© 2014 HDR, Inc., all rights reserved.

Green Infrastructure Performance in NYC

January 8, 2015

Ackerson Hall Rutgers-Newark

Carter H. Strickland, Jr Vice President

NYC Green Infrastructure Plan

Review of post-construction GI monitoring (PCM) results

Evaluating GI for LTCPs and CSO benefits

Discussion

NYC Green Infrastructure Plan

NYC Green Infrastructure

Annu

al C

SO V

olum

e (m

illion

s of

gal

lons

)

21,698

17,896

21,753 19,808 -1,701-1,514

-586

-1,945

-

5,000

10,000

15,000

20,000

25,000

30,000

Cost-EffectiveGrey

Investments(Built &

Planned)

Reduced Flow GreenInfrastructure

(10% Capture)

OptimizeExisting System

Green Strategy Cost-EffectiveGrey

Investments(Built &

Planned)

Potential Tanks,Tunnels, &Expansions

Grey Strategy

-5,666 built/under construction

-2,602 planned -2,547 planned

-5,666 built/under construction

GREEN STRATEGY GREY STRATEGY

2045 BASELINE - PROJECTIONFROM 2007 FACILITY PLANS

Planning Phase: Estimate of Performance

Planning Phase: Estimate of Costs

$2.9 $2.9

$1.5

$0.9 $0.03

$3.9

$-

$1.0

$2.0

$3.0

$4.0

$5.0

$6.0

$7.0

$8.0

Green Strategy Grey Strategy

Potential Tanks, Tunnels, & Expansions Optimize Existing SystemGreen Infrastructure - Private Investment Green Infrastructure - Public InvestmentReduced Flow Cost-Effective Grey Investments

$6.8

$5.3

$2.4

Planning Phase: Estimate of Additional Benefits

Co-benefits: Schoolyards to Playgrounds

Co-benefits: Right of Way Bioswale

Co-Benefits: Grant Program

NYC CSO Consent Decree Modification (2012)

Benefits • $1.4 billion in savings from

substituted green and grey infrastructure

• $2 billion in grey infrastructure deferred

Key elements

• Over $187 million in green infrastructure through 2015

• 3 neighborhood scale pilot projects to be monitored

• 5 year milestones and overall commitment to managing 10% of CSS area for 1” storm by 2030

• Adaptive management structure

Performance Standards

Review of NYC’s Post-Construction Monitoring Program and Results

NYC GI Monitoring (Site Scale)

City-Owned Sites • Right-of-Ways • Agency Buildings

and Parking Lots • Public Housing • City Parks • Public Schools

Monitoring Equipment Roof Drain Inserts ISCO 4230 Bubble Flow

Meter Weather Station Arlyn Series 320D-CR

Scales and Data Logger V-notch Weir and Pressure

Transducer Stage Gauge Water Level Logger and

Weir Plate H-flume Water Quality Sampling

Wells Piezometers Hydrant Testing Infiltration Testing

Site Scale

Inflow and outflow measured with remote monitoring equipment.

Soil moisture and ponding levels measured.

Equipment monitored performance at regular intervals, typically five minutes.

Site visits conducted regularly to download data, maintain equipment and assess qualitative monitoring aspects.

Rain gauges or weather stations at most locations to collect locally-accurate weather data.

Calibrate, calibrate, calibrate !!!!

Monitoring Approach

Blue Roofs Modified Inlet

Trays Check Dams

2”

DEP’s Metropolitan Ave. Storehouse

2”

Blue Roof Monitoring

June 22, 2012 1.3” Storm

Benefit

Benefit

Blue Roof Performance: Volume Reduction

Results for 2011-2012 (~70 storms) • Designed for peak shaving, but

achieve good volume capture through ponding/evaporation

• Trays: most consistent results (50-80% retention)

Blue Roof Performance: Peak Flow Reduction

Results for 2011-2012 (~70 Storms) • All types provide good peak

shaving • Trays most consistent, ~80-100%

reduction of peak flow

Permeable Pavement

Porous Pavement Standard Asphalt FilterPave

21

Far Rockaway Bus Terminal Parking Lot

Permeable Pavement Performance: Volume Retained

2012-2013 Results (96 Storms) • FilterPave consistently captures 100% • Standard and Porous Asphalts variable • Porous Asphalt generally captures

>50% • FilterPave experiencing wear and tear

Volu

me

Ret

aine

d Vo

lum

e R

etai

ned

Volu

me

Ret

aine

d

Rainfall Depth (in) Rainfall Depth (in)

Subsurface Detention & Infiltration

North Parking Lot

South Parking Lot

23

Perforated Pipes

NYCHA Bronx River Houses

Subsurface Systems Performance: Peak Flow & Volume Reduction

Chamber System Perforated Pipe System

Rain Gardens

RAIN GARDENS

RAIN GARDENS

NYCHA Bronx River Houses

Rain Gardens Monitoring: 1.4” Storm, May 24, 2012

(Ponding Depth)

Bio 1 - 7:1 Bio 2 - 6:1

Bio 3 - 9:1 Bio 4 - 17:1

0%

20%

40%

60%

80%

100%

0.0625 0.25 1 4

Volu

me

Ret

aine

d

Effective Storm Depth (in)

0%

20%

40%

60%

80%

100%

0.0625 0.25 1 4

V

olum

e R

etai

ned

Effective Storm Depth (in)

0%20%40%60%80%

100%

0.0625 0.25 1 4

Volu

me

Ret

aine

d

Effective Storm Depth (in)

0%20%40%60%80%

100%

0.0625 0.25 1 4

Volu

me

Ret

aine

d

Effective Storm Depth (in)

20112012

Rain Gardens Performance: Volume Retained

Impervious Area 81,870 ft² DA: GI Footprint 11:1

N&S Conduit Bioretention

N&S Bioretention: Data Summary

Monitoring data from August 2011 to December 2012 Maintenance:

• Removal of debris and sediment from curb cuts

• Weeding and mulching

Storm Characteristics

2011 2012 Number of Storms 20 53

Storm Depth 0.11” to 7.78” 0.12” to 2.78” Peak Intensity 0.24 to 4.92 in/hr 0.24 to 4.2 in/hr Storm Duration 0.2 to 53 hrs 1.5 to 77 hrs

Roadway Median Monitoring: 2.6” Storm, June 12, 2012

Ponding Depth

Only 4 outflow events since installation Typical surface drawdown duration < 8 hours Ponding drawdown rate increasing, and fewer ponding events

occurring, likely due to root growth Vegetated swales effective at infiltrating offsite runoff

0.0

0.5

1.0

1.5

2.0

2.5

Jun-11 Sep-11 Dec-11 Mar-12 May-12 Aug-12 Nov-12

Draw

down

Rat

e (in

/hr)

East West

N&S Bioretention: Observations

0%

20%

40%

60%

80%

100%

0.0625 0.25 1 4

Volu

me

Ret

entio

n

Effective Storm Depth (in)

2011 2012 2013

• Dimensions: 20 ft L x 5 ft W x 5 ft D

• Entirely in right-of-way • Widespread opportunity • Pilot findings:

– Performance results

– Design modifications

– Maintenance program

Enhanced Tree Pits

Enhanced Tree Pits Monitoring: 1.5” Storm, Dec 7, 2011

Blake Ave ETP

Enhanced Tree Pits Performance: Volume Retention at 4 Sites

Results of Monitoring Other Bioswales

• Percent of rainfall captured by 10 bioswales over 185 rain events.

• Bioswales performed best during storms with less than one inch of rain.

Rainfall (in.) Mean Median Below 1” 73% 85%

1”-2” 25% 21%

Above 2” 14% 12%

Total 59% 60%

Percent Capture of 10 Bioswales

NYC Neighborhood Demonstration Projects

Demonstration Areas

Data collected to measure sewer flow reductions

Flow meters located at the point where the sewer exits the Demonstration Area catchment area

Meters record flow and depth within the main outlet sewer

Data acquisition is continuous with measurements recorded at 15 minutes intervals

Piezometers and soil moisture sensors were installed with ROWBs to measure local conditions

Monitoring Approach

Demo Area 2 Demo Area 3

Demonstration Projects: In-Sewer Monitoring Locations

Demonstration Areas Runoff Reduction Observations P

erce

ntag

e o

f R

ainf

all

Flow

ing

in

Sew

er

All source controls have provided benefits for storms < 1” In many cases, bioretention source controls have fully retained the

volume of one-inch storms they receive The condition of underlying soils have an impact on retention

performance and overall source control functionality Source controls designed primarily for detention also retain runoff

volumes Porous pavement performance varied for different types Performance generally improved in vegetated systems due to the

growth and establishment of plants

Preliminary Conclusions about Success of GI Systems

Evaluating GI for LTCPs and CSO Benefits

Sewershed

• Infiltration - Native soil - Engineered

soil • Storage

- Stone porosity

- Soil porosity

• Peak flow reductions

• Long term sewer flow reductions

Site

Neighborhood

Scaling up Performance

Hundreds to Thousands of Acres Tens to Hundreds of Acres

Acres to Tens of Acres

Goals • Demonstrate that the potential reduction

in CSO from areawide application of GI system, when performance of GI installations varies based on location, site conditions and type of GI

• Ensure evaluation of grey and green CSO reduction strategies are equivalent

Solutions • Scale-up or “lump” individual installations

subcatchment-wide • Allows for different types of GI i.e.,

detention and retention to be accounted for in model

• Also allows for other types to be added later dependent rate of installations

Modeling Approach for LTCPs

Attainment of water quality standards Planned/constructed grey controls,

remaining CSO volumes and capital costs Ratio of separate stormwater to CSO

discharges Proximity to public access locations,

planned improvement projects, etc.

Identifying Sewersheds for GI Implementation

Opportunities Analysis

Waterbody Based Targets

Managed Acres

Percent of CSIA

Managed Acres

Percent of CSIA

Managed Acres

Percent of CSIA

Managed Acres

Percent of CSIA

Alley Creek 1,490 0% 0% 45 3.0% 45 3.0%Bronx River 2,331 244 10% 13 0.6% 66 2.8% 322 14%Coney Island Creek 694 0% 0% 7 1.0% 7 1.0%Flushing Bay 4,049 401 10% 11 0.3% 110 2.7% 522 13%Flushing Creek 5,923 314 5.3% 0% 165 2.8% 479 8.1%Gowanus Canal 1,387 135 10% 5 0.4% 22 1.6% 162 12%Hutchinson River 1,128 111 10% 15 1.3% 32 2.9% 158 14%Jamaica Bay & CSO Tributaries 7,891 386 4.9% 23 0.3% 266 3.4% 675 8.6%Newtown Creek 4,524 461 10% 14 0.3% 118 2.6% 593 13%Westchester Creek 3,480 348 10% 17 0.5% 122 3.5% 487 14%

ROW Public Onsite Public Onsite Private TotalWaterbodies/Watersheds

CSIA (Acres)

Future Phase: DEP will explore opportunities for remainder of 10% GI target

Current Phase: Priority Drainage Areas

Typically, a multi-step process is applied: 1. Fatal flaw and feasibility review

• Community Disruption/Potential for Nuisances • Constructability/Permitting • Operating Complexity/Ease of O&M

2. Quantify Impacts • Pollutant Reduction/Water Quality Improvements • Control of Discharge to Sensitive Areas • Flood Control • Environmental Justice • Ancillary Community Benefits • Sustainability i.e., Energy Savings

3. Quantify Costs 4. Knee-of-the-curve selected (for highest ranked, acceptable,

technically feasible CSO control measures)

LTCP Alternatives Evaluations for Green & Grey

Questions: • Application of 2012 EPA Recreational Water Quality

Criteria and associated challenges? • How to define non-economic criteria? • Equally relevant criteria for all member communities? • Weighting of criteria? • Guidance for consistent evaluation process and criteria?

LTCP Alternatives Evaluations for Green & Grey

Monitoring over several seasons is critical to testing model assumptions and controlling for site specific soil and other conditions

A common methodology for green infrastructure stormwater controls is important for comparing green and gray alternatives and for consistency between cities

Learn from early action or pilot projects

Cost-effectiveness can be maximized during site and technology selection

Modeling is an effective way to get a working estimate of CSO reductions from green infrastructure for developing LTCPs

Conclusions

Discussion

Carter Strickland carter.strickland@hdrinc.com

Questions?