Basic Environmental Engineering

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This section covers the scope of environmental engineering and the nature of engineering decisions, the major environmental parameters, units of measurement, values and dimensions, approximations in engineering calculations and the procedure for handling them, ecosystems and the system approach, the water, carbon, nitrogen and phosphorus cycles, mass and energy transfer, the mass balance, conservative and non-conservative substances, and the steady state condition.

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Scope and Engineering Decisions • Environmental engineering applies engineering and scientific principles to protect human health and the environment — covering water supply and treatment, wastewater collection and treatment, air quality management, solid and hazardous waste management, noise control, environmental assessment, and remediation of contaminated land. • Engineering decisions in this field are characterised by having to be made under uncertainty and with competing objectives: technical feasibility, cost, environmental effect, public acceptability, regulatory compliance and equity must all be weighed at once.

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Unlike a purely technical problem, an environmental one usually has no single optimum, and the choice of criteria is itself part of the decision. • Standard decision tools are cost-benefit analysis, cost-effectiveness analysis, multi-criteria decision analysis, risk assessment and life cycle assessment.

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The precautionary principle guides action where the science is incomplete but the potential harm is serious or irreversible.

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Environmental Parameters, Units and Dimensions Parameter Typical measure Significance pH Dimensionless, 0-14; negative log of hydrogen ion activity Controls solubility, corrosion, disinfection and biological activity; a unit change is a ten-fold change in acidity Temperature °C or K Affects reaction and biological rates, gas solubility and stratification Turbidity NTU Measure of cloudiness; shields pathogens from disinfection Dissolved oxygen (DO) mg/L Essential to aquatic life; falls as temperature and organic load rise BOD and COD mg/L Oxygen demand of biodegradable and of all oxidisable matter Total suspended and dissolved solids mg/L Physical load and salinity Hardness and alkalinity mg/L as CaCO₃ Scaling, soap consumption and buffering capacity Particulate matter μg/m³ as PM10 and PM2.5 Principal air quality health indicator Noise dB(A), Leq A-weighting approximates the response of the human ear • Concentration units and their equivalences are examined directly: in dilute aqueous solution 1 mg/L is numerically equal to 1 part per million, because the density of water is 1 kg/L.

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This equality does not hold for gases, where ppm is by volume and the conversion to mg/m³ is mg/m³ = ppm × molecular weight/24.45 at 25 °C and 1 atm (the molar volume being 22.4 L/mol at 0 °C and 24.45 L/mol at 25 °C). • Hardness and alkalinity are conventionally expressed 'as CaCO₃' so that different species can be added together; the conversion uses the equivalent weight of calcium carbonate, 50 g/equivalent. • Dimensional homogeneity: every term in a valid equation must have the same dimensions, and checking dimensions is the quickest way to detect an error in a derived expression. • Approximations in engineering calculations are unavoidable because the input data themselves are uncertain.

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The rules are: quote a result to no more significant figures than the least precise input justifies — typically two or three in environmental work; carry full precision through the intermediate steps and round only at the end; state the assumptions explicitly; and check the answer for order of magnitude and physical plausibility before accepting it.

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A result quoted to six figures from data known to ten per cent is not more accurate, merely more misleading. • Accuracy is closeness to the true value; precision is the repeatability of the measurement.

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The two are independent, and the distinction is asked for regularly.

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Ecosystems and the System Approach • An ecosystem is a community of organisms together with their physical environment, interacting as a unit.

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Its components are the abiotic environment and the biotic community of producers (autotrophs), consumers (heterotrophs) and decomposers. • Energy flows through an ecosystem in one direction and is dissipated as heat; matter cycles round and is reused.

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This contrast is fundamental and is examined directly. • Trophic levels and the ten per cent rule: only about ten per cent of the energy at one trophic level is transferred to the next, the rest being lost in respiration and as heat.

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This is why food chains rarely exceed four or five levels, and why an energy pyramid is always upright. • Bioaccumulation is the build-up of a persistent substance within an organism over its lifetime; biomagnification is the increase in concentration at successive trophic levels.

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Persistent, fat-soluble and poorly metabolised substances such as DDT, PCBs and methylmercury biomagnify, which is why top predators carry the highest burdens. • The system approach defines a control volume with a boundary, identifies all inputs and outputs across that boundary, and accounts for what happens inside.

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The first and most important step in any environmental analysis is to draw the system boundary explicitly, because a boundary drawn differently gives a different answer. • Carrying capacity is the maximum population an environment can support indefinitely, and assimilative capacity the quantity of waste a receiving body can absorb without unacceptable damage.

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The Biogeochemical Cycles Cycle Main reservoir Key transformations Environmental significance Water (hydrologic) Oceans (about 97 % of all water) Evaporation, transpiration, condensation, precipitation, infiltration, runoff Only about 2.5 % of all water is fresh, and most of that is locked in ice; the cycle has no beginning or end Carbon Oceans and sedimentary rock; atmosphere is small but critical Photosynthesis fixes CO₂; respiration, decomposition and combustion release it Fossil fuel combustion transfers carbon from a slow geological store to the atmosphere faster than it can be removed Nitrogen Atmosphere (78 % N₂, but unavailable to most life) Fixation → ammonification → nitrification → denitrification Fertilizer manufacture now fixes nitrogen on a scale comparable with nature, causing eutrophication and nitrate pollution Phosphorus Rock and sediment; no significant gaseous phase Weathering, uptake, decomposition, sedimentation The slowest cycle; usually the limiting nutrient in fresh water, so its release triggers eutrophication Sulphur Rock, sediment and ocean Weathering, bacterial reduction and oxidation, combustion Combustion of sulphur-bearing fuel causes acid deposition • The nitrogen cycle terms must be learnt precisely, since they are examined individually: • Nitrogen fixation — conversion of atmospheric N₂ to ammonia, by Rhizobium and other bacteria, by lightning, and industrially by the Haber-Bosch process. • Ammonification — release of ammonia from decomposing organic nitrogen. • Nitrification — aerobic oxidation of ammonia to nitrite by Nitrosomonas and then nitrite to nitrate by Nitrobacter.

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It consumes oxygen and alkalinity, which is why it matters in wastewater treatment. • Denitrification — anoxic reduction of nitrate to nitrogen gas, requiring a carbon source and the absence of dissolved oxygen; it is the step that returns nitrogen to the atmosphere and the only practical way of removing nitrogen from wastewater biologically. • Assimilation — uptake of nitrate or ammonia into plant and microbial tissue. • The phosphorus cycle differs from the others in having no significant atmospheric or gaseous phase, so phosphorus moves only through water and sediment.

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This makes it slow to recycle and easily lost to deep sediment, and is a certainty in examinations.

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Mass Balance and Steady State • The general mass balance on a defined control volume is the single most useful tool in the subject: • Accumulation = input − output + generation − consumption. • Steady state means no change with time, so the accumulation term is zero — not that nothing is happening, merely that the rates in and out are balanced.

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Steady state is not the same as equilibrium: a steadily flowing reactor is at steady state but far from equilibrium. • A conservative substance does not decay, react or settle, so the generation and consumption terms vanish.

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Examples are chloride, many dissolved salts, and certain tracer dyes.

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At steady state, a conservative substance gives simply input = output, which reduces most mixing problems to a one-line arithmetic calculation — the classic river-mixing question C = (Q₁C₁ + Q₂C₂)/(Q₁ + Q₂). • A non-conservative substance is lost or produced within the system, usually by first-order decay, dC/dt = −kC, so Ct = C₀e−kt, with half-life t½ = 0.693/k.

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Examples are BOD, coliform bacteria, chlorine residual and radioactive substances. • The steps of a mass balance problem: draw the system and its boundary; label every stream with flow and concentration; decide whether the substance is conservative; decide whether the system is at steady state; write the balance; solve.

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Most errors come from an ill-defined boundary rather than from the arithmetic. • Energy balance follows the same structure, with the first law of thermodynamics supplying the conservation statement.

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In environmental work it appears in the heat balance of a digester or reactor, thermal pollution of a river, and the global radiation balance.

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This section covers environmental laws, regulations and guidelines, environmental standards including emission levels and species protection lists, environmental assessment reports, environmental screening and the screening procedures used in Nepal, scoping and the terms of reference, baseline establishment, executing the EIA process, alternatives and their comparison, the environmental management plan, environmental monitoring and environmental auditing.

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Environmental Law, Standards and Principles • The hierarchy of instruments: an Act is passed by the legislature and provides the powers and duties;

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Rules or Regulations are made under the Act and give the procedural detail; standards set enforceable numerical limits; and guidelines and manuals give non-binding advice on good practice.

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Only Acts, Rules and notified standards are legally enforceable; guidelines are not — a distinction examined directly. • The guiding principles: the polluter pays principle (the cost of pollution is borne by the party causing it), the precautionary principle (scientific uncertainty is not a reason to postpone action against serious or irreversible harm), sustainable development (meeting present needs without compromising future generations), public participation and access to information, and intergenerational equity. • Kinds of standard: ambient standards describe the quality to be maintained in the surrounding air or water; emission or effluent standards limit what leaves a source; product standards limit the content of a product; and process standards prescribe the technology or method.

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Ambient standards protect the receiving environment but are hard to attribute to a single source; emission standards are easy to monitor and enforce but take no account of the assimilative capacity of the receiving body. • Species protection lists schedule species as protected, endangered or of special concern, and their presence in a project area triggers additional assessment requirements and may prohibit certain activities outright.

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Internationally, CITES controls trade in endangered species and the IUCN Red List provides the standard conservation-status classification. • In Nepal, the principal instruments are the Environment Protection Act, 2076 (2019) and the Environment Protection Rules, 2077 (2020), which replaced the Environment Protection Act, 2053 (1996) and its Rules of 2054.

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Related instruments include the Solid Waste Management Act, 2068; the Water Resources Act, 2049; the Forest Act, 2076; and the National Parks and Wildlife Conservation Act, 2029.

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National ambient air quality standards, drinking water quality standards and generic and industry-specific effluent standards have been notified under this framework. • Legislation and standards are amended from time to time and schedules are revised, so the applicable requirement for any particular project must be verified against the current official publication.

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The Assessment Tiers and Screening • Environmental assessment is the systematic process of predicting and evaluating the environmental consequences of a proposal before a decision is taken on it.

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Its purpose is to inform the decision, not to prevent development, and it is anticipatory and preventive rather than reactive. • Screening is the first step, and it answers one question only: does this proposal require an environmental assessment, and if so at what level? It does not consider what the impacts are — that is scoping.

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Confusing screening with scoping is the commonest error in this section. • Screening procedures are of three kinds: the list approach, in which schedules prescribe the level of assessment by project type and size, which is objective, quick and predictable but inflexible; the case-by-case approach, using expert judgement against criteria, which is flexible but slower and less consistent; and a hybrid of the two. • Nepal uses the list approach: the schedules to the Environment Protection Rules, 2077 prescribe which proposals require a Brief Environmental Study (BES), an Initial Environmental Examination (IEE) or a full Environmental Impact Assessment (EIA), according to the type, size, location and sensitivity of the proposal.

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A proposal located in or affecting an environmentally sensitive area — a national park, conservation area, wetland or the like — is generally elevated to a higher tier regardless of its size.

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An IEE that reveals significant adverse impacts may be required to proceed to a full EIA. • Approval authority differs between the tiers, with the IEE approved at the sectoral ministry level and the EIA report requiring approval by the ministry responsible for environment.

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The Rules also prescribe public notice, a public hearing and recommendation by the local body as part of the process.

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Because these arrangements have changed with federal restructuring and are periodically amended, the current Rules must be consulted.

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Scoping, Terms of Reference and Baseline • Scoping determines which issues, impacts and alternatives the assessment will examine, and how deeply.

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Its purpose is to concentrate effort on the significant issues and exclude the trivial, so that the study is focused rather than encyclopaedic.

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Scoping involves the public, affected communities and relevant agencies, and identifies the spatial and temporal boundaries of the study. • Terms of Reference (ToR) are prepared on the basis of the scoping exercise and set out formally what the study must cover: the issues, the methods, the study area, the level of detail, the composition of the study team and the reporting format.

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In Nepal the ToR must be approved by the competent authority before the EIA study begins — an important sequencing point. • Baseline establishment is the description of the existing environmental condition before the project, covering the physical environment (air, water, soil, noise, climate), the biological environment (flora, fauna, habitats, protected species) and the socio-economic and cultural environment (population, livelihoods, health, heritage). • Why the baseline matters: it is the reference against which every predicted impact is measured and against which later monitoring is compared — without it, no change can be attributed to the project.

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It must cover a full annual cycle where seasonal variation is significant, and it should record the trend as well as the present state, since the environment may already be changing without the project.

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Executing the EIA Process Stage Purpose Screening Decide whether an assessment is required and at what level Scoping Identify the significant issues, impacts and alternatives to be studied Terms of Reference Formalise the scope, methods and study requirements; obtain approval Baseline study Describe the existing environment against which change will be measured Impact prediction Forecast the nature, magnitude, extent, duration and probability of each impact Impact evaluation Judge the significance of each predicted impact against criteria and standards Mitigation Identify measures to avoid, minimise, rectify, reduce or compensate for impacts Reporting Prepare the EIA report with a non-technical executive summary Public consultation and review Public notice, hearing and expert review of the report Decision Approval, approval with conditions, or rejection Monitoring and auditing Verify actual impacts and the effectiveness of mitigation during implementation • Impact prediction and evaluation classify impacts as direct or indirect; short, medium or long term; reversible or irreversible; local, regional or global; adverse or beneficial; and cumulative.

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Cumulative impacts — the combined effect of the project with other existing and proposed activities — are the most frequently neglected category and are examined for that reason.

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Standard methods are checklists, matrices (the Leopold matrix being the classic), networks, overlays and GIS, and predictive modelling. • The mitigation hierarchy, which must be learnt in order: avoid → minimise → rectify or restore → reduce over time → compensate or offset.

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Avoidance at the design stage is always preferable and cheapest; compensation is the last resort. • Alternatives must be examined and compared, including alternative sites, technologies, designs, scales, raw materials, timing and routes.

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The 'no action' or 'without project' alternative must always be included, because it provides the benchmark against which every other option is judged — a point asked directly.

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Alternatives are compared on environmental, technical, economic and social criteria, and the reasons for rejecting each should be recorded.

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EMP, Monitoring and Auditing • The Environmental Management Plan (EMP) converts the study's recommendations into an implementable programme.

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It specifies each mitigation measure, who is responsible, when it will be done, what it will cost, and how its performance will be verified, together with the monitoring programme, the institutional arrangements and training needs, the emergency response plan and the reporting requirements.

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The EMP is the operative part of an EIA report — the part that is actually enforced as a condition of approval — and an EIA without a costed, assigned EMP is of little practical value. • Environmental monitoring is the systematic, repeated measurement of environmental parameters to verify predictions, check compliance and detect unforeseen effects.

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Its types are baseline monitoring (before), compliance monitoring (against standards and conditions), impact or effects monitoring (of actual change) and receptor monitoring.

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Monitoring must use the same parameters, methods and locations as the baseline, or the comparison is meaningless. • Environmental auditing is a systematic, documented and periodic evaluation of environmental performance against defined criteria.

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Compliance auditing checks against legal requirements and permit conditions; management system auditing checks against ISO 14001 or the organisation's own system; and EIA (post-project) auditing compares the impacts that actually occurred with those that were predicted, in order to improve the accuracy of future assessments. • The distinction between monitoring and auditing is examined: monitoring is continuous or repeated measurement of the environment, while auditing is a periodic evaluation of performance and systems against criteria.

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In Nepal the Environment Protection Act provides for environmental auditing of approved proposals by the ministry, and for monitoring by the proponent and the concerned body.

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This section covers the fundamentals of surveying, the measurement of linear distance, vertical distance, and angles and directions, the principles and applications of topographic survey, and the principles, applications and measurements of hydrographic survey.

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Fundamentals • Surveying is the art and science of determining the relative positions of points on, above or below the earth's surface.

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Plane surveying neglects the curvature of the earth and is adequate for areas up to about 250 km²; geodetic surveying takes curvature into account and is used for large areas and for control networks. • The two governing principles, which are asked as a pair: • 1.

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Work from the whole to the part — establish a framework of high-accuracy control first and fill in the detail afterwards.

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This prevents the accumulation of error, which would be inevitable if the survey were extended point by point from a single origin. • 2.

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Always provide independent checks — every measurement and computation should be capable of verification, so that a blunder is detected rather than propagated. • Errors are of three kinds: gross errors or blunders (mistakes such as misreading or miscounting, which must be eliminated, not adjusted); systematic errors (following a definite law, cumulative, and correctable by calibration or by formula — tape temperature, sag and slope, collimation error); and random errors (small, unpredictable, following the normal distribution, compensating in nature and reducible only by repetition and least-squares adjustment).

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Systematic errors are cumulative and random errors compensating — the contrast is examined directly.

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Linear, Vertical and Angular Measurement Quantity Method Notes Linear distance Chain or tape (direct) Corrections for standardisation, temperature, pull, sag and slope; sag and slope corrections are always subtractive Tacheometry (optical, indirect) Stadia formula D = KS + C, with K usually 100; rapid but of low accuracy Electromagnetic distance measurement (EDM) Measures travel time or phase of a modulated wave; high accuracy over long distances; the basis of the total station GNSS Absolute positioning; differential and RTK methods give centimetre accuracy Vertical distance Differential (spirit) levelling The standard method; back sight and fore sight from each instrument position Trigonometric levelling From vertical angle and distance; needs correction for curvature and refraction over long sights Barometric levelling From atmospheric pressure difference; rapid but of low accuracy, used in reconnaissance Angles and directions Theodolite or total station Horizontal and vertical angles; repetition and reiteration methods Compass Magnetic bearings; subject to declination and local attraction • Levelling relations: height of instrument = known reduced level + back sight, and reduced level of a point = height of instrument − fore sight or intermediate sight.

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The arithmetic check for the rise and fall method is that the sum of back sights minus the sum of fore sights equals the sum of rises minus the sum of falls, which equals the last reduced level minus the first; for the height of instrument method only the first and third of these apply.

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The rise and fall method checks the intermediate sights and the height of instrument method does not, which is why the former is preferred where accuracy matters and the latter where there are many intermediate sights. • A back sight is the first reading after setting up the instrument, taken on a point of known elevation; a fore sight is the last reading before moving it; intermediate sights are all readings between.

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A change point carries both a fore sight and a back sight. • Bearings and directions: a whole circle bearing runs from 0° to 360° clockwise from north; a reduced or quadrantal bearing is measured from north or south, eastward or westward, and never exceeds 90°.

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The fore and back bearing of a line differ by exactly 180°, and a discrepancy indicates local attraction — a standard question.

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Magnetic declination is the angle between true and magnetic north and changes with place and time. • Traversing: an open traverse cannot be checked and should be avoided; a closed traverse returns to its start or to another known point and can be checked and adjusted.

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The closing error is distributed by Bowditch's rule, which apportions it in proportion to the lengths of the lines, or by the transit rule, which apportions it in proportion to the latitudes and departures.

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Bowditch's rule is used where angles and distances are measured with comparable precision.

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Topographic and Hydrographic Survey • A topographic survey records both the horizontal position and the elevation of natural and artificial features, and represents the relief by contours — in contrast to a plane or cadastral survey, which records only horizontal position and boundaries. • Contour properties, which are examined as a set: contours never cross or split, except at a vertical cliff, where they coincide, and at an overhanging cliff, where they cross; every contour closes on itself, though possibly beyond the sheet; closely spaced contours indicate steep ground and widely spaced contours flat ground; equally spaced contours indicate a uniform slope; contours cross a ridge or a valley at right angles and form a V pointing upstream in a valley and downstream on a ridge. • Contour interval depends on the scale of the map, the nature of the terrain, the purpose of the survey and the time and funds available, and is smaller for flat ground and for large-scale maps. • Applications in environmental engineering: delineating catchments and drainage patterns, siting and designing treatment works and landfills, computing earthwork volumes, laying out sewers and water mains at the correct gradient, mapping flood extents, and locating monitoring points. • Hydrographic survey is the survey of water bodies — rivers, lakes, reservoirs, estuaries and coastal waters — to determine the configuration of the bed and the characteristics of the water. • Its objects: preparing bathymetric charts and cross-sections, determining the depth and configuration of the bed, measuring discharge and velocity, locating and designing intakes and outfalls, computing reservoir capacity and sedimentation rates, supporting dredging and navigation, and establishing tidal and water-level datums. • Methods: soundings taken with a sounding rod or lead line in shallow water, or with an echo sounder using the travel time of an acoustic pulse in deeper water, with multibeam systems giving full bed coverage; the position of each sounding is fixed by GNSS, or classically by range and angle, by two angles from the shore, or by intersecting ranges.

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Velocity and discharge are measured with current meters at prescribed depths — the 0.6-depth single-point method or the average of the 0.2 and 0.8 depths — or with an acoustic Doppler current profiler.

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All soundings must be reduced to a common datum using a simultaneous record of water level, which is the essential difference from a land survey and is the point most often examined.

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This section covers the fundamental concepts of green engineering, sustainable design, product life cycle assessment, risk assessment, quality management systems, clean technology and cleaner production.

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Green Engineering and Sustainability • Green engineering is the design, commercialisation and use of processes and products that are technically and economically feasible while minimising the generation of pollution at source and the risk to human health and the environment.

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Its defining characteristic is that it is preventive and designed in, not a control measure added afterwards. • Sustainable development is, in the Brundtland definition, development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

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Its three pillars are environmental, economic and social — often called the triple bottom line of planet, profit and people, and a design that satisfies only one or two of the three is not sustainable. • The twelve principles of green chemistry and green engineering need not be memorised individually, but the recurring themes should be: prevent waste rather than treat it; design for separation and for the end of life; maximise mass, energy, space and time efficiency; output-pulled rather than input-pushed processing; conserve complexity; design for commercial afterlife; use renewable rather than depleting inputs; minimise material diversity; integrate local energy and material flows; and use inherently benign inputs and outputs. • Key design strategies: design for the environment, design for disassembly and recycling, dematerialisation (delivering the same service with less material), substitution of hazardous materials, energy efficiency, use of renewable resources, and the circular economy, which replaces the linear take-make-dispose model with one in which materials are recovered and reused indefinitely. • The ecological footprint and the carbon footprint are the common quantitative indicators; embodied energy is the total energy consumed in producing a material or product, and is the reason a durable, high-embodied-energy material may still be preferable to a short-lived one.

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Life Cycle Assessment • Life cycle assessment (LCA) evaluates the environmental impacts of a product, process or service over its entire life — from raw material extraction, through manufacture, distribution and use, to final disposal.

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This scope is called cradle to grave; cradle to gate stops at the factory boundary and cradle to cradle assumes the material is recovered for reuse indefinitely. • The four stages, defined by ISO 14040 and 14044, must be known in order: • 1.

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Goal and scope definition — state the purpose, the functional unit and the system boundaries. • 2.

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Life cycle inventory (LCI) — compile all inputs of energy and material and all releases to air, water and land. • 3.

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Life cycle impact assessment (LCIA) — translate the inventory into impact categories such as global warming potential, acidification, eutrophication, ozone depletion, human toxicity and resource depletion. • 4.

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Interpretation — draw conclusions, test their sensitivity and make recommendations.

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Interpretation is not a final step only; it interacts with all three of the others throughout the study. • The functional unit is the key methodological concept and is examined directly: it is the quantified performance of the system, which provides the reference to which all inputs and outputs are normalised.

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Comparison between alternatives is valid only if they deliver the same functional unit — for example, '1000 litres of water delivered to a household at a stated quality', not 'one pipe'. • The essential value of LCA is that it prevents burden shifting — the appearance of an improvement achieved merely by moving an impact from one life stage, one medium or one place to another.

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Risk Assessment • Environmental risk assessment estimates the probability and magnitude of adverse effects on human health or ecosystems arising from exposure to a hazard.

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Risk is a function of hazard and exposure: with no exposure there is no risk, however hazardous the substance.

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This is the central insight of the subject. • The four steps of health risk assessment must be known in order: • 1.

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Hazard identification — does the agent cause an adverse effect at all? • 2.

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Dose-response assessment — what is the relation between the dose and the incidence or severity of the effect? For non-carcinogens a threshold is assumed, below which no effect occurs, and a reference dose (RfD) is derived; for carcinogens no threshold is assumed, and a slope factor is used, because a single molecular event is taken to be capable of initiating cancer.

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This threshold/non-threshold distinction is examined directly. • 3.

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Exposure assessment — who is exposed, to how much, by what route, and for how long? Routes are inhalation, ingestion and dermal contact, and the calculation uses the chronic daily intake. • 4.

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Risk characterisation — combine the previous two.

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For a non-carcinogen the hazard quotient is the intake divided by the reference dose, and a value above 1 indicates possible concern; for a carcinogen the lifetime incremental risk is the intake multiplied by the slope factor, with acceptable levels usually set between one in ten thousand and one in a million. • Risk management follows risk assessment and is a separate activity, taking account of technical feasibility, cost, public perception, equity and legal requirements.

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Keeping assessment and management separate is a principle of good practice, because it prevents the science being bent to the desired conclusion. • Risk perception often differs greatly from calculated risk: people tolerate voluntary, familiar and controllable risks far more readily than involuntary, unfamiliar and dread risks, even when the numerical risk is much smaller — which is why communication is part of management rather than an afterthought.

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Quality Management, Clean Technology and Cleaner Production • A quality management system is the organisational structure, procedures, processes and resources used to manage quality.

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ISO 9001 specifies its requirements, built on the plan-do-check-act cycle with a process approach and risk-based thinking.

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What is certified is the management system, not the product — a point examined directly, and the same is true of ISO 14001 for environmental management and ISO 45001 for occupational health and safety.

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Their common structure allows the three to be integrated into a single management system. • Quality control detects defects in the product; quality assurance prevents them by building the system correctly.

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Quality cannot be inspected into a product; it must be built in. • Clean technology is technology that uses less material and energy, generates less waste and emission, and is safer, than the technology it replaces. • Cleaner production, in the UNEP definition, is the continuous application of an integrated preventive environmental strategy to processes, products and services to increase overall efficiency and reduce risks to humans and the environment. • Unpacking the definition, as examinations require: for production processes it means conserving raw materials and energy, eliminating toxic raw materials, and reducing the quantity and toxicity of all emissions and wastes before they leave the process; for products it means reducing impacts along the whole life cycle from raw material to ultimate disposal; and for services it means incorporating environmental concerns into design and delivery. • The crucial contrast is with end-of-pipe treatment: cleaner production is preventive and acts at source, while end-of-pipe treatment is reactive and acts after the waste has been created, often merely transferring the pollutant from one medium to another.

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Cleaner production normally pays for itself, because material not wasted is material that did not have to be bought. • Cleaner production techniques are good housekeeping, input material change, better process control, equipment modification, technology change, on-site recovery and reuse, and the production of useful by-products.

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Good housekeeping typically gives substantial savings at almost no capital cost and is therefore always the first measure attempted.

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This section covers the types of estimate, the methods of estimating, rate analysis, specifications and their purpose, importance and types, and valuation.

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Purpose and Types of Estimate • An estimate is the anticipated or probable cost of a work, computed from the quantities of each item and the rate at which each can be executed.

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Estimating precedes the work and costing follows it: an estimate is a forecast of what the work will cost, while costing is the determination of what it actually did cost.

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This distinction is examined directly. • Purposes: to decide whether a proposal is financially viable, to obtain administrative and technical approval and budget sanction, to arrange finance, to invite and evaluate tenders, to control expenditure during construction, and to plan the procurement of materials and labour.

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Type Basis Purpose and accuracy Preliminary (approximate or rough cost) Plinth area, cubic content, unit base (per bed, per km, per MLD of plant capacity) or service unit Early decision and budget provision; quick but of limited accuracy Plinth area estimate Plinth area × prevailing plinth area rate Buildings; simple and widely used at concept stage Cube rate estimate Volume (length × breadth × height) × cube rate More accurate than plinth area because it accounts for height Detailed (item rate) estimate Measured quantity of every item × its analysed rate The accurate estimate on which tenders and payments are based Revised estimate Prepared when the sanctioned estimate is exceeded by more than a prescribed margin, or the scope changes materially Fresh sanction for the increased cost Supplementary estimate For additional works found necessary while the original work is in progress Sanction for the additional items Repair and maintenance estimate Annual, special or petty repairs Upkeep of existing assets Complete estimate All ancillary costs in addition to the main work Total commitment, not merely the structure • Components of a complete detailed estimate: the quantity (measurement) sheet, the abstract of cost, the rate analysis, the specifications, the detailed drawings, and the report, to which are added contingencies (usually about 3-5 per cent for unforeseen items), work-charged establishment, supervision or departmental charges, and provision for price escalation. • Methods of measurement: the centre line method, in which the total centre line length is multiplied once by the cross-sectional area, is quicker and suits walls of uniform thickness, but requires a deduction at every junction; the long wall and short wall method (also called the out-to-out and in-to-in method) computes each wall separately and suits walls of differing thickness.

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Both must give the same answer, and computing by both is a useful check. • Standard conventions: measurements are taken to the accuracy prescribed by the applicable standard method of measurement; deductions for openings in masonry are made as prescribed and small openings below a stated area are ignored; and earthwork is normally measured in the excavated (in situ) volume, with separate allowance for bulking and shrinkage.

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Rate Analysis • Rate analysis is the determination of the rate for a unit quantity of an item of work by building it up from the cost of its constituent materials, labour, equipment and overheads. • Its components: the quantity and cost of each material including wastage and carriage; the number of each class of labour (mason, mate, unskilled labour) from standard coefficients and their wage rates; the hire or operating cost of plant and equipment; the cost of scaffolding, tools and sundries; water charges; contractor's overheads and profit, typically 10-15 per cent; and taxes as applicable. • Its purposes: to arrive at a defensible rate for an item for which no district rate exists, to examine the reasonableness of a tendered rate, to work out the rate for an extra or substituted item, and to see how a change in the price of a constituent affects the total. • Task or outturn work is the quantity of work an artisan or a gang can perform in a working day, and it is the basis of the labour coefficients used in rate analysis. • The district or standard schedule of rates is issued periodically by the authority and provides rates for common items so that estimates are consistent; a rate analysis is required for items not covered by the schedule, and for a change in specification or in the location or lead of materials. • Lead and lift are the horizontal distance and the vertical height through which material must be carried, and both attract additional rates beyond the prescribed initial allowance.

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Specifications • A specification is the written description of the nature, quality and workmanship of the materials and the work, which the drawings cannot convey.

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The drawing shows the dimensions and arrangement; the specification states the quality and the method.

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Together with the drawings and the bill of quantities, the specification forms part of the contract document, and in the event of a discrepancy the contract normally states which prevails. • Purpose and importance: it defines the standard of materials and workmanship required; enables tenderers to price the work on a common and comparable basis; forms the basis of inspection, testing and acceptance; prevents disputes; and protects both the employer and the contractor by making obligations explicit.

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Without a specification a drawing alone cannot be priced or enforced. • Types: • General specification — a brief description of the class and quality of work for the whole project, giving a general idea of the cost; used with an approximate estimate. • Detailed specification — a full description, item by item, of the materials, their proportions, the method of execution and the workmanship required; forms part of the contract. • The other classification, which is examined, is by how the requirement is expressed: a prescriptive (method or material) specification states exactly what materials and methods must be used, so the employer carries the risk of the result; a performance (end result) specification states the outcome to be achieved and leaves the method to the contractor, who then carries the risk and has scope to innovate.

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Performance specifications are increasingly used in design-build and in plant procurement. • A good specification is clear, complete, unambiguous, consistent with the drawings, capable of being measured or tested, and free of impossible or unnecessarily onerous requirements.

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Referring to a recognised national standard rather than rewriting its provisions is good practice.

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Valuation • Valuation is the determination of the present worth of a property, as distinct from estimating, which forecasts the cost of proposed work. • Purposes: sale and purchase, mortgage and security for a loan, rent fixation, taxation and rating, insurance, compulsory acquisition and compensation, and probate. • Key terms: • Scrap value — the value of the dismantled material alone, after deducting the cost of demolition; sometimes negative. • Salvage value — the value of an asset at the end of its useful life without being dismantled, when it may still be sold for further use elsewhere. • Book value — the original cost less the total depreciation charged to date; at the end of the useful life the book value equals the scrap value. • Market value — the price obtainable in the open market between a willing buyer and a willing seller, which depends on demand and supply and may differ considerably from either the cost or the book value. • Depreciation is the loss in value of an asset with age, wear and obsolescence.

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The usual methods are the straight line method, in which an equal amount is written off each year; the declining balance or constant percentage method, which writes off more in the early years; the sinking fund method, which sets aside an annual sum that accumulates at interest to the replacement cost; and the quantity survey method.

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Depreciation is the loss of value through use and age, while obsolescence is the loss of value because something better has become available, and the two are distinct — a point examined directly. • Capitalised value = net annual income × years' purchase, where years' purchase = 1/rate of interest for a perpetual income.

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Net income is the gross rent less outgoings such as taxes, repairs, management, insurance and sinking fund. • Methods of valuation: the rental or income method (capitalising the net income), the direct comparison method (comparing recent transactions in similar property), the cost or plinth area method (replacement cost less depreciation plus land value), the development method (for land with development potential) and the profit-based method (for hotels, cinemas and similar).

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This section covers the fundamentals and components of a geographic information system, maps, map features and map properties, coordinate systems, raster and vector data, geographic data linkage and matching, and the applications of GIS and remote sensing in environmental engineering.

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Fundamentals and Components of GIS • A geographic information system is a system for capturing, storing, managing, analysing and displaying spatially referenced data.

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What distinguishes it from an ordinary database or a drawing package is its capacity for spatial analysis — asking where, what is near what, and what has changed, rather than merely drawing a map. • The five components, which are examined as a list: hardware, software, data, people and methods or procedures.

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Data is much the most expensive component, commonly accounting for seventy per cent or more of the total cost of a GIS project, and people are the component most often overlooked. • Every item of GIS data has two parts: spatial data, which describe where the feature is, and attribute data, which describe what it is.

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The two are joined by a common identifier, and this linkage is what makes the system work. • The functional capabilities are data capture, storage and management, query and retrieval, spatial analysis, and visualisation and output.

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Maps, Features and Properties • Map features are represented as points (a well, a sampling station, a discharge outfall), lines (a river, a pipeline, a road) and polygons or areas (a catchment, a land parcel, a lake).

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Which representation is appropriate depends on the scale: a town is a point on a national map and a polygon on a local one — a point examined directly. • Map properties are scale, projection, resolution, accuracy, and the coordinate system and datum. • Scale: a large-scale map covers a small area in great detail (1:1,000), and a small-scale map a large area in little detail (1:1,000,000).

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The larger the denominator, the smaller the scale — the relation most frequently inverted in examinations. • Map projection is the systematic transformation of the curved earth onto a flat surface.

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No projection can preserve area, shape, distance and direction simultaneously; every projection distorts at least one of them, and the choice of projection is therefore the choice of which property to preserve.

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Conformal projections preserve shape and local angles (Mercator, transverse Mercator); equal-area projections preserve area (Albers, Mollweide); equidistant projections preserve distance along particular lines; and compromise projections balance the distortions.

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For environmental work involving areas — catchment area, land cover extent, habitat loss — an equal-area projection must be used. • Coordinate systems: a geographic coordinate system uses latitude and longitude in angular units on a defined ellipsoid, while a projected coordinate system uses linear units such as metres on a plane.

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Area and distance cannot be computed reliably in geographic coordinates, because a degree of longitude shrinks towards the poles; a projected system must be used.

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The Universal Transverse Mercator system divides the world into sixty zones each six degrees of longitude wide.

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Nepal falls in UTM zones 44 and 45, and the national mapping uses the Modified Universal Transverse Mercator projection on the Everest 1830 spheroid. • A datum defines the size, shape and position of the reference ellipsoid;

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WGS 84 is the global datum used by GPS.

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Data referenced to different datums will not overlay correctly, and errors of many metres result from ignoring the difference — a standard practical point.

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Raster and Vector Data Aspect Vector Raster Representation Discrete features as points, lines and polygons defined by coordinates Continuous surface as a grid of cells, each holding one value Best suited to Discrete objects with definite boundaries: parcels, pipes, wells, administrative areas Continuous phenomena: elevation, temperature, rainfall, satellite imagery, land cover Resolution Limited only by coordinate precision; scales without loss of definition Fixed by cell size; enlarging produces visible blocks File size Generally compact Generally large; quadruples if the cell size is halved Topology Explicit; supports network and adjacency analysis Implicit; adjacency is simply neighbouring cells Overlay analysis Computationally intensive Simple and fast, being cell-by-cell arithmetic Area and distance Accurate Approximate, depending on cell size • The practical rule: use vector for discrete features and for accurate measurement of length and area, and raster for continuous surfaces and for modelling and overlay analysis.

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Raster resolution should be chosen to suit the phenomenon and the purpose: too coarse loses detail, and too fine multiplies the data volume without adding information. • Topology is the explicit recording of connectivity, adjacency and containment.

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It is what allows a GIS to trace a network, find neighbouring polygons and detect gaps and slivers, and it is the basis of much of the quality checking in vector data. • The digital elevation model (DEM) is the commonest raster in environmental work, and from it are derived slope, aspect, flow direction, flow accumulation, watershed boundaries and stream networks — the standard chain of operations in hydrological analysis.

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Data Linkage, Matching and Analysis • Geographic data linkage joins attribute records to spatial features.

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An attribute join matches records by a common key field; a spatial join matches records by location, for example assigning each monitoring well to the land parcel that contains it. • Geocoding or address matching converts a textual address or place name into coordinates; its accuracy depends on the quality of the reference data and on standardising the address format. • Conflation and edge matching reconcile data from different sources or adjoining sheets, correcting positional discrepancies, mismatched boundaries and duplicate features. • Principal analytical operations: buffering (a zone of specified distance around a feature — the standard method for defining a protection zone around a well or a setback from a river); overlay (intersect, union, clip, erase — combining layers to find where conditions coincide); network analysis (shortest path, service area); interpolation (estimating values between sample points, by inverse distance weighting or kriging); proximity and nearest-neighbour analysis; and terrain analysis from a DEM. • Overlay is the operation that most clearly distinguishes a GIS from a drawing system, because it combines the attributes as well as the geometry, producing new information rather than merely a new picture. • Data quality is described by positional accuracy, attribute accuracy, completeness, logical consistency, lineage and currency, all of which are recorded in the metadata.

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Metadata — data about the data — is essential, because a layer whose source, date, scale, projection and accuracy are unknown cannot safely be used.

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The governing caution is that a GIS output looks equally authoritative whatever the quality of its input, which is why lineage must always be checked.

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Remote Sensing and Environmental Applications • Remote sensing is the acquisition of information about an object without physical contact, by measuring the electromagnetic radiation it reflects or emits.

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Passive sensors record reflected sunlight or emitted thermal radiation and therefore depend on illumination and are obstructed by cloud; active sensors, such as radar and lidar, supply their own energy and can operate at night and through cloud — the contrast most often examined. • Resolution has four aspects, which must be distinguished: spatial (the ground size of a pixel), spectral (the number and width of the wavelength bands), radiometric (the number of grey levels recorded) and temporal (the revisit interval).

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There is an inevitable trade-off: a finer spatial resolution generally means a narrower swath and a longer revisit interval. • Spectral behaviour worth remembering: healthy vegetation absorbs strongly in the red and reflects strongly in the near infrared, which is why the normalised difference vegetation index, NDVI = (NIR − Red)/(NIR + Red), is the standard measure of vegetation vigour, ranging from about −1 to +1, with water strongly negative and dense vegetation above about 0.5.

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Water absorbs almost completely in the near infrared and therefore appears very dark, which makes the infrared band the easiest way to delineate water bodies. • Image classification may be supervised, where the analyst supplies training areas of known class, or unsupervised, where the software clusters the pixels and the analyst then labels the clusters.

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Accuracy is assessed with an error or confusion matrix, from which the overall accuracy, the producer's and user's accuracies and the kappa coefficient are derived, and the reference data used for assessment must be independent of the training data. • Applications in environmental engineering: land use and land cover mapping and change detection; watershed delineation and hydrological modelling; flood extent mapping and inundation modelling; drought and vegetation monitoring; urban growth and heat island studies; glacier and snow-cover monitoring, which is of particular importance in Nepal; landslide susceptibility mapping; site selection for landfills and treatment works using weighted overlay; air quality and thermal plume mapping; deforestation and encroachment detection; and the mapping and management of water supply and sanitation networks.