- A New Paradigm -Sustainable Storm Water Management

NCTCOG12th Annual Public Works Roundup

Ross Gordon, PE, CFM, LEED® APProject Manager, AECOM Houston

ross.gordon@aecom.com

Presentation Overview

• What is LID?• Design contest overview• Green roadway

example design• What we learned…• What’s coming next…

A storm water management 

strategy designed to mimic 

predevelopment hydrology using 

design techniques that infiltrate, 

filter, store, evaporate, and detain 

runoff CLOSE TO ITS SOURCE

What is Low Impact Development?

• Traditional philosophy: – Get the water out of here as fast as possible

– Use large regional or end of pipe facilitiesfor mitigation or treatment 

– Infrastructure intensive

• LID philosophy:– Keep the water here (safely) as long as possible

– Use small distributed LID features located on‐site to mitigate and treat runoff

– Take advantage of nature!

Paradigm Shift in Storm Water Mgmt.

For Quality 

Absorption

Adsorption

Assimilation

Degradation

Filtration

Settling

Impact of Development / LID Goal

Reductions…

TSS

Metals

Nitrogen

Phosphorous

Oil & Grease

Pathogens

LID DESIGN CONTEST

LID DESIGN CONTEST

The goal of the competition was to spur the adoption of LID in the Houston region by educating engineer, developers, and

political leaders and by showing the LID can work in Houston

LID DESIGN CONTEST

• Design contest initiated Oct. 2009• 23 design teams • 49 firms from across the USA• Over 250 professionals

• Finals event held Jan 2010• Round 1 Judging

• 5 preeminent engineers, architects, and planners in the Houston region

• Round 2 Judging• 20 politicians, developers, regulators, local

government leaders

LID DESIGN CONTEST IMPACTS

• Strong new interest in LID• Developers• Local government• Political leaders

• Rapid increase in LID projects underway

• Harris County LID Design Guide Approved

• Independence Parkway Green Roadway Design named TCEC Eminent Conceptor Award Winner

Our Objectives• Develop a new sustainable

standard road section for existing county ROW’s that can serve as a model for future roadways

• Develop an approach that is innovative, affordable, sustainable, and aesthetically pleasing

• Develop an approach that works today and offers more possibilities in the future

GREEN ROADWAY CHALLENGE

DESIGN OVERVIEW

• 13% reduction in construction cost per mile• Approx. 70% reduction in peak discharge• Aesthetically attractive and functional landscapes

Higher Performance - Lower Cost

ROADWAY DESIGN

Green Roadway

Standard Roadway

LANDSCAPING

LANDSCAPING – NATIVE PLANTS

Tripsacum dactyloides

Sorghastrum nutans

Wedelia texana

Taxodium distichum

Phlox divaricata

Wedelia texana

Panicum virgatumAndropogon virginicus

Hibiscus aculeatus

Chasmanthium latifolium

Fraxinus pennsylvanica

Lobelia cardinalis

Conocliniumcoelestinum

0

10

20

30

40

50

60

70

80

90

100

7:00:00 10:00:00 13:00:00 16:00:00 19:00:00 22:00:00

Flow

(cfs

)

Time

100 yr Existing 2-Lane

100 yr Standard 4-Lane

100 yr Green 4-Lane

STORM WATER BENEFITS

Design Event Scenario Peak

DischargeGreen vs. Standard Percentage of Peak

Green vs. Existing Percentage of Peak

100 yrExisting 2-Lane 76.87

30.4% 34.2%Standard 4-Lane 86.32

Green 4-Lane 26.27

10 yrExisting 2-Lane 42.96

26.8% 40.7%Standard 4-Lane 65.24

Green 4-Lane 17.49

5 yrExisting 2-Lane 30.17

27.2% 43.3%Standard 4-Lane 48.09

Green 4-Lane 13.07

100 Yr. flood is contained inside

the median with no roadway flooding

WATER QUALITY BENEFITS

Shows significant reductions in highway runoff pollutants• Predicted 84% TSS removal• Predicted 68% metals removal• Predicted 30% pathogen removal

FIRST FLUSHAbility to treat first 1” of storm water runoff

COST OVERVIEW

Cost estimates prepared for both scenarios, with identical unit costs, to facilitate honest cost comparison

13% Reduction in Construction Cost

9% Reduction in Maintenance Cost

Standard / Mile:$4.97 Million

Green / Mile:$4.32 Million

LESSONS LEARNED

• One tool in our development toolbox• Cost and complexity is variable• Simplicity is key when possible• Not just about choosing good BMPs…

• Consistent, defensible analysis is key

• Rely on locally appropriate solutions and methodologies.

• Must design unique solutions for each client/project

What we learned?

COST REALITIES

• LID can reduce construction and maintenance costs

• LID can result in an increase in upfront cost

• Consideration of off-site benefits is important

• Tradeoff between cost, flood control, water quality, green space, maintenance, etc.

What we learned?

COST REALITIES

• High Cost BMPs– Pervious paving– Rainwater catchment– Green roofs

• Medium Cost BMPs– Bioswales– Bioretention / Rain Garden– Under-drains– Soil modification

• Low Cost BMPs– Vegetated swales– Native grasses– Smart design

• Increasing Interest / Mandates– Federal Government– Cities/Counties/States– Land Developers

• Increased Ease of Use– Updated Design Manuals– Updated Codes and Regulations– Trained Plan Reviewers

What’s Next?

What’s Next?

• National Trends Becoming Local…– New, stricter, MS4/NPDES permits– Requirement to use non structural storm water management strategies to maximum extent practicable

– Requirements to treat runoff from impervious areas

– TMDLs – numeric pollutant thresholds and reduction requirements

What’s Next?

What’s Next?

QUESTIONS?

THANK YOU!

Ross Gordonross.gordon@aecom.com