Metro will be replacing the waterproofing system of the “green roof” over the underground bus parking structure at its North Base, located at 2160 N. 163rd in Shoreline, during the summer of 2012. The waterproof membrane between the grass and the supporting structure is more than two decades old. It must be replaced because it is leaking and causing the supporting structure to deteriorate.
The parking structure has two acres of grass-covered roof that is used as a community green space and one acre of roof that is used for base parking. The roof replacement will require the temporary closure of both the green space and the parking lot.
The new waterproofing system will be installed using best practices and project requirements that are designed to minimize inconvenience and impacts to neighboring properties. After replacement of the membrane, the green space will be returned to its original state, including restoration of the existing decorative concrete pavers, benches, fences, and artwork.
Project timeline and hours
Metro expects to begin work replacing the membrane in late spring 2012. The project will be completed by December 2012; however, the green space will remain closed until spring 2013 to give the site time to re-seed.
Work hours will be 6 a.m. to 6 p.m. on weekdays, and no construction noise will be generated before 7 a.m. The contractor must obtain written approval from King County to work on weekends or holidays or before 6 a.m. or after 6 p.m.
Work will involve removing about 80,000 square feet of sod from the roof and transporting it to King County’s Cedar Hills landfill for environmental restoration projects. Other materials, including about 2,000 cubic yards of topsoil and drainage materials, will be moved to a temporary storage area at the end of N 167th Street and James Keough Park. This material will be reused to rebuild the green roof as one of the key sustainability features of the project.
Effect on street parking
During certain phases of this project, up to 50 Metro employee cars may be temporarily displaced from the on-site parking lot to on-street parking in the neighborhoods next to the base. This on-street parking would occur throughout the day, including early morning and late night periods when peak transit operations occur. To reduce parking on local streets, Metro is arranging for additional parking at King County facilities.
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