Page 35 - TransportationPlanUsetsGuide

Natural Environment
All transportation modes, vehicle types and facilities – even electric vehicles and multi-use trails – have
impacts on the natural environment, from localized habitat degradation caused by the horizontal footprint of
a road or trail, to global climate change influenced by carbon emissions. The TSP divides environmental con-
siderations into three categories: air and climate; land and water and efficiency. (Impacts to the built environ-
ment are addressed under Goal 3: Livabilty.)

Air and Climate
The Portland Air Quality Maintenance Area currently meets all federal air quality health standards. However,
in the past, the Portland Air Quality Maintenance Area did not meet the air quality health standards for
ground-level ozone (smog) and carbon monoxide. Gasoline powered vehicles emit both carbon monoxide
and ozone precursors. Therefore, the Oregon Department of Environmental Quality (DEQ) had established
an emission budget for ozone precursors and carbon monoxide. These emission budgets include a mobile
source (vehicle) category. For regional transportation planning purposes, the transportation network must
demonstrate compliance with the mobile source emission budgets for these pollutants.

Ground-level ozone (smog) is a serious type of air pollution caused by a chemical reaction when nitrogen
oxides and volatile organic compounds are exposed to sunlight and warmer temperatures. Smog discolors
the atmosphere and can harm human health. The ozone precursors of nitrogen-oxides and volatile organic
compounds are criteria pollutants for air quality conformity determinations.

Carbon monoxide is a colorless, odorless gas that can lead to serious human health problems with prolonged
exposure, or short term concentrated exposure. Carbon monoxide exposure issues may occur during winter ADOPTED TEXT
conditions with both cold temperatures and stagnant air.

Both ground-level ozone and carbon monoxide are air quality pollutants monitored by DEQ. These and other
emissions are measured hourly through an air quality surveillance network of established sites throughout
the region that record the chemical composition of the air.

The transportation sector further affects air quality and climate through the emission of greenhouse gases
such as carbon dioxide, airborne toxics such as benzene and particulate matter. Both air toxics and particu-
late matter are known or suspected to cause concern or other health problems. In Oregon, an estimated 34%
of greenhouse gas emissions – the largest single share – can be attributed to transportation related sourc-
es. Recent data from DEQ also suggest that air toxics are disproportionately concentrated in urban Washing-
5
ton County due to stagnant air.
6
Clean air has been a federal mandate since the Clean Air Act of 1970. Clean Air Act Amendments in 1990
required metropolitan planning organizations to demonstrate air quality conformity in their transportation
plans in order to receive federal transportation funds. The air quality/transportation connection is also
part of Oregon’s Statewide Planning Goal 6 (Air, Water and Land Resources Quality), and is enforced by the
Oregon Department of Environmental Quality (DEQ) through OAR 340-200-0040.By developing the Washing-
ton County TSP consistent with the Metro RTP (which complies with federal and state air quality conformity
regulations), Washington County helps the region meet federal, state and regional air quality regulations.

5 Clean Fuels Program, Oregon Department of Environmental Quality, 2012, http://www.deq.state.or.us/aq/cleanFuel/index.htm
6 Portland Air Toxics Report, Oregon Department of Environmental Quality, 2010, http://www.deq.state.or.us/aq/planning/patsRe-
port.htm

PART 2: GENERAL TRANSPORTATION POLICIES FOR WASHINGTON COUNTY 25
Effective November 27, 2015 • Updated December, 15 2016