Low Impact Development

ApplicationsStormwater Compliance Support Workshop

Geoff Smith, P.E.

BP Barber

June 3, 2010

Outline

Background

LID Goals

Design Strategies

Practice Examples

LID Background

What is LID?

Technology based

Hydrologic evaluation

LID Background

LID Mechanisms

Impervious cover reduction

Increased green space

Open space preservation

LID Goals

Discharge reduction

Peak and volume

Water quality treatment

Infiltration

Aquifer Recharge

Less reliance on traditional facilities

Peak and volume

Increased green space

Design Strategies

Non-structural

Regulatory mechanisms

Site Planning

Buffer setbacks

Structural

Water quality improvements

Aquifer recharge

Water reuse

Non-structural LID Practices

Regulatory ordinances

Design requirements

Utility “credits”

Development Design

Cluster development

“Micro” treatment

Source Control

Buffer Setbacks

Green Space

Structural Practices - Overview

Small Scale water reuse

Cisterns

Rain Barrels

Development

Infiltration

Treatment trains

Storage

Structural Practices

Discharge Reductions

Bioretention

Versatile application

Aesthetically pleasing in urban environments

Relatively low maintenance costs compared to

traditional BMPs

Design considerations:

Water quality treatment of first flush

Small water quantity control

Bioretention

Bioretention

BMP Type Pollutant Treated Removal Efficiency

Bioretention Total Suspended Solids 50-85%

Copper 35-70%

Zinc 35-90%

Total Nitrogen 35-55%

Lead 50-90%

Total Phosphorous 55-70%

Pathogens (fecal) 10-60%

Bioretention Areas:

Applications

Parking lots

Individual home sites

Small commercial sites

Advantages

Low maintenance

Size vs. treatment

“Green” applications

Drawbacks

Potential Cost

Size restrictions

Limited quantity control

Pervious Pavement

Infiltration recharge

Reduced runoff

Varied Applications

Design considerations:

Low traffic areas

Pedestrian walkways

Significant reduction in impervious cover

Routine maintenance required

Pervious Pavement

Pervious Pavement

Center for Watershed Protection

Grassed Swales

Reduced Discharge velocities while

maintaining “design” volume capacity

Dry swales vs. wet swales

Design based on soil and landscape conditions

Lining materials can vary

Low maintenance

Grassed Swales

Typical dry swale profile

Typical wet swale profile

Grassed Swales

Infiltration Trenches

On-site storage

Low water table preferred

Used as part of a treatment train

Routine maintenance necessary

Infiltration Trenches

Infiltration Trenches

Conclusion

Design considerations

Regulatory mechanisms

Cost considerations

Water quality treatment

Aesthetic benefits

Discussion