School campus at the limit for impervious surfaces
Published 4:39 pm Monday, November 24, 2008
By Mary L. Grady
Present city codes will not allow any further development or construction at school district property surrounding the high school.
At its Sept. 8 meeting, the School Board heard from construction planners that the site is already over the amount of impervious surface area allowed by the city.
The Mercer Island Boys & Girls Club, along with the school district, is putting together a design for a teen center and field house (called PEAK) to be constructed on school district land.
Planners had incorrectly assumed that 60 percent of the site could be covered by impervious surfaces. City code only allows 40 percent for schools in residential areas to be covered by impervious surfaces, which are parking lots, roofs and sidewalks — anything that stops the flow of rain water into the ground.
The School Board did approve a site for the PEAK project, choosing the “western” site — a piece of unused land facing 86th Avenue S.E. adjacent to the north side of the school district transportation building.
The board also authorized planners to request a code amendment to the city to increase the amount of impervious surface allowed.
“The issue is not that the PEAK project puts the site over the limit; the (high school block) itself is at a point where no more construction is allowed,” explained Brandy Matthews-Fox, the project manager for the school district.
“Even if we were to ask for a building permit (just) to move a wall within the high school or do some remodeling, we would not get one from the city because the (entire) site is already over the 40 percent (impervious surface) limit,” she said.
Planners estimate that the request for a code amendment could take three months. Having the code amendment would ensure that the district would have the flexibility to make changes to other schools and buildings as needed, Matthews-Fox said.
“Asking for a code amendment to allow more development for schools and perhaps churches and community facilities, is just only one of their options,” said city Development Director Richard Hart.
Other options include seeking a deviation or variance, or complying with code requirements by reducing the current amount of coverage on the property to allowed levels, he explained.
When told of the higher-than-allowed site coverage at other Mercer Island School District facilities, Hart said he did not know of any violations.
“To my knowledge the city has done a good job in the past five to 10 years in applying the impervious surface code provisions,” he said. “The city enforces impervious surface requirements according to existing code requirements.”
Hart said if any property fails to meet such requirements, it is most likely the site obtained a 5 percent impervious surface deviation or a larger variance under code provisions. Another possibility is that the site was built and constructed prior to current limits, or some type of error was made in the calculation at the time of construction.
When asked if the city has a low ratio (40 percent site coverage), Hart said he did not know how it compared to other jurisdictions.
“The reason for the ratio is not to limit development as much as to control stormwater runoff and protect the environment,” he said.
“Such code provisions are aimed at preserving water quality, as we are an Island, with all stormwater drainage eventually moving from high ground to Lake Washington,” he added.
The City Council has the final say on code amendments.
