NATIONAL QUALIFICATIONS CURRICULUM SUPPORT
Design, Engineering
and Technology
Civil Engineering
Specialisms
[ADVANCED HIGHER]

Acknowledgements
Learning and Teaching Scotland gratefully acknowledge th is contribution to the National
Qualifications support programme for Civil Engineering, in particular the work of Brian
Cook in preparing it.
Electronic version 2003
© Learning and Teaching Scotland 2003
This publication may be reproduced in whole or i n part for educational purposes by
educational establishments in Scotland provided that no profit accrues at any stage.
CONTENTS
Overview
1
Tutor Guide
2
Student Guide
3
Study Guide 1
Road systems and their structure
Study Guide 2
Traffic engineering
10
Study Guide 3
Water supply and sewerage systems
17
Study Guide 4
Geotechnics
32
Study Guide 5
Civil engineering and the environment
42
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OVERVIEW
These support materials are provided to assist teachers/lecturers in the
delivery of the Advanced Higher Civil Engineering course unit Civil
Engineering Specialisms. They will also help to prepare students for
assessment.
The Tutor Guide offers brief advice on appropriate teaching approaches for
the unit and on additional learning and tut orial materials that will have to be
prepared by teachers/lecturers. A brief description of each Study Guide is
included.
Student’s support materials are provided in the form of five Study Guides.
Each Study Guide covers one outcome of the unit.
The Study Guides are as follows:
Study Guide 1:
Road systems and their structure
Study Guide 2:
Traffic engineering
Study Guide 3:
Water supply and sewerage systems
Study Guide 4:
Geotechnics
Study Guide 5:
Civil engineering and the environment
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TUTOR GUIDE
Introduction
The Advanced Higher in Civil Engineering allows students to apply the skills
acquired in previous studies, such as Higher Civil Engineering, to the
solution of a broad range of problems in structural design, highway and
traffic engineering, and water and public health engineering.
The unit Civil Engineering Specialisms has a unit credit rating of 1.5. It
should attract students with an interest in solving practical problems in a
range of relevant civil engineering issues related to the des ign and
construction of roads, foundations and water systems as well as the
environment.
Teaching and learning
The Study Guides provided in these support materials contain teaching
material that will enable students to acquire a knowledge and understandi ng
of a range of topics at a sufficient level to encourage further study.
Teachers/lecturers should encourage the use of the internet as an important
resource in these subjects which are subject to changing legislative
requirements as well as technological developments, as for example with
environmental issues, or with new systems such as Sustainable Urban
Drainage Systems (SUDS).
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STUDENT GUIDE
Introduction
Civil Engineering covers many aspects of the built environment and
infrastructure and services. Professional civil engineers and technicians
usually specialise in particular areas, such as roads, railways, water and
sewerage. Civil Engineering Specialisms therefore provides a basic
introductory look at:
 Roads
 Traffic engineering
 Water and sewerage
 Geotechnics
 Environmental aspects
Students wishing to further develop their knowledge in any particular
specialism will find a range of HN units, which are component parts of the
HNC and HND in Civil Engineering.
Recommended Texts
Your tutor will advise you on appropriate textbooks for each outcome.
Check your library for the New Civil Engineer journal, which provides up-todate discussions and case studies.
Assessment
Assessments will be ‘closed book’; some team work will be involved,
however, for example, in carrying out traffic surveys.
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STUDY GUIDE 1
Road systems and their structure
Outcome 1
Describe road systems and their structure.
On completion you should be able to:
 Describe the different categories of roads making up the highway network
 Describe the different structural types of road pavement
 Describe the functions of the layers making up the road structure
 Describe road construction materials.
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Introduction
The infrastructure of highways in Scotland comprises motorways, pri mary
routes, major roads and minor roads. These are defined in BS 6100: 1992 as:
Motorway:
Limited access dual carriageway road not crossed on the same
level by other traffic lanes, for the exclusive use of certain
classes of motor vehicles.
Primary route: Route consisting of roads other than motorways, that forms
part of a national network of important through routes.
Major road:
Road to which is assigned a priority of traffic movement over
other roads.
Minor roads:
Road that is assigned a lesser traffic value than that of a
major road.
Within these broad categories we can further describe roads as trunk roads,
classified roads, principal roads and regional roads. Roads of lesser
importance than the aforementioned include single -track roads and private
streets.
The nucleus of Britain’s road system (adopted by Central Government
following the Trunk Roads Acts of 1936 and 1946) were the classified ‘main’
roads or ‘trunk’ roads. The term trunk road is an all -embracing term including
roadways ranging from busy motorways to carriageways less than 5.5m in
width. Similarly all dual carriageways are not necessarily trunk roads. The
system of principal roads was introduced in 1967. Only 10% of the principal
roads are in urban areas. Trunk roads became principal roads when they
crossed a county boundary.
The classification of a road depends upon its importance within the national
system. A glance at a map will reveal A roads and B roads, and also
unclassified roads.
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Urban highway network
This consists of a system of primary distributors, district distributors, local
distributors and access roads. Primary distributors may be motorways or all purpose roads. They allow fast movement of traffic to or from towns and
cities. Typically, access and parking is restricte d. District distributors are the
feeder roads that carry district traffic, allowing free movement within a
particular district. Local roads are bounded by primary and district
distributors. Low speed limits and traffic calming measures are normal.
Parking may be designated. A typical network is shown in fig. 1.1:
Fig 1.1
Rural highway network
This constitutes the majority of the country’s roads network with the
principal routes connecting and bypassing major towns and cities. Secondar y
routes connect smaller towns. In addition, motorways for high -speed traffic
are separated from other traffic movements. Roads of only local importance
are termed all-purpose roads, and are located normally in semi –rural low
populated areas. Further information can be obtained from the Department of
the Environment, Transport and the Regions and the web site
www.detr.gov.uk/itwp/trunkroads.
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Components of the highway
The part of the road or highway constructed for use by vehicular traffic is
called the carriageway. The highway generally has a hardened verge, and in
some cases a hard shoulder. The structure of the road above the sub -grade is
referred to as a pavement. Pavements can be flexible, flexible composite,
rigid, or rigid composite depending upon the design.
Flexible pavement
The wearing course of the road provides its waterproofing and skid resistance.
The base course supports the wearing course and assists in protecting the road.
The road base is the main load-spreading layer of the road structure. Students
should refer to Design Manual Volume 7 Section 2 Part 2 HD 25/94 for suitable
materials. To improve and protect weak subgrades, a capping of cheap material
can be used to increase the stiffness and the strength of the formation. The sub
base assists load spreading, assists subsoil drainage and can act as a temporary
site access road. All layers of the surfacing and road base are constructed from
bituminous bound materials, hence commonly re ferred to as ‘blacktop’. The
Design Manual for Roads and Bridges, Design Criteria, Volume 7, Section 2
Part 3 HD 26/94 permits the use of the following as roadbase materials:
Dense Bitumen Macadam (DBM)
Hot Rolled Asphalt (HRA)
Dense Tar Macadam (DTM)
DBM + 50 penetration bitumen (DBM50)
Heavy Duty Macadam (HDM)
Fig 1.2
In this design of road structure, the road base is non -cement bound. A flexible
road is not made up of a single layer of homogenous material and so the work
of Boussinesq in respect of distribution of stress, where the average stress at
any depth can be contained within an angle of 45 ° , is not appropriate.
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Instead, Burmister’s theory for stresses on layered systems, expressed in
terms of the elastic modulus, is appropri ate. The purpose of the road structure
is to provide a means of reducing the stress due to the wheel load to a value
that the structure can support.
The characteristics of modern flexible roads are that the work can proceed at a
number of points progressively along the road, and the road can be laid in distinct
sections to be joined up later without detriment to the final finished surface. The
road can be laid without joints and to a high degree of accuracy. Care must be
taken with terminology. Frequently called ‘blacktop’ the colour of the road is
determined by the aggregate colour of the chippings or the aggregate in the
wearing coat. The term ‘tarmac’ is generally inaccurate as the common binder is
now bitumen and so the surfacing may be referred to as ‘ bitmac’.
The surfacing layer provides the riding surface and this requires to resist
skidding, be laid to falls, and to protect underlying layers from water ingress
and possible frost action. Materials commonly used are hot rolled asphalt, or
coated macadam. Open texture or ‘friction’ course surfacing with carefully
designed voids are used to avoid icing. The base course is the lower surfacing
layer and is also formed with HRA.
The roadbase is the main structural layer that ensures that underlying
materials are not overstressed. Dense bitumen macadam can be used for this
layer. Where fuel spillage is likely, dense tar macadam might be used.
The sub-base is another distributing layer and may be used as a temporary
site access surface. Materials are commonl y crushed rock type 1 or 2 or weak
cement-bound material.
The capping is a protective ‘cheap’ layer laid to protect the sub -grade. Coarse
grained crushed rock or cement-treated soil can be used.
Flexible composite
Here, the surfacing and upper roadbase materials are bound with bituminous
binder on a lower roadbase of cement -bound material (CBM). Flexible
composite road structure is therefore similar to the flexible, except the road
base is cement bound. Such carriageways are usually built to last twenty
years with an allowance made for annual traffic growth.
This road construction can be used for economy, but the thinner construction
depth is likely to lead to deterioration by general cracking, which is not
mitigated by restricting the individual laid width. Where the pavement is
designed with indeterminate life, limiting the width of the roadbase to 4.75m
minimises the risk of longitudinal cracking.
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Rigid pavement
The slab provides both the wearing course and the main structural layer of the
road. It is termed rigid because there should be no deflection of the slab
under traffic load. The concrete can be unreinforced concrete (URC), jointed
reinforced concrete (JRC), or continuously reinforced concrete pavement
(CRCP). Selection is based on technical or environmental considerations.
Fig 1.3
high strength
concrete or
reinforced slab
sub base
formation
sub grade improvement
layer or capping
The main structural element is a high-strength slab, formed in pavement quality
concrete (PQC), which is also the wearing finish. This transfers the loads to the
sub-grade, resists cracking and provides the ride quality. The sub-base is usually
formed by cement-bound materials to prevent joints or cracks causing damage to
the sub-base. To avoid transverse joints, bituminous surface may be applied for
a rigid composite pavement. Where transverse joints a re unacceptable, the
concrete slab may be reinforced to form a continuously reinforced concrete
pavement (CRCP). Such roads are designed to have a long life without the need
for further strengthening, unlike the flexible pavements which require major
strengthening or partial reconstruction to extend the serviceable period. A
typical example is the A90 Brechin bypass, where a slip -formed drainage
channel was formed as an integral part of the carriageway slabs.
Recent innovations include the ecopave economic pavement where un-reinforced
machine-laid carriageway slabs rely on a system of purpose induced micro cracks to cope with movement. This avoids the need for breaks in continuity and
dowel bars. It allows a blacktop wearing course to be applied over the
continuously reinforced road base without reflective cracks occurring.
Rigid composite
This road construction comprises the continuously reinforced concrete
roadbase (CRCR) with bituminous surfacing.
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STUDY GUIDE 2
Traffic engineering
Outcome 2
Describe, carry out and analyse traffic surveys.
On completion you should be able to:
 Use traffic engineering terminology
 Describe the relationship between speed, flow and concentration
 Describe the reasons for carrying out traffic surveys
 Carry out and analyse a traffic survey.
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Survey methodologies
Why survey?
Surveys are necessary when the requirements for road design cannot be met
from any other source. If the survey is essential then great care should be
taken in the design. It is desirable to avoid di srupting the public. The survey
objectives must be precise. Such clarification leads to a more efficient
survey. Without such studies there can be no factual basis for the
development and evaluation of plans at national, regional and local levels. It
is also necessary to know the distribution and performance of traffic on
existing roads. This is required to allow for predicted traffic movements.
Measurements of both traffic flows and speeds are needed. The traffic
engineer is concerned with spot speeds, run ning speeds and journey speeds.
 Spot speed: This is the instantaneous speed of a vehicle at a specified
location.
 Running speed: This is the average speed maintained over a given route
while the vehicle is in motion.
 Journey speed: This is the overall average time taken to complete the
given journey and includes time when the vehicle is at rest, for example at
traffic lights.
Clearly the major requirement of a road is its ability to accommodate traffic
under specific conditions. This is measured in vehicl es per day or passenger
carrying units (pcu) per day. The traffic engineer is concerned not only with
the number of vehicles passing a specific point in unit time (the flow), but
also with the concentration of vehicles occupying a unit length of road at a
specific time. These relationships can be plotted graphically.
Types of survey
There are surveys which involve interviews and in consequence entail
disruption to the public, and there are traffic counts. Studies can vary from
those based on simple volumetric surveys concerned only with vehicular
flow, to highly sophisticated and complex conurbation studies. The methods
include:
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Questionnaires
Household surveys
Roadside interviews
Pilot surveys
Automatic traffic counts
Manual classified counts
Axle load surveys.
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A transportation study is basically iterative in nature with feedbacks to
preceding elements of study. Surveys can be broadly classified into four
groups:
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Travel characteristics
Transportation facilities
Land use
Economic activity.
Questionnaire
It is vital that the scope of the questionnaire, the definitions, the instructions
and the wording are carefully considered. Normally returns from
questionnaires are disappointing. This method does require less skilled
personnel, as interviewers leave forms at households and collect them
completed (hopefully) two days later. Telephone interviews can also be used
as an alternative to uplifting the completed forms. The framing of the
questions is of great importance to the effectiveness of the survey, and
questions should be objective in style, clear and unambiguous. They should
be designed to enable answers to be classified into predetermined groups.
Household and roadside surveys
Household surveys offer the possibility of follow -up personal interviews.
Roadside interviews are normally short personal interviews. When a home
interview survey is conducted, an imaginary continuous line known as a
cordon will have been drawn around the area, and the study will focus upon
movements out of and through the imaginar y external cordon boundary.
Where further detail is required an area can be further sub -divided by
additional cordons. The most widely used method is the direct interview.
Alternatively, where trained staff is not available, questionnaires may be
used. The success of roadside surveys depends upon the voluntary
cooperation of drivers and the assistance of the police. In terms of sample
size the appropriate formula is:
n = [P (1-P) N 3 ]/ [(E/1.96) 2 (N-1) + (1-p2) N2]
Where
n
N
E
P
=
=
=
=
the sample size
the total number of households
accuracy
proportion of households
Pilot surveys
Where there is no historical data or prior experience it is clear that certain
things require to be clarified before an efficient survey can be carried out.
This is a small survey to give guidance on the sampling frame, the variability
of the population in the study, the adequacy of the questionnaire, and the
efficiency of the instructions.
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Automated traffic counts
This operation requires substantial investment in instrument s, equipment,
data handling systems and staff time. There are intrinsic errors in such
systems of course. Induction loop detection is more reliable than pneumatic
tube detection, but electronic equipment requires to be accurately set and
adjusted. Pneumatic tubes also detect numbers of axles and not vehicles. This
is another factor that can result in undercounting. There are also sampling
errors to be allowed for. The three main types of detectors today are
magnetic, photo-electric and contact strip devices.
Manual counts
The number of enumerators varies with the traffic flow. Roughly one
enumerator can handle about 500–600 vehicles per hour. Each half hour a
fresh recording sheet should be used, and notes should also be kept of factors
such as accidents, weather and convoys. The recording sheet shows
silhouettes of the different categories of vehicles. Typical recording forms are
in Highways and Traffic, Vol 1, by C.A.O’Flaherty. Manual counts have the
advantages of providing more specific information. The moving observer
method requires the use of a test car to facilitate the estimation of the
estimated average traffic speed. The traffic flow in vehicles per hour is given
by:
q = [60(x + y)]/(t a + t w )
Where
q = traffic flow in one direction, vehicles pe r hour
x = number of vehicles met while driving against the flow to be estimated.
Y = number of vehicles overtaking minus the number of vehicles overtaken
while driving with the flow to be estimated.
t a = travel time while driving against the flow to be estimated in minutes.
t w = travel time while driving with the flow to be estimated in minutes.
Hand-held electronic systems
This is the modern alternative to handwritten sheets and results in lower
costs, fewer mistakes, and enhanced data quality. This is particularly useful
at junctions.
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Journey time systems
In the past, vehicle count and speed was taken as the best measurement of
network performance; however, increasingly the journey time is taken as the
lead indicator. There are some systems which read number plate readings to
register details of passing vehicles. This is very useful for modelling and
prediction purposes.
Adhesive loop sensors
These are placed on the road surface and are suitable for months of survey
work. They may also be used to detect pollution, particularly levels of carbon
monoxide.
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Fundamentals
The purpose of the surveys is of course to improve flow and reduce accidents
and delays.
Definitions
Flow, q, is the number of vehicles passing a given point in a unit of time,
commonly the number of vehicles per hour.
Concentration, k, is the number of vehicles in a given length of road,
measured in vehicles per mile.
Speed, u, is the distance covered by a vehicle in a unit of time, measured in
miles per hour.
The relationship between the three is:
q = uk
As fluctuations in flow, concentration and speed are common, it is only
useful to consider average figures.
Example
If a man travels to work at a steady 20miles/h and returns home at a steady 30
miles/h what is the average speed? The man covers the distance x to work in
x/20 and from work in x/30 hours. The total distance is 2x. The average speed
is therefore:
2x/[x/20 + x/30] = 24 miles/h. This is the average of the space distribution of
speed known as the space-mean speed, and this is different from the time mean speed of 25 miles/h which you probably calculated.
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Relationships
There are three fundamental relationships between flow, concentration and
speed.
Figure 2.1
Where qc is the capacity flow, ki is the jam concentration and Vf is the free
spread. In the graphs the section OA corresponds to a free flow condition in
which the concentration of vehicles is low and the speed is at the desired
speed of the drivers. As the flow increases s o the concentration increases and
the speed reduces as vehicles interact with one another. The rate of change
continues until the flow reaches the maximum qc. At point A therefore, small
interferences to the traffic stream can cause rapid fluctuations in f low,
concentration and speed. This is called congestion.
Traffic engineering objectives
This is an empirical specialism but the engineer should try to achieve:
 A design for the capacity of a road or intersection greater than the flow,
which must be accommodated.
 Prevention of the propagation of queues and other disturbances by the
regulation of traffic in severe traffic conditions.
Students should examine the use of detectors for responsive traffic signals
described in the Design Manual for Roads and Bridges, Volume 8, available
from the Stationery Office.
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STUDY GUIDE 3
Water supply and sewerage systems
Outcome 3
Describe water supply and sewerage disposal systems.
On completion of this outcome you should be able to:
 Describe the components of water supply and sewerage systems
 Describe problems associated with water pollution
 Outline the treatment processes of water and sewerage
 Outline the equipment used in the treatment of water and sewerage.
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Introduction
Water is sourced from rivers, lakes and aquifers. The surface water supplies
are augmented by reservoirs. When all the convenient sources have been
tapped we have to turn to reusing polluted water from the lower reaches of
rivers and the sea. Water treatments and desalination are then ess ential. Our
reserves are finite, so it makes sense to conserve our resources and improve
the treatment of effluent.
Catchment area
The boundary of any river basin is defined naturally by the watershed along
the tops of the hill ridges that separate it fr om all the neighbouring valley
catchments. The area within the line of the watershed is called the catchment
area where the rain is collected and drains into a stream, lake, reservoir or
valley. The run-off from the catchment area depends on:
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Rainfall
Size and shape of catchment area
Topography
Vegetation cover
Nature of surface
Nature of subsoil
Level of water table
Reservoirs
Reservoirs are built to store water at times of surplus, for steady release to
the public supply or for controlled release to re gulate river flow during dry
seasons.
Types of reservoir
Upland reservoirs, river regulating reservoirs, lowland storage basins and
storage over estuaries, bays and flats are supplemented by special high -level
reservoirs. Many lowland towns were forced to tap upland sources when local
rivers became polluted and unsafe. As the run -off from the upland catchment
areas can be meagre at times, storage is necessary to ensure continuity of
supply. Sometimes water storage can be created by the construction of dams .
Reservoirs can impact on amenity and the environment, however. At the
Tummel Garry scheme in Perthshire, for example, a fish ladder was provided
to accommodate migrating fish.
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Fig 3.1 Upland surface water system
Groundwater
There is a long history of the use of groundwater in the UK, particularly in
the south. This is in the form of springs, hand -dug wells, boreholes and
aquifers.
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Distribution systems
Water mains
After water has been treated and conveyed to the supply area it has to be
distributed. A network of pipes (mains) of various sizes is laid beneath
streets, pavements and verges of our towns. This network connects individual
consumers to the transmission or trunk main. The system also includes
booster pumps and service reservoirs. Service reservoirs are usually
constructed of concrete and are sunk wholly or partially below the ground. In
flat areas reservoir water towers are necessary to obtain an adequate head of
water pressure to supply the buildings.
Figure 3.2 Water distribution network
Service pipes
The water authority makes the connection between the water main and the
service pipe of the customer. The pipes can be made of a variety of materials
depending upon the corrosive power of local wate r.
Figure 3.3
Figure 3.3 shows typical details of the connection from the town water main
and the service/supply pipe on the site.
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Water treatment
Water may be unsuitable for domestic or industrial use because of natural
impurities or as a result of industrial or domestic pollution. The degree of
pollution by pathogenic bacteria is based upon the count of escherichia coli
per unit volume of water. (This is the most common intestinal bacteria.) Test
laboratories will refer to the coliform count. Water treatment can be seen as
the removal or reduction to acceptable levels of:

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


Suspended matter, which affects the colour, taste or odour
Bacteria
Chemicals
Corrosive properties
Material that might encourage biological growth.
Figure 3.4 Typical water treatment process
Preliminary treatment
Abstracted water is first stained to remove floating debris that might interfere
with the operation of the treatment plant machinery. Then the water is
directed through a preliminary storage area, to allow settlement before being
screened again. Screens are coarse (metal bars 50–150mm apart), or fine
(with a bars spaced at10–25mm). Collected material is removed by raking,
which can be by hand or mechanical. As an alternative, the rotat ing drum
microstainer can be used, in which case the drum and mesh are cleaned by
high-pressure water jets.
Preliminary settlement reduces the suspended solids content and the numbers
of pathogenic bacteria, but in the case of water with low dissolved oxy gen
content, it is then necessary to aerate the water by allowing the water to fall
over a series of steps, and this is known as cascade aeration.
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Coagulation and flocculation
This is used to remove particles that cannot be removed by sedimentation or
filtration alone. Such particles are very small in size and are called colloids.
They can result in turbid water as they include clays, metal oxides, proteins
and organic substances. In peat catchment areas, the water is typically brown
in colour.
When water stands still, suspended solids sink to the bottom. In water
treatment plants large shallow basins are used to stop the flow of water, as
turbulence inhibits the settlement of fine particles. To aid this sedimentation,
engineers introduce chemicals to induce the fine particles to form clusters.
This action is known as flocculation. Common to such particles is the
negative charge and this prevents aggregation of the particles, and hence
prevents settlement. Ions with opposite charge are introduced to overc ome the
charge, thus allowing the particles to be aggregated, which then allows the
colloids to settle. These are called chemical coagulants. Aluminium and ferric
salts are commonly used coagulants.
Sedimentation
When water has little movement, suspended solids sink to the bottom under
gravity. This process is called sedimentation. This is used to settle solids
from waters with high sediment content, and also to settle flocculated
particles of colloids. Clearly the settling velocities are different for th e
various types of suspended solids.
Table 3.1
Nature of solid
Settling velocity/(mm/s)
Clay, silt
0.07
Retention time for settling in
a 3m deep tank/h
11.9
Organic waste
0.42
1.98
Aluminium and iron
flocs
0.83
1.00
Activated sludge
2.00
0.42
Grit
20.00
0.042
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Figure 3.5 Typical sedimentation tank
The principle of upward flow sedimentation is shown above. Raw water with
added flocculants flows from A to the base of the inverted cone. The upward
velocity of the water is reduced with the increasing volume of the cone. A
sludge blanket forms at B. This acts as a filter and clear water is led off at C.
The sludge at D is pumped out.
Sand filtration
A bed of sand acts as a strainer and also as a chemical and bacteriological
filter. The top layer has organisms, which decompose organic matter. Below
this layer non-pathogenic bacteria complete the decomposition of the organic
matter reducing this to inorganic simple substances. Slow sand filters are
expensive to build and maintain whereas rapid gravity sand filters use
flocculated water and are cheaper and faster; but unfortunately they are less
efficient in that a completely sterile effluent cannot be guaranteed. Rapid
gravity sand filters have generally replaced slow filters b ecause the flow is
approximately 20 times that of the slow sand filter. In consequence a smaller
space is required for filtration. No ‘schmutzdecke’ or layer of fine filtration
is formed, and the filter is cleaned, simply by pumping water backward under
pressure through the filter, to wash out impurities. This is known as
backwashing. This method gives higher bacterial counts.
Figure 3.6 Typical rapid gravity sand filter
outlet for backwash
gravel
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Flotation
This is an alternative technique to sedimentation. G as bubbles are used to
increase the buoyancy of the suspended solids by attachment to the particles,
effectively reducing the density and causing the particles to rise to the top.
Once at the top the particles can be removed by a skimmer.
Figure 3.7 Air flotation system
Aeration
Oxygen is a powerful purifying agent. It is beneficial to water with a low
oxygen content to force aeration by use of a cascade, such as a weir or
waterfall, which forces turbulence, or by spraying the water th rough jets into
the air.
Disinfection
Before treated water is passed into the public supply, all pathogenic micro organisms must be removed. Sedimentation and filtration cannot guarantee
this and so the organisms must be rendered inactive. Chlorine is a popular
oxidisng agent which kills most bacteria, but not viruses. It is cheap and
soluble in water, but requires careful handling and in certain circumstances,
where organics are present, can produce trihalmethanes which are
carcinogenic. Also in the presence of phenols, chlorine forms chlorophenols
which have a strong odour and taste.
If the source of a public water supply is consistently suspect, the risk can be
eliminated by using a killing agent such as chlorine or ozone. Chlorination is
the commoner method of sterilizing public water supplies. Although such
treatments render the water wholesome the water may not be aesthetically
desirable with respect to taste, colour and odour.
World Health Organisation (WHO) guidelines recommend a minimum free
chlorine concentration of 0.5mg/l after a contact time of 30 mins at a pH of
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less than 8. An alternative to chlorine is ozone, which is effective against
viruses and spores and does not produce toxic by-products.
Question
List the advantages and disadvantages of chlorine and ozone as disinfecting
agents.
Answer
Chlorination is cheaper and has a residual effect to protect the water in the
distribution system. However, chlorination does not kill all viruses, is not
effective against spores, and can result i n the production of trihalomethanes.
Ozonation acts quickly and kills all bacteria, spores and viruses and reduces
taste and colour effects. Unfortunately, there is no residual germicidal effect.
Other treatments
Nitrate removal
Associated with agricultural run-off and a causal factor in ‘blue baby’
syndrome, nitrate in water is a significant problem. The relevant EC directive
sets a limit of 50mg/l. Nitrates are removed by ion exchange. A typical nitrate
‘scrubber’ unit has recently been constructed at Loch Leven (Kinross). Here
biological fluidised beds grow nitrate-removing bacteria. When a carbon
source is added, the bacteria reduce the nitrate to nitrogen gas.
Trace organics removal
Synthetic organic compounds may affect the taste and odour of water . These
can be removed by granulated activated carbon (GAC) and the effectiveness
of this is measured by the reduction in the chemical oxygen demand (COD) of
the treated water. A typical trace organic would be soluble phenols.
Fluoridation
A controversial treatment incorporated for the beneficial effects in the
reduction of tooth decay. Some waters naturally have a fluoride content.
Where it is added artificially, fluoride is added as the last process in the
water treatment, in the form of sodium fluorosil icate, sodium fluoride, and
fluorosilic acid.
Sludge removal
The sludge collected in the sedimentation tank has to be removed. Wet sludge
can be transported to the sewage works and entered into the raw sewage inlet.
Alternatively, the sludge can be dewatered and the resultant ‘cake’ can be
sent to a landfill site. Dewatering is carried out by pressure filtration, vacuum
filtration or centrifugation.
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Desalination
Desalination is used in the dry climates of the Middle East and some islands
where people are forced to use seawater and brackish water sources, and also
on ships. The two main methods are multistage flash distillation and reverse
osmosis. Recently electrodialysis and solar distillation have been used.
In multistage flash distillation, seawater is distilled in a series of sealed tanks
where the water flashes (evaporates suddenly) at correspondingly lower
temperatures. This causes pure water to condense on cooling coils. In reverse
osmosis dissolved salts are removed by filtering. Electrodialysis i s an
electrochemical process involving ion transfer which separates salt from
water.
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Sewage treatment
Sewage is mainly water, which has been used for a variety of purposes in the
home, at work or during leisure activities, and may include rainwater fro m
roads and roofs. Trade effluents produced at work, including farm effluents,
are often treated at sewage works for admixture with sewage. Sewage
contains a wide variety of human, animal and vegetable material, some of
which is in solution and sometimes in suspended solids form. There are three
main forms of solids:
 Those that sink
 Those that float
 Those that remain suspended in the water.
It is the suspended material, called colloidal matter, which makes settled
sewage look cloudy.
It does not make sense to treat all of the effluent at the one time, when the
flow in a sewer can fluctuate greatly. To provide a limit on the capacity of
the works required, a storm overflow is usually incorporated as a safety
device whereby in times of excessive flows, the treatment works can be bypassed, and the overflow is directed through a coarse screen before entering
the river.
Basic treatment processes are:
 Removal of suspended solids
 Oxidation of dissolved organic material.
These treatments are to reduce the oxygen demand and the proportion of
suspended solids. After the removal of materials that are easily separated
there are further treatments. The processes are:
Primary:
removal of coarse solids
removal of fine solids
Secondary:
biological oxidation of organic matter
removal of solids resulting from biological treatment
Tertiary:
further removal of suspended solids and oxygen demand
Nutrient removal:
removal of phosphorous and nitrogen compounds.
WHO guidelines indicate that a standard of a 30/20 effluent is to leave the
sewage works. Such an effluent is one where the suspended (SS) solids
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content does not exceed 30 g/m 3 and where the biochemical oxygen demand
(BOD), does not exceed 20 g/m 3 . This should be the quality of the effluent
after the secondary treatment. After this the quality of the effluent can be
improved by tertiary treatment and disinfection.
Table 3.2 below shows limits at each stage of the treatment process.
Table 3.2
Crude sewage
Settled sewage
Final effluent
BOD g/ m 3
250
175
Less than 20
SS g/m 3
250
75
Less than 30
Ammonia Ng/ m 3
30
20
Less than 5
Nitrate Ng/ m 3
less than 5
less than 5
5
Sewage works
Sewage works differ in design according to age and local circumstances, in
the strength and volume of sewage received, and in th e time at which the
highest and lowest flows arrive. A plan view of a typical large sewage works
is shown in figure 3.8 below.
Figure 3.8
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Storm overflow
This is a safety device to avoid the plant being damaged by excessive flows.
In the event of storm/flood conditions, the excess flow can bypass the works,
and flow via an open channel to a river. As the initial early flow in a storm
will be contaminated by oil etc from roads, this is directed to storm tanks.
Later, when the tanks are full, the less polluted storm water is allowed to
reach the river. Usually the capacity of the storm tanks is not reached and this
permits the polluted storm water to be collected and pumped back into the
treatment process.
Primary treatment
The comminutor is a unit which screens and macerates. The object in
comminition is to reduce the size of large solids so that they are no longer
likely to cause problems in later stages of the treatment by blocking pumps
and valves for example. To ensure that the sewage can flow under the
influence of gravity, it is sometimes necessary to pump it through a rising
main or pumping main.
With the coarse particles removed, the next stage is for the sewage to travel
at low velocity through large tanks so that the particles in suspension are
allowed to settle. This produces primary sludge that is removed for further
treatment such as anaerobic digestion or dewatering. The tanks used for this
purpose are similar to those used for water treatment and can be circular or
rectangular.
Secondary (biological) treatment
Biological oxidation
The purpose of biological oxidation is to remove from sewage or settled
sewage polluting substances, which may be in solution, as settleable
particulate matter or as colloid. Biological oxidation r equires close contact
between sewage, living organisms and oxygen. This contact is achieved by
providing solid substances in contact with the sewage and air on which the
living organisms develop, or by bringing the air into close contact with
sewage as bubbles or vigorous surface agitation in such a way that the living
organisms develop as free-floating flocculent sludge. The two main
categories of processes that use biological oxidation are the activated sludge
process and biological filtration.
Biological filters
These can be circular or rectangular in shape, and are known as percolating
filters or bacteria beds. Settled sewage is sprayed over the surface of the filter
media (stone or clinker), and as it trickles down, oxidising bacteria on the
media comes into contact with the organic constituents of the sewage and
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oxidation takes place. In the circular bed, a rotating arm distributor sprays the
sewage over the surface of the bed. The media in the bed is typically 1.2 – 2
metres deep. After this stage, further settling is undertaken and from this
tank, humus sludge is removed.
Figure 3.9 Flow arrangements
humus tank
flow
diversion
structure
Activated sludge process
This process is more popular than the percolating filter because it requires
less space. The process produces a flocculent microbial culture that is easily
settled. The elements of the process are:





An aeration tank
An aeration system
A sedimentation tank
A return activated sludge system
A removal system for excess activated sludge.
Air is introduced into the settled sewage by bubbling compressed air through
the liquid, or by mechanical agitation.
Figure 3.10 Section through aeration tank
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Advantages of activated sludge system
Proportion of sludge that is recycled can be varied to contr ol quality of
effluent
Filter flies are avoided
Less loss of head than filter bed saves pumping
Space is saved.
Disadvantages of activated sludge system
Require continual attention
Cannot handle peak loads
They are noisy
They are more vulnerable to toxic materials
They do not convert ammonia to nitrate.
Other forms of biotreatment
Contact stabilisation is another form of biotreatment. It uses the adsorptive
properties of activated sludge, so that finely suspended material is adsorbed
by the sludge, and then the adsorbed organics are adsorbed metabolically.
Figure 3.11 Contact stabilisation process
Local treatment
Where no mains drainage is available, isolated or small groups of properties
are often served by cesspools or septic tanks . Cesspools are storage devices
and the flows have to be tankered away. Septic tanks provide a degree of
treatment by discharging to sub-surface drains or by biological filtration.
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STUDY GUIDE 4
Geotechnics
Outcome 4
Explain the formation, classification, structure and erosion of common rock
types, and their use as civil engineering materials.
On completion you should be able to:
 Describe the formation of rocks
 Identify rock samples
 Sketch and explain features of rock formations
 Sketch and explain landforms resulting from erosion and deposition of
rocks
 Explain the uses and behaviour of rocks as civil engineering materials.
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Rock materials
What is a ‘rock’? Igneous rocks, formed by the crystallisation from a silicate
melt, contain several different kinds of minerals. Sedimentary rocks, formed
by erosion of other rocks, may be predominantly composed of a single
mineral; this indicates some process of selection in the rock cycle that has
favoured its inclusion.
The rock cycle
Geological cycles are important in the production of rocks. When basaltic
ocean crust is created at constructive plate margins, it returns to the mantle
again at a destructive plate margin. The hydrological cycle, in which rain
falling on land is carried to the sea in ri vers and then evaporates, condenses
and falls again over land as rain and snow, can be regarded as another
geological cycle – the sodium cycle. Linked closely to this is the rock cycle
first recognised by the Scottish geologist, James Hutton (1726 –97). In his
book A Theory of the Earth with Proof and Illustrations (1785), he showed
how igneous rocks are eroded to form sediments by weathering and decay.
These sediments are compacted into rocks, which can subsequently be
exposed and subjected to further erosion. This cycle as envisaged by Hutton
is:




Existing rocks eroded
Sediments are deposited
Earth movements throw up rocks
Rocks are subjected to igneous and metamorphic movements.
The three main processes involved in the production of rocks therefore are
igneous, sedimentation and metamorphic.
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Igneous processes
The mantle
The biggest proportion of the Earth’s rocks is mantle rocks. This consists of
mainly peridotite. Peridotite is composed of olivine, which is an iron magnesium rich silicate. Sea floor spreading is driven by convection currents
in the mantle, which rises up and spreads outwards beneath the mid -ocean
ridges.
Volcanic rocks
As a consequence of the Earth’s very hot interior, volcanoes are active on the
surface, producing rocks which have three important characteristics. They
are:
 Crystalline
 Fine structured
 Rest on top of older rocks.
Formed from these processes are typically basalts. Contained within basalts
may be aluminium, calcium, sodium and potassium.
Plutonic rocks
Plutonic rocks are an important group of igneous rocks that originate as
liquid magmas; but unlike basalts, they are squeezed into other older rocks.
As a result plutonic rocks cool extremely slowly, and the centre is therefore
very coarse grained, although at the edges they will be much finer grained
because of the chilled margin. Coarse -grained basalts are called gabbros.
Where partial melting and crystal fractionation occur rocks of a granitic
nature are formed.
Destructive plate margins
Where one slab of oceanic crust is forced down beneath another there is a
great deal of friction and the associated generated heat together with heat
from the mantle leads to the generation of magma from volcanic action. The
first lavas produced are basaltic but the later products a re siliceous rocks
known as andesites. These are generally lighter in colour.
Igneous rocks
These rocks form the bulk of the earth’s crust and have been formed by
cooling and consequent solidification from the molten state. The texture of
the rocks depends upon the rate of cooling and solidification. The slower the
rate of cooling gives more perfect crystallisation with coarser texture.
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Between the plutonic and volcanic rocks there is a third class known as
hypabassal rocks. These were formed by the intr usion of small masses of
magma into fissures in the surrounding rock. This gives a rock of fine texture
intermediate between the plutonic and volcanic varieties. These rocks can be
further subdivided in accordance with their chemical composition, and in
particular the proportion of silica or quartz. Acid rocks have more than 66%
silica, whereas basic rocks have less than 52%.
Table 4.1
Slow cooling
acidic
intermediate
basic
Plutonic
(coarse grained)
granite
dierite
gabbro
Hypabassal
(fine grained)
quartz
syenite
dolorite
Volcanic
(glassy)
rhyolite
andesite
basalt
Rapid cooling
Granite is composed of quartz, feldspar and mica. Feldspar forms the bulk of
the material, and this mineral contains soda and lime.
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Sedimentary processes
The sedimentation of rocks is the next stage in the rock cycle and where
exposed igneous rocks are weathered.
Physical and chemical weathering
Physical weathering is the mechanical disintegration of the rock caused by
freezing of rainwater in cracks. When rainwater fre ezes in rock, splits occur
and blocks of rock fall under gravity and this causes further weathering.
Chemical weathering takes place most effectively when physical weathering
is well advanced and when the presence of dissolved atmospheric gases such
as carbon dioxide causes chemical reactions to take place between the
minerals and the water.
Transportation
Residual products of chemical weathering and large fragments of physical
weathering can be transported by water, wind and ice. This removal of further
material is called erosion. This combined wearing down of mountains is
called denudation. There are three types of movement whereby rocks can be
transported.
Figure 4.1
When particles roll along the bed of streams they can coll ide with each other,
and can be lifted up by the current for short distances. This irregular jumping
is called saltation. Finer grained particles form a suspended load, which is
carried by the water itself. Grain size is important in the way sedimentary
particles are transported. This relationship is known as Stoke’s Law.
Changes in water current velocities are responsible for the natural selection
and deposition of certain grains in sediments. This sorting is a measure of the
size-frequency distribution of grain sizes in sediment. Fast-flowing water
carries the coarsest material. Fine-grained sediments are characteristic of low
energy environments.
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Sedimentary rocks
These can be classified according to the manner of their formation as:
 Mechanical
 Chemical
 Organic.
Mechanically formed rocks are derived from older rocks that are decayed by
the action of the weather, and carried down to the river in fragments. The
loosely deposited material gradually becomes compacted by further layers
being deposited.
Chemically formed rocks are formed due to chemical precipitation in fissures
and crevices, for example calcium carbonate running through chalk or
limestone. Stalactites and stalacmites are formed in this way.
Organically formed rocks are made up from calcareous and siliceous sea
organisms that are deposited on the sea bed and are gradually consolidated.
Sedimentary rocks form 5% of the earth’s crust, and most of this is of shale,
with a little sandstone (0.75%) and limestone (0.25%).
The durability of a sandstone depends upon the cementitious material which
binds the grains together. The presence of mica results in laminations. Such
stone will split easily into slabs.
Limestones are sedimentary stratified rocks containing in excess of 90%
calcium carbonate. Limestones are classified by their structure into granular,
(formed organically), oolitic (rounded grains bound with calcite), shelly
(containing large numbers of shells), and crinoidal (containing sea lily
stalks).
Dolomite is the name given to any stone which contains an appreciable
amount of magnesia, combined as a carbonate.
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Tectonic and metamorphic processes
Tectonic processes
Mechanical deformation of rocks occurs when one layer is deposited on
another. The lower layer is compacted. When the re is a sideways force folds
may form. This results in rocks seeking relief to movements in the earth’s
crust, by rising vertically.
Figure 4.2 Isoclinal folding
Thus mechanical deformation can result from temperature stresses with
compression leading to shear cracks and brittle deformations, and tensile
stresses leading to swelling up.
Figure 4.3
Metamorphic processes
This involves rocks derived from other chemical and physical processes. The
simplest process is contact metamorphism, which occurs when a rock is
intruded with hot magma. Depending upon the size of the intrusion the
adjacent rock will be heated and can result in a baking effect, which produces
hard splintery rock called hornfelses. When muds are subjected to
metamorphism coarsely crystalline schists and finally gneiss is formed.
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Metamorphic rocks
These rocks are sedimentary or igneous in origin, and have undergone some
change of formation due to the effect of heat or pressure or a combination of
both. This can come about through the intrusion of a magma into fissures in
the earth. This heats up the surrounding ‘mother’ rock causing it to
crystallise. An example of this type of rock is marble. More commonly used
in construction is slate. Slates are usually formed from clay that has
undergone metamorphosis due to the action of great heat and pressure.
Table 4.2 Common rocks
Igneous
Intrusive
Granitic
Ultrabasic
Extrusive
Basaltic
Volcanic
Welded tuff
Metamorphic
Foliated
Slate
Schist
Gneiss
Non foliated
Quartzite
Marble
Sedimentary
Detrital
Shale
Sandstone
Conglomerate
Chemical
Limestone
Rocksalt
coarse
coarse
feldspar, quartz
ferromagnesians
fine
mixed
fine
feldspar
feldspar
glass
fine
coarse
coarse
shale, basalt
shale, basalt
shale, basalt, granite
coarse
coarse
sandstone
limestone
fine
coarse
mixed
clay
quartz, feldspar, rock fragments
quartz, feldspar, rock fragments
coarse to fine
coarse to fine
calcite, shells, calcareous algae
halite
Thus metamorphic rocks are changed rocks, and it is difficult to generalise
about their suitability for engineering projects. Consider the fractures formed
during folding.
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Figure 4.4 Fractures formed during folding
Engineering considerations
Foliation planes are potential planes of weakness, as there is a potential to
slide and there is a movement of ground water through the rock along this
orientation.
Figure 4.5 Likelihood of instability
In the situation on the left the foliation is inclined aw ay from the road and
there is less likelihood of rocks falling on the road than in the situation on the
right where the foliation is inclined towards the road.
Foliation planes are also a source of weakness at dams and reservoirs with
associated potential leaks.
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Figure 4.6 Plan view of foliation planes at dam
Engineering properties of rocks
An important use of stone is for aggregate in a concrete mix. Such stone must
be chemically inert, have high resistance to crushing and be of a cceptable
shape. (Spherical preferred to flaky.) Stone as a fill material in roads, or as in
railway ballast, must have a high resistance to abrasion.
Where stone is exposed to weather, for example in external walls, then not
only is compressive strength required, but also the ability to resist the effects
of weathering through excessive porosity and resultant frost action. Such
building stone must be quarried and dressed to be suitable for construction
purposes. The presence of bedding planes (the way the rock was originally
laid down) facilitates this and determines the way that the block should be
laid in a structure.
Figure 4.7 Bedding planes
Activity
Examine six structures in your locality in which stone is the principal
material of construction. Report on the type of stone used, the reason for its
suitability, its appearance and its resistance to weathering.
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STUDY GUIDE 5
Civil engineering and the environment
Outcome 5
Describe the effects of civil engineering projects on the environment.
On completion of this outcome you should be able to:
 Describe the features of the natural environment which may be affected
 Describe the principal impacts on, and the interactions with, natural
environmental systems
 Describe ways of reducing the unwanted effects of projects.
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The Engineering Council’s aims
The Engineering Council’s aims include the following environmental
aspirations:
 To increase awareness of the essential and beneficial part engineering
plays in all aspects of modern life
 To spread best engineering practices to improve efficiency and
competitiveness of UK businesses
 To advance engineering knowledge through education and training.
To achieve these aims the Council emphasises the interdisciplinary aspects of
training programmes for engineers, and the need for a proper balance between
efficiency, public safety and the needs of the environment when carrying out
engineering activities.
Legal obligations
The 1990 Environmental Protection Act indicates the areas where e ngineers
will be involved:
 Pollution control of land, air, and water systems
 Disposal of wastes on land
 Statutory nuisances and clean air
 Litter
 Radioactive substances
 Genetically modified organisms
 Conservation.
Thus the activities of engineers have many ways of affecting the
environment. Materials have to be quarried, transformed, transported and
changed. All of this activity can release dust, water -borne pollutants, erode
landscapes, and can result in secondary effects to wildlife both land -based
and marine, and of course requires large amounts of energy.
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Waste disposal is now regulated to avoid toxic leachate from landfill sites,
and dumping and accidents are also regulated. Excavations for projects or for
obtaining construction materials can also create damage to the environment of
flora, fauna, and marine life and in so doing reduce agricultural land and
woodlands.
Figure 5.1 Aspects associated with a typical engineering site
Landfill disposal of hazardous wastes
This is now strictly regulated and licensed because of the reduction in the
availability of sites, and increasing awareness and regulation of materials that
can be harmful to the environment. There are three basic classes of site:
1.
2.
3.
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Those providing significant containment for wastes and leachates.
Those allowing slow leachate migration.
Those allowing rapid leachate migration and insignificant attenuation.
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Figure 5.2 Attenuation
Attenuation of the concentration may be brought about by:
 Physical processes: Dilution, dispersion, filtration, gas exchange
 Biochemical processes: Organic decay, respiration, cell synthesis
 Chemical processes: Oxidation-reduction reactions, precipitation and
coprecipitation, ion exchange and adsorption.
Sustainable design
Saving energy is the most obvious component of sustainable design but it is
also about making better use of resources. This includes recycled materials,
extending the life of structures, and reducing and recycling waste. The UK
government’s environmental policy encompasses this concept of sustainable
design and there are two alternatives to meet the concept:
 Meeting the needs of the current generation without compromising the
ability of future generations to meet their needs;
 Consumption of resources at a rate no greater than their renewal.
This new design ethic towards resource conservation and ease of recycling is
necessary to bring an end to the ‘magic circle’ growth depicted in fig 5.3.
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Fig 5.3
ISO 14001
When a civil engineer answers the question ‘are we achieving environmental
sustainability in a project’, then the engineer must have regard to
International Standard ISO 14001:1996, which looks at continual
improvement in environmental performance.
Environmental aspects of civil engineering
Typically, engineers are involved in general waste, sewage effluent, energy,
water resources, water quality, oil/chemical storage, air quality, noise,
contaminated land and construction materials and their transportation. The
involvement in sustainable ‘construction’ includes the built environment and
its infrastructure. There are therefore economic and social aspects of concern
to the engineer particularly because of the longevity of the structures erected,
and their impact on future generations. The UK government’s consultation
paper Building a better quality of life has suggested: ‘sustainable
development is about ensuring a better quality of life for everyone, now and
for generations to come’. The paper has four aims:




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Social progress that recognises everyone’s needs;
Effective protection for the environment;
Prudent use of natural resources;
Maintenance of high and stable levels of economic growth and
employment.
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The BRE environmental assessment method (BREEAM) takes into accou nt all
the environmental aspects of a building project, such as materials, design,
operation, management and use. The weightings derived are used to assess
against UK ecopoints, which measure overall environmental impact.
Environmental assessment of materials includes three categories of impacts:
 Resource depletion
 Human health impacts
 Ecological impacts.
It is of course essential that there is standardisation to ensure quality of
environmental assessments.
Risk assessment
For many civil engineering projects, the job is individual and unique, and so
risks of environmental harm cannot be estimated from relevant statistics of
incidents elsewhere. New processes and design concepts, and revised design
standards are examples of such situations. Techniques must be used to assess
the levels of risks to individuals and the environment. If these techniques are
applied at design and planning stages, this will be of economic benefit. The
flow diagram in figure 5.4 is an overall risk assessment procedure.
Figure 5.4
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If after applying the procedure, the risk is unacceptable, then alternative
systems will have to be devised. It is the identification of hazards that is the
most important step, because hazards are inherent in some activities and
materials. Continuing hazards are different from those hazards resulting from
systems failure such as explosion or release of toxic substance.
Formal hazard assessment techniques include:
 Hazard and operability study (HAZOP)
 Failure mode and effect analysis (FMEA)
 Event tree analysis and fault tree analysis (FTA).
From the cradle to the grave
Life-cycle analysis (LCA) is also known as ‘eco-balancing’. The aim of LCA
is to encourage the introduction of products that have less cradle -to-grave
impact on the environment. LCA then involves quantifying the resource and
energy consumption, together with releases to air, land and water associated
with the design, construction, use and disposal of civil engineering products.
LCA is a method for producing an inventory of all material and energy flows.
The environmental issues for LCA are:
 Depletion of renewable and non-renewable resources
 Emission of substances with potential to contribute to global warming,
ozone layer depletion, and acidification
 Disturbance through landfill, transport, noise, smell and radiation.
 Safety issues.
Recycling
Traditionally, construction and demolition waste has been deposited at
landfill sites at low cost. With the increased awareness of environmental
issues, a reduction in the number of suitable landfill sites and an increasing
quantity of waste, there is a need to recycle waste. There is an opportunity to
recycle aggregates as it is difficult now to gain authorisation to open new
quarries. Similarly there is scope for the recycling of crushed concrete if the
qualities of strength, E value and creep and shrinkage can be solved.
Other materials can be recycled by being reused. The BRE information paper
IP7/00 Reclamation and recycling of building materials reports on ways to
reduce waste by reusing demolition timber and reclaimed stone.
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Energy use
Carbon dioxide is produced when fossil fuels are burnt. Increased global
warming and climatic changes are affecting rainfall patterns and sea levels.
The UK government has set limits on CO 2 emissions and targets for reduction
by 2010. Engineers must therefore seek to promote energy efficiency by:
 Tested and proven technologies and good practices
 Energy consumption benchmarks for buildings and end use.
Typical technologies:
 Low-energy windows
 Energy-efficient lighting
 Photovoltaics
 Geothermal energy
 Solar heating
 Heat pumps
 Building energy management systems
Finally, Concurrent design and engineering in building and civil engineering
(CONCUR) has the main objective of composing, develo ping and
implementing integrated systems for computer -integrated construction.
Funded by the EC, CONCUR will build on past and current research to
satisfy the increased governmental regulatory constraints on safety, waste and
energy consumption.
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