Treatment of storm water generated from highways

Sooraj Garg

Department of Civil Engineering

SV National Institute of Technology

Surat 395007

Introduction

Storm water contamination

Causes of Storm water pollution

Effects of Storm water pollution

Storm water treatment

◦Green Infrastructure

◦ Low Impact Development

Factors affecting storm water treatment

Stormwater is water that originates during precipitation events and snow/ice melts, Stormwater is also a resource and ever growing in importance as the world's human population demand exceeds the availability of readily available water

With increasing areas of impervious surfaces (such as

roads, parking lots, and rooftops) in urbanized locations,

more storm water cannot infiltrate into the soil and finally

becomes runoff.

Increased storm water runoff creates two problems: increase

in the rate and volume of runoff, and increase in the variety

and concentration of pollutants contained in the runoff.

Source Arnold and Gibbons(1996), Impervious Surface Coverage

When it rains, runoff from roads and highwaysfrequently washes harmful pollutants into nearbyrivers, streams, and lakes because the surface of roadsis impervious, meaning that water cannot pass throughit.

In a natural environment, 50% of the rain fall isabsorbed in the ground, 40% is evapotranspirate and10% runs off

In an area of 75%-100% impervious surface (such asmany urban areas) 15% of the water is absorbed in theground, 30% is evapotranspiration and 55% runs off.

When it rains, runoff from roads and highways frequently washes

harmful pollutants into nearby rivers, streams, and lakes because

the surface of roads is impervious, meaning that water cannot

pass through it. Therefore, rain that falls on roadways is not able

to soak into the ground as it would naturally.

Storm water generated from highways is most commonly

contaminated by dirt, oil, grease, toxic chemicals, heavy metals,

road salts, nitrogen and phosphorus, pathogens, and trash.

These materials are deposited on roadways as a result of ordinary

traffic activities, such as fluid leakage and the wear and tear of

vehicle parts.

For example, brake pad wear is a source of copper and zinc,

which are the metals most commonly found in highway runoff.

Changes in land use that increase impervious cover lead to

flooding, erosion, habitat degradation, and water quality

impairment.

Everyday activities such as driving, maintaining vehicles

and lawns, disposing of waste, and even walking pets often

cover impervious surfaces with a coating of various harmful

materials.

Construction sites, power plants, failed septic systems,

illegal discharges, and improper sewer connections also

contribute substantial amounts of contaminants to runoff.

Sometime sewer overflows, septic tank leakage also causes

pollution.

This pollution, in turn, impacts important natural resources

as well as other, equally important activities such as

commercial and recreational fishing, swimming, and

boating.

Flooding and Property Damage

Siltation and Sedimentation

Harm to Aquatic Life

Human Illness

Impacts to Drinking Water Supply

Aesthetic Losses

Basic Principal is to prevent pollutants from entering the water in

the first place

In case of Storm Water, we need to ensure that surfaces through

which stormwater run-off passes over should as far as possible be

free from solids and other wastes.

Structural Method

◦ Treatment systems

◦ Erosion and sediment controls

◦ Vegetated volume reduction devices

Typical structural methods are include grassy swales, infiltration

trenches and basins, sand filters, Bio-retention cells, wet and dry

retention ponds, constructed wetlands, and porous pavement.

Non Structural Method

◦ Impervious cover minimization

◦ Land-use planning

◦ Conservation of natural areas

Some Best Management Practices, such as green

infrastructure, Low Impact Development however, are

more effective than others, because those BMPs that

are infiltration-based also help maintain or restore the

natural hydrology of the watershed.

Green infrastructure (GI) can be defined as the natural

and man-made landscapes and features that can be used

to manage runoff.

Examples of natural green infrastructure include

forests, meadows and floodplains.

Examples of man-made green infrastructure include

green roofs, rain gardens and rainwater cisterns.

Green infrastructure replicates the natural functions of

a landscape by integrating functions like storage,

detention, infiltration, evaporation, and transpiration, or

uptake by plants.

Bio swales or Grassed swales◦ Bioswales are vegetated, mulched, channels that

provide treatment and retention

◦ Vegetated swales slow, infiltrate, and filter stormwater flows

Rain gardens◦ it is a planted depression or a hole that allows

rainwater runoff from impervious urban areas.

◦ It reduce the rain runoff by percolating or consuming rain water

Wetlands◦ These can be work like constructed wetland

Source NRDC Report 2011: Storm Water

Source NRDC Report 2011: Storm Water

LID employs principles such as preserving and recreating natural landscape features

Minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product

Example of LID are Bio-retention facilities, rain gardens, vegetated rooftops, rain barrels, and permeable pavements.

Objectives of LID are Preserve and recreate natural landscape features, Reduce effective impervious cover, facilitate detention and infiltration opportunities.

LID works on the natural principal of trap and treat the runoff.◦ Physical - increases interception, infiltration, and

evapotranspiration; facilitates sediment removal, filtration, and volatilization; stabilizes soils to reduce sedimentation and erosion

◦ Chemical - facilitates adsorption, ion exchange, and organic complexion.

◦ Biological - increases transpiration, nutrient cycling, direct uptake, and microbial decomposition.

Low impact DevelopmentGreen Infrastructure

LID is a subset of practices/approaches within green infrastructure.

Storm water is treated as resource rather than a waste product

Example of LID are Bio-retention, Rain barrels, Permeable pavement etc.

Green infrastructure

generally refers to a

broader, big picture view of

BMPs

Storm water is treated as

waste product

Example of GI are Bio-

Swales, Rain Garden,

wetland etc.

Traffic volume

Roadway design

Surrounding land use

Regional climate

Accidental spills

Frequency of Rainfall

For Example-

roadways carrying an average of 30,000 vehicles per day may produce runoff with two to five times the pollutant levels found in runoff from rural, less-traveled highways or roadways in arid areas.

Title-“The Design of a Bioretention Area to Treat HighwayRunoff and Control Sediment.”

Site Location “Southern California along State Route 73”.

The Best Management Practices (BMPs) includes twopretreatment devices to help remove litter and sediment

Storm water runoff is ponded to a depth of 150 mm (6 in).The ponding area will be planted with Creeping Wild rye,Salt Grass, Mexican Rush, and Clustered Field Sage.

The bioretention area consists of a 75 mm organic layer, a 1.2 m planting soil layer, a 0.3 m sand layer, and a 0.3 m gravel layer with a PVC under drain system.

(The California Department of Transportation Report: The California Department of Transportation)

(The California Department of Transportation Report: The California Department of Transportation)

In urban areas, Storm water is a major source of pollution of surface water bodies.

In rural areas agriculture runoff is a big problem due to excess use of chemical fertilizers and pesticides.

Some European and American countries have taken a step towards the treatment of storm water generated from highways, by using of some techniques like rain garden, bioretention and wetlands.

To support this report I studied one case study on Bioretention titled “The Design of a Bioretention Area to Treat Highway Runoff and Control Sediment.”

Treatment of storm water is limited to the developed

countries, in developing countries like India, there is no

scope of treatment of storm water some suggestions are

following that I conclude on the basis of this report –

◦ We can provide a vegetable layer along our water bodies.

◦ Some onsite treatment can be provided like filtration, wetland

etc.

◦ We can plant vegetables along the highways so that they

reduce the runoff

Davis P.A. and Hsieh C., 2003, Evaluation of Bioretentionfor Treatment of Urban Storm Water Runoff, World Water & Environmental Resources Congress, pp 1-8.

Kayhanian M., Singh, A., Suverkropp C., and Borroum S. (2003), Impact of Annual Average Daily Traffic on Highway Runoff Pollutant Concentrations, J. Environ. Eng., 129(11), 975–990.

Khan, S., Lau, S., Kayhanian, M., and Stenstrom, M. (2006), Oil and Grease Measurement in Highway Runoff—Sampling Time and Event Mean Concentrations, J. Environ. Eng., 132(3), 415–422.

NRDC, September 2011, After the Storm, “How Green Infrastructure Can Effectively Manage Stormwater Runoff from Roads and Highways”.

Web Sources◦ http://water.epa.gov/infrastructure/greeninfrastructure/index.cf

m◦ https://www.teachengineering.org/view_lesson.php?url=collectio

n/usf_/lessons/usf_stormwater/usf_stormwater_lesson02.xml