TO: Mayor and City Council
THROUGH: Keith Stahley, ICMA-CM, City Manager
FROM: Brian D. Martin, PE, Public Works Director
SUBJECT:
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Update on City of Salem’s Cyanotoxin Preparedness and Results of Drinking Water Treatment Processes during the 2024 Algal Toxin Season.
Ward(s): All Wards
Councilor(s): All Councilors
Neighborhood(s): All Neighborhoods
Result Area(s): Safe, Reliable and Efficient Infrastructure.
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SUMMARY:
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Water is the most valuable natural resource in the world today, and the City of Salem is fortunate to have an extremely high-quality, reliable, and abundant source. The Geren Island Water Treatment Facility continues to safeguard Salem’s drinking water from cyanotoxins (microcystin and cylindrospermopsin) produced by cyanobacteria in the North Santiam River Watershed. Due to multiple investments in water treatment technologies including upgraded slow sand filters, ozone treatment, and chlorination/dechlorination processes, Salem’s drinking water remains high quality for all water customers.
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ISSUE:
In the summer of 2024, the North Santiam Watershed experienced elevated levels of microcystin, a toxic chemical produced by naturally occurring cyanobacteria in Detroit Reservoir and the North Santiam River that feed the City’s drinking water system. Since 2018, the City has invested over $80 million in new infrastructure to protect the City’s drinking water supply. The results of these investments have proven successful in reducing the microcystin toxin to levels that are not detectable in our treated drinking water.
RECOMMENDATION:
recommendation
Information only.
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FACTS AND FINDINGS:
• Since 2018, the City has planned for a robust response to a potential cyanotoxin event in our drinking water source.
• The Public Works Department has completed several large-scale infrastructure improvement projects to treat cyanotoxins and provide resiliency including:
o Construction of the Ozone Treatment Facility at the Geren Island Water Treatment Facility
o Improvements to Slow Sand Filters at the Geren Island Water Treatment Facility
o Construction of the Southeast Collector Well
o Installation of two in-house Enzyme-Linked Immunosorbent Assay (ELISA) testing machines
o Increased testing capability, capacity, and training for staff at Willow Lake
• This past summer, staff began testing for cyanotoxins in the North Santiam Watershed on April 10th, 2024.
• Beginning June 10th, routine testing of the North Santiam River at the Middle Intake, the raw water intake to the Geren Island Water Treatment Facility, indicated levels of microcystin were elevated.
• Levels continued to rise throughout the summer, peaking at over 18 µg/L on July 16th, 2024, at the Middle Intake. This was almost 3 times higher than the highest level experienced during the 2018 cyanotoxin event.
• The Oregon Health Authority issued a Recreational Advisory for the Detroit Reservoir, Big Cliff Dam, and North Santiam River for all recreational users on July 16th, 2024.
• The City of Salem released information on July 16th, 2024, providing further details for our current drinking water conditions and reiterating that our water remains safe to drink, due to the success of specific infrastructure improvements to the slow sand filters and Ozone Treatment Facility.
• Levels of microcystin at the Middle Intake remained above health advisory levels for vulnerable populations levels until September 2, 2024.
• The City of Salem treated 5.157 billion gallons of drinking water from May through September.
• At no time was microcystin detected in the treated drinking water supplied to Salem water customers.
BACKGROUND:
Testing of the North Santiam River began in late April. On June 10th, 2024, results showed an increased level of microcystin, a type of cyanotoxin, in the North Santiam River near the Geren Island Water Treatment Facilities main river water intake. This was the first occurrence of cyanotoxins at an elevated level since the Ozone Treatment Facility was commissioned in 2022. Treatment processes at the water treatment facility successfully reduced microcystin levels in the treated drinking water that is supplied to the City of Salem’s customers. Results of tests for microcystin in treated drinking water were well below the minimum reporting levels and were considered non-detectable.
Lacey Goeres-Priest
Water Quality Supervisor
Attachments:
1. 2024 Summary Graph
2. OHA Recreation Advisory
3. Cyanotoxin News Release_07162024