Stormwater GreenHomeNYC August 2008

Water

August 20 Forum

Häfele Showroom

S.W.I.M.

• Clean Water Act = Fishable and Swimmable

• Storm Water Infrastructure Matters

• Over 45 members, including Gowanus Dredgers, Nos Quedamos, Cook + Fox, NRDC, Sustainable South Bronx

• www.swimmablenyc.info

PROBLEM

• CSO = combined sewer overflow

• More than 27 billion gallons of untreated stormwater and raw sewage per year

• 460 CSOs in NYC

SOLUTION• Green infrastructure, Low

Impact Development (LID), Best Management Practice (BMP), Source Control

• Interagency BMP Task Force

• Citizen Implementation

Natural Resources Defense Council

• Larry Levine, Project Attorney• a S.W.I.M. member organization• Local Law 5 – requires a “Sustainable

Stormwater Management Plan” for NYC– 1/30/08: Intro 630-A approved unanimously – 2/19/08: Bloomberg signs into law– 10/1/08: First draft due, for public review &

comment– 12/1/08: Final Plan DUE

Local Law 5

• Mayor’s Office of Long Term Planning and Sustainability has lead responsibility; quarterly public meetings to solicit input – next meeting anticipated in Oct.

• Key Plan Elements:– focus on “green infrastructure”– code revisions for new development and redevelopment– financial and other incentives for retrofitting– design specs for public projects– long-term and interim goals and milestones– public notification of CSO events

• Complete progress report due every 2 years

Local Law 5

Example BMPs:• Rain gardens• Downspout disconnection• Green roofs• Enhanced street tree pits and planting strips• Rain barrels • Pervious pavement• Rainwater harvesting• Water conservation; greywater re-use• Stormwater Utility Fee (separated from water rates)

Sustainable South Bronx

• Rob Craudereuff

• Green Roof Tax Abatement

• Passed NYS in June 2008

Rob CrauderueffSUSTAINABLE SOUTH BRONX

USA USA= 5% 25%

World’sPopulation ?

USA USA= 5% 25%

World’sPopulation

World’sIncarcerated

•Unemployment: 25%•Living in POVERTY: 40%

•Median Household Income: $20K

•Problems to be addressed:

Bronx Ecological Stewardship Training

Source: Columbia University Urban Planning Studio, 2006 Instructors: J. Rosenthal & K. Bakewell

Green Roof Tax Abatement

• $4.50/s.f. up to $100,000

• 3 year maintenance plan

• Agreement for City to inspect

• Applications:1/1/09? - 3/15/13

Green Roof Tax Abatement

• At least 50% of the roof, green roof defined as:– Roof Membrane– Root Barrier– Insulation– Drainage– Growth Medium (3 inches or irrigation or certified)

– Vegetation (80% covered)

EDAW

• Timothy Terway

• Urban Design Meets Urban Ecology

• Interdisciplinary Practice: Different Disciplines engaged in Studying Systems

How do we make this…. function like this?

Green Stormwater Infrastructure: What is it?

• Integrated, landscape-based approach to sustainable development

• Set of strategies to maintain existing natural systems, hydrology, ecology

• Flexible approach based on a toolkit of simple techniques

Stormwater Goals

• Water quality improvement– Filter pollutants and

contaminants• Water conservation• Peak flow control • Volume reduction

Complimentary Goals

• Wildlife habitat• Greening cities,

aesthetics• Recreation and open

space• Environmental education

& stewardship• Shading / heat island

reduction

The NEW Paradigms – Urban Water Cycle

Landscape Transition

SFPUC 2007

What is your primary goal?

– Water quality– Aquifer recharge– Combined Sewer Overflow (CSO) reduction– Green streets– Flood reduction

Toolkit

• Green Roofs• Cisterns• Downspout Disconnection• Rain Gardens• Bio-Retention• Detention Basins• Constructed Wetlands• Permeable Paving• Stream Daylighting• Urban Forest

Case Studies:

• Jordan Cove, CT

• 100 acre Urban Regeneration Masterplan (New York Metro)

Stormwater Research: Jordan Cove

• Was Designed to Determine Water Quantity/Quality Benefits of BMP’s

• Monitoring took place over 10 years

• More info: www.jordancove.uconn.edu

FindingsActivity Traditional ($) BMP ($)

Cul-de-sac bioretention1,275 2,183

Driveway (asphalt)/lot 2,800 --

Driveway (paver)/lot --    7,896

Erosion & sediment control/lot

322 625

Plantings 500 650

Planning and design/lot 401 808

Road and curb 23,494 102,500

Rain gardens/lot 0 575

Stormwater collection 7,770 3,600

36,562 118,837

1. To implement BMPs on 100% of the lots in the BMP portion of the subdivision - goal met.

2. To maintain post-development peak runoff rate and volume at levels equal to predevelopment rates. – volume and peak rate goal met

3. To maintain post-development loading of TSS at levels equal to predevelopment rates – goal not met.

4. To retain sediment onsite during construction. – goal not met.

5. To reduce nitrogen export by 65% - goal met.

6. To reduce bacterial export by 85%. – goal not met.

7. To reduce phosphorus export by 40%. – goal met.

EDAW

Can you infiltrate on site?

• Soils• Depth to groundwater• Liquefaction dangers• Underground utilities• Slope• Contamination

Tools that require infiltration:– Rain gardens– Pervious Pavement

Tools that do not require infiltration:– Cisterns– Eco-roofs (or roof

gardens)– Bioretention planters– Urban forest– Stormwater wetland– Detention basin

Using the Toolkit

Gauging Impact of Tools

Functions of ToolsRunoff Minimization

Rainwater Capture

Landscaping Infiltration Conveyance WQ Treatment

Permeable Pavement O x x

Bioretention x x O x O

Bioswales x x O O

Stormwater Planters

x x O x x

Green Roofs

O x x

Wetlands O x O

Turf Replacement x x O x x

Infiltration Devices

x O x

Source: Dan Medina, CH2MHillO Main function

x Secondary Function

• Sizing: 4% of catchment• Vegetation: Native vegetation, drought tolerant,

medium to tall stem height• Filter Media: Sandy Loam, < 5% fines (clays)• Pretreatment: Always incorporate pretreatment

separated from system till catchment built out and veg. established

Inundation tolerance

2/3 Veg Height

80%ile compliance in summer months

General Rule of Thumbs

BMP Sizing Factor Summary

IMP Sizing Factors

Flow-Through Planter

Group D: 0.05

Vegetated/Grassy Swale

Group A: 0.10 to 0.14

Group D: 0.07 to 0.115

Bioretention Basin

Group A: 0.13Group D: 0.06

Under-Drain or Infiltration:

• Source: NRCS

Group A – low runoff potential (<10% clay)Group D – high runoff potential (>40% clay)

Next Month’s Forum:

International Green Building Showcase

September 17

Location TBA