Hello Newman Lake Community!

What is happening?

  • A one-time alum treatment application is happening next week at Newman Lake.

Where is the treatment occurring?

  • In an area that is approximately 120-140 acres in size, where the depth of the lake is greater than 8 meters deep (primarily around the Speece Cone and in-lake water quality equipment east of Sutton Bay).

Who is doing the treatment?

  • AquaTechnex is the selected applicator.

When is it happening?

  • Application may occur any time between May 18th and May 26th. AquaTechnex has stated that their current plan is to mobilize on May 19th, and anticipate the treatment to take 2-½ to 3 days (so Wed, Thurs and part or all of Fri next week).

Are there any recreation or lake water usage restrictions?

  • Boating activity is permitted on the lake during treatment, but should yield to the application barge while working. Also, signage will be posted by AquaTechnex 48 hours prior to application, which will describe any additional information regarding water use or activities restrictions.

Why not use the existing alum injection system?

  • All three alum lines are plugged with hardened aluminum sulfate, which is a dense and viscous material – highly temperature sensitive. The District has been operating with just one clear line for quite some time, as there is no effective way to clear a plugged line – it must be replaced (which is expensive). The alum system is getting a design overhaul with the State Capital Budget Grant Award for Capital Improvements which should decrease the odds of this happening again in the future.

What is the reasoning for this treatment option?

  • The existing system could not be fixed to engage the alum injection system before summer stratification.
  • Consultation with multiple limnologists resulted in strong support that a one-time, high dose, partial-lake alum treatment in the springtime will likely be more effective than continuous injection.

What benefits might be realized from this treatment option?

  • Immediate results should be seen in the upcoming summer due to a large concentration of alum that strips suspended phosphorus in the water column (which typically is highest in spring); this should aid in reducing algal blooms.
  • The higher concentration of alum applied all at once will provide a more effective “cap” on the sediments in the deepest parts of the lake (below 8m), inhibiting them from releasing phosphorus when conditions become anoxic. If the sediments are capped before the anoxic conditions, the phosphorus is inhibited from release later in the season. This layer can also last for multiple seasons due to the high concentration of alum applied.
  • Alum will bind more efficiently to phosphorus due to lack of algal mass in the spring; i.e. applying alum when algal blooms are occurring (i.e. traditionally in the fall at Newman Lake) reduces the efficacy of the alum because it will bind to the algae, not the phosphorus.


Thank you!

Colleen S. Little, P.E.
Environmental Programs and Floodplain Manager, and,
Newman Lake Flood Control Zone District Manager
Spokane County Public Works Department
(509) 638-5895