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Thurston County, Washington

The content on the Thurston County website is currently provided in English. We are providing the “Translation” for approximately 10 languages. The goal of the translation is to provide visitors with limited English proficiency to access information on the website in other languages. The translations do not translate all types of documents, and it may not give you an exact translation all the time. The translations are made through an automated process, which may not result in accurate or precise translations, particularly of technical and legal terminology.

Public Health and Social Services


The TC Water Laboratory previously located at 2000 Lakeridge Dr. SW, Olympia WA. has moved to 412 Lilly Rd. NE, Olympia WA. 

Update in Pick-Up Time for Mason County - Starting March 11, 2024 water samples will be picked up at 4pm, samples MUST be submitted by this time in order to be tested

Attention Drinking Water Lab Effective 10/31/2023

The water quality lab carries out bacterial analyses of drinking water, surface water, suspected sewage discharges, treatment plant effluent, marine water, and soils. The lab also performs nitrate analyses of drinking water.

Scientist is analyzing and testing a water concept

Water Testing

Drinking water may contain contaminants that could pose a human health concern. An important way to assure that drinking water quality is safe for human consumption is to test the water. Testing can help to determine: 1) if a contaminant is present, and 2) if present, whether the level of concentration is high enough for concern.

Pick Up and Drop Off Information

The Atrium, 3000 Pacific Avenue SE,

Suite 225

(360) 867-2631 PICK UP: Mon – Fri, 8am-4pm
DROP OFF: Mon-Wed, 8am-1pm for Coliform Bacteria and Mon-Tues 8am-1pm for Nitrate.

Public Health & Social Services Building,

412 Lilly Road NE

(360) 867-2631

PICK UP: Mon – Fri, 9am-4pm
DROP OFF: Inside Front Counter Mon-Wed, 9am-4pm for Coliform Bacteria and Mon-Tues 9am-4pm for Nitrate

External Water Sample Mailbox Mon-Wed, 8am-5pm and Thur 8am-12:30pm for Coliform Bacteria and Mon-Tues 8am-5pm for Nitrate.

If you wish to attach payment with the water sample(s) please make checks payable to Thurston County Environmental Health (TCEH) and rubber band to sample with lab slip.  Please check the current fee schedule for total fees due. 

Sample will NOT be accepted October 26-30

Sampling Instructions

Mason Health Department, 415 N 6th Street

(downtown Shelton)

(360) 867-2631 PICK UP: Mon – Fri, 8am-4:30pm
DROP OFF: Mon-Tues, 8am-4:00pm for Coliform Bacteria and for Nitrate

Important Note: You must collect and submit samples to the Mason County Health Department on the same day or else they will exceed allowable holding times prior to being tested by the lab.

No sample pick up in Mason County on Monday October 30, 2023. 

Sampling Instructions 

Rainier Town Hall, 102 Rochester St W (360) 867-2631 PICK UP: Mon – Thurs, 8am-5pm
DROP OFF: Tuesday ONLY, 8am-12pm for Coliform Bacteria and for Nitrate
Tenino City Hall, 149 S. Hodgden (360) 867-2631 PICK UP: Tues– Fri, 8am-4pm
DROP OFF: Tuesday ONLY, 8am-12pm for Coliform Bacteria and for Nitrate
Rochester (R.O.O.F), 10140 Highway 12 (360) 867-2631 PICK UP: Mon – Fri, 9:30am-5:30pm
DROP OFF: Tuesday ONLY, 9:30am-12pm for Coliform Bacteria and for Nitrate
Yelm Public Works, 901 Rhoton Rd SE (360) 867-2631 PICK UP: Mon – Fri, 8am-5pm
DROP OFF: Tuesday ONLY, 8am-12pm for Coliform Bacteria and for Nitrate

Sampling Instructions


Follow these directions for disinfecting your well if your water has coliform bacteria in it. This disinfection process treats only biological contaminants, not chemical or mineral contaminants. Disinfecting Your Well 

1. Flush the System.

  • If your water is cloudy, let the water run for 10-15 minutes before disinfecting.

2. Chlorinate the well.

  • Use household bleach which typically has a chlorine concentration of 6%. Do not use “ultra” concentrated bleach or bleach products with additives or perfumes.
  • The amount of bleach to use is according to the chart on page 2. If you have problems calculating the amount of bleach to use, contact Thurston County Environmental Health.
  • Mix bleach in a bucket of water. Remove well cap, plug, or vent (see diagrams on page 2); using a funnel, pour the bleach into your well.

3. Mix the bleach with the well water.

  • Attach a hose to the nearest outside faucet and allow the water to run onto the ground for 1-2 minutes until you smell chlorine. Then place the hose in the hole where you poured the bleach, allow the water to run back into the well for 15-20 minutes.
  • Remove the hose and replace the well cap, plug, or vent.

4. Chlorinate the lines.

  • Turn on each tap attached to the well (kitchen, bathroom, outdoor spigot, etc.), starting with the nearest tap to the well, and let the water run until you smell bleach, turn off and then go to the next tap.
  • Turn off electricity to the pump and let sit overnight.

5.  Flush the chlorinated water out of the system.

  • Choose any outdoor spigot and let the water run onto the ground, away from your septic system (also keep water flow from going into creeks, streams, or where fish or vegetation can be harmed), until you no longer smell bleach. This empties the bleach from the well.
  • Turn on each faucet inside the house until you no longer smell bleach. 

Once the system has been flushed of all bleach, the water can be used for laundry and bathing, but you should not yet use it for drinking, brushing teeth, making ice or preparing food. 

Wait 3-4 days after flushing the bleach out to collect coliform bacteria samples. You may need to repeat this process several times before coliform test results are “satisfactory”. Also, be aware that the bleach may disturb built-up minerals in your pipes and temporarily discolor your water. This discoloration should disappear once the bleach is flushed out of your system. 

For more information, call Thurston County Environmental Health Division at (360) 867-2673.

​Stop drinking the water. Have your water tested for coliform bacteria, see Testing Your Well for more information. Contact our office at 360-867-2631.

​If you know the name of the water system, you can find that information by searching the DOH Public Water System Database. Or you can call our office at 360-867-2673.

Contact our department or email us at if you have additional questions.

Water Quality Lab 360-867-2631 General Drinking Water & Wells 360-867-2673 Public Water Systems 360-867-2630