Additional Approved Method and Parameter Information

This page lists letters and memorandums of approval for methods by various authorities including the Director of the Division of Water Resources, EPA and the Division of Waste Management UST and Solid Waste Sections.

*Fecal Coliform Testing with Colilert® 18*

Colilert® 18 is included in Table IA  of Part 136.3 in the 2017 Method Update Rule (MUR) of 40 CFR. This allows for the use of Colilert® 18 (only, not Colilert® ) for the analysis of wastewater, including when wastewater is used in an application such as spray irrigation or used for beneficial reuse as reclaimed water. Footnote 21 in Table IA states: Approved for enumeration of target organism in wastewater effluent; indicating that it is not for use in sewage sludge samples. The 2017 MUR did not include Colilert® 18 in Table IH for Fecal Coliforms. Therefore, this method may not be used for fecal coliform analysis of storm water samples, stream monitoring tied to NPDES permits (e.g., upstream, downstream), groundwater monitoring wells or for biosolids monitoring under 503 regulations.

In reply to inquiries about the use of Colilert® 18 in ambient water, EPA Region 4 stated that the vendor of this product, IDEXX, never applied for this method/product/procedure to be considered for ambient water approval.  Therefore, the method was never EPA approved for this matrix and the Region had previously determined to not allow the use of this method for the detection and enumeration of fecal coliform in ambient water.

However, per recent guidance from the National ATP Coordinator, laboratories may work with the Laboratory Certification Branch and Region 4 to obtain limited-use approved for Colilert® 18 in ambient water (i.e., upstream and downstream monitoring). A limited-use ATP may be given for Colilert® 18 for fecal coliform in ambient water once an ATP study has been reviewed and approved by EPA Region 4. If a lab would like to obtain approval for Colilert® 18 for the analysis of fecal coliforms in ambient water the process can be found in the EPA Microbiological Alternate Test Procedure (ATP)  Protocol for Drinking Water, Ambient Water, Wastewater and Sewage Sludge Monitoring Methods.  (Link to Micro ATP Protocol: . All requests must come from Laboratory Certification, so any laboratories that are interested in pursuing the limited-use ATP needs to contact their assigned auditor.

Individual Organic Analyte Certification

We often receive requests for certification for individual organic analytes. The NC WW/GW LC program is a method certification program and we do not certify for individual organic analytes. If the laboratory holds certification for a method in which the analyte is published within the scope of that method, the laboratory is considered to be certified for analysis of that analyte. In the case where the analyte of interest is not within the scope of a published certifiable method (an example of this would be Tetrahydrofuran by SW-846 Method 8260 B), the laboratory is advised to maintain Method Detection Limit (MDL) and Initial Demonstration of Capability (IDOC) study summary data on file at the laboratory and follow the quality control requirements outlined in the reference method. Any questions (such as whether an analyte of interest may be reported as a Tentatively Identified Compound [TIC] or whether it must be quantitated) should be directed to the regulatory agency receiving the data. This office does not have the authority to certify or otherwise offer any approval for analysis of individual analytes not within the scope of a certifiable method.

Ferrous Iron

The NC WW/GW LC program does not have the authority to certify specifically for the Ferrous state of Iron. We do certify for Total Iron by a method that also allows for measurement of the ferrous state (i.e., Standard Methods 3500-Fe B, 20th Edition and beyond). To measure the ferrous state, however, samples must be analyzed at the sampling site. The program will only certify:

  1. entities which intend to report Total Iron by this method, or
  2. entities which intend to report Ferrous Iron by this method and have the capability to analyze samples at the sampling location 

Data analyzed, reported and qualified as out of hold time is unusable for the regulatory data receivers' objectives. 

For Approved Procedures for the Analysis of Field Parameters

Click here to link to the approved procedures for Total Residual Chlorine, pH, Dissolved Oxygen, Specific Conductance, Temperature and Settleable Residue.

DWR Director Approval Letters for Additional Certifiable Parameters 

Approval to certify for Acidity, Ignitability, Paint Filter Liquids, Boron, Potassium, Sodium and Total Organic Halides (TOX) 10/28/2002
Approval to certify for Strontium, Titanium, Lithium, Silica, CBOD, DOC, VSS, E. coli and Enterococci 03/02/2007
Approval to certify for Volatile Solids and Salinity 10/05/2007
Letter removing approval of Chlorophyll a by HPLC 10/11/2007
Approval to certify for Free Available Chlorine 09/27/2012
Approval to certify for Bromide 10/11/2012
Approval to certify for Clostridium perfringens and Coliphage  


DWR Point Source Branch Letters

Total Residual Chlorine instrument sensitivity must detect below NPDES discharge permit requirements 08/14/2001
Total Residual Chlorine Compliance Limit is 50 µg/L 05/01/2008
NPDES Mercury Requirement - EPA Method 1631 08/12/2003
Total Residual Chlorine Detection and Compliance Levels Policies Letter 03/11/2015


EPA Approval Letters

US EPA Letter of approval for additional Metals not included in 40 CFR Part 136.3, Table IB - Methods 200.7 and 200.8 11/07/2007
US EPA approval letter to Regional Administrators for use of Luminescence Dissolved Oxygen (LDO) technology for DO and BOD analysis of wastewater - ASTM D888-05 01/03/2006
US EPA Region 4 approval letter for use of LDO technology for DO and BOD analysis of wastewater - ASTM D888-05 06/01/2006
US EPA letter regarding allowable modifications to EPA Method 1664 A - HEM: Oil and Grease 01/16/2009
US EPA letters regarding ATP review of Colilert®-18 for Fecal Coliform analysis *ATP no longer needed; method added to 40 CFR in 2017 MUR*  N/A 
US EPA Region 4 Colilert®-18 ATP approval requirements for the Detection and Enumeration of Fecal Coliforms in Wastewater Samples *ATP no longer needed; method added to 40 CFRpart 136.3 in 2017 MUR*  N/A
US EPA Letter regarding ATP approval of NCASI Method 71.01, "An Update of Procedures for the Measurement of Color in Pulp Mill Wastewaters", May 2000 11/08/2001

US EPA Letter (Lem Walker) regarding approval of editorially revised Standard Methods for the Examination of Water and Wastewater 2011 methods. The methods listed are considered acceptable versions of the approved methods in 40 CFR Part 136.3 Tables IB and IC and may be used for compliance monitoring under the Clean Water Act. *now incorporated in 40 CFR part 136.3 through 2017 MUR*


US EPA Letter regarding ATP approval of Hach Company Method 10206 - Spectrophotometric Measurement of Nitrate in Water and Wastewater *ATP no longer needed; method added to 40 CFR part 136.3 in 2017 MUR*

US EPA Letter regarding ATP approval of Hach Company Method 10242 - Simplified Spectrophotometric Measurement of Total Kjeldahl Nitrogen in Water and Wastewater *ATP no longer needed; method added to 40 CFR part 136.3 in 2017 MUR*  N/A

Division of Waste Management - UST and Solid Waste Section Guidelines

Link to UST Update on the January, 1998 MADEP Method, effective 02/01/2006, to the May, 2004 Revision 1.1 12/07/2005
UST Section request to certify commercial laboratories for EPA SW-846 method 8015B for Total Petroleum Hydrocarbons 03/26/2003
Memorandum regarding changes in UST guidelines 12/1/2013
Guidelines for Site Check, Tank Closure and Initial Response and Abatement for UST Releases  12/1/2013
Guidelines for Assessment and Corrective Action for UST Releases 12/1/2013
Guidelines for Sampling - UST [Summary of Appendix B changes 05/01/2012] 05/01/2012
Solid Waste Section Memorandum regarding THF monitoring at Construction and Demolition Landfills 06/25/2010
Guidelines for North Carolina Action Limits for Total Petroleum Hydrocarbons (TPH) - UST Section

NOTE: There one statement that is causing some confusion: "BTEX should be calculated from the TPH GRO peaks." This implies that they should be reported from the GRO analysis (i.e., 8015). UST acknowledged that the wording is not clear and that is not what they were trying to convey. They want TPH GRO and TPH DRO or EPH and VPH and now they want to also monitor BTEX to evaluate if the action levels for initial petroleum contamination cleanup can be raised. The BTEX can be reported by 8260.

Memo concerning implementation of the updated VPH Method (February 2018, Rev. 2.1)  03/10/2018

Soil Reporting

Memo from Director requiring soil to be reported on dry weight basis 05/24/1994

Aquifer Protection Section 

APS Policy for Metals determination required by 15A NCAC 2L - SM 3030C is no longer required. 04/13/2013


Animal Waste Testing

MOA for Animal Waste Testing  06/14/2013


Additional Links

Information on the 2007 Methods Update Rule (MUR)

Information on the use of Discrete Analyzers

Information on SW-846 Updates IVA and IVB

Information on Horizon EPA Method 1664 A Compliance Options


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