First Hill Booster Pump Station System Tuning

Project Details/Neighborhood:

The First Hill Booster Pump Station (BPS) is located at SE 32nd Street and 74th Avenue SE, in the northwest corner of the island.

Background

The City of Mercer Island operates two booster pump stations within its water distribution system: the primary station at the reservoir site, which serves most of the Island (the Pumped Zone), and the First Hill Booster Pump Station, which serves the smaller First Hill Zone, supplying approximately 230 single-family homes and 20 fire hydrants.

The First Hill station was upgraded in 2011 to improve capacity and reliability. It currently includes six pumps with variable frequency drives (VFDs): four 1.5-horsepower pumps for everyday domestic water use, and two 40-horsepower pumps intended for fire flow. Over time, however, system demand has increased, and the fire flow pumps are now frequently needed to meet peak domestic demand, indicating that the original design assumptions may no longer reflect current usage patterns or system conditions.

A re-evaluation of the site is now necessary to ensure the system is tuned for today’s water demands and recent infrastructure changes.

Description

The first steps of the project include reviewing existing information, installing flow meters to measure water use during high-demand times, and evaluating how well the station meets current and future water needs—both for everyday use and fire protection.

Based on this assessment, the City will make improvements to address any issues. This may include upgrades to pumps, valves, pipes, and electrical systems. One planned improvement is the replacement of the station’s variable frequency drives (VFDs), which help control pump speed and are now approaching their expected lifespan.

Project Timeline

• Planning/Design: August 2025 – January 2026
• Construction: April 2026 – September 2026

Estimated Budget

$300,000

Contact:

Christopher Marks, Utilities Engineer, 206-677-1027; chris.marks@mercerisland.gov