Sorrento’s water has frequently been turbid in the Spring run off, notably in the 2017 and 2018 freshets which deposited large amounts of sediment into the lake via Newsome Creek.
At the Community meeting, January 22 , 2019 Terry Langlois, Team Leader of Utilities at the CSRD, shared the following information.
Sorrento draws its water from the Markwart Intake located 520 metres off shore at a depth of 23 metres, and the pipe is about 10 inches in diameter (300mm). At 23 metres deep the lake water is cooler and more stable, therefore it’s cleaner and better suited for the intake and pumping equipment. In this part of Shuswap Lake there is a current moving west to east, which has been confirmed in a study by Larratt Aqatic Consulting done in 2015; Source Assessment of the Sorrento Shuswap Lake Drinking Water Intake. It’s this current that pulls silt from the mouth of Newsome Creek 550 metres to the intake. While this may seem like a long way from shore, water results in the Spring freshet have indicated an undeniable correlation between outflows from the Newsome Creek and turbidity in Sorrento’s water supply.
FYI: CSRD measures turbidity on a scale of 0 to 10 using an instrument called a nephelometer which uses a detector set up to the side of a light beam. If there are lots of particles in the water the light will bounce off the particles and the sensor will detect the scattered light beams. Fewer particles will trigger lower readings. The units of turbidity from a calibrated nephelometer are called Nephelometric Turbidity Units (NTU). More info on turbidity and NTUs.
Normally Sorrento’s water reads 0.2 NTU, and it’s not uncommon to rise to 0.8 in a freshet. A Water Quality Advisory is posted at 1, and a Boil Water Advisory is posted at 5. In the freshets of 2017 and 2018 the readings were 10, and they would have been significantly higher but the nephelometer only goes to 10.
In 2017 and 2018 Sorrento had Boil Water Advisories that lasted four to six weeks, which is highly irregular. Most Boil Water Advisories in the Shuswap are one, maybe two weeks.
In a follow up conversation with Mr. Langlois he added that turbidity makes it difficult to treat water because the turbidity can act like a curtain around harmful bacteria. Sorrento’s water is treated first by ultra violet rays, then by chlorination. The UV rays kill off bacteria in the water, but too much silt shields the bacteria from the rays.
(As a side note, this system of UV rays first, then chlorine, allows for a much lower concentration of chlorine to be used after the UV rays have done their job.)
Boil Water Advisories
The following Boil Water Advisories were issued the Columbia Shuswap Regional District in 2017 and 2018;
Boil Water Notice – Sorrento Water System
Tuesday, May 1, 2018High Turbidity levels have been detected in the Sorrento Water System’s drinking water supply. High turbidity (cloudiness) levels may occur in surface water sources due to seasonal weather changes causing excessive surface runoff, flooding or lake turnover. A high turbidity level may impair the effectiveness of the disinfection treatment system. If disinfection is impaired, disease-causing micro-organisms may escape into the water distribution system, resulting in an increase risk of intestinal illness…
Boil Water Advisory – Sorrento Water System
Sunday, May 7, 2017
12:00 PMHigh Turbidity levels have been detected in the Sorrento Water System’s drinking water supply. High turbidity (cloudiness) levels may occur in surface water sources due to seasonal weather changes causing excessive surface runoff, flooding or lake turnover. A high turbidity level may impair the effectiveness of the disinfection treatment system. If disinfection is impaired, disease-causing micro-organisms may escape into the water distribution system, resulting in an increase risk of intestinal illness…
The 2017 Boil Water Advisory lasted approximately six weeks (rescinded Tuesday, June 13, 2017) and occurred at the same time the culvert at Highway 1 crossing clogged. A report done by Kerr Wood Leidal in May 2017 states;
It appears a large block of material on the left bank (looking downstream), immediately downstream of the Highway 1 culvert outlet, fell into the channel, most likely the result of toe erosion due to high flow in Newsome Creek. The material appears to have temporarily dammed the creek, backing up the water and subsequently releasing, causing a flood wave to propagate down the channel. The destabilization includes channel migration fully contained within the ravine, significant erosion, bank sloughing, and vegetation loss.
For more information see; Site Observations on page 2 of the KWL Report.
It is clear that the undersized culverts along Newsome Creek are contributing to contamination of our water supply. These culverts are not able to handle the water coming off the watershed. They get clogged and cause water surges. They bottle neck the water which accelerates the speed of the creek, which increases erosion and turbidity.
Are You Effected?
Click the map to view a PDF of the Sorrento Waterworks Service Area.
