Projects: Water Quality: Pine Lake

The Pine Lake Watershed is located along the western slopes of the Cascades in Washington and has experienced a rapid increase in urban development. Historically plagued with large blue-green algal blooms composed of primarily Aphanizomenon, the City of Sammamish contracted Tetra Tech, Inc. to develop a lake and watershed management plan to protect against future degradation of the lake’s water quality.

In support of the management plan, water quality data was sampled at bi-weekly intervals to monitor nutrient and physical changes with the lake. Additionally, external loading from the surrounding development was sampled. Results from the sampling effort were reviewed for quality control and assurance and used to develop a phosphorus prediction model. This model addressed the internal dynamics of phosphorus flux between the surface and bottom waters of Pine Lake and also defined the effect of external loading of phosphorus from different land-uses within its watershed. To account for future conditions, land-use scenarios were varied to model a spectrum of potential land-use zoning regulations, build-out conditions, and best management plans including LID scenarios to identify cost effective measures to maintain the positive renewal of Pine Lake. Currently the management plan is being prepared and reviewed by the City of Sammamish.