Department of Community and Government Services (CGS), Government of Nunavut (GN)
retained exp Services Inc. (exp) to prepare the detailed design for the new water treatment
facility and an expansion of the community raw water storage. The scope of the exp
assignment includes preparation of the schematic design, design development, preparation of
detailed construction drawings and preparation of construction documents such as
specifications.
Early in this design assignment, representatives of CGS and exp met with the Hamlet Council.
Several issues were raised by members of Council.
• Safe manoeuvring of trucks at the truck-fill facility was viewed to be an important
safety concern, both for water truck drivers and community members.
• Appropriate arrangements at the truck loading arm to minimize spilled water and the
resulting ice accumulation was considered important.
• Measures to minimize the impacts of snow-drifting were viewed to be important.
The water treatment plant facility will include two pump houses, the reconditioned pump house
which will supply water from the existing reservoirs #1 and #2, and a new pump house
supplying water from the new reservoir. The facility will also include a treated water storage
tank to provide chlorine contact time for disinfection and process wastewater storage tank to
collect waste water from the treatment process (backwashing of the filters). The wastewater
storage tank will require to be emptied by the Hamlet’s sewer trucks. The water treatment
plant will have a dual truck fill arm for simultaneous filling of water trucks. The fill rate for the
water trucks will result in the trucks being filled in approximately 13 minutes
The water treatment processes that have been incorporated into the design include the
following.
• Self Cleaning Strainers
This step will remove large colloidal contaminants such as dust and larger debris
(grass, sand and weed growth). This step makes the next stage (pressure media
filters) last longer and be protected from large items that may be picked up by the
pumps.
• Pressure media filtration
This is the main filtering stage that filters down to 5 microns in size. This is not
absolute but gets most of the particles down to 5 microns in size.
• Cartridge filtration downstream of the media filters.
The first set of filters is to remove particles down to 5 microns in size. If the pressure
media filters are working appropriately this filter will see very small amounts of
particles and will not need to be changed more than a couple of times a year. This is
also the location where the use of carbon filters for taste can be installed if an event
occurs.
The second set of cartridge filters is for particles down to 1 micron in size. With the
previous filters working properly these filters will see very little amount of dirt and
should last for extended periods of time. The use of 1 micron filtration is for the
removal of crypto and giardia oocysts that can be between 1-5 microns in size.
The pumps have been sized to handle a variety of duty points and can change the
pump speed automatically. With pumps speeds set to achieve a flow rate, as the
filters will begin to plug, the pumps will work harder to force the same amount of water
to go through them. This should eliminate the effects of partially plugged filters on the
treatment process and maximize the filter usage.
• Ultraviolet disinfection
This type of disinfection “deactivates” pathogens. It is only present when the water is
passing thru the filter. It does not kill them, but it makes them unable to reproduce,
and therefore much less harmful.
• Chlorination
This type of disinfection “kills” pathogens. The chlorine will stay in the water for an
extended period of time. This is measured as chlorine residual. With chlorine
residual in the water, should a contamination event occur (ie dirt in the home storage
tank) the chlorine will be present to kill any pathogens that enter in.
In addition to this, chorine is an chemical oxidizer. It causes dissolved metals (iron
and manganese typically) to come out of the dissolved state and get caught in filter
media. This improves the look and taste of water.
• Treated water storage.
This provides the time for chlorine to react and kill pathogens. Additionally, it allows
the truck filling operation to be separate from the treatment process, ensuring fill rates
and allowing multiple trucks to be filled simultaneously.
Water storage tank will provide the contact time for the chlorine, thereby eliminating
the wait period after trucks are filled.
• Flocculation – Space for this process will be provided to allow for its inclusion if
required in the future, but the plant will be commissioned without flocculation.
Flocculation is the addition of chemical to water that cause particles to “come
together”. This takes very small particles (smaller than 1 micron and larger ones too)
and combines them into larger particles that can be filtered out. If water quality can
be achieved without this step, then the water treatment plant is much easier to
operate. If the use of chlorine on the pre-filter side does not work to achieve the
desired output, then liquid flocculant can be used.
The flocculation process is not being included at this time for operational reasons.
This is a liquid chemical that is delivered in barrels or totes and has a finite shelf
life. Additional backwashing and therefore wastewater trucking will result with
additional loading on the pressure filters. It is thought this is addition complexity that
may not be required. Allowance has been included for this at a later date if required.
• Fluoridation
It is expected fluoridation will be continued as a batch addition process at the time of
reservoir filling as per existing operations.
Fluoride addition is common in many water distribution systems and is considered to
be a method to improve dental health of the water consumers.
The project includes expansion of the raw water storage capabilities to meet the projected
needs of the community until the year 2038. The new water reservoir will have a capacity of
103,000 m3 for a total storage capacity of 262,000 m3. Drawing C103 provides a site plan for
the new reservoir. This drawing illustrates the location of this new reservoir with respect to the
existing reservoir cells and the proposed building. It is proposed that the new reservoir cell be
constructed in a fashion that is very similar to the adjacent existing storage cell.
The Site Grading Plan, drawing number C201, illustrates the proposed locations of the water
treatment plant, treated water storage and process wastewater storage. This drawing
illustrates the proposed truck access route. It is proposed that a truck turn-around be
provided west of the new building. This permits direct access for water trucks to the truck
loading arm with a minimum of conflict with traffic travelling to the community.
The details regarding the truck loading arm and measures to reduce spilled water are
currently being designed. These details will be provided in the next drawing submission to
CGS.
In response to concerns relating to snow-drifting, Novus Environmental, a specialist consultant
was engaged to examine this matter. Based upon the advice of this consultant, the proposed
building will be situated above grade, resting upon a piled foundation. This will permit wind
scour of snow and will also reduce the amount of snow deposition between the truck lane and
the building.
In summary, the project is advancing as anticipated. The concept of treatment, followed by
treated water storage and a pair of truck loading arms has been carried forward into the
design. The proposed water treatment process is similar to that proposed in the feasibility
study. Project completion is currently anticipated by late 2018.