Green Roadway LID

1

Balancing

Nature & Neighborhood

1

Final Concept Design

Design

Process 2

Site

Visit

Base

map

Review

RequirementsBrainstorm

Establish priorities

GoalsDesign

details

Final Concept Design

Balance of professionals

• Landscape Architects

• Civil Engineers

Existing

Residential Neighborhood 3

• 17 residences and only14 driveways

• Unrestricted on-street parking for a total of 39 +/- spaces

• The road is crowned with a single low point

• Existing trees do not form a consistent tree canopy

Existing

Parking

Zoning Requirements

Single family dwellings:

1 space/ residence

Existing Parking:

14 Driveway Spaces: 14 spaces

On Street Spaces: 39 spaces

Total Spaces: 53 spaces

Existing Parking Ratio: 3.1 spaces/ residence

4

LID

Strategies

Our team explored a variety of LID techniques before

determining the best LID measures that seemed fitting for

the existing conditions of this neighborhood.

These included:

• Decrease impervious area

• Converting pavement into bio-retention areas

• Use pervious pavement

• Reduce traditional storm water infrastructure

• Encourage parking in existing paved areas

• Use of native/ adapted plants

• Use decentralized LID’s

5

LID

Strategies 6

LID Strategies

Site Plan

Proposed Parking:14 Driveway Spaces: 14 spaces

On Street Spaces: 30 spaces


Proposed

Parking Ratio: 2.6 spaces/ residence

Loss of 9 on-street parking spaces

Zoning Rqmt : 1 space/residence

Existing Parking:14 Driveway Spaces: 14 spacesOn Street Spaces: 39 spaces


Existing Parking Ratio: 3.1 spaces/ residence

7

LID Strategies

Landscape Plan

• Overhead power lines on North

side of street

• Use of small to medium street trees

• Uniform street tree canopy to

compliment existing trees

8

Landscape Palette9

Native, low maintenance, and durable in urban

and bioretention environments

Spireae tomentosa

(Steeplebush)

Clethra alnifolia ‘Hummingbird’

(Sweet Pepperbush)

Myrica pensylvanica

(Northern Bayberry)

Ilex verticillata ‘Nana’

(Red Sprite Winterberry)

Ilex glabra ‘Shamrock’

(Shamrock Inkberry)

Gleditsia triacanthos inermis ‘Imperial’

(Imperial Honeylocust)

Liquidamber styraciflua ‘Rotundiloba’

(Rotundiloba Sweetgum)Betula nigra

(River Birch)Nyssa sylvatica

(Black Tupelo)

Red Maple

(Acer rubrum)

Iris versicolor

(Harlequin Blueflag)

Deschampsia caespitosa

(Tufted Hairgrass)

Aster divaricatus

(Dwarf Aster)

Phlox stolonifera

(Creeping Phlox)

Eupatorium fistulosum

(Joe Pye Weed)

10

Balancing

Nature & Neighborhood

• Using Stormwater to provide Neighborhood character

• Attractive and native landscaping

• Interconnected LID practices

LID Strategies

Bioretention Planting 11

LID Strategies

Bioretention

12

LID Strategies

Pervious Pavement 13

The Green Roadway

converts asphalt into

pervious pavement.

Bioretention planters are

used in series and

interconnected through

an underdrain system.

LID Strategies

SWM (Quantity Control) 14

Design Event Scenario

Peak

Discharge

(cfs)

Peak Discharge Reduction

Percentage (Green VS.

Existing)

5 -yr

Forested Condition 2.23

58.48%Existing Condition 5.13

Green Roadway 2.13


Peak

Discharge

(cfs)



Existing)

10-yr



Green Roadway 2.35

0.00

2.00

4.00

6.00

8.00

10.00

12.00

540 600 660 720 780 840 900

Dis

char

ge (

cfs)

100-YR Storm Hydrographs

Existing Condition

Green Roadway


Peak

Discharge

(cfs)



Existing)

100-yr



Green Roadway 2.82

Highlights

• No reliance on infiltration, applicable to any

soil condition

• No Adjusted/ reduced Curve Numbers due

to pervious pavement or runoff reduction

• No Flooding: 100-YR Runoff is contained

within LID practices

LID Strategies

SWM (Quality Control) 15

Summary

Phosphorus Removal (based on Virginia Runoff Reduction Worksheet)

ScenarioPhosphorus Load

Phosphorus Removed by Pervious Pavement

Phosphorus Removed by Bioretention

Phosphorus Leaving the Site

Phosphorus Removal

Percentage

Phosphorus Leaving the Site Reduction Percentage

(Green Roadway VS. Existing Condition)(lb/yr) (lb/yr) (lb/yr) (lb/yr)

Existing Condition 1.79 0.00 0.00 1.79 0%

90%Green Roadway 1.64 0.50 0.96 0.18 89%

Nitrogen Removal (based on Virginia Runoff Reduction Worksheet)

ScenarioNitrogen Load

Nitrogen Removed by Pervious Pavement

Nitrogen Removed by Bioretention

Nitrogen Leaving the Site

Nitrogen Removal

Percentage

Nitrogen Leaving the Site Reduction Percentage

(Green Roadway VS. Existing Condition)(lb/yr) (lb/yr) (lb/yr) (lb/yr)

Existing Condition 12.77 0.00 0.00 12.77 0%

91%Green Roadway 11.70 3.55 6.99 1.16 90%

Runoff Reduction (based on Virginia Runoff Reduction Worksheet)

Scenario

Treatment Volume (Runoff from 1"

Rainfall)

Runoff Reduced by Pervious Pavement

Runoff Reduced by Bioretention

Runoff Leaving the Site

Runoff Reduction Percentage

Runoff Leaving the Site Reduction Percentage

(Green Roadway VS. Existing Condition)(cf) (cf) (cf) (cf)

Existing Condition 2,841 0 0 2,841 0%

83%Green Roadway 2,603 605 1,503 495 81%

Highlights

• 90% Phosphorus

removal

• Approach utilized

Runoff Reduction

Methodology

• Phosphorus and

Nitrogen reductions

helps meet Bay

TMDLs

Cost Analysis16

$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

Site Preparation

Pavement Curb, Edging and Sidewalks

Storm Drainage Systems

Landscaping Total

LID

Conventional

Highlights

• Conventional Cost

assumed use of a

conventional sand

filter for Quality

Control and an

underground

concrete vault for

Quantity Control.

• Conventional Cost

resulted in additional

cost for pavement

and storm drainage

systems

• LID Design resulted in

increased costs for

curbing and

landscaping.

The LID Design resulted in savings of $125K for 715LF

of roadway construction.

Conclusion17

• innovative design, real world solution through

interconnected decentralized facilities

• Enhanced quality of life through landscaping

• mimics natural hydrologic function of the site

and will help meet Bay TMDL’s

• lower construction costs compared to

conventional design

Documents

Green Roadway LID