Slides, rain damage still possible this spring

The city’s project to improve the First Hill neighborhood’s water system began this month and will continue for most of the year. - Rebecca Mar/Staff Photo
The city’s project to improve the First Hill neighborhood’s water system began this month and will continue for most of the year.
— image credit: Rebecca Mar/Staff Photo

It seemed like Mercer Island might escape into spring with a fairly mild winter, without the torrential downpours that sometimes come with the colder, wetter time of year. Alas, the last couple of weeks have proven that La Niña wasn’t quite finished with the area, bringing rain, snow and wind.

Luckily, the Island hasn’t seen drainage or landslide issues as much as could have happened.

“Even with all the rain we’ve had at the end of the winter and beginning of spring, the public system has done fine,” said Assistant City Manager Glenn Boettcher. “There’s been no significant problems or damage.”

Typically, rain equals landslides around the Island, as the slopes lose integrity after becoming saturated. Last week, a small slide near 80th and 65th did some damage to private property.

Don Cole, the building official for the city, said a portion of one house and the entry to the lot of another were yellow-tagged, meaning engineers would need to work with the homeowners to improve the area before it could be reopened.

“We’ve done a lot of training with homeowners,” said Cole about how to prepare and avoid landslides. He said so far this landslide season, which is almost over, slides have not damaged any public areas.

“It’s been good this year,” said Cole, of slides. “This was really the first one.”

Cole said the city has several handouts available to Island residents, and the city also publishes several information pieces about prevention.

In a typical year, there are between six and 15 slides on the Island, which can greatly affect homes built on steep slopes. The city estimates that damages run from a few thousand dollars to fix, to several hundred thousand.

On the city’s website, a landslide hazard assessment map shows the areas on the Island that are most susceptible to slides. The city uses the United States Geological Survey’s system of indicators, which can help show the likelihood of a landslide based on current conditions. Cole said, recently, the Island has been at a level 2, which indicates there is a potential for slides.

The city can do assessments for homeowners about where landslides on property are most likely and how to prevent them from happening. Some of the major points to preventing slides include: controlling drainage features, controlling surface water, avoiding slope disturbance, preserving natural vegetation, verifying the integrity of site features such as retaining walls, performing periodic inspections of the property and staying informed about slide potential.

While the landslide season will be ending soon, several days of heavy rains could increase the potential of slides at any time.

Water system improvement

The First Hill water system improvement project continues, with the third phase continuing this year.

The goal of the project is to update the water infrastructure for the neighborhood.

The final phase, the one underway, will replace and increase the water main, replace 140 water services and seven fire hydrants, add 13 water main connections and make property and pavement upgrades.

The third phase is expected to take 30 weeks, starting this month and running through October. The project is expected to cost around $1.2 for the final phase, with an overall budget of $2.5 million.

To learn more, visit the city’s Capital Improvement Program website.


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