How to Choose a Laboratory
Accreditation:
If you want a lab to analyze your environmental samples, you must choose a lab that has been
accredited by the Department of Ecology. The accreditation process is the way labs demonstrate
they have the equipment and training necessary for producing good test results. To say that a
lab is accredited is not a guarantee of good test results; it indicates the lab possess all of the
tools required to do the job well.
You might be surprised how many labs perform pH and turbidity tests--there is probably an
accredited lab near you. For a list of all the labs in the State of Washington that are accredited by
Ecology for turbidity, pH or any other analysis, check out the Lab Accreditation Unit’s website
at http://www.ecy.wa.gov/programs/eap/labs/labs_main.html . Alternatively, you can call
360.895.6149 or write Ecology Lab Accreditation Section, P.O. Box 488 Manchester WA 98353.
Location:
Both pH and turbidity samples must be tested in the lab very soon after they have been
collected in the field. Turbidity samples must be analyzed within 48 hours, pH samples within
24. It would be prudent, if possible, to choose a lab nearby to ensure that the sample can be
delivered to the lab in enough time to be analyzed within this timeframe. For example, if you
collect a sample on a Friday morning, will you be able to deliver it to the lab in enough time to
be analyzed that day? (Many labs are closed on the weekends).
Contact the lab prior to sampling:
 Introduce yourself and explain that you will be sampling stormwater runoff from a
construction project for turbidity and/or pH, etc.
 If the lab expresses an interest in analyzing samples for you, verify the analytical method
used. They should be adhering to established protocols.
Parameter
Turbidity
pH
Phosphorus (TP)


Units
NTU
Standard units (0-14)
mg/L
Method
SM2130 or EPA 180.1
Any laboratory method?
EPA 365.1, 365.3, or SM 4500PH/PI
Not all labs produce the same quality results. While you are comparing prices between
labs, you may also want to ask how often they perform your procedure or what their
quality control criteria are.
Make an appointment to pick up clean sample containers. Most labs supply you with
the containers you will need for sampling. Your visit is a good time to ask any sampling
questions you may still have, sort through any paperwork the lab might require and
verify the hours they accept samples for analysis.