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9611 SE 36th Street
Mercer Island, WA 98040
Phone: 206.275.7600
Fax: 206.276.7663
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City of Mercer Island / City and Regional Projects / Capital Improvement Program / Emergency Water Supply 2009 Well Project

Emergency Water Supply 2009 Well Project

Rotary Park

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Neighborhood: Mid-Island


Exact Location: 88th Ave SE & SE 44th St.


Project Type: Water


Description: Preventing a major disaster from disrupting Mercer Island’s water supply has been a top priority of the City and its Water Utility for many years. With the successful completion of the test well phase of the Emergency Water Supply Well Project at Rotary Park, the City is poised to make a tremendous leap forward in preparedness.


This project includes construction of a permanent well facility to provide a water supply to Mercer Island residents in the case of an emergency when other water systems are compromised.



Estimated Budget (2009): $1,075,000


Project Timeline (Estimate): starting end of July/August to be completed by end of year


Project Status (as of 7/31/09):

Construction of the Emergency Water Supply Well Facility at Rotary Park is scheduled to start in mid-August, 2009.  Since the well was drilled in 2007, the project has evolved through the pre-design phase, temporary use planning, and the final design.  The City is now ready to construct the well facility.


The proposed well facility is located at the northwest corner of Rotary Park.  The contractor will set up the construction perimeter with a temporary chain-link fence.  Please be advised that part of the pedestrian pathway will be inside the construction zone, so pedestrians will need to use roadway shoulder when passing through this area.  The contractor has been asked to take extra precaution for the equipment and vehicles to enter and exit the construction site.


At this time, the contractor is planning to mobilize on the week of August 17.  The project duration is estimated to be 5 to 6 months.  The contractor’s proposed working schedule is 7 am to 5 pm, Monday through Friday.   Rotary Park, with the exception of the construction fenced area, will remain open to the public throughout the project. 


Like most construction projects, some noise and a slight increase of traffic is expected in the area surrounding the site.  Thank you in advance for your cooperation and patience. 


Contact Information: Rona Lin, Maintenance, 275-7806,



For information about Rotary Park Improvements, click here.




City Council allotted $410,000 for the emergency water test well drilling in 2007. Funds were allocated from the City’s water fund and unspent 2005-2006 water capital project dollars. The final production well could potentially supply Islanders with seven days of emergency water.  Council approved an additional $135,000 on April 21, 2008 for the design of a permanent well facility.

The test well, which was drilled to a depth of 570 feet in 2007, has produced water of both the quality and quantity to serve as a short-term source in the event of an interruption in the Island’s supply from Seattle Public Utilities. Some treatment will be required before the well can be activated due to the presence of manganese and coliform bacteria. During pump tests in April, the test well produced 300 gallons per minute (gpm) for 24 hours. The threshold established for the project was 220 gpm, which would be enough water to provide about five gallons per person on a daily basis for up to seven days.  At the City Council Meeting on April 21, 2008, Council directed staff to move forward with the design of a permanent well facility.

Why was Rotary Park chosen as the site for test well drilling?

The City evaluated several sites and concluded that Rotary Park is the best option because it is centrally located and accessible to all islanders. It is also located on the more stable “spine” of the Island- areas along the perimeter of the island are less likely to be stable in a major catastrophe such as an earthquake.


Some residents have asked why the City is drilling a test well rather than setting up systems to filter lake water in an emergency. A major catastrophe such as an earthquake is likely to rupture sewer lines throughout the lake, so lake water will be highly contaminated.  The City explored filtration options and found that filtration would be more expensive and less reliable than a well.


What happens if sufficient water is reached?

If sufficient water is found, city staff would immediately begin the design of a production well and associated facility. If the test well proves to provide an adequate supply of emergency water, the test well will be converted to a production well and an associated facility will be constructed.  The estimated 20-foot-by-25-foot well facility would be designed to blend with the park landscape.


Park Improvements

A new landscape design has been developed from two preliminary concepts that were distributed after discussions with neighbors at a public open house. Both concepts were subsequently combined and public feedback strongly favored planting oak trees as replacements to the poplar trees.  Plaza improvements will be implemented later and work will proceed based upon the availability of additional funds.


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