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Water Quality
The City of Issaquah is committed to delivering the best quality drinking water. To that end, we remain vigilant in meeting the challenges of source water protection, water conservation and community education while continuing to serve the needs of all of our water users.

Water Quality Reports
Each year, we take hundreds of water samples to determine the presence of any radioactive, biological, inorganic, volatile organic or synthetic organic contaminants. Our annual Water Quality Reports illustrate the results of those tests, as well as other valuable information.

Most Recent Water Quality Report

All Available Water Quality Reports


This information has been updated to reflect most recent data and better describe how our water is blended.

                  PFC Test Results: Lower Issaquah Valley Aquifer    
 (units of measurement)
 Well 4
 Well 4
 Well 4
 At the Tap 
Maximum Level
(November 2015)
 At the Tap 
Maximum Level
(February 2016)2
Advisory (issued 2009) 
 At the
Level (May 2016)
At the Tap Maximum Level (June 2016)4 
 EPA Lifetime Health Advisory (issued May 2016)5
 PFBS (ppb)  ND  ND  0.0695  ND  ND  None  ND  ND  None
 PFHpA (ppb)
 0.0258  0.0234
 0.0207  0.00531  ND  None  ND
 ND  None
 PFHxS (ppb)
 0.241  0.201
 0.194  0.0473  0.0375  None
 ND  None
 PFNA (ppb)
 0.0280  0.0266
 0.0221  ND  ND  None
 ND  None
 PFOA (ppb)  0.0215  0.0200
 0.0181  ND  ND  0.4
 ND  0.07
 PFOS (ppb)  0.600  0.514
 0.472  0.106  0.0772  0.2
 ND  0.07 
 ND — not detected
For the test results taken “At Well 4,” this water was then blended with at least one other well before it was distributed. For more information, view our PFCs webpage.

After publication of its 2014 Water Quality Report, the City of Issaquah received the following corrected information from the testing lab. 

This test was conducted after the City reduced the amount of water pumped from Well 4.

3 This test was conducted after the City stopped pumping from Well 4 in the winter of 2016.

This test was conducted after the City started to use a filtration device on Well 4.

5 Advisory is combined PFOA and PFOS levels. 

While 2009 test results for combined radium (pCi/L) — which found no violation — were included in the City's 2009 Water Quality Report, the same results were inadvertently not included in the 2010 Water Quality Report. Subsequent samplings in May and October of 2012 found no level of combined radium.