A Critical Overview and Analysis of Erosion

and Sediment Controls at Construction Sites

Nahyan Muhammad Rana

2B Environmental Sciences – Geosciences Specialization

UNIVERSITY OF WATERLOO

Faculty of Science

A CRITICAL OVERVIEW AND ANALYSIS OF EROSION AND SEDIMENT

CONTROLS AT CONSTRUCTION SITES

MMM Group Limited

Kitchener, Ontario

Nahyan Muhammad Rana

2B Environmental Science (Geosciences Specialization)

ID 20486918

October 28, 2014

130 Lincoln Road

Waterloo, Ontario

N2J 4N3

December 19, 2014

Mr. William Taylor,

Department Chair,

Department of Earth and Environmental Sciences,

University of Waterloo

N2J 3G1

Dear Mr. Taylor:

This report, entitled “A Critical Overview and Analysis on Erosion and Sediment Controls at

Construction Sites” was prepared as my 2B work report for MMM Group Limited. This is my

first work term report. The purpose of this report is to evaluate various sediment and erosion

control measures that are implemented at construction sites, while also comparing the

effectiveness of the different sediment and erosion control measures according to seasonal and

climatic variations and under different circumstances.

MMM Group Limited is a multidisciplinary consulting firm that provides a wide range of civil

engineering and environmental engineering services which include, but are not limited to,

hydrogeology, transport management, GIS services, environmental planning, water resource

management, community design and infrastructure development.

The Environmental Management Division, in which I was employed as a Hydrogeological

Assistant, is managed by Peter Hayes. Our work consisted of working with clients to perform

groundwater studies (surface water and groundwater monitoring), private water well surveys

(water quality assessments), erosion and sediment control inspections, and apply for regulatory

permits, including Ontario Ministry of the Environment and Climate Change Permit-To-Take-

Water (PTTW) applications, amongst other activities.

This report was written entirely by me and has not received any previous academic credit at this

or any other institution. I would like to thank Mr. Peter van Driel (supervisor) for his everlasting

support and guidance and for proof-reading my report. I received no other assistance.

Sincerely,

Nahyan Rana

20486918

TABLE OF CONTENTS

1.0 Introduction………………………………………………………………………………1

2.0 Rain Erosion……………………………………………………………………………...2

3.0 Environmental Hazards Caused by Accelerated Erosion………………………………...4

4.0 Erosion and Sediment Control from a Regulatory Perspective…………………………..5

5.0 Erosion and Sediment Control Practices: Permanent and Temporary Works……………7

5.1 Types of Erosion Controls………………………………………………………..8

5.2 Types of Sediment Controls……………………………………………………...10

6.0 Project Case Studies……………………………………………………………………...13

6.1 Case Study 1: Erosion Controls on Sloped Bare Soils (Visual Analysis)………13

6.2 Case Study 2: Effectiveness of In-Water Sediment Controls (Quantitative Data

Analysis)…………………………………………………………………………15

7.0 Conclusion……………………………………………………………………………….17

8.0 Recommendations………………………………………………………………………..18

9.0 References………………………………………………………………………………..19

10.0 Appendices……………………………………………………………………………….21

LIST OF APPENDICES

Appendix A – Figures*………………………………………………………………………….21

Appendix B – Case Study 1: Location Schematic Diagram Initial Conditions (July, 2014)…30

Appendix C – Case Study 1: Location Schematic Diagram Current Conditions (December,

2014)…………………………………………………………………………………………….31

Appendix D – Case Study 1: Photographs (July 29, 2014 – December 16, 2014)……………32

Appendix E – Case Study 2: Photographs……………………………………………………..38

Appendix F – Case Study 2: Table of Turbidity Measurements………………………………41

Appendix G – Case Study 2: Graph of Turbidity Measurements……………………………..42

Appendix H – Case Study 2: Location Schematic Diagram…………………………………...43

*Figures in Appendix A are listed on the next page

LIST OF FIGURES (in Appendix A)

Figure 1: Splash erosion

Figure 2: Sheet erosion

Figure 3: Gully erosion

Figure 4: Rill erosion

Figure 5: Diagram of erosional processes along a sloped hill

Figure 6: Appearance of sediment-laden water

Figure 7: Turbidity level comparison

Figure 8: Dust control truck

Figure 9: Mulching

Figure 10: Sod blankets

Figure 11: Riprap

Figure 12: Design of riprap channels

Figure 13: Riprap at banked slopes

Figure 14: Erosion control blanket

Figure 15: Compost blanket

Figure 16: Silt fences

Figure 17: Silt fences – limitations

Figure 18: Filter logs

Figure 19: Filter soxx™

Figure 20: Check dam

Figure 21: Turbidity curtain

Figure 22: Inlet protection

SUMMARY

This purpose of this report is to perform an evaluation and analysis on erosion and sediment

control measures that are typically implemented at construction sites. Firstly, the various kinds of

erosion, including splash, sheet, rill and gully erosion, are explored. Then, the environmental and

biological hazards that occur on construction sites as a result of erosional processes are

discussed, before examining erosion and sediment control work in terms of regulations and

legislation. The various kinds of erosion and sediment control measures are then evaluated and

analysed. Finally, two project case studies are presented to the reader.

In Case Study 1, bare and exposed soils are sloping downward towards a residential driveway.

Concentrated flow is present along the slope due to roadside ditches. In order to prevent erosion

and sediment deposition on the driveway, various sediment control techniques were implemented

over the course of four months. Low-cost methods were proven to be relatively ineffective when

compared to high-cost methods, which were shown to be necessary in this case.

In Case Study 2, the subject area consists of a bridge reconstruction site. The effectiveness of in-

water sediment controls was analyzed; namely turbidity curtains. Quantitative analysis (daily

turbidity measurements) showed that turbidity barriers are efficient and effective in preventing

entry of sediment-laden water into the river such that, other than a few instances, turbidity of the

water downstream was similar to or slightly higher than the turbidity levels upstream.

It is recommended that cost-effect and cost-benefit studies be carried out in order to assess what

measures could be suitable and practical, expense-wise, considering the site-specific conditions

and circumstances at any given time.

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1.0 INTRODUCTION

Soil erosion is a naturally occurring process that affects all landforms. It involves the wearing

away of the surface of the land by the action of four (4) natural factors: wind, water, ice and

gravity. Soil erosion can also be accelerated as a result of the influence of human activities, as

observed on construction sites. Erosion and sediment-laden runoff is a concern during and after

construction projects, whereby rainfall and runoff events may trigger accelerated erosion and

sediment transport. This in turn negatively impacts environmentally sensitive areas (waterways,

creeks, rivers, woods, lakes, etc.) nearby, and also may cause damage to properties or

infrastructure. All of this leads to costly damages to natural environments, properties and

infrastructure.

In order to understand and control the damages and impacts caused by soil erosion in

construction sites, Erosion and Sediment Control (ESC) plans are created, and inspectors are

hired by the Contractor in order to conduct environmental assessments in the construction Site.

Field observations of on-site conditions can help the stakeholders identify environmentally

sensitive areas, potentially-problematic areas or other areas of concern, while also providing a

high level of detail with regards to identifying and assessing the magnitude of potential ESC

concerns.

This report presents detailed examinations on the various types of soil erosion and the numerous

kinds of ESC techniques that are implemented in order to control soil erosion. Two case studies

are also provided, which involve critical analysis of the effectiveness of different ESC measures

at a given location.

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2.0 RAIN EROSION

Natural soil erosion is caused by the influences of water, wind, ice and gravity. Soil erosion can

be an ongoing occurrence at a slow and uniform rate, or it can be accelerated during extreme

weather such as high winds, storms, cyclones, heavy rainfall and snow melt. These extreme

events tend to result in the exposure of bare soils to wind or water, which then leads to the

unprotected soils being subject to rapid erosion. There are four (4) interrelated principal factors

which determine the erosion potential of any area that is covered by sediment or mass soil: soil

structure and properties, climate, topography and vegetative cover (Konatsotis and Corrente,

1993).

When raindrops are falling with significant impact onto the soil surfaces, there are four (4)

‘stages’ of erosion that tends to occur if the vicinity remains undisturbed over a prolonged period

of time. Splash erosion is considered to be the first stage of erosion, as it occurs when raindrops

fall from the sky and hit bare and exposed soils. The explosive impact caused by the forces of the

falling raindrops result in the breaking up and loosening of the soil aggregates, leading to

individual soil particles ‘splashing’ loose, as seen in Figure 1.

As the rainfall event continues, the individual soil particles accumulate and slide down the slope

(gravitational effect) along with the flow of water. Therefore, the intensity and duration of

rainfall is a significant factor in the amount of soil erosion that may occur. Higher intensity and

longer duration of rainfall generally leads to higher amounts of soil erosion.

Sheet erosion is regarded as a secondary stage in erosion, where soil particles and aggregates are

removed in thin layers due to raindrop impacts and shallow surface flow. When the soil particles

are dislodged due to the impacts from the falling raindrops (splash erosion), the sediment-laden

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runoff water tends to flow down the slope due to gravity and picks up other soil particles in the

process. This erosional process is more uniform (sheet flow) and has an increased surface flow

whereby all the running water (sheet flow) accumulates and flows in a uniform manner. This is

illustrated in Figure 2. As the runoff moves down the slope, the flowing water follows the lowest

pathway, due to gravity, which results in rivulets (small streams) forming. Rivulets lead to small

channels, called “rills”, and as the channels scour deeper into a bare soil slope, they become

enlarged and are then called “gullies”. The overall process is illustrated in Figure 5. Rapid

erosion occurs in rills and gullies where the energy of the water flow scours out the bare soil.

Rill erosion (Figure 3) is considered to be the intermediate stage between sheet erosion and

gully erosion. This begins when the accumulated runoff begins taking its preferred narrow paths

and running down sloped channels due to uneven surfaces that are typically present pm a sloping

surface of bare soils. As a result, when water flow is concentrated into channelized paths, the

surface flow and velocity of the runoff increase where flow is concentrated, resulting in

accelerated erosion, thus forming rills. As stated by the Northern Rivers Catchment Management

Authority on their website, rills are defined as ‘shallow drainage lines less than 30 centimeters

deep’ (Northern Rivers Catchment Management Authority, n.d).

Gully erosion (Figure 4) is evident when rainwater and / or runoff has eroded pathways

(channels) deeper than 30 centimeters. Even higher velocity flow may occur in gullies, making it

increasingly difficult for vegetables to grow and stabilize soil. Extended amounts of gully

erosion over prolonged periods of time (hundreds to thousands of years) will lead to the

formation of river and stream channels.

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3.0 ENVIRONMENTAL HAZARDS CAUSED BY ACCELERATED EROSION

Soil erosion and sedimentation can be accelerated at construction sites as a result of human

activities on the site. Construction-related activities such as soil grading, clearing, grubbing and

drilling can lead to accelerated erosion rates up to two to four thousand (2-4,000) times greater

than natural erosion rates (Harbor, 1999). Such disturbances may cause permanent damages to

nearby natural features (surface waters, woods, wetlands, etc.) and are the sources of pollution

which degrades surface water quality. The primary consequences on surface water quality

include increased Total Suspended Solids (TSS), Total Dissolved Solids (TDS) and turbidity

levels (Figure 7); which compromise habitats for fish, amphibians and plant species, while soil

quality is also negatively impacted due to increased amounts of sediment accumulation within

the soil (Figure 6). Soil erosion may also carry nutrients and other chemicals into surface waters,

when such chemicals (nitrate, phosphate, ammonia) are sorbed to soil particles being eroded.

Many aquatic species normally found in relatively clear waters cannot tolerate such conditions,

especially fish.

Drainage patterns in the site vicinity can also be disturbed after construction is completed due to

the high magnitude of land and soil clearing activities that physically alters and destabilizes the

environment. This can result in flash floods during heavy rain events. Furthermore, wind erosion

across bare soils will generate dust, as finer soil particles become airborne (Harbor, 1999). This

may lead to long-term health problems for on-site workers due to inhalation of dust particles. To

combat dust and wind erosion, dust control efforts are necessary; dust control operations and

regulations; namely the use of dust control trucks which spread water using sprays around the

site in order to keep the soil on the ground and reduce levels of airborne sediments (Figure 8).

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Restoring disturbed lands after erosion has occurred requires a great deal of effort, manpower

and resources which can lead to increased economic losses, while damage to properties and

infrastructure can demand expensive repairs. The phenomenon of sediment and erosion control

has been extensively studied over the past century, and legislation has been developed to prevent

or minimize erosion or sediment damage.

4.0 EROSION AND SEDIMENT CONTROL FROM A REGULATORY

PERSPECTIVE

An important aspect of any outdoor construction project is to create an erosion and sediment

control plan (ESC plan). Environmental inspections and assessments are carried out by

specialized geoscientists in an effort to identify land disturbing activities and minimize erosion

potential within the construction sites. These inspectors recommend Best Management Practices

(BMP`s), for soil erosion and sediment control, all of which is part of the ESC plan. The ESC

plan lays out environmental protection objectives which primarily depend on the nature of

construction activity and the physical and geological characteristics of the construction site, and

includes strategies such as (Ministry of Transportation, 2007):

• Preventing sediment-laden runoff from going off-site and / or natural features,

• Slowing down the runoff across the site using ESC measures, and

• Minimizing the amount of disturbed soil at any given time.

Therefore, all the stakeholders of a civil project are responsible for the effective planning and

implementation of ESC practices and also storm water pollution prevention practices (SWP).

These stakeholders include (Alberta Transportation, 2007):

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• The Project Proponent – government or industry project leaders who ensure that the

ESC plan is prepared and followed at the satisfaction of all stakeholders and regulatory

agencies.

• Regulator – establish guidelines and enforce the federal, municipal and provincial

regulations as required.

• Consultant – designs the ESC plan, inspects, and advises improvements as necessary to

meet erosion and sediment control objectives according to the specific site conditions.

• Engineering Project manager – provides engineering and environmental assessment and

design details while overseeing all the phases of construction.

• General contractor – carries out construction works on the site while implementing ESC

measures as required by the ESC plan.

Extensive regulations have been enacted by federal, provincial, municipal and conservational

authorities to guide construction activities away from natural environments. These authorities

include, but are not limited to, the following (Toronto Region of Conservation Authority, 2006):

• Federal Fisheries Act – requires that fish species and habitats are protected at all times

during construction while avoiding the release of deleterious (damaging) substances into

their habitats.

• Navigable Waters Protection Act – a federal act that requires the protection of coastal,

inland or any body of water that is capable of being navigated by ships, boats or any

vehicle for use of commerce, recreation or transportation.

• Canadian Environmental Assessment Act (CEAA) – the basic guiding principle for

environmental-based activities.

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• Ontario Water Resources Act (OWRA) – protects the quality and quantity of surface

water and groundwater, administered by the Ministry of the Environment and Climate

Change (MOECC).

5.0 EROSION AND SEDIMENT CONTROL PRACTICES: PERMANENT AND

TEMPORARY WORKS

During a construction project, when bare soils are exposed, sites need to be temporarily

stabilized using ESC practices (silt fences, filter logs, etc.), in order to stabilize the existing soils,

capture eroded sediments and control runoff. Without such practices in place, the volume of off-

site sediment-laden discharge and runoff would significantly increase and lead to

environmentally and economically hazardous outcomes.

After a construction project has been completed, it is recommended to place permanent

restoration and landscaping measures, in areas which were disturbed or altered by the

construction, thus stabilizing the soils permanently.

It is necessary to distinguish between the terms erosion controls and sediment controls. Even

though both terms have been used simultaneously as a single term, `ESC`, throughout this report,

erosion controls refers to minimizing the amount of earth blown or washed away, while sediment

controls involve keeping dirt within a given area and protecting adjacent environments.

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5.1 Types of Erosion Controls

Erosion control measures are designed to minimize and reduce erosion, in order to eliminate the

use and need of sediment controls as erosion leads to elevated amounts of sediment runoff. They

prevent and control water or wind erosion and are implemented in agricultural areas,

construction sites, land development sites, and also coastal areas. Erosion controls involve the

implementation of a physical barrier (rocks, vegetation, etc.) to reduce the energy (by absorbing

the energy) of the runoff. They can also be implemented along with sediment controls such as

silt fences.

Vegetation is the most effective and commonly used erosion control method by property owners,

landscapers, engineers and contractors. The application of vegetation in a sloped area is an

essential and rudimentary technique to reduce the speed of storm water runoff and therefore

reduce sheet erosion. The leaves of existing plants help in dissipating the energy of falling

raindrops and therefore reduce splash erosion. The raindrops that do fall and begin to run down

the slope are slowed down by the presence of plant stems and leaves. Finally, the roots help

anchor the strength of the soils and reduce erosion. The fact that vegetation is living means that it

is constantly being regenerated. However, a limitation to vegetation is the amount of time it takes

to grow vegetation in a given area.

Mulching (Figure 9) is an alternative to vegetation. Mulching has been utilized to protect

exposed and bare soils from splash erosion while protecting the moisture content within the

existing soil. Mulching uses materials such as grass cuttings, hay, wood chips and fibers, straw

cuttings and gravel. This mixture, when applied in large amounts to exposed soils, is able to

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reduce storm water runoff velocity and energy, therefore making this an effective slope

protection practice against soil erosion.

Sod (turf), shown in Figure 10, has also been used as an alternative to vegetation in construction

sites as an erosion control practice. Sod is grass and the part of the soil that is held together by

the grass roots. Sod is usually harvested in farm fields and used in landscaping or erosion control

on construction sites. It is primarily used to stop erosion both on flat areas right up to severe

slopes. According to Turfgrass Producers International (TPI), sod, because of its thick root mass,

total weight and high density of grass blades, is documented to be the most effective erosion

control material that is available (TPI, n.d).

Riprap channels are utilized as temporary or permanent erosion controls and consist of large,

loose and angular stones or rocks to protect areas where there is concentrated flow. The bed of

rocks absorbs the energy of the fast flowing water by slowing down flow. These rocks are

usually placed on top of a layer of geotextile, which is a permeable fabric made from polyester or

polypropylene used for filtration or drainage purposes (Figure 12). This layer of fabric also

helps protect the underlying soil surfaces from erosion. Riprap channels are usually constructed

at the end of storm outfalls or culverts where there is concentrated flow of water, as seen in

Figure 11. Riprap channels are also constructed along river or stream banks to protect the

aquatic environments from sediment and debris-laden runoff, as sloped unprotected soils are

extremely susceptible to water erosion (Figure 13).

Erosion control blankets (Figure 14) are temporary erosion control measures primarily used for

slope stabilization. Eroded slopes are protected from further erosion from fast-flowing runoff by

slowing down the speed of the water as it moves across the surface. This is accomplished

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through the use of rough woven natural or synthetic fibers, such as coconut fibers, with tiny gaps

and various obstructions that helps the slowing down of the running water and thus reduces soil

erosion (The City of Calgary, Water Services, 2011).

Compost blankets (Figure 15) are layers of composted material that is generally applied and

placed on soils in disturbed areas in order to reduce storm water runoff and erosion. Compost is

defined, by the United States Environmental Protection Agency (US EPA), as the “product of

controlled biological decomposition of organic material sanitized through heat and stabilized

enough to be beneficial for plant growth.” Compost blankets act as cushions to absorb the

impacts generated by falling raindrops thus preventing splash erosion. They are able to retain

large volumes of water which allows for vegetation growth within the compost blankets.

According to the US EPA, compost blankets are also effective in removing pollutants such as

heavy metals, oil and grease particles, nitrogen, phosphorus and petroleum hydrocarbons from

running water, therefore improving downstream water quality (US EPA, 2012).

5.2 Types of Sediment Controls

Sediment controls are physical applications designed to prevent eroded soil from going off-site

onto an adjacent property, or into a nearby water body. They are generally considered to be

temporary measures.

Silt fences (Figure 16) is a commonly used temporary sediment control practice at construction

sites, and often used at site perimeters or at the edge of a disturbed area. The purpose of silt fence

barriers is to intercept sheet flow and pond water temporarily in case of heavy rains. These

barriers can thus be used to protect water quality in nearby watercourses, and are constructed

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using geotextile materials (polypropylene or polyester), similar to the layered material placed

under riprap channels as was discussed earlier in Section 5.1. The barriers are held up in long

linear distances using stakes or fencing, and the fabric is anchored into the ground (Filtrexx

website). Silt fences are most common due to their relative low cost and simple design; however

they have limitations. Silt fences are not strong enough to hold back piles of soil leaning or

falling against the silt fence (Figure 17). Silt fences are also not capable or intended to be placed

across areas of concentrated flow of water, such as drainage swales, unless it is part of check

dams. Finally, silt fence must be installed properly to be effective, which includes trenching the

fabric into the ground.

A swale is defined as a low zone or area of land for the purpose of concentrated flow of storm

water runoff into a drainage culvert or storm sewer, and can be a natural landscape feature or a

man-made one.

Filter logs (Coir logs) have similar material characteristics to erosion control blankets such that

they both use natural or synthetic fibres. However, those blankets are curled up into cylindrical

shapes for the purpose of filtration, re-channeling storm water runoff, and slowing down the

energy of runoff. Coir is natural extracts from coconut skins and has been found to be an

excellent material. Filter logs may be placed across areas of concentrated flow (drainage swales)

as check dams (Figure 18).

Filter soxx (silt soxx) ™ are products manufactured by Filtrexx International. They contain

composted materials inside a geotextile mesh containment system and are able to remove

sediment and pollutants through natural filtration and deposition. Filter soxx ™ and filter logs

are similar in appearance; however filter soxx ™ are highly adaptable, durable and are effective

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in various kinds of applications, such as: perimeter control fencing, inlet protection (Figure 19),

check dams, concrete washout boundaries, slope maintenance, runoff diversion and sediment

traps (Filtrexx website).

Check dams are small temporary devices constructed across a drainage swale / ditch or a channel

in order to reduce the velocity and energy of the storm water runoff in the channel that helps

reduce erosion. Check dams usually consist of piles of rock and gravel, sandbags, filter logs or

straw bales, and are most effective in small channels with a contributing drainage area (Figure

20).

Turbidity curtains are flexible sediment control barriers that are designed to prevent the

spreading of silt (sediment) in water bodies such as lakes, rivers, streams or creeks. These

barriers are primarily used around in-water construction projects, such as bridges, in order to

protect the aquatic environment from silt pollution and excess turbidity. As illustrated by Figure

21, sediment is held back inside of the turbidity curtain in order to protect the water outside of

the turbidity curtain from turbidity. A case study from a recent bridge reconstruction project,

involving a turbidity curtain in a river around a bridge reconstruction project in South Central

Ontario, is provided in Section 6.2.

Straw bales (hay bales) are bundles of grass and other herbaceous plants that can be used to

filter out silt during sediment-laden runoff. They are relatively inexpensive and easy to maintain;

however their weak and loose structure makes them non-durable. They must be installed tightly

together and carefully anchored down in order to be effective for sediment control.

Inlet protection (Figure 22) is a sediment control measure designed to protect storm drains or

inlets in case of heavy rains from sediment-laden runoff. Inlet protection can be accomplished in

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numerous ways. Products such as filter soxx™ can be placed around the inlet in order to slow

down the runoff, effectively filter the chemical pollutants out of the runoff and ensure that only

clean runoff enters the catch basin.

6.0 PROJECT CASE STUDIES

During the fall of 2014, MMM Group Limited had been actively involved in weekly erosion and

sediment control inspections at various sites in Southern Ontario. Two of those locations have

been selected as project case studies in order to visually and quantitatively analyze the

effectiveness of the existing erosion and / or sediment controls in place. The photographs relating

to Case Study 1 are provided in Appendix D, while the photographs and tabular / graphical data

of Case Study 2 are presented in Appendix E.

6.1 Case Study 1: Erosion Controls on Sloped Bare Soils (Visual Analysis)

The subject location in Case Study 1 is an area of bare and exposed soils sloping down towards a

driveway to a residential property, as is shown in the Location Schematic Diagram (Appendix

B) and the photographs (Appendix C) which were taken from the first site visit on July 29,

2014, up to the most recent site visit on December 9, 2014. As illustrated in the Location

Schematic Diagram, the bare soils were observed to be sloping downward (to the east and

southeast) towards the residential driveway due to the roadside ditches; therefore it was

anticipated that concentrated flow would occur during heavy rains and runoff. The objective was

to prevent erosion and sediment deposition on the driveway following rain events; therefore it

was suggested that filter logs and silt fences be placed along the lower ends of the ditch, as per

the ESC plan.

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Several erosion control methods were used over that period of time, starting with low-cost

methods and progressing to higher-cost methods when it was found that the low-cost methods

were not meeting the objectives of the ESC plan. It was not possible to quantitatively measure

erosion rates and sediment accumulation on the driveway; however through weekly ESC

inspections the amount of sediment accumulating on the driveway plus evidence of erosion was

observed and documented through photographs.

July 29: Silt fences were seen to be in place around the corners of the ditch; however sediment

was piling up in the driveway which indicated that one line of silt fence was not effective enough

to prevent erosion.

August 19: To combat erosion, multiple filter logs, filter soxx™, silt fences and straw bales

were placed along the lower ends of the ditch. However, following heavy rains and sediment-

laden runoff, considerable amounts of silt was seen to be deposited on the driveway, which

indicated that additional sediment controls (i.e filter logs) may be necessary to prevent further

silt deposition on the driveway.

September 18: Additional filter logs were placed in the ditch prior to the site visit on September

18. Nonetheless, silt was still accumulating on the driveway following heavy rains. It was

understood that a combination of low-cost practices were not going to be enough to prevent

erosion, and an alternative solution was sought.

October 10: Soils in the ditch were graded and a new drainage culvert was constructed

underneath the residential driveway to redirect the flow of storm water runoff and to prevent

further erosion. Even though erosion was still occurring, less sediment was accumulating on the

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driveway. However, rills were forming on the graded soils as the soils were unprotected from

erosion.

November 24: The site inspection was conducted during a heavy rain event. Over the preceding

week, some soil was dug out and the ditch was re-graded to construct a new ditch for the south

end of the culvert. The driveway appeared to be sediment-free and most of the runoff was

settling in the ditches through the culvert. However, gullying was observed on the road shoulders

and a riprap was recommended to cover up the gullies.

December 9: To prevent gullying in soils, a riprap channel was constructed by the north end of

the culvert and the ditch was paved with asphalt. This condition is expected to hold up

throughout the winter months. The current conditions are shown in schematic view in Appendix

D.

It can be determined from the visual data that the lower-cost methods were not proving to be

effective enough in preventing erosion on sloped bare soils; therefore higher-cost methods,

including the construction of the culvert, the asphalt pavement and riprap channel, have proven

to be necessary and effective in preventing sediment accumulation on the driveway so far.

6.2 Case Study 2: Effectiveness of In-Water Sediment Controls (Quantitative

Data Analysis)

Case Study 2 involves an analysis on the effectiveness of turbidity curtains at containing

sediments around bridge abutments associated with a bridge reconstruction project over a small

river. A diagram illustrating the location schematics is provided in Appendix H. The

performance of turbidity curtains was quantitatively assessed through collecting daily turbidity

measurements of the water inside the turbidity curtain, plus the water upstream and

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downstream of the work site. These measurements were taken in Nephelometric Turbidity Units

(NTU).

The data highlights the effectiveness of the turbidity curtain at keeping sediment-laden water out

of the river channel around the bridge reconstruction project, and is presented in tabular form in

Appendix E and in graphical form in Appendix F.

Instances which caused short-term increases in turbidity levels in the main river channel

included:

1. Removing the old abutments of the bridge generated turbidity in the river,

2. Driving down sheetpiling into the ground, which generated turbidity in the river,

3. Rock protection being placed around the west abutment, and

4. The river water was frozen; therefore breaking the ice to take water samples generated

elevated turbidity levels in the river.

Apart from the four instances of short-term increases, the turbidity levels in the water

downstream of the work site were generally similar to that or slightly higher than that in

upstream, which shows that the turbidity curtains were efficient and necessary in preventing

sediment-laden runoff into the main river channel and thus keeping turbidity levels stable.

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7.0 CONCLUSION

ESC measures are highly necessary in preventing on-site erosion. However, different measures

have varying strengths and limitations; therefore it is up to the stakeholders, especially the ESC

specialist, to determine and analyze which technique may be suitable and applicable under the

site-specific conditions.

Results from Case Study 1 show that in cases of erosion caused by sloping bare soils, high-cost

methods may prove to be more effective than low-cost techniques. Grading the soils and

constructing ditches around the recently built culvert, along with implementing riprap channels

at the north face of the culvert, significantly reduced the amount of erosion.

Results from Case Study 2 determine that turbidity curtains are necessary techniques for in-water

construction works, such as bridge reconstruction projects. Turbidity levels downstream of the

work site were somewhat similar, or slightly higher than turbidity levels upstream. Even though

turbidity may be generated from sheetpiling activities, rock protection placement and ice

breakage in the river, turbidity levels are able to revert back to accepted and expected levels, in a

given amount of time.

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8.0 RECOMMENDATIONS

An extensive analysis should be conducted into the costs of various ESC techniques. Cost-

benefit and cost-effective studies would help in assessing what measures are practical and

suitable considering the site-specific conditions and circumstances at any given time.

A more detailed study could be carried out into the benefits and drawbacks of the different kinds

of ESC measures, along with those that were not mentioned in this report. Additional project

case studies should be looked into for further knowledge.

More thought and research should be given into the design of the ESC plan; given that

controversial circumstances may arise if, suppose, the existing works are ineffective at a given

location or measures are being placed at locations where ESC works are not considered to be

necessary. The budget should be considered, and all the stakeholders should be considered while

making decisions regarding the implementation of the ESC plan.

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9.0 REFERENCES

Konatsotis, J., & Corrente, P. (1993). Types of Erosion. In On-Site Mitigation for Construction

Activities (p. 103). Connecticut, United States.

The City of Calgary, Water Services. (2011). Guidelines for Erosion & Sediment Control (2011

ed.). Calgary, Alberta, Canada.

Northern Rivers Catchment Management Authority. (n.d.). Soil Erosion Solutions: Fact Sheet 1 -

Types of Erosion. Retrieved December 16, 2014, from URL:

http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0003/255153/fact-sheet-1-types-of-erosion.pdf

Alberta Transportation. (n.d.). Retrieved December 16, 2014, from URL:

http://www.transportation.alberta.ca/Content/docType372/Production/7ErosSediCntrlMthds.pdf

J, R. (2012, October 1). Soil Erosion - Causes and Effects. Retrieved December 16, 2014, from

URL: http://www.omafra.gov.on.ca/english/engineer/facts/12-053.pdf

Ministry of Transportation. (2007, February 1). Environmental Guide for Erosion and Sediment

Control During Construction of Highway Projects. Retrieved December 16, 2014, from URL:

http://www.raqsb.mto.gov.on.ca/techpubs/eps.nsf/8cec129ccb70929b852572950068f16b/7ff7c9f

a7def430f852572b300578dec/$FILE/MTO Env Guide for ESC Final Feb 2007.pdf

Toronto Region of Conservation Authority. (2006, December 1). Erosion and Sediment Control

Guidelines for Urban Construction. Retrieved December 16, 2014, from URL:

http://www.trca.on.ca/dotAsset/40035.pdf

Turfgass Producers International. (n.d.). Turfgrass Sod vs Other Erosion Controls. Retrieved

December 16, 2014, from http://www.turfgrasssod.org/pages/consumer-resources/stop-erosion

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Filtrexx. (n.d.). Retrieved December 18, 2014, from http://www.filtrexx.com/

Jon, H. (1999). Engineering Geomorphology at the Cutting Edge of Land Disturbance: Erosion

and Sediment Control on Construction Sites. Geomorphology, 31, 247-263.

United States Environmental Protection Agency. (2012, March 1). Stormwater Best Management

Practice: Compost Blankets. Retrieved December 18, 2014, from

http://water.epa.gov/polwaste/npdes/swbmp/upload/compostblankets.pdf

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APPENDIX A

FIGURES

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Figure 1: Splash erosion.

Figure 2: Sheet erosion.

Figure 3: Rill erosion along an unprotected slope of soil.

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Figure 4: Deep gullies forming as a result of erosion over prolonged periods of time.

Figure 5: A typical example of the erosional process along a sloped hill.

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Figure 6: Sediment-laden water with high TSS and turbidity levels.

Figure 7: Comparison of turbidity levels (in NTU), in order of increasing from left to right.

Figure 8: Dust control truck.

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Figure 9: Mulching is seen here applied to slopes as an erosion control product for roadside maintenance.

Figure 10: Sod blankets.

Figure 11: Riprap channels at the end of a culvert.

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Figure 12: Design of riprap channel construction at river banks. The filter material is geotextile material.

Figure 13: riprap at banked slopes.

Figure 14: Erosion control blanket on a slope of unprotected soil to protect the underlying soil against erosion.

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Figure 15: A construction worker is ‘blowing’ compost onto the stream banks by a construction site.

Figure 16: Silt fences are seen here placed at the ends of the slope to protect the field from sediment-laden runoff.

Figure 17: The lack of durability and strength of silt fences, when faced with sediment encroachment, is visible here.

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Figure 18: Filter logs are in place to protect the wetland (behind) from storm water runoff.

Figure 19: Filter soxx™ have been applied here as inlet protection measures.

Figure 20: A check dam has been constructed in a ditch to control storm water runoff and pollution.

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Figure 21: Turbidity curtains are seen here protecting the river from silt pollution.

Figure 22: Inlet protection fencing is observed here; however sediment encroachment and heavy runoff has

damaged the silt fences.

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APPENDIX B

CASE STUDY 1

LOCATION SCHEMATIC DIAGRAM

INITIAL CONDITIONS (JULY, 2014)

Case Study 1Location Schematic Diagram

Prior to July 29, 2014

Driveway

Ex

isti

ng

Ro

ad

Bare Soils

Legend

Anticipated concentrated

flow path based on slope

(soil sloping in direction

of arrowhead)

Sediment accumulation

on driveway

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APPENDIX C

CASE STUDY 1

LOCATION SCHEMATIC DIAGRAM

CURRENT CONDITIONS (DECEMBER, 2014)

Case Study 1Location Schematic Diagram

Current Conditions as of December 9, 2014

Driveway

Ex

isti

ng

Ro

ad

Bare Soils

Legend

Anticipated concentrated flow

path based on slope

(soil sloping in direction of

arrowhead)

Sediment accumulation on

driveway has reduced

Asphalt

Pavement

Riprap

Sediment controls (filter logs,

straw bales and filter soxx™)

Silt fence barriers

Culvert

New

Ditch

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APPENDIX D

CASE STUDY 1

PHOTOGRAPHS

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JULY 29, 2014

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AUGUST 19, 2014

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SEPTEMBER 18, 2014

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OCTOBER 10, 2014

South end of the culvert

North end of the culvert

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NOVEMBER 24, 2014

DECEMBER 9, 2014

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APPENDIX E

CASE STUDY 2

PHOTOGRAPHS

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Turbidity Curtains

(September 3, 2014)

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View of Downstream

(September 3, 2014)

View of Upstream

(September 3, 2014)

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APPENDIX F

CASE STUDY 2

TABLE OF TURBIDITY MEASUREMENTS

CASE STUDY 2

Table of Turbidity Measurements

July 31 - November 20, 2014

DATE UPSTREAM (NTU) DOWNSTREAM (NTU)

TURBIDITY BEHIND

TURBIDITY CURTAIN

(NTU)

REMARKS

31-Jul-14 5.09 2.47

01-Aug-14 1.82 2.00

02-Aug-14

03-Aug-14

04-Aug-14

05-Aug-14 3.15 4.65

06-Aug-14

07-Aug-14 5.75 4.60

08-Aug-14 2.95 3.22

09-Aug-14

10-Aug-14

11-Aug-14 4.32 3.74

12-Aug-14 5.97 11.45

13-Aug-14 6.53 12.70

14-Aug-14 3.19 6.50

15-Aug-14 4.38 4.74

16-Aug-14

17-Aug-14

18-Aug-14 1.94 4.23

19-Aug-14 1.96 1.56

20-Aug-14 2.20 3.14

21-Aug-14 2.56 3.16

22-Aug-14 3.88 4.23

23-Aug-14

24-Aug-14

25-Aug-14 2.23 2.51

26-Aug-14 5.84 3.16

27-Aug-14 4.98 6.89

28-Aug-14 4.98 6.89

29-Aug-14 5.49 13.45

During driving of

sheetpiling - turbidity

behind turbidity curtain

30-Aug-14

31-Aug-14

01-Sep-14

02-Sep-14 3.25 2.26

03-Sep-14 4.63 7.89

04-Sep-14 4.27 3.91

05-Sep-14 2.43 3.50

06-Sep-14

07-Sep-14

08-Sep-14 3.91 4.44

09-Sep-14 1.78 3.13

10-Sep-14 2.52 3.12

11-Sep-14 5.02 4.88

12-Sep-14 3.37 2.44

13-Sep-14

14-Sep-14

15-Sep-14 2.87 4.29

16-Sep-14 3.16 4.10

17-Sep-14 3.26 3.56

18-Sep-14 3.28 2.92

19-Sep-14 4.03 4.44

20-Sep-14

21-Sep-14

22-Sep-14 6.44 5.01

23-Sep-14 2.85 3.78

24-Sep-14 2.50 2.53 6.85

25-Sep-14 2.85 7.54

26-Sep-14 2.55 31.06

27-Sep-14

28-Sep-14

29-Sep-14 4.72 13.62

30-Sep-14 5.60 7.25

Short term increase in

turbidity while removing

old abutment

Higher turbidity was

generated by contractor

placing rock protection

around the west abutments

in the river

CASE STUDY 2

Table of Turbidity Measurements

July 31 - November 20, 2014

DATE UPSTREAM (NTU) DOWNSTREAM (NTU)

TURBIDITY BEHIND

TURBIDITY CURTAIN

(NTU)

REMARKS

01-Oct-14 4.23 6.30

02-Oct-14 3.17 5.39 14.18

03-Oct-14 2.70 3.89

04-Oct-14

05-Oct-14

06-Oct-14 2.52 17.57

07-Oct-14 2.85 4.63

08-Oct-14 2.60 4.49

09-Oct-14 3.67 4.13

10-Oct-14 2.04 2.52

11-Oct-14

12-Oct-14

13-Oct-14

14-Oct-14 1.34 4.76

15-Oct-14 1.80 2.87 7.61

16-Oct-14 2.20 4.39

17-Oct-14 2.90 5.65

18-Oct-14

19-Oct-14

20-Oct-14 2.47 4.42

21-Oct-14 3.11 5.60

22-Oct-14 3.51 4.77

23-Oct-14 3.99 5.61

24-Oct-14 2.33 4.11

25-Oct-14

26-Oct-14

27-Oct-14

28-Oct-14 2.11 5.50

29-Oct-14 4.07 6.76

30-Oct-14 1.70 5.14

31-Oct-14 2.69 3.17

01-Nov-14

02-Nov-14

03-Nov-14 1.66 6.17

04-Nov-14 3.12 2.09 7.87

05-Nov-14 4.18 2.64

06-Nov-14 3.38 3.97

07-Nov-14 5.80 3.04

08-Nov-14

09-Nov-14

10-Nov-14 2.63 4.91

11-Nov-14

12-Nov-14

13-Nov-14 4.05 25.13

14-Nov-14 3.09 3.78

15-Nov-14

16-Nov-14

17-Nov-14 3.96 4.97

18-Nov-14 9.42 7.74

19-Nov-14 31.09

20-Nov-14 38.25

River water was frozen -

breaking ice to get water

samples generates

turbidity

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APPENDIX G

CASE STUDY 2

GRAPH OF TURBIDITY MEASUREMENTS

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

20-Jul-14 09-Aug-14 29-Aug-14 18-Sep-14 08-Oct-14 28-Oct-14 17-Nov-14 07-Dec-14

UPSTREAM (NTU)

DOWNSTREAM (NTU)

TURBIDITY BEHIND TURBIDITY CURTAIN (NTU)

Case Study 2

Graph of Turbidity Measurements

1 2

3

4

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APPENDIX H

CASE STUDY 2

LOCATION SCHEMATIC DIAGRAM

Case Study 2

Location Schematic Diagram

River

West Abutment East Abutment

Legend

Turbidity Curtain

Water inside

turbidity curtain

Upstream

Downstream