District of 100 Mile House operations director Phil Strain and Dave Underwood of TRUE Consulting presented the draft report of the Efficient Use of Clean Water Project to council on March 25.
The project study has been in the works since Feb. 5, 2013 when the District received a $265,000 grant from its Gas Tax application. In June, TRUE Consulting of Kamloops was hired to provide the study.
The study has two purposes: develop a reliable, long-term water supply strategy for District residents and businesses; and review and update the District’s water conservation plan.
The latter purpose was discussed briefly during this presentation because there is a plan in place that needs updating and review, and the key in this portion of the study was determining a long-term clean water supply.
However, Strain noted the conservation plan and its implementation is very important in terms of being successful in the search for grants.
In February, the District relied on the Bridge Creek water, with slow sand filtration, ultraviolet light and sodium hypochlorite treatment, as the primary source, and Well #4 by the Red Coach Inn, with hypochlorite treatment only, as the backup supply in times of high usage (summer or when the Bridge Creek Water Treatment Plant [WTP] needed to be shut down for maintenance).
Currently, the District is running a blend of the two water sources, as per instruction of Interior Health until a backup well is “in sight” because there is less chance of getting disinfection byproducts, which is when chlorine reacts with the organics. If the disinfection byproducts elevate too high, they could go outside the Canada Drinking Water Standards, Strain said, adding the District is well below the level, and it is blending 17 litres per second (L/s) from both the creek and the well.
Water sources
TRUE studied the existing water sources:
• Bridge Creek WTP has a design capacity of 42 L/s, with an actual maximum capacity of 33 L/s and an average capacity achieved of 27-29 L/s.
• Well #4 had an original yield of 53.7 L/s in 2003, but the current yield is 30-35 L/s. The District has budgeted $75,000 for well rehabilitation, which is expected to increase the available yield close to 2003 levels.
Water demand
The current water demand for the District is 15 L/s on an average day, but it jumps to 35 L/s on maximum day demand.
The existing WTP cannot sustain the District’s existing maximum day demands, Strain noted.
Water quality/quantity concerns
• Bridge Creek has reliability issues, including turbidity and potential drought, as was the case in the 1990s – resulting in the drilling of Well #4. It also has elevated total organic carbon (TOC) because the creek winds through ranches and “everything else,” Strain said, adding the surface water requires a high level of treatment.
• Well #4, which almost 600 feet deep, has elevated manganese that has led to a blackish “precipitate” in the drinking water.
Previously, it was assumed Well #4 was “Groundwater under Direct Influence of surface water” due to elevated TOC, but recent tests showed there are ancient organics between volcanic layers where the well is drilled.
Tests show these organics don’t participate with chlorine, Strain says, adding that means the District doesn’t have to use additional treatment other than to take the manganese and iron out of the ground water.
Water source options
The study also looked at possible water source options for the District, but ranked groundwater only (Well #4) and a blend of Well #4 and Bridge Creek blend, which would require a new supply main and upgrades to the existing WTP, as the top 2 choices due to cost effectiveness.
Other options included Bridge Creek stand alone – reliability issues; Horse Lake stand alone – supply main costs prohibitive; Well #4/Horse Lake blend – supply line costs; and other ground water – disregarded due to Well #4 capacity.
