development of a method to compare storm water best management pr

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Theses and Dissertations

2012

Development of a method to compare storm waterbest management practices at The University ofToledoChristopher Michael WancataThe University of Toledo

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Recommended CitationWancata, Christopher Michael, "Development of a method to compare storm water best management practices at The University ofToledo" (2012). Theses and Dissertations. Paper 461.

A Thesis

entitled

Development of a Method to Compare Storm Water Best Management Practices at The

University of Toledo

by

Christopher Michael Wancata

Submitted to the Graduate Faculty as partial fulfillment of the requirements for the

Master of Science Degree in Civil Engineering

_________________________________________

Dr. Cyndee Gruden , Committee Chair

_________________________________________

Dr. Patrick Lawrence, Committee Member

_________________________________________

Dr. Ashok Kumar, Committee Member

_________________________________________

Dr. Patricia Komuniecki, Dean

College of Graduate Studies

The University of Toledo

December 2012

Copyright 2012, Christopher Michael Wancata

This document is copyrighted material. Under copyright law, no parts of this document

may be reproduced without the expressed permission of the author.

iii

An Abstract of

Development of a Method to Compare Storm Water Best Management Practices at The

University of Toledo

by

Christopher Michael Wancata

Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master

of Science Degree in Civil Engineering

The University of Toledo

December 2012

Storm water runoff has become a concern in urban environments. Urban

environments have a very large percentage of impermeable area, creating large amounts

of surface runoff. This surface runoff carries contaminants (nutrients, sediments,

pathogens, oils and greases) into storm water collection systems, which drain directly into

natural waters. These contaminants degrade water quality, harming human health and

aquatic life. In order to address these concerns, storm water best management practices

(BMPs) have been developed to reduce flow rates and improve water quality. However,

many sites that require the use of the BMPs have no means of deciding which BMP is the

best fit for the site in question. To address this problem, a Storm Water BMP Model was

developed to analyze three different BMPs (porous pavement, bioswales, and rain

gardens) for effectiveness. A comparison is made using input parameters including water

quality information and permeable/impermeable areas, and potential. BMPs are ranked

iv

based on flow quantity reduction, pollutant reduction, and payback period. The payback

period includes capital costs associated with constructing the BMP as well as monetary

values associated with environmental gains from implementing the BMP. This model

provides the opportunity to see a side by side comparison of BMPs in a retrofit situation

and to evaluate their implementation based on cost and performance.

v

Table of Contents

Abstract .............................................................................................................................. iii

Table of Contents .................................................................................................................v

List of Tables ................................................................................................................... ix

List of Figures ......................................................................................................................x

List of Abbreviations ........................................................................................................ xii

1 Introduction .........................................................................................................1

2 Literature Review.....................................................................................................2

2.1 Storm Water Regulatory Context....................................................................2

2.1.1 The National Pollutant Discharge Elimination System ......................3

2.1.2 Municipal Separate Storm Sewer Systems .........................................5

2.2 Urban Storm Water ............................................................................................6

2.2.1 Combined Sewer Systems...................................................................7

2.2.2 Non-Point Source Pollutants ...............................................................8

2.2.3 The First Flush ....................................................................................9

2.3 Storm Water Pollutants and Their Sources ......................................................10

2.3.1 Physical Contaminants ......................................................................10

2.3.2 Chemical Contaminants ....................................................................12

2.3.3 Biological Contaminants ...................................................................15

vi

2.4 Issues with Heavy Flows in Storm Water ........................................................16

2.5 Local Storm Water Implications ......................................................................17

2.6 Local Storm Water Regulations .......................................................................22

2.7 Introduction to Urban Storm Water Controls ..................................................23

2.7.1 Hydraulic Controls ............................................................................24

2.7.1 A Flow Attenuation...............................................................24

2.7.1 B Reduction of Volume ........................................................25

2.7.2 Unit Processes ...................................................................................27

2.7.2 A Physical Treatment Processes ...........................................28

2.7.2 B Biological Treatment Processes ........................................30

2.7.2 C Chemical Treatment Processes..........................................30

2.8 BMP Design Type............................................................................................33

2.8.1 Structural BMPs ................................................................................33

2.8.2 Non-structural BMPs ........................................................................35

2.9 Criteria for BMP Selection ..............................................................................38

2.10 Selected BMPs ...............................................................................................42

2.10.1 Permeable Pavement ......................................................................43

2.10.2 Rain Gardens ...................................................................................46

2.10.3 Bioswales ........................................................................................47

3 Methods ........................................................................................................50

3.1 Water Quality Methods ....................................................................................50

vii

3.1.1 Nitrates ..............................................................................................51

3.1.2 Orthophosphates ...............................................................................51

3.1.3 Coliform/E.coli .................................................................................52

3.2 Calculation of Overall Flow Rate ....................................................................53

3.3 Site Specific Goals ...........................................................................................54

3.4 Developing Solutions for Storm Water Management ......................................55

3.4.1 Water Quality Inputs .........................................................................56

3.4.2 Drainage Areas..................................................................................56

3.4.3 Construction Cost..............................................................................58

3.4.4 Runoff and Pollutant Reduction........................................................60

3.4.5 Economic and Decision Analysis .....................................................62

3.5 Sensitivity Analysis .........................................................................................65

4 Experimental Results .............................................................................................67

4.1 Water Quality Results ......................................................................................67

4.2 Drainage Areas.................................................................................................68

4.3 Example 1 (Drainage Area A) ......................................................................69

4.4 Example 2 (Drainage Area H) .....................................................................75


5 Discussion .......................................................................................................83

5.1 Example 1 (Drainage Area A) .....................................................................83

5.2 Example 2 (Drainage Area H) .....................................................................85

viii

5.3 Comparison to CNTs Green Values National Storm Water Calculator .........86


6 Conclusion and Future Work ................................................................................89

References ..........................................................................................................................91

A Appendix A ............................................................................................................95

A.1 Overall Site Information at The University of Toledo ....................................95

ix

List of Tables

2.1 NPDES Monitored Pollutants ..................................................................................5

2.2 Origins of Nonpoint Source Pollutants ....................................................................9

2.3 Common Forms of Nitrogen and Phosphorus in Receiving Waters ......................14

2.4 Measure of Progress for the Great Lakes Restoration Initiative ............................21

2.5 Structural BMPs listed by Fundamental Process Category and Unit Operation ...32

2.6 Proprietary BMPs in Current Use ..........................................................................35

2.7 Non-structural BMPs .............................................................................................36

2.8 Groups of Pollutants and Relevant BMPs Listed Based on FPCs .........................37

2.9 BMP Objective Checklist ......................................................................................42

3.1 Summary of Nitrates Concentrations .....................................................................51

3.2 Summary of Orthophosphates Concentrations ......................................................52

3.3 Coliform/E.coli Results..........................................................................................53

3.4 Site Specific Storm Water Goals ...........................................................................55

3.5 Water Quality Analysis (1 of 2) .............................................................................56

3.6 Water Quality Analysis (2 of 2) .............................................................................56

x

List of Figures

2-1 Black Swamp Area ................................................................................................18

2-2 Demonstration of Water Infiltration through Permeable Pavement ......................44

2-3 Cross Section of Vegetated Swale .........................................................................48

3-1 Drainage Area Calculation .....................................................................................57

3-2 Construction Cost Calculation ...............................................................................58

3-3 Runoff and Pollutant Reduction.............................................................................61

3-4 Payback Period for Porous Pavement ....................................................................63

3-5 Results for Combined BMP Processes ..................................................................64

3-6 Percent of Water Quality/Quantity Goals Attained ...............................................64

3-7 BMP Ranking System ............................................................................................65

4-1 Nitrates/Phosphates Data for Sites A and H (2012) ..............................................68

4-2 Pathogen Water Quality Data for Sites A and H (2012) .......................................68

4-3 Proposed Area for Porous Pavement/Rain Gardens (A) ...................................69

4-4 Total Surface Runoff Calculations (A) .............................................................70

4-5 Construction Costs for Porous Pavement .............................................................71

4-6 Construction Costs for Rain Gardens ....................................................................71

4-7 Runoff and Pollutant Reduction Calculations .......................................................72

4-8 Payback Period Calculations for Porous Pavement ..............................................73

xi

4-9 Payback Period Calculations for Rain Gardens ....................................................73

4-10 Percentages of Goals Attained by Porous Pavement ............................................74

4-11 Percentages of Goals Attained by Rain Gardens ..................................................74

4-12 Decision Analysis Calculations for Drainage Area A .......................................75

4-13 Proposed Areas for Bioswale/Rain Garden (H) ................................................76

4-14 Total Surface Runoff Calculations (H) .............................................................77

4-15 Construction Costs for Bioswale/Rain Garden .....................................................77

4-16 Runoff and Pollutant Reduction Calculations (H) ............................................78

4-17 Payback Period Calculations for Bioswale/Rain Garden .....................................79

4-18 Percentages of Goals Attained by Bioswale/Rain Garden ....................................80

4-19 Decision Analysis Calculations for Drainage Area H .......................................80

4-20 Sensitivity Analysis for Porous Pavement .............................................................81

4-21 Sensitivity Analysis for Bioswales ........................................................................82

4-22 Sensitivity Analysis for Rain Gardens ...................................................................82

A-1 Water Quality Data for The University of Toledo .................................................95

A-2 Outfall Locations (West)........................................................................................96

A-3 Outfall Locations (East) .........................................................................................96

A-4 Map of The University of Toledo ..........................................................................97

xii

List of Abbreviations

EPA ............................Environmental Protection Agency

NPDES .......................National Pollutant Discharge Elimination System

1

Chapter 1

Introduction

In the past few decades, storm water has become an increasing concern.

Agricultural activities, stream channelization, and urbanization have caused degradation

of landscapes that had once slowed flow, acted as detention basins, and a means from

controlling sedimentation. For example, in the Maumee River Basin, 41% of the river

basin is considered impaired due to urbanization. (US Army Corps of Engineers, Buffalo

Division, 2011) Storm water has also been collected into combined sewer system, in

which storm water and sewage are combined in one sewer system. During large rain

events, wastewater treatment plants become over loaded, and raw sewage is bypassed

into rivers and streams, creating a hostile environment for aquatic life. In order to

separate these sewer structures, millions of dollars must be spent. Flooding due to large

rain events has also proven to be costly. Some storms in the Greater Toledo area have

caused damages estimated at over $1,000,000. In order to address developing storm water

concerns, a tool shall be developed that objectively compares potential BMPs using cost

and environmental benefits. (US Army Corps of Engineers, Buffalo Division, 2011)

2

Chapter 2

Literature Review

2.1 Storm Water Regulatory Context

The Clean Water Act (1972), initially written in 1948 as the Federal Water

Pollution Control Act, provides the basic principles for regulating pollutant discharge into

the water of the United States, as well as quality standards for surface waters. The United

States Environmental Protection Agency (EPA), under authority from the Clean Water

Act, has developed certain standards, such as pollution monitoring programs, which

provide guidelines for wastewater effluent for industries. Under the Clean Water Act, it is

illegal to discharge any pollutant from a point source directly into a water source, unless a

permit is obtained. The U.S. EPA enacted the National Pollutant Discharge Elimination

System (NPDES) in 1972, which further controls discharges into water sources.

Industrial, municipal, as well as other facilities need to obtain permits if any of their

discharges enter into surface waters. Individual homes connected to water collection

systems, use septic systems, or do not have a surface water discharge are not required to

obtain a permit. NPDES does not directly apply to storm water discharges; it applies to

surface and receiving waters in the United States. Storm water contributes to receiving

water pollution, which is why storm water pollution control is becoming more important.

(United States Environmental Protection Agency, 2012)

3

2.1.1 The National Pollutant Discharge Elimination System

More recent concerns, through the NPDES program, have focused efforts to

address storm water discharges. In 1987, the United States Congress amended the Clean

Water Act, which allowed the U.S. EPA to establish NPDES permits for storm water.

The initial permit established by the U.S. EPA focused regulations for storm water

discharges on industrial activity, as well as large separate storm sewer systems, typically

with a population greater than 100,000 people (NPDES Phase I). These permits establish

a means for monitoring pollutant discharge, as well as establish proper controls for

pollutants. (U.S. EPA, Department of Water, 1996)

The U.S. EPA has broadly defined the idea of industrial storm water discharge.

Any industrial activity that discharges storm water through a municipal storm sewer

system, or directly into a water source, must obtain a NPDES permit. Any discharge to

combined sewers or a Publicly Owned Treatment Plant (POTW) can be excluded from

permits. Included in industrial activities are the following: manufacturing plants,

construction sites greater than 5 acres, hazardous material, landfills, sewage treatment

facilities, recycling plants, power plants, mining, oil and gas facilities, airports, and other

transportation related operations. (U.S. EPA, Department of Water, 1996)

In terms of permits, municipalities and industries have three options for dealing

with storm water discharges. The options include the following: (i) individual permit; (ii)

group permits; or (iii) general permits.

4

Individual permitting can occur when facilities of industrial activity choose not to

participate in a group permit or do not receive permit under a general permit, in which the

information required by an individual permit must include a drainage map for the site,

site descriptions identifying pollutants that can be present at the site, as well as testing

data. Group permits can be used when industries of similar work require a permit.

Finally, general permitting can be done when an industry would like to be involved in a

permit that covers an entire area. (U.S. EPA, Department of Water, 1996)

In August 1995, the U.S. EPA developed regulations for Phase II of the NPDES

permit. Phase II of the NPDES program includes all storm water discharges not included

in Phase I. Phase II includes storm water discharges from small municipal separate storm

sewer systems, as well as commercial and industrial activities. Phase II has been designed

for discharges that the NPDES program, regulated by the U.S. EPA, has identified as

contributing to poor water quality or a significant addition to pollution to U.S. waters.

(U.S. EPA, Department of Water, 1996)

Protecting human life and aquatic habitats is the primary concern for the NPDES

permit. In order to do so, the NPDES permit program determines site specific effluent

standards, site specific management programs, and data reporting goals. If a site fails to

comply with these standards, the EPA can enforce fines. If the situation requires aid to

meet standards, the EPA will step in to offer assistance to meet NPDES requirements.

(U.S. EPA, Department of Water, 1996)

5

Each NPDES permit is valid for a period of 5 years. Renewal of the permit must

take place at least 180 days prior to the expiration date of the previous permit. For each

applicant, it becomes imperative to become familiar with the details of the NPDES

permit. The NPDES permit has data reporting and management standards that applicants

need to be aware of. Although each site has specific regulations, the pollutants generally

being regulated can be seen below:

Table 2.1: NPDES Monitored Pollutants

Monitored Pollutants

Conventional

Human wastes

Food from garbage disposals

Bath Waters

Fecal Coliform

Bacteria found in the digestive systems of

humans and animals; can lead to growth of

pathogens

Oils and Greases Can produce sludge solids that are difficult

to treat

Toxic Pollutants Organics, such as pesticides

Metals

Nonconventional Nutrients, such as phosphorus and nitrogen

(Pennsylvania Department of Environmental Protection)

2.1.2 Municipal Separate Storm Sewer Systems

Polluted storm water is frequently transported through Municipal Separate Storm

Sewer Systems, also known as MS4s. Through an MS4, untreated water is emptied

directly into a body of water. Operators of an MS4 must obtain a NPDES permit and

develop a feasible storm water management system to prevent pollutants from entering

into a sewer system. (United States Environmental Protection Agency, 2012) A MS4

6

permit is generally a system of conveyances that is state, city, town or village owned.

These cities that discharge to U.S. waters require an MS4 that is to be designed to collect

storm water, and is not to be collected in a combined sewer situation. Finally, an MS4 is

not to be part of a Publicly Owned Treatment Works, otherwise known as a sewage

treatment plant. (United States Environmental Protection Agency, 2012)

City municipalities, along with guidance from the EPA, have developed these

regulations for many reasons. Heavy runoff flows are being seen in urbanized areas,

creating sediment transport and erosion problems. Contaminants are entering into the

ecosystem through runoff that enters into a citys storm sewer system. Ultimately,

NPDES and MS4 permitting has been developed to address urban storm water problems.

2.2 Urban Storm Water

Urban storm water runoff is created when water flows across lawns, streets, and

paved surfaces during and after a rain event. Surfaces can be classified into two

categories: permeable and impermeable. Permeable surfaces allow the movement of

water through a surface (soil, porous pavement, etc.), while impermeable surfaces forbid

movement of water through the surface (concrete, roofs, etc.). Impermeable surfaces

prevent storm water from naturally percolating through the ground, which filters water

prior to becoming ground water. During a rain event, water removes pollutants from the

air through which it falls, as well as collects debris, litter, and animal refuse from the

ground over which is travels. Storm water, in essence, carries pollution from one place to

another, without treatment. Storm water can have a huge environmental impact due to the

7

fact that all pollution washed away with storm water usually ends up in a water source

somewhere else. (The Pennsylvania State University Institute of State and Regional

Affairs, 1980)

2.2.1 Combined Sewer Systems

Typically, storm water runoff is a major concern in urban areas. Much of the area

taken up by an urban area is considered to be impermeable, or simply impassable, to rain

water trying to infiltrate the surface. In an urban setting, water flows across an

impermeable surface, in which it collects all pollutants it comes in contact with before

entering a storm sewer system. A municipality has two options for storm water:

combined sewer systems, in which wastewater and storm water are combined into one

sewer system, or separate sewers, in which storm water and wastewater have their own

systems, respectively. (The Pennsylvania State University Institute of State and Regional

Affairs, 1980)

Some cities, such as Toledo and Cleveland, have combined sewer systems that

carry sanitary waste from homes and storm water from streets and roofs. In the past, these

systems were beneficial. Storm water was captured and treated along with the sanitary

waste before re-entering the environment. However, as city population and density grew,

these systems became overloaded and high flows were untreatable. This problem has lead

to combined sewer overflows (CSOs), in which raw sewage and storm water is bypassed

directly into rivers and streams to avoid overflowing a treatment plant during a large rain

8

event. This has obvious environmental implications. Solving this problem has proven to

be expensive. The first option thought of was to separate the combined sewers into two

separate systems: sanitary and storm.

Other options have included constructing underground storage tunnels to store

combined sewer overflow. The City of Cleveland has one of these tunnels in operation

currently, and will begin constructing another segment that will run 3,000 feet under

Lake Erie in the next few years. The tunnel is again an expensive option, costing nearly

$198 million. (Scott, 2012)

2.2.2 Non-Point Source Pollutants

In past decades, water quality management had been directed towards point

source pollution (i.e. an individual source of pollution, such as a factory). In this case,

pollution sources are relatively easy to address once identified. However, recent studies

have shown that even though point source pollution is being regulated, storm water

quality is still of concern. A study performed by the Council of Environmental Quality

showed that 75% of urban areas were impacted by nonpoint source pollution. Some

factors that play into nonpoint source pollution can be seen in the table below:

9

Table 2.2: Origins of Nonpoint Source Pollutants

Nonpoint Source Pollutant Origins

Automotive Traffic Construction Air Quality Refuse

Heavy Metals Dirt Smokestack Debris Animal

Acid-Producing Substances Asphalt Coal Plant

Salts Paint Dirt Street Debris

Oil Trash

(The Pennsylvania State University Institute of State and Regional Affairs, 1980)

As seen in the table above, construction sites pose a large problem for overall

water quality in storm water. Due to loose, non-compacted materials, runoff rates from

construction sites can be up to one hundred times greater than that of a non-construction

site. (The Pennsylvania State University Institute of State and Regional Affairs, 1980)

2.2.3 The First Flush

Urban storm water runoff that is of the most concern usually occurs during the

first 30-60 minutes of an event. This is also known as the first flush, in which most

contaminants that will be collected in storm water runoff enter into the ecosystem. Even

though the first flush lasts for a short duration, storm water has a much larger impact on

the environment as compared to treated wastewaters. When compared to treated

wastewater, urban runoff contains much larger amounts of suspended solids (TSS),

metals, and nutrients that enter back into a water source during the storm event. Large

storm events, such as thunderstorms that last 15-30 minutes, contribute the largest

10

amount of pollution in urban runoff. Large amounts of rain lead to heavy runoff. The

heavy runoff can pick up any contaminant it can come in contact with, as well as

contribute to erosion. Erosion is of concern due to high velocities and flow rates through

man-made channels and storm sewer systems, as well as natural streams and rivers. (The

Pennsylvania State University Institute of State and Regional Affairs, 1980)

2.3 Storm Water Pollutants and Their Sources

Not only is water quantity an issue in understanding storm water runoff, water

quality is an issue as well. Decreased water quality hinders aquatic ecosystems and limits

the amount of use for humans. When contaminants are in storm water that is being

collected and released at high flow rates, the delivery of contaminants to waters can be

quite significant.

2.3.1 Physical Contaminants

Temperature

Storm waters can have fluctuating temperatures depending upon their source.

Temperature can be a big contributor to decreased habitat sustainability. Temperature

variations, especially those that increase water temperature, are detrimental to cold water

fish. Water temperature can affect the life cycle of fish, which survive best with water

temperatures of 14 C. Once the temperature of the water reaches 25 C, aquatic life

becomes almost inexistent. (Natarajan & Davis, 2010) Temperature variations can be

caused by cooling water from power plants, runoff from hot parking lots, which can be as

warm as 29 C, as well as the removal of shade from streams and rivers. (Anisfeld, 2010)

11

pH

Another contributor to water pollution is unbalanced pH levels. Typical pH ranges for

natural waters occur between 5 and 9. If a discharge, typically found from industrial

processes, of highly acidic (low pH) or highly basic (high pH) enters into a water source,

can create a toxic environment for aquatic life, as well as damage infrastructure.

(Anisfeld, 2010)

Turbidity/Total Suspended Solids

Turbidity and total suspended solids (TSS) measures the amount of sediment that

is suspended in a water sample. Sediment levels can vary from water source to water

source naturally, through storm events, as well as other sources. Human activities can

increase TSS, especially those activities involved with industrial discharges. TSS and fine

sediments can modify the physical and chemical qualities of rivers and streams.

Invertebrates and other aquatic life can be affected by suspended particles that affect food

and habitats. Also, suspended solids decrease the amount of light entering the water,

which directly hinders the amount of photosynthetic activity that can occur. (Izagirre, et

al. 2008) Turbidity is usually measured in nephelometric turbidity units, otherwise known

as NTUs. Turbidity can be measured by determining the degree to which light is

scattered by particles in a water sample. Total suspended solids are a measurement based

on mg/L of sediment in a water sample. (Anisfeld, 2010)

12

2.3.2 Chemical Contaminants

Conductivity

Conductivity, which is the ability of water to conduct a current, measures the

amount of dissolved material in water. Higher conductivity goes hand in hand with higher

amounts of dissolved materials. High levels of conductivity can be caused by mineral

weathering (natural cause) as well as sewage discharge (human cause). (Anisfeld, 2010)

Dissolved material, commonly referred to as dissolved organic carbon (DOC), indicates

that there is a potential pollution source found in the water. This dissolved organic carbon

is the most common occurring form of organic matter found in water, easily digested by

bacteria found in the same waters. This process by bacteria then limits the amount of

oxygen in the water source, making it difficult to sustain aquatic life. (Moitra, 2012)

Dissolved Oxygen

The next contributor to water pollution is dissolved oxygen (DO). It is imperative

for organisms in a stream or river to have an adequate amount of dissolved oxygen in

order to sustain its life. Physical, as well as biological, processes can control oxygen

levels. Good aeration, or contact between air and water, typically results in 100% oxygen

saturation. The 100% saturation of oxygen in water represents a balance between air and

oxygen in the water. The level of saturation is dependent on a few factors: temperature

and salinity. At high temperatures and salinity, DO can be as low as 6mg/L; at low

temperatures and salinity, DO can be as high as 14 mg/L. Although saturation levels can

depict a certain percentage of oxygen, biological processes can cause a significant

13

difference in actual oxygen levels in water. Respiration, otherwise known as the

consumption of oxygen, is a leading problem found in a water source with high levels of

organic matter. This organic matter is consumed by bacteria, which use DO found in the

water. This scenario can lead to hypoxia (DO levels with less than 3 mg/L), in which

aquatic life will be unable to sustain life. (Anisfeld, 2010)

Biochemical Oxygen Demand

Biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total

organic carbon (TOC) reflect the amount of organic matter found in a water sample, and

can be a sign of wastewater present. Organic matter will consume oxygen needed by

living organisms in the receiving waters. (Anisfeld, 2010)

Nutrients (Nitrates and Phosphates)

Nutrients, specifically nitrogen and phosphorus, are required by plants and algae

to grow. However, high levels of these nutrients lead to eutrophication, which leads to

increased rates of photosynthesis. This increased rate can cause algae blooms, which can

then lead to hypoxia in the water source. Agricultural activities, fossil fuel combustion

and sewage lead to increased nutrient levels. The following are the typical forms of

nitrogen and phosphorus found in surface waters:

14

Table 2.3: Common Forms of Nitrogen and Phosphorus in Receiving Waters

Dissolved Inorganic Nitrogen (DIN)

includes forms of nitrogen that include

NH4+ (ammonium), NH3 (ammonia), and

NO3- (nitrates). All of these forms are

typically used by plants during

photosynthesis

Total Nitrogen

includes both DIN and organic nitrogen.

Organic nitrogen reflects the amount of

nitrogen that has entered into organic

matter through photosynthesis

Dissolved Inorganic Phosphorus (DIP) commonly found as an orthophosphate

(PO43-

)

Total Phosphorus includes DIP and organic phosphorus

(Anisfeld, 2010)

Nitrates are of concern in urban storm water runoff. High levels of nitrates can

lead to eutrophication. Eutrophication (also an implication of high phosphorus and carbon

levels) can lead to algae blooms, which deplete oxygen levels in rivers, streams, and

lakes, making it difficult for fish and other aquatic life to exist. Due to health concerns,

nitrate levels in drinking water can be no more than 10 mg/L. Consequently, it is

important to limit the amount of nitrogen entering a water supply. (Kim, Seagren &

Davis, 2003)

Phosphorus is found naturally in receiving waters in the form of phosphates.

(Geosyntec Consultants, Inc. & Wright Water Engineers, Inc., 2010) Phosphates are also

another source of storm water pollution. Phosphorus can enter into storm water through

the use of fertilizers and other home use. Like nitrates, phosphates can lead to

15

eutrophication. To limit eutrophication, phosphate concentrations should be limited to 0.1

mg/L. (Pretorius & De Villiers, 2000) Also excess phosphorus concentrations can lead to

hindered water clarity, odors, and loss of aquatic habitats. Excess phosphorus can also

indicate the presence fecal indicator bacteria. (Geosyntec Consultants, Inc. & Wright

Water Engineers, Inc., 2010)

Metals

Metals and other organic contaminants, also known as toxic micro pollutants, are

found at much lower concentrations than other pollutants. Metals, although naturally

occurring, are widely used in human activities. Synthetic compounds are emerging as a

leading pollutant under this category as well. There are more than 100,000 different

synthetic compounds today, which is why minimal information exists about them. These

compounds are typically found in sediments, in a process known as sorption, as well as in

organisms, through bioaccumulation. Human exposure to these harmful metals typically

occurs through the consumption of fish and animal products. (Anisfeld, 2010)

2.3.3 Biological Contaminants

Bacteria

Bacteria in a water source are the biggest concern to human health. Human and

animal waste, found in a water source can indicate the presence of pathogens that can be

detrimental to human health. In order to determine the presence of pathogens, certain

indicators can be used that, by themselves, are not harmful but tend to coexist with

pathogens. When these indicators reach a certain concentration, the water is deemed

16

unsafe for human use. Indicators include total coliform, fecal coliform, Escherichia coli

(E. coli), and enterococci. All of the above bacterial indicators indicate the possibility for

the presence of pathogens, and require further water testing to confirm the extent to

which the water quality is contaminated. (Anisfeld, 2010)

2.4 Issues with Heavy Flows in Storm Water

Although contaminants polluting watersheds cause issues for an ecosystem, heavy

flow rates due to large amounts of urban storm water runoff also wreak havoc on an

ecosystem. Although stream and river velocities vary over time due to increased sediment

and water flows from upstream locations, urbanization has drastically increased the rate

as to which this occurs. (Bledsoe, 2002) In an ever-changing urban environment, river

and stream sizes are enlarging. Due to increased runoff caused by impermeable surfaces,

and a decrease in sediment travel, stream and river reliability is diminishing. Damage to

the integrity of river/stream banks and ecosystems are occurring due to structural/shape

changes to channels, changes in channel materials, increase in TSS, and loss of habitats

due to increased flow rates.

Increase of flow rate is becoming a concern to urban watersheds. With an increase

in impermeable material, due to roofs and asphalt, more water is being collected in storm

water systems. Many times, the flows enter directly into a river or stream. An increase in

impermeable surface increases quantity of flow, and subsequently a higher flow rate of

water through a system. (Bledsoe, 2002) A study done in an urban Alabama city shows

17

that from 1990-2002, the amount of impermeable surfaces increased from 73.62 acres to

148.28 acres. This amount of impermeable surface has more than doubled over the past

12 years, which is a direct indication that the amount of runoff has increased by the same

amount. As a result of urbanization, impermeable surfaces are increasing in cities

nationwide. To minimize flow rate, best management practices such as permeable

pavement, detention/retention basins, as well as any other practice that can improve the

infiltration rate of storm water, can be selected to improve the effect of heavy flows on an

ecosystem. (Bledsoe, 2002)

2.5 Local Storm Water Implications

The Greater Toledo area is comprised of land included in the lower Maumee

watershed (approximately 692,000 acres). Activities in the area are primarily agricultural,

accounting for 85% of the land usage. Included in the lower Maumee watershed is 2,150

miles of stream, of which 41% is considered impaired. Agricultural activities, stream

channelization, erosion, and urbanization have degraded much of the landscape that once

slowed flow of storm water, acted as a detention facility, and help control sedimentation

downstream. (US Army Corps of Engineers, Buffalo Division, 2011)

Before the area became urbanized, the area made up a portion of the Black

Swamp. This swamp was once one of the largest wetlands in the United States, until it

was officially drained in the late 1800s. The area initially was settled in the 1850s, after

which the State of Ohio began efforts to drain the area to improve roadway quality.

18

Draining of the Black Swamp was done primarily through the use of clay tiles. Figure 2-1

shows the Black Swamp area:

Figure 2-1: Black Swamp Area

(US Army Corps of Engineers, Buffalo Division, 2011)

In recent years, strong storms have traveled through the area, dumping rainfall

amounts as high as 7.25 inches during one rain event. Due to improper flood controls,

damages caused were estimated as high as $1,000,000. These storms have drastically

overwhelmed drainage ditches, as well as the storm sewer system in Toledo. These

overflows are creating a situation in which wastewater treatment plants, which are part of

the combined sewer network, must bypass overflowing raw sewage into the Maumee

River, as well as local streams in the surrounding area. The raw sewage is leading to E.

coli concerns for the surrounding waters. Aquatic life is becoming hindered and algae

blooms are starting to also become of concern. (US Army Corps of Engineers, Buffalo

Division, 2011)

19

Studies performed by the US Army Corps of Engineers are now being done to assess the

current state of the watershed in Northwest Ohio. The assessment will develop a means

for assessing the situation, as well as cost breakdown and project management. (US

Army Corps of Engineers, Buffalo Division, 2011)

Outside of the Maumee River Basin, the Great Lakes, as a whole, are

experiencing large water quality issues. The demands placed on the Great Lakes have

resulted in severe levels of stress on the ecosystem, and the ecosystem simply cannot

keep up with the demands that are being placed on it. It is becoming imperative that not

only harm be minimized, but to be proactively restoring the ecosystem of the Great

Lakes. (U.S. Environmental Protection Agency, 2010)

In order to achieve this goal, President Barack Obama and the U.S. EPA proposed

a $475 million proposal that would execute the Great Lakes Restoration Initiative. The

initiative is intended to operationalize the intentions made by the Great Lakes Restoration

Initiative. The Great Lakes Regional Collaboration Strategy (GLRC Strategy) provides

the backbone for the Action Plan. This Action Plan points out which factors contribute to

ecosystem problems, as well as combine efforts to address these problems. (U.S.

Environmental Protection Agency, 2010)

The Action Plan focuses on five specific areas of concern. These areas include the

following: toxic substances and areas of concern, invasive species, near shore health and

nonpoint source pollution, habitat and wildlife protection and restoration, and finally

accountability, education, monitoring, evaluation, communication and partnerships. With

20

these five factors in place, the Action Plan then develops measurable goals for the

ecosystem. This plan is intended to further enhance the work that has already been done

by the states surrounding the Great Lakes. Overall, the goals behind the initiative are

simple and are as follows: the fish need to be safe to eat, the water needs to be safe to

drink, beaches and waters need to be safe for recreational activities, native species and

habitats are being protected, and finally, no community will suffer from the effects of

pollution. President Obama has also implemented a measure of progress that can be seen

in the table below:

21

Table 2.4: Measure of Progress for the Great Lakes Restoration Initiative

Measures of Progress for GLRI Project

Measure Baseline 2010 2011 2012 2013

2014

Cumulative

Target

Number of Areas of

Concern in the Great

Lakes where all

management actions

necessary for delisting

have been implemented

1 AOC 1 AOC 1 AOC 3

AOCs

4

AOCs 5 AOCs

AOC BUI (Beneficial

Use Impairments)

Removed

11 BUIs 20

BUIs

26

BUIs

31

BUIs

41

BUIs 46 BUIs

BUI delisting project

starts at AOCs

30 national

and bi-

national

projects

60

projects

80

projects

110

projects

140

projects

170

projects

Cubic Yards (in millions)

of contaminated sediment

remediated

5.5 million 6.3

million

7.0

million

7.2

million

8.6

million 9.4 million

Pollution (in pounds)

collected through

prevention and waste

prevention projects

0 10

million

15

million

25

million

35

million 45 million

Cumulative percentage

decline for the long term

trend in average

concentrations of PCBs in

fish

0% 34% 37% 40% 43% 46%

(U.S. Environmental Protection Agency, 2010)

This initiative is the starting point for reducing pollution in the Great Lakes

region. Using this initiative as a basis for information, smaller areas such as the Greater

22

Toledo area can implement smaller treatment solutions to reduce flow and contaminants

entering into the Great Lakes receiving waters. (U.S. Environmental Protection Agency,

2010)

2.6 Local Storm Water Regulations

Although there arent any specific standards for storm water effluents, the State of Ohio

has certain criteria all surface waters must comply with. The surface waters must meet

the following standards:

Waters added through human activity must be free of suspended solids that could

potentially cause sludge deposits

Waters must be free of debris, oil, and scum that can be considered unsightly

Free from materials causing odor or color change

Waters must be free of toxic substances that could cause harm to human, animal,

or aquatic life

Waters must be free of nutrients that could lead to the growth of aquatic weeds

and algae

Waters must be free of substances associated with raw sewage.

Public health issues occur when the following conditions are met: water samples

that contain five thousand fecal coliform counts per one hundred milliliters in two or

more samples when five or less samples are taken, or in more than twenty percent when

more than five samples are taken, are potential concerns to public health. Similarly, water

23

samples that contain 576 E. coli counts per one hundred milliliters in two or more

samples when less than five are taken, or more than twenty percent when more than five

samples are taken, are also deemed issues to public health. (Ohio EPA, 1998)

Following the actual water quality restraints, a few restraints on testing are also

included in the Ohio EPA code. The collection of samples must adhere to the following:

Samples are to be collected when conditions specify steady state conditions

Samples must be collected at least 2 hours apart

Sample collection must not exceed 30 days

(Ohio EPA, 1998)

The above restraints to surface waters took effect in 1998, and have been

reviewed in 2007, as well as in 2012. (Ohio EPA, 1998)

2.7 Introduction to Urban Storm Water Controls

Control of water quantity (controls for flow and volume) will always be the front-

runner in storm water management since pollutant concentrations will always be

dependent upon flow quantity. Pollutant removal using best management practices

follows the same routines found in conventional water and wastewater treatment, which

use physical, chemical, and biological principles to treat water. Best management

practices not only treat water, but also involve the storage, filtration, and education

behind storm water issues. (Transportation Research Board, 2006)

24

2.7.1 Hydraulic Controls

Hydraulic controls are a significant factor in determining a best management

practice to implement. Flow alteration is the leading idea behind hydraulic controls. The

goals of hydraulically controlling runoff are to reduce volume, reduce peak flows, and to

create uniform flow rates at all times. Hydraulic controls can be broken into two different

ideas: flow attenuation and volume reduction, and are discussed below. (Transportation

Research Board, 2006) Flow alteration solutions include practices such as runoff,

infiltration, detention, storage, and evaporation.

2.7.1.A Flow Attenuation

Flow attenuation aims to reduce peak flow discharge quantities, and can be

broken down into interception, conveyance, and detention. Interception of storm water

occurs when a drop of water is temporarily stored in a leaf, stem or branch. Throughfall,

or water that drips from a leaf to the ground, accounts for the majority of intercepted

storm water. A small portion of this intercepted water is retained on the surface area of

plants and is lost through evaporation. The amount of water that can be intercepted varies

depending on the density of vegetation, but percentage of rainfall intercepted can be as

much as 20%. The idea of conveyance deals with the transport of runoff over the entirety

of a flow path for a single drop of water. In a typical collection system, conveyance aims

for efficiency in collecting runoff. However, with a best management practice,

conveyance is provided, as well as the increase of infiltration, improves water quality,

increases travel time for runoff, also known as time of concentration (Tc). These controls

25

are becoming increasingly important with the idea of treatment trains, or a system of best

management practices that aim to increase water quality and reduce flow. Finally,

detention temporarily stores excess amounts of storm water until can be released over a

determined period of time. A commonly mistaken term is known as retention (part of

volume reduction), in which water is never released after capture. No matter how the

water is stored (either through ponded water or contained in soils), storm water enters

into the storm sewer system. Detention systems are designed to release collected storm

water and release it back into the sewer system so that flooding will not occur.

(Transportation Research Board, 2006)

2.7.1 B Reduction of Volume

The second concept of hydraulic controls deals with the idea of reduction of

volume. Reduction of volume can occur through any of the following ideas: retention,

infiltration, or evapotranspiration. Retention, introduced earlier, captures storm water and

never releases it back into a storm sewer system. Retention can occur when runoff is

captured through interception, evaporation, transpiration and reuse. Evapotranspiration

(ET), which is the combination of evaporation and transpiration, can occur in many

different scenarios. Transpiration aims volume reduction for the root zone of soil.

Infiltration occurs when water enters through the soil and recharges ground water. In a

setting such as a meadow or forest, this movement of water is quite easy. However, in an

urban setting soil becomes very compacted, and infiltration is restricted. Soil moisture

content determines how much volume can be reduced. The volume able to be captured is

26

a direct correlation to a soils field capacity. Field capacity can be defined as the point

where drainage of water through gravity stops and water is then collected in soil through

capillary action. Any water that enters after this point typically requires under drains that

will move storm water back into a system. Infiltration rate can be affected by soil type,

amount of vegetative cover, as well ground water conditions. Infiltration can be increased

through the use of the following BMPs:

Porous pavement

Lawns, which increase green area and promote runoff infiltration

Green roofs

Bioswales/rain gardens

Finally, the combined idea of evaporation and transpiration, or evapotranspiration,

reduced water in vegetated areas. Water found in the root zones of soils are taken up

through the root systems of plants and them becomes transpired through the leaves of the

plants. The removal of water by the root systems of plants may remove excess

contaminants, especially nutrients such as phosphorus and nitrogen. ET is typically the

dominant volume control once excess water is removed through infiltration and under

drains, and field capacity is once again achieved. The following equation reflects the total

volume that can be removed by ET:

27

where:

V = transpired volume

Dr = root depth

A = surface area of soil

FC = field capacity

WP = wilting point

The wilting point can be defined as the point in which the soil loses the amount of suction

force required to draw more amounts of water from the ground. The difference between

field capacity and wilting point produce the amount of moisture available for

transpiration. Systems such as rain gardens have low field capacities (the amount of water

stored by capillary action once drainage by gravity has concluded), which maximize

drainage potential and filtration of pollutants. (Transportation Research Board, 2006)

2.7.2 Unit Processes

The second way of characterizing best management practices involves unit

processes. FPCs (fundamental process categories) depict the efficiency of pollutant

removal for certain best management practices. FPCs deal with both unit operations (an

actual force removes contaminants) and unit processes (a biological or chemical process

performs contaminant removal). Similar to wastewater treatment technologies, some

BMPs can be considered both a unit operation and a unit process. Certain variables can

determine the effectiveness and practicality of each BMP, and are known as static and

state variables. Static variables deal with design parameters of a given system, which

28

include volumes and dimensions, location, size, slope, state of permeability, amount of

vegetation, and soil type. State variables take into account rainfall volumes and

intensities, detention times, season, vegetation, and maintenance. (Transportation

Research Board, 2006)

2.7.2 A Physical Treatment Processes

Sedimentation. Sedimentation occurs in two phases: settling of storm runoff

during harsh conditions, followed by longer sedimentation times during non-storm

conditions. Sedimentation aims at removing contaminants that include TSS and heavy

metals. Dynamic removal and particle settling are dependent upon factors that include

hydraulic loading rate and particle size. As a general rule, sedimentation is a highly

effective removal option with high pollutant concentrations (anything greater than 400

mg/L) and large particle size (anything greater than 50 ). Sedimentation is the leading

treatment system used in detention/retention ponds, as well as wetlands and biofilters.


Filtration. Filtration is a contaminant removal process in which certain media are

able to remove contaminants from storm water as the water moves through the media

through gravity. Sorption refers to the combined processes of absorption and adsorption.

Absorption occurs when one substance is assimilated into another substance of a different

state. Adsorption occurs when one substance adheres chemically to the outside structure

of another substance. These processes aim to remove contaminants associated with

roadways. The absorption process aims to remove petroleum byproducts, while

29

adsorption focuses on nutrient, metal, and organic removal. The media used in BMPs that

deal with filtration and sorption can have a broad range. Media used can range anywhere

from vegetation and compost to activated carbon and engineered media. The extent of

filtration is determined by particle size and media type. The chemical process involved in

sorption is a little more complex. Chemical removal through sorption involves ion

exchange between water and media, absorption and adsorption. These processes can

remove dissolved contaminants such as metals nutrients and hydrocarbons. The sizing

and media selection must be based on the contaminants one is trying to remove. The

contaminants will control which media is used, and how often the media will need to be

replaced. Filtration and sorption are commonly associated with BMPs such as bioswales,

sand filters and ponds. These filters need to constantly remain in an aerobic state. If the

filter becomes anaerobic, the redox state will change, causing all sorbed metals to be

released. Dissolved contaminants are much more difficult to remove compared to solids,

which tends to lead to higher contaminant removal when solids concentrations are much

higher. (Transportation Research Board, 2006)

Flotation. Flotation tends to act in an opposite way compared to sedimentation.

Flotation takes advantage of differences in densities in contaminants and water. Flotation

is common when dealing with oils and greases, as well as trash, found in storm water.

Water has a specific gravity of 1.0. Anything having a specific gravity less than 1.0 is

less dense than water, causing the contaminant to float to the surface of the water. The

difference in specific weights determines the rise rate for the contaminant, allowing

30

someone to be able to design a proper size and depth for a removal mechanism. Oil-water

separators use this idea to remove contaminants from storm water. (Transportation

Research Board, 2006)

2.7.2 B Biological Treatment Processes

Biological processes use organisms such as plants, algae, and microbe to remove

organic and inorganic pollutants found in storm water. Biological treatment processes can

be broken down into two categories: microbially mediated transformations and uptake

and storage. Microbially mediated transformations involve chemical processes performed

by bacteria and algae in which pollutants are removed from a water source. Uptake and

storage involves processes in which plants are able to remove contaminants from a water

source through nutrient uptake and bioaccumulation. (Transportation Research Board,

2006)

2.7.2 C Chemical Treatment Processes

Chemical processes target the following problems commonly found in storm

water: pH, alkalinity, hardness, redox conditions, organic carbon, and ions. Typically,

treatment options from a chemical standpoint involve sorption, coagulation, or chemical

disinfection.

Sorption. Sorption involves the combined processes of absorption and adsorption.

Absorption involves a process in which a substance in one state is integrated into another

substance. Adsorption occurs when one substance is linked to the surface of another

substance, but is not integrated into the second substance. In storm water treatment,

31

sorption is commonly used, especially in treatment of highway runoff. Absorption is used

to treat hydrocarbons and byproducts of petroleum, and adsorption is used to treat

contaminants such as metals, nutrients, and pesticides. (Transportation Research Board,

2006)

Coagulation. Coagulation aims to form larger particles of contaminants by

destabilizing the particles so that they can grow. Ultimately, the particles will eventually

become large enough so that standard filtration can remove the contaminants. Usually,

this process can occur naturally, but in order to be efficient for storm water treatment, the

process must be sped up with the addition of chemicals. One negative impact of

coagulation is that large amounts of sludge can form, which will need to be removed to

keep treatment running efficiently. (Transportation Research Board, 2006)

Chemical disinfection. Chemical disinfection removes pathogens found in storm

water using chemicals such as chlorine and ozone. At times, chemical disinfection can be

cheaper than natural disinfection. Chemical disinfection has an added benefit, in which

residual from disinfection prevents the re-growth of pathogens and helps to treat water

downstream. (Transportation Research Board, 2006)

Table 2.5 shows how many processes overlap in the various types of contaminant

removal:

32

Table 2.5: Structural BMPs listed by Fundamental Process Category and Unit

Operation

Fundamental Process Category

(FPC) Unit Operation or Process BMPs

Hydrologic Operations

Flow/Volume Attenuation

Extended detention basins

Retention/detention ponds

Wetlands

Tanks/vaults

Equalization basins

Volume Reduction

Infiltration/exfiltration trenches

Permeable pavement

Bioretention cells

Dry swales

Dry well


Physical Treatment Options

Particle Size Alteration Comminutors

Mixers

Physical Sorption

Nutrients, metals, petroleum,

compounds

Engineered media, activated carbon,

and sands

Size Separation

Screens/bars/trash racks

Biofilters

Permeable pavement


Manufactured bioretention systems

Engineered media

Hydrodynamic separators

Catch basin filters

Density, Gravity, and Inertial

Separation


Retention/detention ponds

Wetlands

Settling basins

Tanks/vaults

Swales with check dams

Oil-water separators

Hydrodynamic separators

Aeration and Volatilization

Sprinklers

Aerators

Mixers

Physical agent disinfection Shallow detention ponds

33

Ultraviolet systems

Biological Processes

Microbiotically Mediated

Transformation

Metals, nutrients and organics

Wetlands

Bioretention systems

Biofilters

Retention ponds

Engineered media

Uptake and Storage

Metals, nutrients and organics

Wetlands/wetland channels

Bioretention systems

Biofilters

Retention ponds

Chemical Processes

Chemical Sorption Processes

Subsurface wetlands

Engineered media


Coagulation/flocculation

Detention/retention ponds

Coagulant/flocculent injection

systems

Ion Exchange Engineered media

Chemical Disinfection Custom devices for mixing chlorine

or aerating with ozone


2.8 BMP Design Type

The final way to categorize a best management practice is based on the design of

the treatment system. The three options for categorization are structural BMPs, which are

constructed at the site of the problem, proprietary, which are pre-engineered solutions,

and non-structural BMPs, which involve source controls to reduce contaminants.


2.8.1 Structural BMPs

Structural BMPs rely on the idea of a treatment train, which involves two or more

processes to effectively remove contaminants from storm water. Selection of structural

BMPs depends on a few factors, including which BMPs can be used, site constraints, and

34

percentage removal of contaminants needed. The most commonly found structural BMPs

include the following:

Wet ponds

Retention ponds

Infiltration trenches

Wetlands

Bioswales and filter strips

Oil-water separators

Sand filters

Proprietary systems may also be part of a treatment train for contaminant removal. These

systems are popular in urban settings, since most processes are compact in design. The

table below shows commonly used BMPs, as well as product names for these devices:

35

Table 2.6: Proprietary BMPs in Current Use

Proprietary BMP Product Name

Wet Vaults

StormCeptor

BaySaver

StormVault

ADS Retention/Detention System

Constructed Wetlands StormTreat

Hydrodynamic/Vortex Separators

Vortechs

Aquafilter

V2B1

Downstream Defender

Continuous Deflective Separation (CDS) Unit

Sorptive Media Filters StormFilter

Flow Splitter StormGate

Modular Pavement Various


2.8.2 Non-structural BMPs

The last of these options include non-structural BMPs, which include source

controls to limit the amount of contamination entering into storm water. These controls

attempt to install educational programs in order to reduce the amount of pollution coming

from human activities. These educational programs help people make more

environmentally-friendly decisions. These best management practices see the highest rate

36

of success when an entire community becomes involved, and is aware of the issues at

hand. Below is a list of non-structural BMPs that can be implemented with little or no

cost to reduce storm water contamination:

Table 2.7:Non-Structural BMPs

Non-Structural BMP Type

Source Control/Maintenance

Street sweeping

Catch basin cleaning

Covering of stockpiles

Safer construction materials, herbicides, and road

salts

Material storage control

Reduce vehicle use

Used oil recycling

Vehicle spill control

Above ground spill control

Illegal dumping control

Vegetation control

Storm drain flushing

Roadway and bridge maintenance

Detention and infiltration device maintenance

Litter control

Litter pickup

Public Education and Participation Newspapers, brochures

37

Land use planning

Adopt-a-Highway

Integrated pest management

Storm drain system signs

Other

Curb elimination

Reduction of runoff velocity


Overall, the selection of the BMP should be based on treatment goals for an

individual site. The following table depicts which BMPs can target which pollutants:

Table 2.8: Groups of Pollutants and Relevant BMPs listed based on FPCs

Pollutant BMPs

Gravity

Settling/Flocculation

Filtration/Sorption Infiltration Biological Chemical Other

Particulates Sediments

Solids

Metals

Organics

Nutrients

Retention Ponds

Detention Ponds

Wetlands

Tanks/Vaults

Biofilters

Media Filters

Compost Filters

Wetlands

Trenches

Basins

Porous

pavement

Swales

Biofilters

Biofilters

Wetlands

Flocculation Wet vaults

Vortex

separators

Modular

wetlands

Solubles Metals

Organics

BOD

Nutrients

Media Filters

Compost filters

Wetlands

Retention ponds

Trenches

Basins

Porous

pavement

Biofilters

Wetlands

Precipitation

Flocculation

Activated

carbon

StormFilter

Trash/Debris Trash

Debris

Screening Vortex

separators

Skimmers

Floatables Oil

Greases

Retention ponds

Wetlands

Hooded catch basins

Catch basin

inserts

Vault filters

Compost filters

Biofilters

Wetlands

Oil/water

separators

Absorptive

media

filters


38

2.9 Criteria for BMP Selection

In order to properly select a best management practice to incorporate into a storm

water management plan, proper storm water goals must be in place, such as flow

reduction percentage and water quality goals. Pollutants of concern (nitrates, phosphates,

coliform, E.coli) must be addressed. If the overall pollutants are addressed, quality of

effluent and percent capture can be designed to meet NPDES standards. The following

process should help any entity plan and install the proper BMP system for a site.


1. Problem Definition

Before any solution can be designed, a quality understanding of the pollutant and

runoff issues (i.e. high flow, high concentrations of pollutants) associated with the site

must be defined. The end result for the storm water plan must also be determined, so that

a proper system can be designed. The problem statement should have all criteria needed

for the project to be specified (i.e. strictly retrofitting and new construction). All

objectives for the project also need to be listed and ranked based on importance to the

project. Also accompanying these objectives should be specific goals the project is

required to meet (reduction of volume by a certain percentage, removal of pollutants).

39

2. Site Characterization

The next step in selecting a best management practice is to characterize the site in

question. It is imperative to know all site conditions and constraints before the design

process even begins. This step can initially eliminate some options that simply are not

feasible for a given site. Hydrologic and soil conditions also help narrow down which

BMPs will work at the given site. Infiltration rates of certain soil types are imperative for

the success of BMPs. High infiltration rates allow BMPs to handle a higher quantity of

flow, thus allowing for more effective treatment of runoff.

3. Identification of Fundamental Process Categories

Once site conditions and constraints, as well as initial water quality, are

documented, certain processes need to be evaluated and ranked based on how well they

can reduce flow and treat contaminants. Soil types and infiltration rates are a key factor in

this step, simply because these factors depict how well a BMP can operate given the site

conditions. As discussed earlier, these FPCs can be divided into hydrologic, physical,

biological, and chemical operations. The selection of the best available process should be

done based on the types of pollutants found, and specific site goals for effluent storm

water quality.

40

4. Selection of BMPs and Other Treatment Options

Once the overall unit processes available to the site are specified, specific best

management practices can be identified and selected. A general understanding behind

how certain BMPs work (i.e. hydrological, chemically, biologically) is key to selecting

the proper solution. The goal should be to select a BMP that addresses all issues on site.

However, if one solution does not address all issues, multiple solutions may need to be

bundled together to create a treatment train. Once feasible solutions are addressed, the

next step is to analyze the solutions to see if one BMP works better given site constraints

than any other potential solution.

5. Practicability of Proposed Treatment Systems

Once certain BMPs are selected as potential solutions for storm water runoff

issues, the practicality of each solution needs to be evaluated. The evaluation process is

based on the following criteria:

Performance for target pollutants

Hydrology and hydraulics

Space availability, both above surface and subsurface

Maintenance

Economics

Aesthetics

41

Other factors go into the practicality of each solution, including downstream impacts,

health effects, climate, and overall budget for the project. This process should once again

narrow down which BMP would be most effective for the problem at hand.

6. Sizing the Conceptual BMP

Once the selection process is complete, a conceptual design for the BMP needs to

be completed. This conceptual design not only needs to meet projects criteria, it also

needs to be designed within the restraints of EPA. Typically, the conceptual design is

based on hydrology, in which the BMP is designed for flow attenuation, volume

reduction, or flow duration. The sizing of the BMP can be done using factors such as

design storms, rainfall frequency analyses, and continuous runoff models.

7. Development of Performance Monitoring and Evaluation

Once design is completed, a long-term evaluation plan must be developed. This

plan should aim to address management, regulatory and research goals. These goals are

based on the success of project objectives, which includes hydraulics and water quality.

This monitoring plan, like the rest of the project is based upon cost and time available.

Overall, it is important to get long-term data to effectively analyze the performance of the

BMP selected and installed. (Transportation Research Board, 2006)

Overall, the selection of the correct best management practice can seem like an

open-ended question. Multiple solutions could potentially work just as well as another

42

solution. As a general guideline, the following criteria should be taken into account,

which is shown in the BMP objective checklist table below:

Table 2.9: BMP Objective Checklist

Category Typical Objectives for Urban Runoff

Hydraulics Manage flow characteristics

Hydrology Eliminate flooding while improving runoff quality

Water Quality

Reduce pollutants loads downstream

Improve downstream temperature impacts

Obtain desired pollutant concentrations

Remove trash and other debris

Toxicity Reduce acute and chronic toxicity of runoff

Regulatory

Comply with NPDES permitting

Comply with local, state, and national water quality

regulations

Implementation Function within management structure

Cost Minimize life-cycle costs

Aesthetics Improve appearance of site while reducing odors

Maintenance Operate within maintenance and repair schedule

Design BMP to allow for future retrofitting

Longevity Allow for long-term functionality

Resources

Improve downstream aquatic life/erosion control

Improve wildlife habitats

Achieve multiple use functionality

Safety, Risk, Liability

Function without significant risk or liability

Minimize environmental risk downstream

Contain any spills

Public Perception Help the public understand the importance of runoff

quality, quantity, and impacts on receiving waters


2.10 Selected BMPs

There are many best management practices available used to treat storm water

runoff issues. Of these BMPs available, much focus has been put on permeable

pavement, bioswales, and rain gardens, due to their ability to effectively reduce volume

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and contaminants simultaneously. These various BMPs also have well documented

performance data, specifically flow reduction ability, contaminant reduction potential, as

well as cost information. Local stakeholders also have interests in these BMPs. Since this

information is needed to carry out a comparison that includes environmental benefits,

these BMPs were the focus of this work.

2.10.1 Permeable Pavement

Storm water quantity has become one of the largest areas of concern as

urbanization has occurred. (Brattebo & Booth, 2002) More and more surfaces are

becoming impermeable, creating larger quantities of runoff, flooding, channel erosion,

destruction of aquatic habitats, and landslides. (Booth & Leavitt, 1999). These surfaces

increase stream loadings, causing channel erosion, bank erosion, and sediment

movement. Impermeable surfaces reduce infiltration, causing a lack of groundwater

recharge, while increasing pollutant concentrations. Due to urbanization, significant

portions of permeable material (grasses, forests) have been destructed. This area had

acted as a large reservoir, capable of infiltrating and storing large amounts of water

runoff. This reservoir was capable of holding water for an extended period of time, but

now that it is gone, water is rapidly moving through urbanized areas causing significant

damage. One solution to this effect of urbanization is to seamlessly find a way to store all

of the excess water that is running off from impermeable surfaces. However,

retention/detention ponds capable of storing that amount of water are quite ineffective.

These ponds would have to be immense, which is virtually impossible in an urban

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environment. The solution to this problem involves permeable pavement. (Booth &

Leavitt, 1999)

Much of these surfaces, however, are used for light/medium traffic (parking lots,

driveways, road shoulders, etc.). These surfaces are design to allow for peak loading

conditions, which occur infrequently. One solution that offers infiltration benefits is

permeable pavement. Permeable pavement is set up in a web-like structure with voids,

filled with material such as sand or soil. These voids allow water to percolate through the

surface and re-enter into the ground water. Permeable pavement can be constructed with

numerous materials, such as asphalt, concrete, or plastics. The image below depicts how

water can infiltrate through the pavement (Brattebo & Booth, 2002):

Figure 2-2: Demonstration of Water Infiltration through Permeable Pavement

(Kujac, 2009)

Various studies have been completed that have tested the usefulness and

effectiveness of permeable pavement to reduce runoff quantity and pollutant

concentrations. In a study performed by the Civil Engineering Department at the

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University of Washington, a study was completed that tested water quality and quantity

performance of 4 different permeable pavement systems. The systems tested include

Grasspave, which is a plastic grid system filled with sand, then planted with grass,

Gravelpave, which is the same as Grasspave, except with gravel instead of sand,

Turfstone, made up of concrete blocks, and UNI Ecostone, made up of smaller concrete

blocks. Three questions were to be answered by this study: Are these surfaces durable

enough to withstand long-term use? Do these systems remain permeable, or do they clog

up over time? Finally, what is the water quality after the water infiltrates the system?

(Brattebo & Booth, 2002)

Overall, all permeable pavement systems tested well in terms of durability,

infiltration capacity, and improved water quality when compared to standard asphalt

systems. Turfstone and UNI Eco-Stone held up as well as an asphalt system during daily

loading. The highest rate of precipitation seen during this test was 7.4 mm/h, in which

each system was able to infiltrate all runoff. The site had positive drainage

characteristics, which increased the amount of water able to infiltrate. Under drains are

recommended to be installed with these pavement systems if soil conditions are less than

favorable to provide positive infiltration. Particulates, such as sand, dirt, and other debris

can clog this system over time, and is recommended to be flushed and swept with a street

cleaning system once per season. (Brattebo & Booth, 2002)

In conclusion to this study, it is apparent that permeable pavement can

significantly reduce the amount of runoff that is channeled into rivers and streams,

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minimizing damages such as erosion and pollutant travels. Permeable pavement also

reduces pollutant concentrations through the process of filtration. Specifically, nutrients

(nitrates and orthophosphates) are removed through adsorption of storm water solids.

Nutrients are often adhered to the outside structure of solids found in storm water runoff.

(Brattebo & Booth, 2002)

Another study testing the same 4 permeable pavement systems, performed by the

Center for Urban Water Resources Management, compared surface runoff from

permeable pavement systems to that of traditional asphalt surfaces. A storm with a

maximum rainfall of intensity of 4mm/hr was tested, in which 0.1% of the total rainfall

was considered runoff, and was mainly attributed to leaks in the gutter collection system

used to test the various pavements. In essence, all water was infiltrated through the

permeable pavement system, eliminating surface runoff, and as a result, damages caused

by rapid storm water runoff. (Booth & Leavitt, 1999)

2.10.2 Rain Gardens

Rain gardens are an effective tool used to reduce or remove pollutants from urban

storm water runoff. These gardens are typically shallow (approximately 2-3 deep), and

are planted with trees, shrubs and other plants, and covered with mulch. These gardens

allow water to infiltrate through the garden material, effectively recharging groundwater

and reducing large flow quantities of storm water runoff. Rain gardens are also effective

in pollutant removal, using processes such as adsorption and decomposition to remove

pollutants. (Dietz & Clausen, 2005) As such, rain gardens function as both a hydraulic

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control and unit process BMP. Rain gardens aim to infiltrate surface runoff diverted to

the system. Once surface runoff enters into a rain garden, runoff quantity, as well as

pollutant concentrations are reduced through plant uptake and storage.

Prince Georges County, MD, was the first area to recommend rain gardens as an

effective storm water treatment option. Prince Georges County published the

Bioretention Design Manual in 1993 to aid in the design and implementation of rain

gardens. However, it is still quite vague as to how to size certain rain gardens, as well as

development of a method to compare storm water best management pr

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