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Water Boil Order

What happened during the Water Boil  Order in Lethbridge?

 

The City of Lethbridge Water System


 

The City of Lethbridge consists of one treatment plant, located in the river valley, across the river from the University.

Treated water is pumped from the plant to reservoirs, then to water customers via underground pipes.

 

 

There are two water reservoirs in each of the south, north and west

 

 

 

 

System Capacity - Information


    The diagram below displays three things:
  1. The Water Treatment Plant (WTP) has the capacity to create 150 ML/D of potable water. The plant typically produces 50 ML/D for all users.
  2. 32 ML of stored water is reserved for fire suppression and safety.
  3. The reservoirs also hold a fluctuating amount of potable water for distribution (60 ML).
  4.  

ML - million litres

ML/D - million litres per day

**click on the picture to enlarge. This diagram will be used to describe the production, storage, and demand for water throughout the week of the water boil order.
 
 

Three components are needed to understand the Water Boil Order in March, 2014:

  • Production
  • Storage
  • Demand

 

Actual Daily Production:

  • Summer = 120ML/D
  • Winter= 45ML/D

Total storage capacity of the storage reservoirs is about 92 ML. The water storage allows for large swings in demand for water at different times.

The demand for water is the total amount of water being used by all water customers at any time and this constantly changes throughout the day.

 

What Happened Each Day During the Water Boil Order?


 

Friday, March 7, 2014

The week prior to the water boil order was typical for production, storage, and demand.

This is what a typical winter day looks like - on average 75ML in the reservoirs with a production of 50 ML/D to meet the demand.

 

 

What was happening in an environmental aspect the week prior to the water boil order (what lead up to this event)?

 

 

The above diagram is the Oldman Watershed.

     
  • During the weeks leading up to the event, there were a number of freeze-thaw cycles
  • Some days were colder than seasonal, with more snow fall.
  • The first week of March saw day-time high temperatures of -12C to -24C, and night-time lows of -17C to -32C
  • West of Lethbridge, in the foothills, they received over 5cm of snow that week, and Lethbridge received less than 1cm of snow fall.
  • Areas upstream of Lethbridge that naturally drain into the Oldman River were snow covered, but the ground was frozen solid.
  • The temperatures jumped from -12C to +13C on Sunday.
  • This caused rapid melting and because the ground was solid ice, the water could not soak into the ground. The water flowed over the solid ground, carrying debris and waste from on land.
  • This affected the Oldman River's water quality.
  • The turbidity (dirt and silt) increased, making the water cloudy, with sharp increases in:
    • Natural Organic Matter (NOM)
    • Ammonia
    • Colour
    •  

Sunday, March 9, 2014

 

River conditions changed, and adjustments to the process were made.

 

As NOM and ammonia increased and chemical processes struggled, it was hard for the plant to keep up with the demand for water, accompanied by the warm weather.

 

Monday, March 10, 2014

 

River conditions changed drastically by 7pm, the plant was unable to produce water to the quality standard required by the Provincial and Federal regulations.

 

The high lift pumps from the plant to the reservoirs were stopped and the unfit treated water was sent to the river, while operators tackled the issues.

  • The general manager was notified and went to the plant to provide technical assistance.
  • Consumption continued, and storage levels continued to drop.
  • Plant staff worked throughout the night.
     

Tuesday, March 11, 2014

Early Tuesday morning, the plant still was not producing clean water and storage levels were approaching the “fire level”. Progress on the water quality front was slow. 

 

 

 

  • The Director of Infrastructure and the City Manager were informed of the situation
  • The Fire Chief was asked to alert the water plant of any responses to fire to ensure that high volume water use would be supported. 
  • The regional water communities were informed of the situation.
  • A voluntary request to the community to conserve water was issued that morning to buy time and hopefully avert a boil order. 

 

The water treatment process improved through the day and production was restored and water pumping resumed at 5:30 pm and continued through the night.  River conditions were also improving hour to hour.

 

Wednesday, March 12, 2014

Progress at the treatment plant was made through the night, though water conservation results were negligible.  

Unfortunately, an unexpected rapid change in the river water quality at about 3:00 am resulted in yet another treatment plant upset.

Depleted water storage levels were dipping into the water reserved for fire protection. Once again, pumping ceased at 9:20 am

With the uncertainty of how long it would be before production of potable water would start again, the Fire Chief in consultation with the City Manager activated the Emergency Operation Centre (EOC) at 10:35am. 

Briefed on the situation the Mayor declared a State of Local Emergency.

This allowed for the enforced closure of:

  • industry
  • carwashes
  • laundry mats
  • pools
  • rinks

The regional water communities were all notified and asked to impose similar conservation measures.

By 2:00 pm, the City was down to only 8 hours worth of potable water in storage and faced the prospect of having to pump partially treated water from the plant sometime late that evening. 

 

In consultation with the Mayor and City officials, Alberta Health Services issued a Boil Water Order at 4:00 pm.  Fortunately, no contaminated water had to be pumped into the distribution system as conditions at the treatment plant improved and pumping from the plant resumed at a slow rate by 5:30 pm.

 

Thursday, March 13, 2014

 

 
Plant water production steadily increased through Thursday.  Thanks to community conservation efforts storage levels also slowly increased. 

 

**Though the water in the system at no time was unsafe to drink, the situation remained uncertain hour to hour**

 

A large fire in Lethbridge or in one of the regional communities could have resulted in contaminated water entering the system.

Friday, March 14, 2014

The river conditions and treatment process performance improved through the night and early Friday morning. 

By 12:00 noon the rate of production and storage levels were high enough for the City to lift the conservation measures and Alberta Health Services to lift the boil water order

Because the contamination of the water distribution system was averted, the systems within Lethbridge, Coaldale, Coalhurst, and Picture Butte did not have to be flushed prior to safe water consumption.  Some rural co-op systems were isolated to avoid the potential of contamination. However, this resulted in no water pressure for a time and those systems had to be flushed in the end.

Sunday, March 16, 2014

By Sunday, the levels in the storage reservoirs were fully restored and the plant production had to be reduced to match the community demand for water. 

** Taste and odour of the water was poor as elevated amounts of chlorine added to the water combined with the NOM and ammonia entering the treatment plant. 

These conditions improved through the following week and returned to normal.

 

More Information:

 

Water Boil Order FAQ

Water Conservation FAQ