Changes to the MDL (LOD) determination procedure

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October 31, 2017

On August 28, 2017, the EPA issued a final rule notice that changes the procedure to determine an MDL effective 9-27-2017.  We have opted to allow a gradual progression into the new requirement that allows labs to continue with their existing MDL/LODs until September 1, 2018.  This date coincides with our projected date that changes to our administrative rule (ch. NR 149, Wis. Admin. Code) would take effect.  

What do you need to be doing?

1. If you are scheduled to do an annual MDL determination between now and September 1, 2018, you get a pass for this year.  We'd rather you work towards developing an initial LOD using the new protocol.

2. Analyze 2 LOD spikes and 2 method blanks, per instrument used for a given test, per calendar quarter.  Start now!  Do 2 spikes (each on separate days) between now and December 31, 2017.  Then  do another set during each of the next 2 quarters (Jan-Mar, Apr-Jun).  Then analyze a final set between July 1, 2018  and late August 2018.  That should give you 8 LOD spikes and almost a year's worth of blank data.  You will use this data to calculate a new LOD using the new procedure. 

3. Also collect and record all your method blank data for each test that requires a method blank (except BOD and TSS).  You will need this data to help calculate the new LOD.

4.  The goal is for all labs to have a new LOD, using the new protocol, by Sept. 1, 2018.

5.  If you have questions or need help, contact your auditor, or Rick Mealy, using the contact information below.

NOTE:  The MDL spike concentration must be the same throughout the year.  Use the same concentration that has worked for you in the past.

 

We will have more information available (e.g., benchsheets) as we develop materials and will post links to them on the LabCert website:   http://dnr.wi.gov/regulations/labCert/index.html

 

DNR presentation at 2017 WWOA Annual Conference:

http://dnr.wi.gov/Regulations/labCert/documents/guidance/MDLchanges.pptx.pdf

 

The new procedure (as it appears in federal rule):

https://www.epa.gov/sites/production/files/2016-12/documents/mdl-procedure_rev2_12-13-2016.pdf

 

Base EPA info page:

https://www.epa.gov/cwa-methods/method-detection-limit-frequent-questions#intro

   

EPA FAQ page

https://www.epa.gov/cwa-methods/method-detection-limit-frequent-questions

 

Questions?  Contact the DNR Lab Certfication Program:

http://dnr.wi.gov/regulations/labcert/index.html#tabx5