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Clean Air Markets

Rectangular Duct Wall Effects


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EPA is allowing the use of an optional rectangular duct wall effects conditional test method CTM-041 (PDF) (17 pp., 45 K) for source personnel that perform flow monitor relative accuracy testing in a rectangular stack or duct.

As further described below, CTM-041 must be approved as an alternative before a source may use it to meet Federal requirements under 40 CFR Parts 60, 61, 63 or 75. Additional information on conditional test methods is available on EPA's Emission Measurement Center Website.

For a Part 75-affected unit with a rectangular stack or duct, the Designated Representative (DR) or Alternate Designated Representative (ADR) may submit to the overnight mail address below a one time, written petition request under §75.66 use CTM-041. A single petition may be submitted to cover all such units for which the DR or ADR is responsible. At a minimum, each petition must contain the plant name(s), unit ID(s), stack/pipe ID(s), ORISPL number(s), and the start date(s) and time(s) that the rectangular duct wall effects will be applied to the flow data.

Although EPA is likely to approve petitions to use CTM-041, all approvals will be conditioned with the following language: "The rectangular duct cross-sectional area may not be adjusted to account for any build-up of particulate matter or other material in the bottom of the duct when calculating stack gas volumetric flow."

Part 75-affected units using CTM-041 must follow the applicable portions of the ECMPS Reporting Instructions. i.e., the "RATA Summary Data" record in §2.4.3 of the ECMPS Certification and QA Test Reporting Instructions, and then "Rectangular Duct WAF Data" record in §12.0 of the ECMPS Monitoring Plan Reporting Instructions.

For performing CTM-041 calculations, EPA recommends the following:

For Part 75-affected units, the written request to use CTM-041 should be sent to:

Regular Mail:
USEPA
Clean Air Markets Division
1200 Pennsylvania Avenue, N.W.
Washington, D.C. 20460
Attn: Mr. Reid Harvey

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