infrastructure” like detention
ponds and filters
Protect land—
Maintain natural areas,
especially in urban settings

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

16. IDEA: BUILD A RAIN GARDEN –
IN YOUR OWN BACKYARD

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

21. And this can be done on a larger scale –
GIS analysis of Aberjona River watershed
(Burlington, Winchester, Woburn and Reading)

23. High feasibility:
Group A (sand, loamy sand or sandy loam soils, with low runoff potential and high infiltration rates)
Group B (silt loam or loam)
High feasibility:
sand/gravel/
alluvium

24. High feasibility:
<25% slope
High feasibility:
2-7 feet

26. APPLYING THE CONCEPT IN DENVER

27. Combined Sewer
Overflows (2018)
CCSO Totals (2018)

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”)

30. Thank You! Questions?
rrussell@merrimack.org
?