Mercer Island, WA - Potable Water Tanks

Project Overview

Coatings Unlimited successfully completed comprehensive coating systems for two critical potable water storage tanks in Mercer Island, Washington, demonstrating our expertise in water infrastructure protection. The first tank was completed in 2024, with the second tank nearing completion this month, showcasing our commitment to reliable water system maintenance and protection.

About Mercer Island

Mercer Island is a prestigious island city located in Lake Washington between Seattle and Bellevue, with a population of approximately 25,000 residents. Mercer Island is connected to the mainland by Interstate 90 bridges and is considered one of the 100 richest ZIP codes in the United States.

The community's high standard of living and significant property values make reliable municipal infrastructure absolutely critical. Water is delivered to Mercer Island by Seattle Public Utilities via 16" and 24" water supply lines, and the water is stored in two 4-million gallon reservoirs for domestic use and fire protection. These reservoirs serve the entire island through an extensive distribution network of water lines ranging from 4" to 30" in diameter, supplying approximately 7,800 water meters across the community.

Critical Infrastructure Importance

These two 4.0 million gallon potable water storage tanks represent essential infrastructure for Mercer Island's water security and emergency preparedness. The water is stored in two 4-million gallon reservoirs for domestic use and fire protection, serving as the primary water storage for the entire community.

The tanks are particularly critical given Mercer Island's unique geographic position as an island community. During planned construction work on the supply lines that provide water to Mercer Island, Seattle Public Utilities encountered an unexpected problem and Mercer Island is currently not being supplied with incoming water. The Island's water system is currently operating from reserve tanks, highlighting how these storage facilities serve as vital backup infrastructure during supply line emergencies.

With the city's aging water infrastructure requiring significant modernization, the City Council unanimously adopted Ordinance No. 24-09 which authorizes the issuance of bonds to fund critical improvements to the City's water utility infrastructure, making the protection and maintenance of these storage tanks through professional coating systems even more essential to the community's long-term water security.

The tanks support not only daily domestic water needs for thousands of residents but also provide crucial fire protection reserves for a community with property values averaging nearly $2 million per home. Proper coating maintenance ensures these critical assets continue to deliver safe, clean drinking water while protecting the substantial municipal investment in water infrastructure.

Project Scope

Location: Mercer Island, Washington
Structure Type: (2) 4.0 Million Gallon Potable Water Storage Tanks
Project Timeline: Tank 1 completed 2024, Tank 2 completion June 2025
Client Focus: Municipal water infrastructure protection

Technical Specifications

Interior Coating System

The interior coating system was designed specifically for potable water contact, ensuring both durability and safety for drinking water storage:

• Primer Application: Tnemec Series 94-H20 Primer - a specialized low VOC Zinc Primer designed for potable water applications
• Lid and Structural Elements: Tnemec Series 21 - high-performance coating for interior structural components
• Shell and Floor Protection: Tnemec Series 22 - premium interior coating system engineered for water tank shells and floors

Exterior Coating System

The exterior restoration involved comprehensive surface preparation and multi-coat protection:

Surface Preparation:

• Complete power washing for contamination removal
• Power tool surface preparation to SP3 standards for spot repairs
• Thorough preparation ensuring optimal coating adhesion

Coating Application:

• Spot Priming: Tnemec Series 27FC for localized repair areas
• Full Prime Coat: Tnemec Series 109 - high-solid primer for complete coverage
• Finish Coat: Tnemec Series 1095 - durable topcoat providing long-term UV protection

Project Highlights

• Dual-System Expertise: Successfully executed both interior NSF-600 approved, potable water-safe coatings and exterior weather protection systems
• Quality Surface Preparation: Implemented industry surface preparation protocols
  
• Municipal Infrastructure Focus: Specialized experience in critical water system infrastructure

Technical Excellence

This project demonstrates Coatings Unlimited's comprehensive capabilities in water infrastructure coating systems. The interior specifications meet stringent potable water safety requirements while the exterior system provides long-term protection against environmental exposure. The systematic approach to surface preparation and multi-coat application ensures maximum coating performance and service life.

Results

Both Mercer potable water tanks now feature state-of-the-art coating protection designed to extend service life, maintain water quality standards, and provide reliable performance for years to come. The successful completion of these projects reinforces Coatings Unlimited's position as a trusted partner for critical municipal infrastructure coating needs.