1. Crystal Lake Outlet Modifications
Crystal Lake has one outlet which controls the discharge of Crystal Lake to the downstream storm water system. In order to reduce the drawdown time of Crystal Lake, it is proposed that the existing outlet structure be removed and a new outlet structure be installed. The proposed new outlet structure will increase the drainage rate out of Crystal Lake which is estimated to help Crystal Lake drawdown roughly 37% faster allowing for shorter high water and No-Wake periods.
2. New South Twin Lake Outlet
In order to reduce the high water level and duration of flooding of South Twin Lake and North Twin Lake during significant rainfall events, it is proposed that a new outlet structure be installed at South Twin Lake. The existing outlet will remain in place as it provides a critical connection to North Twin Lake. The new outlet structure will be similar in design to the outlet structure that currently exists on the west side of North Twin Lake. This outlet structure is estimated to lower the high water levels of both North and South Twin Lake during flood events. The new outlet structure will also reduce the duration of flooding by up to 29%. A second outlet is critical because in the event debris builds ups, North Twin Lake can rely on this outlet without reduction in capacity.
3. Regional Pond Expansion
The regional pond, just north of North Twin Lake is proposed to be expanded to create additional live storage to reduce flooding within Twin Lakes. This expansion is proposed to reduce high water levels and the duration of flooding within Twin Lakes. In addition, a townhome development is being proposed for the area directly west and north of the regional pond. This expansion will also help to ensure that there will be no negative impacts to the Twin Lakes system as a result of the townhome development. Costs for this portion of the project will be shared with the PUD developer.