In-Use Emission Measurements of Snowmobile and Snowcoaches in Yellowstone National Park

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Final Report prepared for the National Park Service




Large growth in wintertime snowmobile visits to Yellowstone National Park in the 1990's led to a series of lawsuits and environmental impact statements resulting in the adoption of a Temporary Winter Use Plans Environmental Assessment (EA).1-4The temporary winter use plan will be in effect for three winter seasons beginning in December of 2004. It allows motorized winter visits on snowcoaches and a limited number (up to 720/day in Yellowstone and an additional 140/day in Grand Teton) of guided snowmobiles which meet a Best Available Technology (BAT) standard.5Additionally the EA allows the National Park Service (NPS) the opportunity to collect additional data on the BAT approved snowmobiles and snowcoaches in use in the park.

In-use snowmobile and snowcoach emission measurements are scarce. Snowmobile emissions have been measured by the University of Denver in Yellowstone National Park in two previous studies in 1998 and 1999.6, 7Both studies utilized the University of Denver's on-road remote vehicle exhaust sensor to measure the tailpipe emissions of snowmobiles entering the parks west entrance. Several researchers have reported in-use and dynamometer emission measurements on 2-stroke and 4-stroke snowmobiles.8-11 In addition there is one report of dynamometer emission measurements of a vehicle used in the winter as a snowcoach under a simulated load by Southwest Research, Inc.12

The two goals of this research were to repeat the gate measurements on the current crop of 4-stroke snowmobiles and to collect as much in-use emission data from snowcoaches as possible during the time frame. The snowmobile measurements would be used to directly compare and contrast with the previous data sets. The snowcoach measurements are primarily aimed in assisting with the air quality dispersion modeling. This modeling has been an integral part of the previous air quality studies in the park and have had to rely on limited emissions data.13Typically this type of modeling likes to have g/mi or g/sec emissions data for several vehicle-operating modes (at a minimum idle, low and high speed cruise) and time estimates for the frequency of each. The goal to instrument as many different coaches as possible is not to establish an average snowcoach emission factor but to help establish the emission and activity boundaries that coaches operate in.