green roadway lid
TRANSCRIPT
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
Total Spaces: 44 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
Total Spaces: 53 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
Design Event Scenario
Peak
Discharge
(cfs)
Peak Discharge Reduction
Percentage (Green VS.
Existing)
10-yr
Forested Condition 3.15
61.91%Existing Condition 6.17
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
Design Event Scenario
Peak
Discharge
(cfs)
Peak Discharge Reduction
Percentage (Green VS.
Existing)
100-yr
Forested Condition 7.67
73.86%Existing Condition 10.79
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