11 July 1997

US EPA announced that Nelson notification of intent to certify equipment is available for public review and comments for a 45 day period.

Nelson Industries, Inc., Nelson Division applied for EPA certification for urban bus retrofit/rebuild (UBRR) equipment consisting of an oxidation catalyst combined with a noise muffler which replaces the original muffler unit installed on the engine. The equipment is intended for use on all petroleum-fueled Detroit Diesel two-stroke cycle urban bus engines from 1979 through 1993 model year, exclusive of the 1990 model year DDC 6L71TA. Nelson requests certification of this equipment for use on engines rebuilt using the DDC 6V92TA mechanical unit injector (MUI) and electronic control (DDEC II) engine upgrade kits previously certified by EPA under the retrofit/rebuild program.

Nelson applied for the 25% or more particulate matter emission reduction relative to the original PM level of the engine. Certification of the Nelson equipment would affect operators as follows. For the 1979 through 1989 6V92TA MUI engine models, EPA has previously certified equipment which triggered the requirement to use equipment certified to the 0.10 g/bhp-hr level beginning 15 September 1997. Therefore, under the UBRR Program 1, operators who rebuild or replace 1979 through 1989 model year DDC 6V92TA MUI engines after this date will be required to use equipment certified to meet the 0.10 g/bhp-hr PM level. For all other engine models to which this certification would apply, EPA has previously certified equipment which triggered the requirement to use equipment certified as providing a minimum 25% reduction in PM beginning 1 December 1995. If the candidate Nelson equipment is certified to reduce PM by at least 25%, then its use under Program 1 will meet this requirement for these other engine models. This requirement will continue for the applicable engines until such time that equipment is certified to trigger the 0.10 g/bhp-hr emission standard. If EPA certifies the Nelson equipment, then operators who choose to comply with Program 2 (fleet emission averaging) and install this equipment, will use the PM emission level(s) established during the certification review process, in their calculations for target or fleet level as specified in the program regulations.

For information contact Tom Stricker, EPA, tel. 202.233.9322.