What is MICA's plan to stabilize the hillside, manage water runoff, and improve drainage, trails and stairs?

A:

The hillside will be stabilized where necessary with a retaining wall. The trails will not be changed or impacted by MICA. The stairs leading to First Hill will be integrated into the MICA plaza area.

Storm drainage requirements for the City of Mercer Island adhere to the Washington State Department of Ecology Stormwater Management Manual (2005 Edition).  The manual requires on-site stormwater management, runoff treatment and flow control, and MICA will be required to and is committed to meet those requirements. 

Surface runoff from the hillside will be intercepted by swales that will be strategically graded into the hillside to minimize impacts to the existing vegetation. The northern swales will be connected to the existing Trellis public storm drain line on the north edge of the site and the southern swale will convey hillside runoff to the wetland buffer due north of the wetland. The wetland will overflow into a catch basin located north of the wetland. Flow control will occur through onsite detention. A storm water detention tank is designed to be underground and will not be visible.

The trails will not be changed or impacted by MICA. The western slope, with its trails and stairway, will remain wooded and intact. The stairs leading to First Hill will be integrated into the MICA plaza area. When MICA is complete, the current park uses will all be continued. There will be a walkway around the park lawn, the pergola, the children’s play area and the skateboard park. The wooded area between the skateboard park and MICA – currently in poor ecological health – will be smaller as a result of the project. MICA has undertaken to work with the City to re-landscape and turn this area into a space all Islanders can enjoy.