CWA Methods Support Documents

Support documents for specific analytes and analytical methods:

Analytical Methods for Mercury in National Pollutant Discharge Elimination System (NPDES) Permits; Memorandum (pdf) (56.57 KB, August 23, 2007)
Explains use of Methods 1631E and 245.7 as most sensitive for measurement of mercury and appropriate for use in NPDES permits in most cases
Analytical Method Guidance for EPA Method 1664A Implementation and Use (pdf) (138.54 KB, February 2000, 821-R-00-003)
Addresses potential differences between results obtained with Method 1664A and an approved method that employs CFC-113 (1,1,2-trichloro-1,2,2-trifluoroethane) as an extracting solvent
Preliminary Report of EPA Efforts to Replace Freon For The Determination of Oil and Grease (Rev. 1) (pdf) (3.36 MB, September 1993, 821-R-93-011)
Report of EPA Efforts to Replace Freon for the Determination of Oil and Grease and Total Petroleum Hydrocarbons: Phase II (pdf) (3.13 MB, April 1995, 820-R-95-003)
Modifications to Method 1664A; Memorandum (pdf) (113.26 KB, January 16, 2009)
This memorandum answers several questions about allowed modifications to Method 1664A. Although analyst modifications to method-defined parameter methods are generally not allowed, some changes are acceptable.

Clean Water Act Analytical Methods