Aquatic scientist Rob Zisette (bottom left) and Snohomish City Engineer Yosh Monzaki (looking at something on the table) during the May 20 Blackman Lake cyanobacteria meeting.
Photo by Michael Whitney.
SNOHOMISH — A proposal to protect the Blackman Lake watershed would place new requirements on development in the immediate area of the lake.
The city is thinking of declaring the watershed a phosphorous-sensitive area, which would affect handling surface water discharges. The rules would require all new development and redevelopment in the watershed to use phosphorus treatment controls.
Phosphorus is one of the two key ingredients that encourage cyanobacteria blooms in the lake. Phosphorous gives nutrients that aquatic life feeds on. An overabundance of nutrients, though, creates conditions that encourage the blooms.
Cyanobacteria is concerning because it has organic toxins that can make people and animals sick. The bacteria is commonly called blue-green algae, or simply “bad algae.”
Studies found that the lakebed itself is releasing the most phosphorous.
The phosphorous requirement follows through on a suggestion from a city consultant to help control phosphorous intake into the lake.
Overall to reduce toxic algae blooms, a city consultant has recommended to use algae treatments at first, while keeping an eye on modern underwater oxygen pumps as a future non-chemical option to implement.
Last summer, the City Council signed off a plan to use alum treatments to control the algae. The treatments lock in phosphorous to the bottom of the lake.
The draft plan is posted to the city’s Blackman Lake Cyanobacteria Management Plan web page, www.snohomishwa.gov/808/Blackmans-Lake-Management
A shortened link to the 314-page draft plan is www.tinyurl.com/blackmanlakedraftplan
