Chapter 3: General design considerations

This chapter provides an overview of the general design requirements for typical drinking-water systems. The design of a water supply system or treatment process encompasses a broad area and application of this chapter is dependent upon the type of system and processes involved. Additional details are provided in the following chapters.

3.1 General

The following design guidelines are related to the most commonly used water treatment practices in the province of Ontario. In addition to the guidelines included in the chapter, consideration should be given to the design requirements of other federal, provincial and regional/municipal regulatory agencies, including accessibility, electrical and building code, and construction in the flood plain requirements.

3.1.1 Systems Serving Fewer than 500 People

Although the guidelines are intended primarily for permanent residential developments, they should also be taken into consideration by designers of systems serving seasonal occupancy developments. Seasonal developments may eventually evolve toward extended or full-term occupancy and the drinking-water system should be designed with this possible change in mind.

The decision about whether a communal water supply should be provided rests with the municipality/owner. However, the following recommendations are provided for guidance:

  1. Where ten or more residential lots or dwelling units are to be developed or exist and the average lot size is less than 0.8 hectares (2 acres), a communal water supply system should be provided as long as local conditions are favourable to the development of a suitable ground or surface water supply; and
  2. In the case of a new subdivision, where the lot size is to be 0.8 hectares (2 acres) or greater, individual wells may be acceptable, unless the subdivision is located within or adjacent to a hamlet or settlement which may be provided with municipal supply in the future. In this case, as a minimum, watermains complete with house connections should be provided at the time of installation of other services. It should be the decision of the municipality as to whether a communal water supply should be provided in the interim or whether private wells will be allowed.

Systems serving fewer than 500 people may be governed by the Drinking-Water Systems Regulation (O.Reg. 170/03), under the Safe Drinking Water Act, 2002 (SDWA), or other SDWA regulations. The designer should ensure that the requirements of the appropriate regulations are met.

3.2 Pre-design study

3.2.1 Water Source, Quality & Quantity

In selecting the source of water for a drinking-water system, the designing engineer should ensure that an adequate quantity of water will be available and that the treated water will meet the Ontario Drinking-Water Quality Standards Regulation (O.Reg. 169/03) under the Safe Drinking Water Act, 2002 and O.Reg. 170/03 as well as the Procedure for Disinfection of Drinking Water in Ontario (Disinfection Procedure) adopted by O.Reg. 170/03 through reference. The water should also be aesthetically acceptable and palatable. The designer should refer to the latest edition of the Technical Support Document for Ontario Drinking Water Standards, Objectives and Guidelines (Technical Support Document) for a description of operational goals and aesthetic objectives.

In cases where the designer has a choice between two alternate sources, the designer should investigate the source protection and potential development status of each water source, ensure that the water source has sufficient safe yield to provide an adequate quantity of water, and compare treatment requirements and their associated costs prior to selecting a particular source. For municipal drinking-water systems, this is normally done under the provisions of the Municipal Engineers Association Municipal Class Environmental Assessment (MCEA) under the Environmental Assessment Act (EAA).

Refer to Section 5.1.1 Blending of Dissimilar Waters/ Treatment Changes if more than one water source is being considered.

3.2.2 Risk and the Multi-Barrier Approach

The drinking-water system should have, and continuously maintain, multiple barriers appropriate to the level of risk of contamination facing the raw water supply and the drinking-water system. The main categories of barriers are:

  • Source protection;
  • Treatment;
  • Distribution;
  • Monitoring; and
  • Responses to adverse conditions, including emergencies.

In addition, multiple barriers may exist within each category of barrier. For example, the treatment barrier may consist of several treatment processes such as coagulation/flocculation, sedimentation, filtration and chemical disinfection, each providing a barrier.

The types of barriers and risk management measures applicable for each water supply will generally be influenced by characteristics of the source water and the watershed, the hazards and an assessment of the risk.

3.3 Technology development

Implementation of technologies and re-rating of existing facilities require special considerations. For the purpose of this guide, new technology and proven technology means:

3.3.1 New Technology

Any method, process, or equipment proposed to collect, convey, treat or distribute drinking water that is being tested or has been tested at pilot-scale or at full-scale level, but lacks an established performance record.

3.3.2 Proven Technology

A proven technology has an established performance record and means a technology with:

  • A minimum of three separate installations, operated at or near design capacity;
  • A minimum of three years of operating record at three separate locations; and
  • A minimum of three years operating record showing reliable and consistent compliance with the design performance criteria without major failure of either the process or equipment.

The designer should be aware that new technologies may have a higher risk of failure than proven technologies. The degree of risk of failure can be evaluated through review of sequential stages of a new technology development where the risk of failure is reduced with each of the following subsequent steps:

  • Theoretical concept;
  • Development at the laboratory or bench-scale;
  • Experimental stage consisting of pilot-scale program and field application testing;
  • Extensive pilot or full-scale testing; and
  • Established performance record.

Only proven technologies should generally be considered for full scale applications to produce drinking water for consumption.

A new technology that is considered for a site-specific application as an experimental or pilot program should meet the following general requirements:

  • The size of the principal components and duration of the pilot program should be such that physical, chemical, and/or biological processes are accurately simulated;
  • Process variables normally expected in full-scale application have been simulated;
  • All recycle streams have been considered;
  • Variations in influent raw water characteristics substantially affecting performance in full-scale application have been anticipated and simulated;
  • The time of testing has been adequate to ensure process equilibrium and subsequent consistent performance;
  • The service life of high maintenance or replacement items has been accurately estimated;
  • Basic process safety, environmental and health risks have been considered and found to be within reasonable limits;
  • Types and amounts of all required process additives have been determined; and
  • A contingency plan should be in place in case of the new technology failing to meet the expected performance.

Designers considering a full-scale application of any new treatment technology should evaluate the above information and other details of any testing programs which have been undertaken by independent testing agencies necessary to ensure the viability of the proposed treatment and document their findings in the Design Brief (Section 2.4.1 Design Brief/Basis of Design). Specific new technologies are not discussed in this guideline.

3.4 Design flow

3.4.1 General

In general, water treatment plants should be designed on the basis of projected flows for a 20-year period. For large treatment plants, or where construction cost is an overriding factor, a lesser design period may be selected, but the minimum design period should not be less than 10 years. For intakes and/or outfalls, where the cost of the work is not substantially dependent on the size, a design period in excess of 20 years is recommended. Depending on circumstances, including the reliability of projections, a design to satisfy the ultimate requirements of the official plan for the plant service area under consideration may be appropriate. In all cases, the designer should also consider the flows at the start of the operation of the facilities and the potential for impact on unit process efficiency, delivered treated water quality due to stagnation, as well as flow metering difficulties.

The drinking-water system including the water treatment plant and treated water storage should be designed to satisfy the greater of the following demands:

  • Maximum day demand plus fire flow (where fire protection is to be provided); or,
  • Peak hour demand.

The maximum day demand is the average usage on the maximum day. When actual water demand data are available, the designer should review the data and eliminate statistical outliers (e.g., excessive water demands that occurred as a result of a major trunk main break, and erroneous metering or recording) before selecting a value.

The fire flow demand will vary with the size of the municipality (chance of multiple fires at any time) and the nature of development (type of construction materials, building height and area, and density of development). The magnitude of the fire flow allowance is the responsibility of the municipality and the designer should consult with the municipality regarding its fire flow

requirements (Section 8.4 Sizing of Storage Facilities and Section 10.1.2 Fire Protection).

The capacity of the treatment processes should be greater than the highest demand (typically maximum day demand) since allowance is needed for water required for in-plant use and process losses. Depending on the processes in the treatment plant, water may be lost as clarifier blowdown or membrane reject streams and treated water may be used for practices such as filter washing, service water, and chlorine injectors. Allowance is also needed for filter downtime during a wash cycle. The designer should be particularly careful in designing small treatment plants since in-plant water use can be a significant portion of total production.

The designer should consider the capacity of the plant to ensure that it is possible to produce sufficient water to satisfy the most onerous regularly occurring combination of water demand and raw water quality. This may occur in the spring when raw water quality from surface sources is often worse than average and raw water temperatures are low (reaction times are longer and the efficiency of sedimentation tanks and filters is reduced under peak solids loading). The design should be evaluated against the expected water demand at that time of the year. A most onerous condition also may occur at any time as a result of algal blooms. The designer should review the records for such challenging occurrences (Section 3.6 Plant Capacity Rating).

3.4.2 Domestic Water Demands

Domestic water demands vary greatly from one water system to another. Depending upon such factors as the presence of service metering, lawn-watering practices, use of bleeders to prevent freezing, water quality, water conservation programs and leakage (Section 3.5 Water Conservation), daily per capita consumption can vary from less than 180 Litres (48 USgal) to more than 1,500 Litres (396 USgal). For design purposes, existing reliable records should be used wherever possible. Domestic water demand used in design historically has ranged from 270 to 450 L/(cap·d) [70 to 120 USgal/(cap·d)]. With increased use of water metering and increased water conservation, the designer may find values at the low end of this range.

Minimum rate, maximum day and peak rate factors for the system should be based on existing flow data, where available. Table 3.1 provides peaking factors for use with average day demand when actual data are not available or are unreliable.

Table 3-1: Peaking Factors
Population Minimum rate factor (minimum hour) Maximum day factor Peak rate factor (peak hour)
500 - 1000 0.40 2.75 4.13
1001 - 2000 0.45 2.50 3.75
2001 - 3000 0.45 2.25 3.38
3001 - 10000 0.50 2.00 3.00
10001 - 25000 0.60 1.90 2.85
25001 - 50000 0.65 1.80 2.70
50001 - 75000 0.65 1.75 2.62
75001 -150000 0.70 1.65 2.48
greater than 150000 0.80 1.50 2.25

3.4.3 Commercial and Institutional Water Demands

Institutional and commercial flows should be determined by using historical records, where available. Where no records are available, the values in Table 3.2 should be used. For other commercial and tourist-commercial areas, an allowance of 28 m3/(ha·d) [3000 USgal/(acre·d)] average flow should be used in the absence of reliable flow data.

When using the above unit demands, maximum day and peak rate factors should be developed. For establishments in operation for only a portion of the day such as schools and shopping plazas, the water usage should also be factored accordingly. For instance, with schools operating for 8 hours per day, the water use rate would be at an average rate of 70 L/(student·day) [19 USgal/(student·day)] × 24⁄8 or 210 L/student (55 USgal/student) over the 8-hour period of operation. The water use will drop to a residual amount during the remainder of the day. Schools generally do not exhibit large maximum day to average day ratios and a factor of 1.5 will generally cover this variation. For estimation of peak demand rates, an assessment of the water-using fixtures is generally necessary and a fixture-unit approach should be used.

Table 3-2: Typical Water Demands for Selected Commercial and Institutional Users
Commercial and Institutional Use Water Use (Daily Average)
Shopping Centres (based on total floor area) 2500-5000 L/(m2·day) [60-120 USgal/(ft2·day)]
Hospitals 900-1800 L/(bed·day) [240-480 USgal/(bed·day)]
Schools 70-140 L/(student·day) [20-40 USgal/(student·day)]
Travel Trailer Parks (min.with separate hook-ups) 340 L/(space·day) [90 USgal/(space·day)] 800 L/(space·day) [210 USgal/(space·day)]
Campgrounds 225-570 L/(campsite·day) [60-150 USgal/(campsite·day)]
Mobile Home Parks 1000 L/(space·day) [260 USgal/(space·day)]
Motels 150-200 L/(bed-space·day) [40-50 USgal/(bed-space·day)]
Hotels 225 L/(bed-space·day) [60 USgal/(bed-space·day)]

3.4.4 Industrial Water Demands

Industrial water demands are often expressed in terms of water requirements per gross hectare of industrial development when the type of industry is unknown (e.g., new industrial parks). These demands will vary greatly with the type of industry, but common allowances for industrial areas range from 35 m3/(ha·d) [3740 USgal/(acre·d)] for light industry to 55 m3/(ha·d) [5880 USgal/(acre·d)] for heavy industry. These are average daily demands. Peak usage rates will generally be 2 to 4 times the average rate depending on factors such as the type of industry and production schedule.

When the type of industry is known, discussions should be held with representatives of the industry to determine water requirements.

3.4.5 Demand Considerations for Systems Serving Fewer than 500 People

3.4.5.1 Household (Interior) Water Demands & Peaking Factors

As a minimum, the water supply/treatment facility should be designed to meet the projected maximum daily flow requirement of the service area with peak hourly, outdoor use and fire demands met from storage. Where it is possible to develop the source of supply to meet more than the projected maximum daily flow, the storage volume can be reduced accordingly.

Average daily domestic consumption rates can vary from less than 180 L/(cap·d) [48 USgal/(cap·d)] to more than 1,500 L/(cap·d) [396 USgal/(cap·d)]. These values represent the average flow over a 24 hour period and do not reflect the fact that there are maximum day and peak hour/instantaneous demands in the system each day which will exceed the average value by a significant amount. It is essential that the source of supply and the distribution system be capable of meeting these maximum and peak demand rates without overtaxing the source or resulting in excessive pressure loss in the distribution system.

In general, small systems have higher peaking factors for maximum day and peak hour demand than large systems. The minimum rate, maximum day and peak rate factors for the system should be based on existing flow data or data from a similar nearby system where available. Table 3.3 provides peaking factors for use with average day demand when actual data are not available.

Table 3-3: Peaking Factors for Drinking-Water Systems Serving Fewer than 500 People
Dwelling units serviced Equivalent population Night minimum hour factor Maximum day factor Peak hour factor
10 30 0.1 9.5 14.3
50 150 0.1 4.9 7.4
100 300 0.2 3.6 5.4
150 450 0.3 3.0 4.5
167 500 0.4 2.9 4.3
3.4.5.2 Outdoor Water Use

For outdoor water use, it should be assumed that a maximum of 25% of the homeowners could be using an outdoor tap at any one time at a rate of 20 L/min (5.3 USgpm) for one hour per day. Where fire protection is provided, then this outdoor use need not be considered.

3.4.5.3 Fire Protection

The decision as to whether or not fire protection will be provided via the communal water supply system is a municipal responsibility. In deciding upon

the need for such protection, the municipality should consider such factors as the:

  • Availability of adequate supply of water;
  • Additional capital and operating costs associated with such a system;
  • Availability of an adequate fire department, fire service communication and fire safety control facility; and
  • Alternatives to a piped communal fire facility such as residential sprinkler systems.

For small systems, the designer should also consider that provision of fire flow can impact residual chlorine in the distribution system due to the need for increased pipe sizes (Section 10.1.3 Maintaining Water Quality).

More information regarding fire protection via the communal water supply is provided in Section 8.4 Sizing of Storage Facilities and Section 10.1.2 Fire Protection.

3.4.5.4 Campgrounds

The peak water usage rates in campgrounds will vary with the type of facilities provided (e.g., showers, flush toilets, and clothes washers) and the ratio of these facilities to the number of campsites. A peaking factor of 4 times average day is recommended and this factor should be applied to the average expected water usage at full occupancy of the campground.

3.5 Water conservation

Water conservation and efficiency measures to reduce domestic, industrial, commercial and institutional use of water should be considered along with efforts to estimate and reduce distribution system leakage. Simple estimates for excessive leakage in the distribution system can be obtained by measuring the outflow from storage. The best conditions are after rainfall, when irrigation systems would not be operated, and between the hours of 2:00 and 4:00 a.m. when domestic water use would be at a minimum.

Where flow records or estimates for an existing distribution system suggest that unaccounted-for-water exceeds 15% of average daily demand, then, in consultation with the municipality/owner, an average value within the range of 270 to 450 L/(cap·d) [70 to 120 USgal/(cap·d)] should be considered and the cause of the unaccounted-for-water determined and reduced/eliminated as much as is practical. Metering of water service connections has been found to be effective in controlling excessive water demand, and is therefore recommended by the ministry.

The designer is reminded that, when a Permit to Take Water (PTTW) is required, the Water Taking and Transfer Regulation (O.Reg. 387/04) made under Section 34 of the OWRA requires that the application for the permit document all water efficiency measures and practices that have been undertaken or will be undertaken for the duration of the PTTW.

3.6 Plant capacity rating

3.6.1 Design Capacity

In the case of a new municipal treatment system, a conceptual design capacity will be developed through the Municipal Engineers Association MCEA process and will be documented in the Environmental Study Report (ESR). Once the ESR has met the requirements of the MCEA, this conceptual design capacity will form the basis of detailed engineering design resulting in plans and specifications which, in turn, will be used for obtaining a Certificate of Approval (C of A) or a Drinking Water Works Permit (DWWP) and Municipal Drinking Water Licence (Licence)1 from the approving Director at the ministry. This conceptual design capacity documented in the ESR and confirmed as the proposed rated capacity in the final design brief will be specified in the C of A or DWWP-Licence as the rated capacity of the approved treatment system.

In cases where an expansion, alteration or modification is required to an existing treatment system, the proponent will need to determine the applicable Schedule (Schedule A, B or C) of the MCEA that is relevant to the undertaking. One of the factors in making this determination is the "existing rated capacity" of the "existing water treatment plant" referred to in the Schedules included in Appendix 1 of the MCEA document. This "existing rated capacity" is the rated capacity of the treatment system specified in the existing C of A or DWWP-Licence for the system. If a proposed undertaking involving an expansion, alteration or modification results in treated water flows from the treatment system to the drinking water distribution system that would be beyond the rated capacity stated in the existing C of A or DWWP-Licence, the expanded flow requirements must form the basis of further MCEA considerations and subsequent detailed engineering design.

3.6.2 Rated Capacity

The rated capacity of a water treatment plant is the volume of treated water that meets all applicable Ontario drinking water quality regulations including the aesthetic water quality objectives and that may be made available by the water treatment plant for delivery to the drinking water distribution system in any 24 hour period (usually provided as a rate in m3/d). Normally, it should be equal to the projected maximum day water demand of the drinking-water system, which is the maximum volume of water required in any 24 hour period during the design period (usually, the next 20 years). The designer should undertake detailed design to meet these requirements in the context of the issues addressed in these design guidelines. The rated capacity of the treatment system will be confirmed in the review of the design by the ministry as part of the C of A or DWWP-Licence application review process, and will be included in the C of A or DWWP-Licence issued after the review is completed.

The rated capacity of a water treatment plant is essentially the net drinking water production rate (i.e. rate of overall drinking water production minus the sum of all in-plant losses and/or demand). The designer is encouraged to consider the following list when determining in-plant losses and/or demand:

  • Maximum rate at which water may be withdrawn from the source allowed by the PTTW. This value would take into account all water taking required at the plant;
  • Ability of the water treatment plant to consistently produce drinking water meeting all applicable Ontario drinking water regulations as well as aesthetic water quality objectives and other identified site specific treatment needs;
  • "Rated capacity" of a water treatment plant is normally distinct from "firm capacity" (Section 7.3.1 Firm Capacity and Station Capacity) of either low lift or high lift pumping. The high lift pumping rate may exceed the plant rated capacity;
  • Flow(s) into the treatment system and/or trains and/or stages (the gross daily total, gross instantaneous and net instantaneous flow rates for each individual treatment process and the overall plant);
  • Quantity of reject water associated with treatment processes which would not be available for supply to the distribution system;
    • Worst reasonably predictable raw water quality and the periods of time it may occur, and the highest drinking water demand during those periods, considering the:
    • Number of filters out of production for backwash and rest;
    • Volume of water which can be treated through available process trains (e.g. filters and disinfection contact time);
    • Volume of waste water (backwash water, membrane reject water, sludge blow down, chemical make-up water, service water, and any other in-plant treated water uses); and
    • Net flow available for pumping into the distribution system (treated water minus waste water).
  • Available volume of the clearwell/reservoir at the water treatment plant and its ability to balance maximum day demand with the rate of flow (m3/d) into the clearwell; and
  • Rated capacity should be established by assessing potential performance of each process in isolation and in conjunction with the entire process train operating as a system to identify the treatment rate of its slowest unit operation - the rate controlling step.

Notwithstanding the above, there could be circumstances where the treatment system has been designed to accommodate, and the C of A or DWWP-Licence may specify, multiple treatment system rated capacities under specified conditions. For example, the capacity of a conventional or membrane filtration plant could have one rating for summer temperatures and a lower rating for winter temperatures. A chlorine contact process could also be a temperature-based rate controlling step with winter flows limited by the CT which can be achieved under cold water conditions. In such cases of multiple specified capacities, the C of A or DWWP-Licence will also specify which of these should be considered the nominal rated capacity for purposes of the MCEA process.

The rated capacity as established in the final design brief would be based on a combination of treatment processes and their performance, including allowances for downtime and redundancy. The designer should document the proposed capacity of each process along with the engineering and water quality parameters on which this capacity is based.

The water treatment plant rated capacity, as defined in the final design brief and subsequently in the C of A, or DWWP-Licence is a point-in-time value. Improvements to operational knowledge and technology, and changes to source water quality and physical facility condition can impact the rated capacity of the plant.

3.6.3 Hydraulic Capacity

The overall water treatment plant hydraulics should be designed for more than the gross flow rates. The designer should consider the sizes of physical hydraulic restrictions (channels, gates, valves, openings, pipe sizes) and consider increasing their hydraulic capacity by 50% over gross flow rates. Equipment and/or provisions should be included in the design so that in the future if process innovations occur, the design would allow the higher flow rate by implementing low cost modifications to the existing plant.

3.7 Site selection criteria

Municipal water projects are subject to the MCEA and the site selection should be planned according to the requirements of the MCEA, including an evaluation of technical, social, historical/archaeological, natural environment and economic criteria. Whether for municipal or non-municipal facilities, factors which should be considered when selecting a site for new treatment works or the extension of an existing facility include:

  • Adequacy of separation from residential areas or other non-compatible land uses;
  • Optimum location of the plant with regard to the location of the raw water source and the area to be serviced;
  • Susceptibility of the site to flooding;
  • Suitability of subsurface and soil conditions;
  • Adequacy of the site for future expansion;
  • Minimizing adverse environmental impact both during construction and operation of the facility;
  • Avoidance of construction adjacent to a shore line except where unavoidable, since suitable measures would be necessary to prevent erosion, and to protect structures from potential wave action or ice-piling; and
  • Waste disposal considerations.

Information pertaining to water source selection is provided in Chapter 4 Source Development.

3.8 Plant/building layout

The general arrangement within the selected site should take into consideration the suitability of subsurface conditions to provide the necessary facilities at minimum cost. Where possible, the designer should take advantage of natural grades in arranging the various process units. Consideration may be given to the use of inter-stage transfer pumps where they are more economical (capital and operating) than extensive construction in adverse ground such as rock.

In the layout of the plant, the designer should locate the buildings to allow adequate flexibility for the economical expansion of the various treatment sections, as well as plant waste treatment and disposal facilities. Plant layout should consider making best advantage of prevailing wind and weather conditions to minimize energy consumption, for example, locating units which need only moderate temperatures on northern exposures.

Plant design should consider functional aspects of the plant layout, access roads, access to the power grid, site grading, site drainage, walks, driveways and chemical delivery and receiving areas. The plant design should also incorporate spill control features for bulk chemical off-loading areas.

Roadways for chemical deliveries should be designed to be sufficient to accommodate the largest anticipated delivery [typically a 27,000 Litres (7,132 USgal) tank truck], with allowance made for vehicle turning and forward exit from the site. Roadways should be designed for truck traffic in accordance with the Ontario Ministry of Transportation Ontario Provincial Standards for Roads and Public Works (OPS).

The design of the building layout should provide for adequate ventilation, lighting, heating and drainage, dehumidification equipment, accessibility of equipment for operation, servicing and removal, flexibility of operation, and operator safety. The plant layout should also allow for the probability of snow drifting, and entrances and roadways should be located to minimize the effect of snow drifting on operations.

Plant designers should also consider all aspects of plant security and layouts that protect critical areas from vandalism or sabotage.

Within the constraints mentioned above, the designer should prepare a plant layout where the various processing units are arranged in a logical progression to avoid the necessity for major pipelines or conduits to transmit water from one module to the next, and also to arrange the plant layout to provide convenience of operation, accessibility of equipment for servicing and removal, as well as to ensure operator safety. Whenever possible, the process units should be located adjacent to each other to minimize the use of space and materials, and to minimize travel distances for maintenance crews. The plant layout should provide adequate protection for all treated water units. The design should include chemical storage and feed equipment in separate room(s) to reduce hazards and dust problems. Chemical storage should be designed for full spill containment and be separate from process structures to ensure that any spills or structural failures for chemical systems will not impact any process streams.

The designer should review all of the above considerations regarding plant/building layout with both the municipality/owner and certified operator at an early stage of the planning and design.

3.9 Hydraulics

The design of a new water treatment plant should take into consideration the existing and proposed hydraulic grade lines to determine if raw or treated water pumping will be required. The use of gravity flow can often result in lower capital and operating costs, but may restrict the siting of the treatment facility and may not be suitable for use with some treatment processes. Such factors should be carefully considered to determine the best possible hydraulic and siting configuration such that the treated water quality objectives of the facility are fully met (Section 3.6.3 Hydraulic Capacity).

3.10 Electrical components

All electrical work should conform to the requirements of the Canadian Electrical Code (CSA C22.1-06) and to relevant provincial and/or local codes.

Main switch gear electrical controls should be located above grade in areas not subject to flooding. The designer should consider switchgear facility sizing requirements if variable frequency drive (VFD) type equipment is to be employed.

Consideration should be given to providing voltage stabilization in the electrical services to laboratory and/or sensitive process control equipment, since a relatively constant voltage may be required for proper operation.

3.11 Instrumentation & Control

Instrumentation and controls should be provided to allow safe and efficient operation of all parts of the drinking water treatment plant and the associated distribution system (Chapter 9 Instrumentation and Control).

3.12 Standby power

The need for standby power and the extent of equipment requiring operation by standby power should be individually assessed for each water treatment plant and water distribution system. A plan should be developed to ensure that average day demand can be met during a power outage, and that at least an emergency level of lighting and process control operations can be maintained. The plan should take into account the availability of storage capacity in the distribution system (elevated or ground-level storage with standby power).

Some of the factors which should be considered in making the decisions regarding standby power and the process units to be operated by the standby power equipment are as follows:

  • Frequency and length of power outages in the area;
  • Reliability of primary power source (number of power feeder lines supplying grid system, number of alternate routes within the grid system, and number of alternate transformers through which power could be directed to the water treatment plant);
  • Available treated water storage within the system;
  • Type of water storage (underground or elevated);
  • Requirements for fire protection;
  • Type of standby power; and
  • Lower level of emissions provided by alternative fuel technologies.

Depending on the complexity of the plant, standby power may or may not be provided for auxiliary services such as lighting, instrumentation and control. In consultation with the municipality/owner, the designer should consider what critical equipment should be operated from the emergency power system to maintain water quality integrity during a power outage.

The designer should be aware that a sustained loss of water supply that allows reservoirs to empty represents a significant risk to public health. As a distribution system dewaters due to continuous water demand, negative or atmospheric pressures are induced, starting at the higher elevations. This creates the potential for uncontrolled backflow, e.g., garden hoses connected to open faucets and an environment in which any exfiltration from a leaky distribution system becomes infiltration, drawing in untreated groundwater.

This is even more acute for direct-pressure systems (i.e., systems without on-line storage).

In designing generator systems, the designer should consider the efficient operation of the engines and whether the plant is staffed at all times or is unattended. Timers should be provided to bring equipment on-line in such a way that the generators are not overloaded by the starting current requirements of motors. Similar protection is necessary to avoid overload of the normal electrical supply on resumption of power following a power failure.

The standby power equipment should be located so that it fits conveniently into the electrical distribution system of the plant. Under some circumstances, it may be preferable to locate the generator set remote from the treatment plant in a separate building to satisfy air and noise requirements under the Environmental Protection Act (EPA). Self-contained generator sets that can be pad mounted externally may also be considered.

Engine cooling water may not be returned to any process units. Where cooling water is discharged to a storm sewer system, the designer should ensure that the storm sewer system has adequate capacity, or an alternate diversion of cooling water will be required.

Generator units should be mounted on a pad and surrounded by a containment system to retain any fuel spills. Generator units or fuel storage should not be located above any water treatment process unit or raw or treated water reservoir to avoid any chance of contamination. A clear space for inspection and servicing not less than m (3 ft) on all sides of the unit should be provided.

Internal combustion engines used to drive auxiliary pumps, service pumps through special drives, or electrical generating equipment should be located above grade with adequate ventilation of fuel vapours and exhaust gases. Carbon monoxide detectors are recommended where fuel-fired generators are housed.

The designer should refer to the applicable Technical Standards and Safety Authority (TSSA) standards for requirements associated with the safe storage, handling and use of hydrocarbon fuels (such as gasoline, diesel, propane and natural gas).

3.12.1 Diesel Fuel Storage

Sufficient fuel storage should be provided, taking into account the historical data on length of power outages in the area, and any weather or other conditions which might prevent deliveries of fuel. A minimum 500 L (132 USgal) storage should be provided for generator set capacities up to 25 kW and 1,000 L (264 USgal) storage for generator set capacities from 30 to 100 kW.

Either underground or inside fuel storage tanks may be used. Factors such as corrosion potential, leakage and spill protection, storage volume needed and need for fuel pumps should be evaluated. Fuel storage tanks should not be located above any water reservoir or clearwell. The design of fuel storage tanks and supply lines must conform to all applicable federal and provincial legislation and regulations.

3.13 Emissions of contaminants to air

For all sources of emission of contaminants to the air from drinking-water facilities (e.g., gases from air striping processes, exhaust emissions and noise of diesel generators, and noise of air blowers or compressors) the requirements of Section 9 of the Environmental Protection Act (EPA) need to be satisfied.

The Air Pollution - Local Air Quality regulation (O.Reg. 419/05), under the EPA, specifies the maximum allowable concentration of specific air contaminants at the point of impingement. Compliance is achieved by maintaining the point of impingement concentrations of the contaminants discharged from the source of emission below the maximum concentrations stipulated in the regulation. Typical points of impingement are the property line and all critical receptors, such as building air intakes or windows.

3.14 Personnel facilities

The personnel facilities needed will be largely dictated by the number and gender of operating staff required and the time periods during which the plant is staffed. As a minimum, it is recommended that provisions be made for storage lockers, preferably two for each employee (one for work clothes, one for clean clothes), and change rooms/washrooms with showers. Water efficient fixtures should be used. A lunch room of adequate size to serve as a meeting or training room for plant staff and a suitable office for plant supervisory staff and record keeping should be provided. Whenever possible, these personnel facilities should be separated from the plant facilities, but with convenient access to the plant.

Drinking water service to most buildings should be provided. Refer to Section 3.20.4 Backflow Prevention/ Cross-Connection Control in this chapter for information regarding backflow prevention.

The provision of drinking water and sanitary facilities for operators may lead to a significant increase in cost for small remote plants. In communities where such facilities may be available elsewhere, the designer should consult with the municipality/owner to determine whether such facilities are required.

3.15 Building services

All building services should conform to the applicable codes.

Adequate and safe heating systems with controls should be provided. In many areas of the plant, sufficient heat need only be provided to prevent freezing of equipment or treatment processes. Buildings should be well ventilated by means of windows, doors, roof ventilators or other means. All rooms, compartments, pits and other enclosures below grade which must be entered should have adequate forced ventilation provided when it is necessary to enter them. Rooms and galleries containing equipment or piping should be adequately heated, ventilated, and dehumidified to prevent excessive condensation. Switches should be provided for convenient control of the forced ventilation.

Buildings should be adequately lighted throughout by means of natural light and artificial lighting. Control switches should be conveniently placed at each entrance to each room or area. Emergency lighting should be provided.

Communications systems should be provided including connections between buildings.

Power outlets of suitable voltage should be provided at convenient spacing through plant buildings to provide power for purposes such as maintenance equipment and extension lighting. Power outlets located on the outside of buildings may be advantageous. Ground fault interrupter (GFI) type outlets are desirable throughout (where appropriate). Outlets supplied by uninterruptible power supply (UPS) or emergency power systems should be located such that they are easily accessible during a power outage.

Adequate shop space and storage for the designed facilities should be provided. A bridge crane, monorail, lifting hooks, hoist or other adequate facilities should be provided for servicing or removing heavy and/or large equipment.

3.16 Sampling & Monitoring equipment

Regulatory monitoring requirements are described in the Drinking-Water Systems regulation (O.Reg. 170/03) under the Safe Drinking Water Act, 2002, as well as the Disinfection Procedure. Smooth-nosed sampling tap(s) should be provided for collection of water samples for both bacteriological and chemical analyses. The sample tap(s) should be easily accessible and located in an area that can be maintained in a sanitary condition. Sample withdrawal lines should be located to provide samples that are representative of the composition of the whole process stream at that point. Sample lines should be stainless steel from the sampling point to the sampling tap. Provisions for back-flushing or cleaning should be made available. The basic sampling locations in a water treatment plant are: raw water prior to any chemical addition; effluent from specific process unit(s); residuals streams; treated water to be delivered to the distribution system. In certain instances, it may be necessary to provide "intermediate" sampling points in a process unit.

On-line process monitoring is discussed in Section 9.4 Monitoring. Additional equipment to monitor the process is described in the following section.

3.17 Laboratory facilities

Each drinking-water system should have its own equipment and sufficient facilities for routine laboratory testing necessary to ensure proper operation and process control of the system. Laboratory equipment selection should be based on the characteristics of the raw water source and the complexity of the treatment processes involved. Laboratory test kits which simplify procedures for one or more tests may be acceptable. Methods for verifying adequate quality assurances and for routine calibration of equipment should be provided. A certified operator or water quality analyst qualified to perform the necessary laboratory tests is essential; tests which may be performed by a certified operator or water quality analyst are controlled by the Drinking-Water Testing Services Regulation (O.Reg. 248/03) under the Safe Drinking Water Act, 2002.

Analyses conducted to determine compliance with drinking water regulations must be performed in a drinking water testing laboratory that is licensed under Part VIII of SDWA for classes of parameters indicated.

Sample lines may be used to convey a continuous sample stream to the laboratory from the various stages of the treatment process, for example, raw water, settled water, filtered water and treated water, but not flocculated water. These sample lines should run continuously to provide representative samples and be kept as short as possible. In more remote systems a continuous flow can represent a significant wastewater issue. Where continuous flows are required or are being considered, the designer should also consider carefully how the wastewater will be disposed.

Smooth-nosed sampling tap(s) should be provided. Stainless steel sample lines from the sampling point to the tap are recommended.

3.17.1 Testing Equipment

As a minimum, the following laboratory equipment should be provided:

  • Water treatment plants that chlorinate must have test equipment for determining free and total residual chlorine (O.Reg. 170/03);
  • All water treatment plants should have a bench or portable nephelometric turbidimeter;
  • Each water treatment plant using coagulation, including those which lime soften, should have a pH meter, titration equipment for both hardness and alkalinity, jar test equipment to aid in establishing the optimum coagulant dosage for changing water conditions and test equipment for measuring residual aluminum or iron (depending on the coagulant used);
  • Each ion-exchange softening plant and lime softening plant treating only groundwater should have a pH meter and titration equipment for both hardness and alkalinity;
  • Each iron and/or manganese removal plant should have test equipment capable of accurately measuring iron to a minimum of 0.01 mg/L, and/or test equipment capable of accurately measuring manganese to a minimum of 0.005 mg/L;
  • Water supplies which fluoridate should have test equipment for determining fluoride;
  • Water supplies which feed poly and/or orthophosphates should have test equipment capable of accurately measuring phosphates from 0.1 to 5 mg/L;
  • Where the process treatment involves reduction of raw water colour, equipment should be provided to determine both true and apparent colour in the raw water and treated water quality ranges; and
  • Where UV treatment is used, ready access to a UV meter capable of measuring transmission of 254 nm wavelength light through a path length of 1 cm (0.4 in) of water to an accuracy within +/-2% should be provided.

Sufficient glassware and general reagents should be provided to conduct all the required analyses, as well as appropriate cleaning agents. Sample and reagent storage and refrigeration should also be provided.

3.17.2 Physical Facilities

Sufficient bench space, adequate ventilation, adequate lighting, storage room, laboratory sink, and auxiliary facilities should be provided. Air conditioning may be necessary. The minimum linear bench space should be 3 m (10 ft), including a wash-up sink. Where space is available, or the size of the laboratory permits, the space should be divided into "dry" and "wet" areas so that sensitive equipment is not subjected to undesirable conditions. At larger treatment plants, the designer should consider providing pilot-scale facilities, with sufficient flexibility to alter coagulation, flocculation, filtration and other process operations, to assist in determining optimum plant operating conditions. If a pilot plant is not currently being considered, space for future addition should be provided.

3.18 Flow metering

All drinking-water systems should have flow measuring devices to measure the flow from each source (well or surface water intake) and conveyed to and through the water treatment plant, the flow of any blended water of different quality and the flow of treated water supplied to the distribution system. In addition, flow through unit processes, backwash flow, chemical and gas flows should be metered for monitoring and controlling the treatment process (Section 9.4 Monitoring).

The designer should consider the importance of meter accuracy, specifically as it relates to compliance with Approval/DWWP-Licence conditions.

In addition, design considerations for flow measuring equipment include:

  • Parts in contact with drinking water should be easy to clean and disinfect (Section 3.26 Chemicals and Other Water Contacting Materials);
  • Parts in contact with fluids should be suitable for the conditions, including aggressive chemicals or solids that can cause abrasion;
  • Instruments should be compatible with the environment in which they are located (e.g., high humidity, temperature, outdoors, and electromagnetic interference);
  • Instruments should be located so that they provide accurate and reliable data (e.g., straight pipe requirements upstream and downstream) according to the manufacturer specifications;
  • Convenient access to the instrument for maintenance and calibration should be provided. Isolation should be provided so that an instrument can be removed and serviced or replaced. A bypass, pipe spool piece or standby unit should be provided if servicing or calibration will disrupt production;
  • Instruments should include a local display;
  • Instruments should be selected to provide reliable data over the entire range required; the turndown of the instrument should be considered in instrument selection. The accuracy and precision required for the process should also be considered (cost generally increases as accuracy increases); and
  • Lifecycle cost, including maintenance and calibration requirements and hydraulic head loss (pumping costs), should be considered.

The main process flows are usually measured using mass flowmeters, magnetic, ultrasonic or differential pressure (e.g., venturi) flowmeters. Where low head loss is required, magnetic or ultrasonic meters are preferred. Rotameters are suitable for small flows of liquids and gases. Table 3.4 provides some characteristics of commonly-used flowmeters.

3.19 Facility drinking water supply

The facility drinking water supply service line should be supplied from a source of treated water at a point downstream of all treatment process units and disinfectant contact time. There should be no cross-connections between the facility drinking water supply service line and any piping, troughs, tanks or other treatment units containing wastewater, treatment chemicals, or raw or partially treated water.

3.20 In-plant piping

3.20.1 General

All piping used in water treatment plants should be manufactured in accordance with AWWA or CSA standards. Material selection will depend upon economic and corrosion rate factors, as well as the type of equipment used and connections required. The designer should be aware of the greater potential for deflection in thin wall pipe systems than in other systems. Refer to Section 3.26 Chemicals and Other Water Contacting Materials for more information on materials contacting drinking water.

In the design of the piping, allowance should be made for future capacities and also the ease of extending the piping without major disturbance to the plant. In the general piping arrangement, sufficient space should be provided for piping to be removed, and the pipe design should provide for the proper isolation through valves and pipe sections to allow for repair or replacement. The designer should allow for the possibility that piping could be installed during construction when temperature conditions could be substantially different from the design condition [for example, piping could be installed in temperatures anywhere between 40°C and -20°C (104 °F and -4 °F) and substantial differences in pipe dimensions could occur]. For this reason, the use of polyvinyl chloride (PVC) pipe with cast iron mechanical joint fittings should be avoided. Where piping is cast-in-place, allowance should be made for differential expansion between pipe material and structures. Pipe appurtenances should be of similar materials; otherwise, dielectric couplings should be employed to reduce galvanic corrosion.

Table 3-4: Commonly Used Flowmeter Characteristics
Design parameter Magnetic Ultrasonic Venturi tube Rotameter
Typical uses Main process flows or small flows Main process flows or small flows Main process flows Small flows of liquids and gases
Flow range Up to very large Up to very large No theoretical upper limit Up to 920 m3/h (4050 USgpm) for liquids; Up to 2210 m3/h (1300 scfm) for gases
Straight Pipe Requirements (Confirm with manufacturer) 3-5 diameters upstream, 2 -3 diameters downstream 10-20 diameters upstream, 5 diameters downstream upstream depends on type of upstream fitting and ratio of throat diameter to inlet diameter; 4 diameters downstream Meter specific; must be installed in vertical position
Accuracy ~ ± 1% (±0.5% at velocities >1m/s) ~ ± 1% ±1% to ±2% with a transmitter ±1% to ±3%

Piping should be arranged so that all valves, flow meters, and other items which may require regular inspection or maintenance are conveniently accessible. Piping should be provided with drains at all low points and air-release valves at all high points. Sludge piping should be provided with clean-outs and flushing facilities.

The design of the piping should allow for proper restraint under all anticipated conditions, particularly where surges may occur and high transient pressures could result or where different temperatures occur seasonally. Supply pressure should be considered and pressure reducing valves employed, where necessary. Plastic or PVC type pipe should be fitted with a shrapnel guard on its entire length if the system is to be operated pneumatically. Plastic or other pipe materials that may shatter on impact should be suitably guarded or protected from physical impact, especially for essential and/or hazardous systems.

Where piping connections are made between adjacent structures, at least one flexible coupling should be provided if any possibility of settlement exists. Particular attention should be given to pipe bedding in areas adjacent to structures to avoid damage due to settlement.

3.20.2 Pipe Sizing

Process water piping should normally be designed for flow velocities as listed in Tables 3.5 and 3.6 with a recommended minimum size of 100 mm (4 in).

Table 3-5: Maximum Velocity Limited by Process Consideration
Process Maximum velocity (m/s)
Flocculated Water 0.60 (2 ft/s)
Pre-settled Water 0.60 (2 ft/s)
Post-settled Water 0.30 (1 ft/s)
Filter Influent 0.20 (0.7 ft/s)
Table 3-6: Maximum Velocity Limited by Hydraulic Considerations
Process Maximum velocity (m/s)
Raw Water (pumped) 3.0 (10 ft/s)
Filter Effluent 2.0 (6.6 ft/s)
Wash Supply 3.0 (10 ft/s)
Wash Drains 2.5 (8.2 ft/s)
Treated Water (pumped) 3.0 (10 ft/s)

3.20.3 Piping Identification Requirements

The Industrial Establishments regulation (R.R.O. 1990, Regulation 851) under the Occupational Health and Safety Act (OHSA), makes piping identification, as to contents and flow direction, mandatory for piping systems containing hazardous substances. Identification should comply with the requirements of Canadian General Standards Board (CGSB) standard CAN/CGSB 24.3-92 Identification of Piping Systems2 to simplify operation and maintenance procedures and improve safety. Under this standard, pipes are identified by background, legend, and pictogram colour.

The background and legend, and pictogram colours and code numbers used to identify materials contained in a piping system are provided in Tables 3-7 and 3-8. The code numbers are from CGSB 1-GP-12c Standard Paint Colours, Part 1 Colour Identification and Selection. Piping may be identified by paint, decals, plastic bands, or polyethylene or detectable ribbon.

Table 3-7: Piping Identification Background and Legend Colour
Contents classification Background colour Background colour: CGSB Equivalent* Legend colour Legend colour: CGSB Equivalent*
Hazardous Yellow 505-101 Black 512-101
Inherently Low Hazard Green 503-107 White 513-101
Fire protection Red 509-102 White 513-101

* Colour numbers are those in CGSB standard 1-GP-12

Where there is no previously existing standard colour code, it is suggested that the guidelines in Tables 3.9, 3.10 and 3.11 be used. Where alternative chemicals are used, it is suggested that a coherent code be developed which consistently identifies the degree of hazard associated with the material contained in the pipe.

3.20.4 Backflow Prevention/ Cross-Connection Control

Within a water treatment plant, considerable potential exists for cross-connections between drinking and non-drinking waters. Typical examples are drinking water supplies for chemical solution make-up, cooling water supplies to mechanical equipment, seal water supplies to pumps and filter surface-wash piping. While pump seal water supplies need only be of better sanitary quality than the water pumped, it is frequently more convenient to use the treated water system to provide seal water. For information on cross-connection control, refer to the AWWA Manual of Water Supply Practices M14 Recommended Practice for Backflow Prevention and Cross-Connection Control and USEPA Cross-Connection Control Manual, 2003.

Table 3-8: Piping Identification Pictogram Colour
Contents classification Colour 1 CGSB Equivalent*   Colour 2 CGSB Equivalent*
Hazardous 1 Black 512-101 On Yellow 505-101
Hazardous 2 Black 512-101 On White 513-101
Inherently Low Hazard n/a n/a n/a n/a n/a
Fire protection 1 White 513-101 On Red 509-102
Fire protection 2 White 513-101 On Black 512-101

* Colour numbers are those in CGSB standard 1-GP-12

Table 3-9: Process Piping Colour Codes
Contents Colour
Raw Water Dark Blue
Settled Water Mid Blue
Finished Water Light Blue
Backwash Waste Mid Brown
Settled Backwash Light Brown
Sludge Dark Brown
Drainage Light Grey
Sanitary Waste Black

There are several types of backflow prevention devices available including air gaps, double check valve assemblies, reduced pressure principle devices, dual check valves, atmospheric vacuum breakers and pressure vacuum breakers.

Table 3-10: Chemical Piping Colour Codes
Material Primary colour Secondary colour
Aluminum Sulphate Light Green -
Ferric Chloride Light Green Orange
Silicate Compounds Light Green White
Polyelectrolytes Light Green Grey
Chlorine Gas* Yellow -
Sodium/Calcium Hypochlorite Solution Yellow White/Red
Chlorine Dioxide Solution Yellow Orange
Lime White Orange
Sodium Carbonate White Grey
Sodium Bicarbonate White Yellow
Carbon Dioxide* White -
Alkali Hydroxide White Red
Sulphuric Acid Orange Red
Sulphur Dioxide* Orange -
Ozone* Brown -
Potassium Permanganate Purple -
Fluoride Chemicals Purple Red
Ammonia* Bright Blue -
Flammable Gas Red -

* All gas solution lines to have light blue secondary.

For applications involving health hazards, only air gaps or reduced pressure principle devices should be used.

For information on backflow prevention equipment, refer to:

  • Applicable municipal by-laws;
Table 3-11: Colour Code Numbers for Process and Chemical Piping
Colour CGSB equivalent*
Grey 501-103
Light-Grey 501-108
Dark-Blue 502-103
Bight-Blue 502-104
Light-Blue 502-106
Mid-Blue 502-208
Light-Green 503-323
Dark-Brown 504-102
Brown 504-105
Mid-Brown 504-107
Yellow 505-101
Light-Brown 505-206
Orange 508-102
Red 509-102
Purple 511-101
Black 512-101
White 513-101

* Colour numbers are those in CGSB standard 1-GP-12

  • Part 7 of Division B of the Building Code (O.Reg. 350/06) under the Building Code Act 1992;
  • CAN/CSA-B64 SERIES-01 Backflow Preventers and Vacuum Breakers, CAN/CSA-B64.10-01/B64.10.1-01 Manual for the Selection and Installation of Backflow Prevention Devices/Manual for the Maintenance and Field Testing of Backflow Prevention Devices, and CAN/CSA-B64.10S1-04/B64.10.1S1-Supplement #1 to CAN/CSA-B64.10-01/CAN/CSA-B64.10.1-01;
  • AWWA Standard C510: Double Check Valve Backflow Prevention Assembly and AWWA Standard C511: Reduced-Pressure Principle Backflow Prevention Assembly; and
  • AWWA Manual of Water Supply Practices M14 Recommended Practice for Backflow Prevention and Cross-Connection Control.

3.21 Disinfection after construction or repairs

All wells, pipes, tanks and equipment which can convey or store drinking water should be disinfected in accordance with AWWA Standard C650-series (Disinfection of Facilities) before being placed into operation after construction, maintenance or repairs as required by the Procedure for Disinfection of Drinking Water in Ontario (Disinfection Procedure). Plans or specifications should outline the procedure and include the disinfectant dosage, contact time and method of testing the efficacy of the procedure.

3.22 Manuals & Training

3.22.1 Operations Manual

An operations manual should be supplied to the water works as an essential part of the design. The operations manual should include detailed descriptions and explanations of the treatment process and operational strategies for meeting the requirements of O.Reg. 170/03 and the Disinfection Procedure. All standard operating procedures developed for the plant should be included in the operations manual. The manual should be provided in standard electronic form and cover the following topics:

  • A plant overview and process control philosophy statement;
  • Detailed unit operations and chemical dosing for normal operation and emergency situations;
  • Simplified system schematics that take into account the spatial relationships involved;
  • Storage and transmission descriptions and operational procedures;
  • Descriptions and operational procedures for facility utilities (HVAC, plant service water, security);
  • General safety information, including provisions to keep up-to-date Material Safety Data Sheets (MSDS) as set out under the federal Hazardous Products Act and associated Controlled Products Regulations;
  • Spill containment and emergency procedures;
  • Emergency power systems and electrical system operation;
  • Security of infrastructure, treated water, electronic files and/or programs and response procedures to breaches or intrusions;
  • Applicable regulations;
  • Monitoring, reporting and documentation procedures;
  • Disinfection procedures for bringing equipment on-line after maintenance;
  • Reliability and redundancy analysis of system components;
  • Detailed routine maintenance procedures;
  • Alarm notifications and response procedures;
  • A list of emergency contacts and locations of contingency plans; and
  • A list of major equipment suppliers.

3.22.2 Equipment Manuals

Equipment manuals including parts lists and parts order forms, operator safety procedures and an operational troubleshooting section should be supplied to the municipality/owner as part of any proprietary unit installed in the facility.

3.22.3 Training

Provisions should be made for operator instruction at the start-up of any new facility, equipment or process, with full documentation.

3.23 Safety

Consideration must be given to the safety of water plant personnel and visitors. The designer should refer to all applicable safety codes and regulations, including the Occupational Health and Safety Act (OSHA), Building Code (O.Reg. 350/06) under the Building Code Act, 1992 and Fire Code (O.Reg. 388/97) under the Fire Protection and Prevention Act, 1997. Items to be considered include noise arresters, noise protection, confined space entry, protective equipment and clothing, ergonomics, gas masks, safety showers and eye washes, handrails and guards, ladders, warning signs, smoke detectors, toxic gas detectors and fire extinguishers.

Equipment and chemical suppliers should also be contacted regarding particular hazards of their products and the appropriate steps taken in the facility design to ensure safe operation.

3.24 Security

Design measures to ensure the security of the drinking-water system should be incorporated, installed and instituted. Such measures, as a minimum, should include means to lock all exterior doorways, windows, gates and other entrances to source, treatment and water storage facilities. Other measures may include fencing, signage, closed-circuit monitoring, real-time water quality monitoring and intrusion alarms.

3.25 Flood protection

Other than surface water intakes, all water supply facilities and water treatment plant access roads should be protected to at least the 100 year flood elevation or maximum flood of record.

3.26 Chemicals & other water contacting materials

All chemical additives and water contacting materials used in the construction and operation of drinking-water systems should meet all applicable quality standards set by AWWA and, in addition, the consumer safety standards NSF/ANSI3 Standard 60: Drinking Water Treatment Chemicals - Health Effects and NSF/ANSI Standard 61: Drinking Water System Components - Health Effects. For uncertified water contacting materials that have been in common and traditional use, such as cement mortar lining or water pipe meeting AWWA specifications, the NSF/ANSI safety certification may not be necessary.

The designer should be aware of the standard condition imposed on Approvals/DWWP-Licences for municipal residential drinking-water systems making the above recommendation a requirement for such systems with the following exceptions:

  • Water pipe and pipe fittings meeting AWWA specifications made from ductile iron, cast iron, PVC, fibre and/or steel wire reinforced cement pipe or high density polyethylene (HDPE);
  • Articles made of stainless steel, glass, HDPE or Teflon®;
  • Cement mortar for watermain lining and for water contacting surfaces of concrete structures made from washed aggregates and Portland cement;
  • Food grade oil and lubricants; and
  • Any other material or chemical where the municipality/owner has written documentation signed by the Director that indicates that the ministry is satisfied that the chemical or material is acceptable for use within the drinking-water system and that the chemical or material is only used as permitted by the documentation.

3.27 Water treatment plant residuals & sanitary waste

The nature and treatability of the waste residuals to be produced as a result of the treatment processes should be adequately characterized. Waste characterization, in addition to the ultimate disposal requirements, should be given a high degree of consideration in the planning and selection of water treatment processes. Methods of reducing process residual volumes should be considered (Chapter 11 Residuals Management).

All sanitary wastes from water treatment plants, pumping stations, and other water works should be discharged to a sanitary sewer system, a subsurface sewage disposal system or to a sewage treatment facility providing suitable treatment. Sanitary wastes should be kept separate from all process residuals to avoid the need for treatment of all plant residuals in the same manner as sanitary wastes.

3.28 Energy conservation

Typically, the highest energy expenditures in water treatment plants result from high lift pumping. Minimizing energy consumption, while recognizing the need to maintain acceptable water quality, should be included in the design of the distribution system immediately served by the high lift pumps and the selection of the high lift pumping units.

Lighting and HVAC systems consume a significant proportion of the total energy used in a water treatment plant; consideration should therefore be given to energy efficient alternatives or systems. The designer should carefully examine work environment items such as heating, lighting, ventilation, and air conditioning, both in the design and operation stages to ensure that heating and lighting levels are matched to job requirements without safety hazards. Time-delayed switches on lights should be provided in those parts of the plant rarely used, and heating requirements should be reduced not only by adequate insulation in exterior walls, but also by separating areas which need different temperature levels; for example, providing walls between filter operating galleries and filters.

Many organizations and government departments at the municipal, provincial and federal level provide information and guidance with respect to energy conservation. The implementation of water conservation measures, and the resulting decrease in water demand, will also decrease energy usage.

3.29 Reliability & Redundancy

The design of water treatment plants should be based on the premise that failure of any single component must not prevent the drinking-water system from satisfying all applicable regulatory requirements and other site specific treated water quality and quantity criteria, while operating at design flows.

A water treatment plant that is designed with a limited number of treatment barriers, and/or has less treatment contact time than conventional processes, must have a commensurate level of reliability and redundancy of its components.

The designer should consider the following for designing and documenting the reliability of the proposed drinking-water system:

  • Regulatory requirements and other site specific treated water quality and quantity criteria during the full range of design flows;
  • Likelihood of the system having reduced levels of treatment/performance;
  • Risk to the performance of the system and in turn to the environment, public health and safety if the level of treatment and performance of system components is reduced;
  • Local conditions and constraints, such as accessibility of the site, reliability and redundancy of the power supply, etc.;
  • Manner and methods by which reliability is provided so that reduced treatment or performance and bypasses can be eliminated; and
  • Individual process unit/equipment reliability and redundancy analysis to define the following:
    • Critical process unit/equipment;
    • Critical event;
    • Estimated event duration;
    • Actions/safeguards; and
    • Effect on treated water quality and/or quantity.

This reliability and redundancy analysis may be provided using Table 3.12 as an example.

Table 3-12: Reliability Analysis of Water Treatment Plant Components
Elements Example events Event duration Frequency Action/ safeguard Effect on treated water
Pumps Pump failure 7 days 1 in 5 years Firm capacity standby pump off-peak hours storage None
Chemical System Components failure Seconds 1 per year Alarm, analyzer auto switch; backup system spares Minimal
Chemical System Pump failure 6 hours 1 in 3 years Auto switch; backup system spares Minimal
Conventional Filters Backwash 30 minutes Daily Storage at least 3 units None
Conventional Filters Break through Minutes Seasonal Alarm, turbidity meters on each filter Yes
Membrane Filters Integrity failure Minutes 1 in 3 years Alarm, particle counter, firm capacity; standby cleaning, storage, lower flux Yes
Membrane Filters Automatic controls Seconds 1 in 3 years Alarm, particle counter, firm capacity; standby cleaning, storage, lower flux Yes
Membrane Filters Clogging Minutes 1 in 3 years Alarm, particle counter, firm capacity; standby cleaning, storage, lower flux Yes
Membrane Filters Temperature changes Season Seasonal Alarm, particle counter, firm capacity; standby cleaning, storage, lower flux None, low water demand
Power Power outage 24 hours 1 in 5 years Alternate grid None
Power Equipment failure 24 hours 1 in 3 years Generator None

3.30 Operability

Drinking-water systems should be designed to ensure ease and reliability of operation and to facilitate maintenance over the life of the facility.

3.31 Constructability

The design of the drinking-water system should allow for the following factors:

  • Practicality/ease of construction;
  • A phased approach;
  • Maintaining operations during construction; and
  • Planning for future additions/expansion.

3.32 Climatic factors

The designer should consider potential variations in water levels, water temperatures, depth of frost, number of frost free days, depth and duration of snow cover, frequency and size of storm events, as well as other climatic factors associated with climate change.

Chapter 4: Source development

This chapter addresses the selection and development of surface and groundwater sources, including water quality and minimum treatment requirements. It also provides guidance on the design of intake structures and wells.

4.1 General

In selecting the source of water for a drinking-water system, the designing engineer should ensure that an adequate quantity of water will be available, and that the treated water to be delivered to the consumers is in accordance with the requirements of the Ontario Drinking-Water Quality Standards regulation (O.Reg. 169/03) and the Drinking-Water Systems regulation (O.Reg. 170/03), under the Safe Drinking Water Act, 2002, as well as the Procedure for Disinfection of Drinking Water in Ontario (Disinfection Procedure) adopted by O.Reg. 170/03 through reference. The treated water should also be aesthetically acceptable and pleasant to drink.

The control of certain unregulated water quality parameters such as taste, odour and colour, should result in drinking water which is clear, colourless and free of objectionable or unpleasant taste or odour. Other aspects of water quality such as corrosiveness, a tendency to form incrustations and excessive soap consumption should be controlled on the basis of economic considerations because of their effects on the distribution system and/or the intended domestic and industrial use of the water. For the assessment of aesthetic water quality objectives and treatment needs, the designer is referred to the ministry document Technical Support Document for Ontario Drinking Water Standards, Objectives and Guidelines (Technical Support Document).

Each water supply should take its raw water from the best available source which is technically possible and economically reasonable to treat to the above standards and objectives.

4.1.1 Source Water Protection

A source water protection plan enacted for protection of groundwater or surface water from potential contamination should be provided as determined by the Clean Water Act, 2006 (CWA).

4.2 Surface water

Surface water, in this document, refers to water bodies (lakes, wetlands and ponds, including dug-outs), water courses (rivers, streams, water-filled drainage ditches), infiltration trenches and areas of seasonal wetlands. Many of these locations described as surface water would be unsuitable as a source water supply but are included in the description for full consideration by the designer as these surface water sources may impact the quality of ground water (e.g., GUDI).

4.2.1 Quality

A survey and study should be made of the factors, both natural and human, which may affect water quality. Such survey and study should include, but not be limited to the following elements:

  • Determining the degree of control of the watershed area by the municipality/owner;
  • Assessing the degree of hazard to the water supply source by agricultural, industrial, recreational and residential activities in the watershed, and by accidental spillage of materials that may be toxic, harmful or detrimental to the treated water quality;
  • Identifying and assessing all waste discharges (point source and non-point source) and activities that could impact the water supply source. The location of each waste discharge should be shown on a general plan;
  • Obtaining samples over a sufficient period of time to assess variability in the microbiological, physical, chemical and, when applicable, UV transmissivity and radiological characteristics of the water; and
  • Consideration of currents, wind and ice conditions, and the impact of other contributing water sources.

4.2.2 Minimum Treatment

As required by O.Reg. 170/03, drinking-water systems that obtain water from a source which is surface water must have a treatment process that is capable of producing water of equal or better quality than a combination of well operated, chemically assisted filtration and disinfection processes would provide. This treatment process must achieve an overall performance that provides, in accordance with the Disinfection Procedure, a minimum of 2-log (99%) removal and/or inactivation of Cryptosporidium oocysts, 3-log (99.9%) removal and/or inactivation of Giardia cysts and 4-log (99.99%) removal and/or inactivation of viruses before the water is delivered to the first consumer.

Higher log removal or inactivation may be needed for a raw water supply where there is a presence of sewage effluent or other sources of microbial contamination, such as runoff from livestock operation, and manure storage, handling or spreading.

The determination of any additional log removal or inactivation required may also be based upon pathogen monitoring of the raw water. For monitoring details, the designer is referred to the United States Environmental Protection Agency (USEPA) guidance manuals Long Term 1 Enhanced Surface Water Treatment Rule and Long Term 2 Enhanced Surface Water Treatment Rule.

Where necessary, additional treatment should be provided to ensure that the finished water meets the health based standards described in O.Reg. 169/03, and to satisfy aesthetic water quality objectives in accordance with the Technical Support Document.

4.2.3 Intake Location

The design objective in locating the intake should be to provide adequate quantities and a high and consistent quality of raw water, as confirmed by samples taken over four seasons at the location and depth of the proposed intake.

All available water quality information should be examined and the designer should take particular note of both present and future planned outfalls from sewage treatment plants and industrial installations, as well as any inshore pollution, especially during high run-off conditions. Data on current flows and directions should be reviewed, as well as potentially infrequent occurrences such as thermoclines or falling plume dispersions, to determine an intake location that would provide the highest quality water.

Zebra mussels and other molluscs may impact intakes and should be assessed at the proposed location in the water source.

The final intake location will be affected by bottom contours, subsoils and available water depths. The submerged depth will also depend on the type of shipping, if any, which frequents the general location. The designer is referred to the Navigable Waters Protection Act for guidance. The minimum submergence from top of intake structure to minimum recorded water level should be m (10 ft) wherever possible.

4.2.4 Intake Structures

Because of the difficulty and high cost of marine construction, it is suggested that intake size be sufficient for the projected plant requirement for an extended design period. This will often result in only a single size difference in the intake when compared to a 20-year design period. The hydraulic design for the intake for its final capacity should assume a Hazen-Williams coefficient, C, of 100.

The intake design and its anchoring should take into account peak wave height and frequency, and provide adequate protection against ice scouring and dragging anchors.

The designer should obtain historical information on water depths at the proposed location and determine whether or not the source level is controlled and also whether historical minima occurred before or after control measures were implemented.

The designer should consider the potential occurrence of frazil ice on intakes when determining crib design and inlet velocities. Intake crib materials should be of low thermal conductivity, with racks of smooth materials. The design should provide for low entry velocities below 75 mm/s (3 in/s) and uniform acceleration of water from inlet to intake pipe.

Entrance ports to intakes should be located to prevent sediments from being picked up. Both top entry and side entry designs are acceptable and may be evaluated on the basis that:

  • Side entry designs are less likely to be damaged by anchors; and
  • Top entry designs provide greater clearance above the river or lake bottom, and the required inlet area can be more readily attained.

All designs should be checked for transient pressure problems, particularly if the intake pipe is long or has high design velocities.

For small intakes, consideration should be given to providing means for back-flushing the intake, if practical.

The designer should consider the need for duplicate intakes, particularly where:

  • Damage to an intake may occur by objects such as anchors and nets;
  • A second intake provides redundancy in the event of changes in water quality caused by thermoclines; and
  • Ambient water quality prevents the use of chlorine for mussel control. Where deemed necessary, provisions should be made in the intake structure to control the influx of mussels or other aquatic nuisances (Section 4.2.5 Mussel Control).

Under certain circumstances, an intake may not be necessary and a forebay may be constructed. The designer should ensure that sufficient depth of water will exist in the forebay under any source conditions, and that the bay can remain relatively clear of ice.

The design of river intakes differs substantially from that for lakes in that a substantial current may exist and both anchoring and bottom scouring considerations will assume greater significance. Where possible, river intakes should ideally be located well upstream of known point sources of pollution.

The design of intake structures should also provide for:

  • Withdrawal of water from more than one level if quality varies with depth and during seasonal events;
  • Inspection manholes for pipe sizes large enough to permit visual inspection and/or diver entry for larger intakes; and
  • Occasional cleaning of the inlet line.

A diversion device capable of keeping large quantities of fish or debris from entering the intake structure should be provided.

When buried surface water collectors are used, sufficient intake opening area should be provided to minimize inlet headloss. Particular attention should be given to the selection of backfill material in relation to the collector pipe slot size and gradation of the native material over the collector system.

Refer to Section 7.4.1 Raw Water Pumping and Section 7.5.1 Raw Water Pumping (for systems serving fewer than 500 people) for more information regarding the design of raw water pumping stations. Where the intake or well is remote from the treatment plant, refer to Section 9.6 Automated/Unattended Operation for information regarding the design of instrumentation and control systems for remote operation.

4.2.5 Mussel Control

Mussels have the potential to obstruct public water supply intakes and cause loss of intake capacity, as well as contribute to taste and odour problems. Water suppliers should periodically assess the condition of their intakes to determine if mussels are or potentially may be present and implement a system of control.

The most accepted and currently recommended forms of chemical treatment for public water supplies are the use of oxidants such as chlorine, chlorine dioxide, potassium permanganate and ozone. Chemical dosages are typically applied at the intake through solution piping and a diffuser to prevent the formation of mussel colonies within the intake and piping. The type of chemical selected and frequency of application will depend on the type of existing chemical treatment facilities, mussel breeding season, potential for trihalomethane (THM) formation, other pre-treatment objectives such as taste and odour control, safety and economy.

In addition to the chemical methods described above, intake screens manufactured with special alloys that prevent the growth of zebra mussels on the intake itself are also available.

The following items should be addressed in the design of a mussel control system:

  • Solution piping and diffusers should be positively anchored. Piping should have appropriate valving and should be installed within the intake pipe or in a suitable carrier pipe;
  • A spare solution line should be provided for redundancy;
  • Chemical feeders should be interlocked with plant system controls to shut down automatically when raw water flows stop;
  • Provisions should be included for obtaining raw water samples not influenced by chemical treatment;
  • Means to provide adequate flushing; and
  • The designer may wish to consider the provision of a suitable alternate intake, as periodic alternating use/zero flow conditions has been demonstrated to control mussel infestation, where economical.

4.2.6 Impoundments & Reservoirs

Although uncommon in the Province of Ontario, the implementation of source water protection legislation may create a need for impoundments or reservoirs for a number of drinking-water systems.

The designer should be aware that changes in water quality may occur in impoundments and/or reservoirs, and the intake(s) should be designed accordingly.

Impoundments and reservoirs should be adequately secured through the use of fencing, signage and/or patrolling, if necessary.

4.3 Groundwater

4.3.1 General

While other sections of these guidelines apply equally to surface water sources and groundwater sources, there are a number of special considerations which relate to groundwater systems that should be reviewed by the designer.

For the purpose of defining minimum treatment of groundwater, a raw water supply which is groundwater means water located in subsurface aquifer(s) where the geological materials (sediments) act as an effective filter that removes micro-organisms and other particles by straining and natural attenuation of potential pathogens, to a level where the water supply may already be potable but disinfection is required as an additional health risk barrier.

Groundwater under direct influence of surface water(GUDI) means groundwater having incomplete or undependable subsurface filtration of surface water and infiltrating precipitation. The designer should refer to O.Reg. 170/03 under which some groundwater supplies are deemed to be groundwater under the direct influence of surface water systems, unless a report prepared by a professional hydrogeologist proves otherwise.

4.3.2 Hydrogeological Studies (GUDI or Groundwater Sources)

Prior to the design of a supply structure, adequate geological, hydrological and water quality studies on the aquifer should be carried out to assess the suitability of the source and confirm that the proposed groundwater supply is not a groundwater under the direct influence of surface water. The report should be prepared by or under the direction of a qualified hydrogeologist.

In particular, the studies should address such factors as establishing the wells' perennial yields, maximum short-term yields (i.e., over 1 day, 7 days or 90 days) and recommended pump sizing based on a hydrogeologist’s rating of the long term yields of the wells. This report should also deal with possible interference with other existing wells in the area and the potential for contamination by surface water. Where there is concern about contamination, an assessment should be completed based on the ministry document Terms of Reference for Hydrogeological Study to Examine Groundwater Sources Potentially Under Direct Influence of Surface Water (PIBS 4167e).

4.3.3 Minimum Treatment

The minimum treatment for groundwater (that is not GUDI) is disinfection. This treatment process must achieve an overall performance that provides, in accordance with the Disinfection Procedure, a minimum of 2-log (99%) removal and/or inactivation of viruses before the water is delivered to the first consumer.

Where necessary, additional treatment should be provided to ensure that the finished water meets the health based standards described in O.Reg. 169/03 and to satisfy aesthetic water quality objectives in accordance with Technical Support Document for Ontario Drinking Water Standards, Objectives and Guidelines (Technical Support Document) .

4.3.4 Wellhead Protection

The designer should prepare a wellhead protection plan for continued protection of the water supply from potential sources of contamination, such as mechanical protection or run-off diversion, in accordance with the requirements of the ministry document Protocol for Delineation of Wellhead Protection Areas for Municipal Groundwater Supply Wells under Direct Influence of Surface Water (PIBS 4168e).

4.4 Groundwater under the direct influence of surface water

4.4.1 Minimum Treatment

In accordance with O.Reg. 170/03, drinking-water systems that obtain water from a raw water supply which is GUDI should have a treatment process that is capable of producing water of equal or better quality than a combination of well operated, chemically assisted filtration and disinfection processes would provide. This treatment process must achieve an overall performance that provides, in accordance with the Disinfection Procedure, a minimum of 2-log (99%) removal and/or inactivation of Cryptosporidium oocysts, 3-log (99.9%) removal and/or inactivation of Giardia cysts and 4-log (99.99%) removal and/or inactivation of viruses before the water is delivered to the first consumer.

Where necessary, additional treatment should be provided to ensure that the finished water meets the health based standards described in O.Reg. 169/03, and to satisfy aesthetic water quality objectives in accordance with the Technical Support Document.

4.4.1.1 Bank Filtration (Shore Wells)

Bank filtration is best suited to systems that are located adjacent to rivers with reasonably good surface water quality and that plan to use bank filtration as one component of their treatment process. For certain systems, bank filtration can be an efficient, cost-effective pre-treatment option to improve water quality or control the extent of sudden changes in raw water temperature and quality after a storm event; however, only certain sub-surface conditions provide improved quality.

The designer should consider the type of bed and aquifer material present, the dynamics of groundwater flow, and the potential for scouring of riverbed materials at any potential bank filtration site. The degree to which any particular contaminant will be removed via bank filtration depends on site-specific conditions and may vary over time. A similar raw water characterization as for surface water may apply.

4.4.2 GUDI with In-Situ Filtration

When a hydrologeologist report prepared in accordance with the ministry document Terms of Reference for Hydrogeological Study to Examine Groundwater Sources Potentially Under Direct Influence of Surface Water (PIBS 4167e) concludes, and the Director agrees, that adequate in-situ filtration is provided by the geological materials (sediments), and adequate wellhead protection measures are being provided, the required minimum treatment may be achieved, without chemically-assisted filtration, through disinfection alone.

The disinfection process or combination of disinfection processes should be capable of providing the required inactivation of oocysts, cysts, and viruses. To achieve the overall performance specified above, the designer may use a combination of both ultraviolet disinfection and chemical disinfection.

The development and implementation of microbial contamination control plans, subject to approval by the ministry, is required for residential drinking-water systems using GUDI with effective in situ filtration where the municipality chooses not to provide chemically assisted filtration, or equivalent treatment, ahead of disinfection. The designer is referred to the ministry document Development of Microbial Contamination Control Plans for Municipal Groundwater Supply Wells under Direct Influence of Surface Water with Effective in situ Filtration4 (PIBS 4008e) for more detailed information.

4.5 Wells

4.5.1 Wells Design

The design objectives for a well should be to provide a hydraulically efficient and structurally sound well that will produce the required water quantity on a continuous basis, and which is protected from external contamination.

For specific details of yield and drawdown tests in addition to design and construction criteria, the designer should refer to the Wells Regulation (R.R.O. 1990, Regulation. 903 as amended) under Ontario Water Resources Act and AWWA Standard A100: Water Wells.

The scope of the hydrogeological study undertaken to determine the aquifer and well yields should take into account the requirements of the Permit to Take Water (PTTW) program under Section 34 of the OWRA.

4.5.2 Well Pumphouse Design

In general, the design criteria for well pumping stations follow those presented for raw and treated water pumping stations. In addition, the following special considerations apply to wells. The use of well pits to house pumping equipment is discouraged because of the maintenance and safety problems associated with this type of construction.

For lineshaft pumps, a pedestal should be provided around the casing to support the full weight of the pump and to prevent any weight from being placed on the working casing or any associated well casing. Submersible pumps may be supported by the casing.

Where wells are completed in flowing artesian conditions, piezometric control of the aquifer is required. This may be achieved by installing a suitably sized, valved discharge-to-waste line to convey water from the inner well casing to outside the building. Flow to waste is discouraged, where possible.

A watertight seal should be provided between the pump base plate or submersible discharge head and the pump pedestal or between the well casing and the pump discharge column to prevent the entrance of contaminants.

An aperture for air venting must be provided to the inner well casing. Where there are indications of excessive quantities of explosive or toxic gases in the water, the pumphouse should be vented to the outside.

For wells housed within a pumphouse, the well should be located within 1.2 m (4 ft) of an exterior wall of the pumphouse and centred under a hatchway in the roof, at least one metre square, to facilitate access by crane.

The piping layout in the pumphouse should include an in-line free discharge pipe to the outside of the building to permit future testing of the well. The end of the pipe should be equipped with a free discharge pipe orifice and manometer tap, calibrated to the design yield of the well. If high static water levels exist, the designer should consider the use of a by-pass to waste from the pump to avoid transient high discharge pressures on start-up.

A combination flow controller, with pressure gauges upstream and downstream, a suitable check valve and an indicating flow meter should be installed in advance of the free discharge pipe.

A suitable sampling point should be provided upstream of chemical addition for monitoring well water quality. Water level monitoring equipment should be provided by including at least one opening in the well head, typically 25 mm (1 in) diameter, which allows vertical access to the inner casing for equipment installations.

Wells equipped with line shaft pumps should have the casing firmly connected to the pump structure or have the casing inserted into a recess extending at least 10 mm (0.4 in) into the pump base. The pump foundation and base should be designed to prevent water from coming into contact with the joint. Oil lubricants, if necessary, should be food grade.

Where a submersible pump is used, the top of the casing should be effectively sealed against the entrance of water under all conditions of vibration or movement of conductors or cables. The electrical cable should be firmly attached to the riser pipe at 6 m (20 ft) intervals or less.

The discharge piping should be designed so that the friction loss will be low, and have control valves and appurtenances located above the pumphouse floor when an above-ground discharge is provided. Piping should be protected against the entrance of contamination. Discharge piping should be equipped with a check valve in or at the well, a shutoff valve, a pressure gauge, a means of measuring flow, and a smooth nosed sampling tap located at a point where positive pressure is maintained.

Where applicable, the discharge piping should be equipped with an air release-vacuum relief valve located upstream from the check valve. An air gap of at least 150 mm (6 in) or two pipe diameters, whichever is greater, should be provided between the exhaust/relief piping and the flood rim.

Appropriate valving should be provided to permit test pumping and control of each well.

All exposed piping, valves and appurtenances should be protected against physical damage and freezing.

Piping should be properly anchored to prevent movement and be protected against transient pressure.

The discharge piping should be provided with a means of pumping to waste or discharge to irrigation through an air gap backflow preventer. The provision of facilities for regular, short duration discharges to waste on pump starts can have a highly beneficial effect on distribution system maintenance requirements where iron, manganese or sediment are present.

4.5.3 Decommissioning Wells

Unless used for monitoring, all test holes, wells or partially completed wells should be properly abandoned or decommissioned in accordance with the requirements of Wells Regulation (R.R.O. 1990, Regulation 903 as amended) under the Ontario Water Resources Act.

1 With the implementation of the Licensing Program, a Certificate of Approval will be replaced by the combination of a Drinking Water Works Permit (DWWP) for the establishment or alteration of the system and a Municipal Drinking Water Licence (Licence) to authorize the use and operation of the system.

2 The CAN/CGSB 24.3-92 document is not up-to-date and this matter is currently under review.

3 In Ontario, certification of conformance to NSF/ANSI standards may be provided by one of the agencies approved for this purpose by the Standards Council of Canada.

4 Development of Microbial Contamination Control Plans for Municipal Groundwater Supply Wells under Direct Influence of Surface Water with Effective in situ Filtration(PIBS 4008e) comprises two documents, Reference