Innovative Approachesto Green Roadways

Philadelphia LID SymposiumSeptember 26, 2011

Ross Gordon, PE, CFM, LEED APProject Manager

ross.gordon@aecom.com215-399-4378

Presentation Overview

LID in Houston, TX

• State of LID in 2009• Design Contest Overview• Green Roadway Design• Lessons Learned

STATE OF LID IN 2009

State of LID in 2009

• Very few LID projects in Houston

• Developers very confident in their existing business models

• General beliefs:• LID does not work in Houston• LID would cost more• Why should I?

“It’s Different Here!”

LID IMPEDIMENTS IN HOUSTON

• High intensity / volume rainfall• Design Storm:

• 100 yr = 13.2 inches• 2 yr = 5+ inches

Primary considerationis always flood control

• Little experience with separate flood control / water quality features

LID IMPEDIMENTS IN HOUSTON

• Predominantly clay soils• Minimal infiltration capacity• Where does the water go?• Can we use infiltration?

LID IMPEDIMENTS IN HOUSTON

• Strong resistance to changing the development strategy

• No interest in paying more for LID• Who cares about water quality?

• Updated COH Design Manual• Allows LID features but does not

mandate or encourage use• Copied from other design manuals

• Difficult to get LID permitted & approved

LID DESIGN CONTEST

Spur the adoption of LID in the Houston region by educating engineers, developers, and political leaders and by showing

that LID can work in Houston

Green Roadway UrbanRe-development

Suburban Res.Development

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

WHAT HAPPENED?

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

GREEN ROADWAY DESIGN

DESIGN OVERVIEW

• 13% reduction in construction cost per mile• Approx. 70% reduction in peak discharge• Aesthetically attractive and functional landscapes• A solution tailored to and designed for Houston

Higher Performance - Lower Cost

ROADWAY DESIGN

Green Roadway

Standard Roadway

LANDSCAPING – NATIVE PLANTS

Tripsacum dactyloidesTripsacum dactyloides

Sorghastrum nutans

Sorghastrum nutans

Wedelia texana Wedelia texana

Taxodium distichumTaxodium distichum

Phlox divaricataPhlox divaricata

Wedelia texanaWedelia texana

Panicum virgatumPanicum virgatumAndropogon virginicusAndropogon virginicus

Hibiscus aculeatusHibiscus aculeatus

Chasmanthium latifoliumChasmanthium latifolium

Fraxinus pennsylvanica Fraxinus pennsylvanica

Lobelia cardinalisLobelia cardinalis

ConocliniumcoelestinumConocliniumcoelestinum

LANDSCAPING

STORM WATER STRATEGY

Basic Design• Linear detention concept utilizing

restrictors at cross-over culverts• Maximize detention storage in the ROW• Vegetated swales reduce flow velocities

and filter storm water

100 yr Green WSE Profile

Methodology• Existing, Standard design and Green design all modeled in same manner• Dynamic hydrology and hydraulics using EPA-SWMM• No additional or enhanced infiltration assumed or adjusted CN• Benefits are due to hydraulic attenuation of runoff through the swales /

linear detention

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

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

LESSONS LEARNED

• 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

• Every site is unique and requires a custom solution

• Accept your limitations - don’t fight your constraints

LESSONS LEARNED

• It is possible to design dual purpose LID systems• Stretches traditional LID design

specifications

• LID can lead to major cost savings

Understand the hydrologic principles

Understand your client’sgoals and needs

QUESTIONS?

THANK YOU!Ross Gordon

ross.gordon@aecom.com215-399-4378