Glossary

Description
Obliterate
To remove all or part of the roadway and/or pavement.
Office of Human Environment (OHE)
See Human Environment Unit (HEU).
Office of Natural Environment (ONE)
See Natural Environment Unit (NEU).
Off-site Mitigation
Off-site mitigation may be used when there is no practicable opportunity for on-site mitigation, or when off-site mitigation is environmentally preferable. According to pending Federal guidance, one of the best tools for determining when off-site or out-of-kind mitigation is environmentally preferable is a holistic watershed plan. http://environment.fhwa.dot.gov/strmlng/newsletters/jul04nl.asp
On-site Mitigation
On-site, in-kind mitigation means compensatory mitigation which replaces wetlands or natural habitat area or functions lost as a result of a highway project with the same or like wetland or habitat type and functions adjacent or contiguous to the site of the impact. (23 CFR 777.2) http://www.fhwa.dot.gov/hep/23cfr777.htm
Origin/Destination (O/D) Study
Study of travel patterns for a town/city/region in which households or vehicles (depending on study type) are asked questions related to their daily travel. Examples of data may include: type of trip, length of trip, time of day and starting and ending points of trips. Data collected allows for calibration of a travel demand model to the traveler characteristics of an area.
Orthophotography
A digital image that has been corrected to account for image distortion due to the tilt of the camera. Digital orthophotography has an x, y coordinate system and typical resolutions of 0.5", 1', and 2'.
Outer Banks Task Force (OBTF)
A multi-agency work group which has several primary goals: Preserving the natural barrier island system in N.C.; minimizing impacts to Hatteras and Ocracoke islands; and maintaining access to and on the islands so that the transportation system is safe, efficient, and has minimal impact on the environmental. Primary agencies on the OBTF include NCDOT, FHWA, USACE, NPS, FWS, NMFS, and NCDENR.
Outlet
The end of a culvert where flow exits the culvert. Also used to describe the location at which storm water exits a storm drainage system or roadway ditch system.
Outstanding Resource Water (ORW)
Unique and special waters of exceptional state or national recreational or ecological significance which require special protection to maintain existing uses.
Overbank Flooding
Any situation in which inundation occurs as a result of the water level of a stream rising above bank level. (USACE; Technical Report Y-87-1, Corps of Engineers Wetlands Delineation Manual, Department of the Army, Waterways Experiment Station, January 1987;)
Overstory
The trees in a forest of more than one story that form the upper or uppermost canopy layer. (Silvicultural Systems, U.S. Forest Service, Agricultural Handbook 445, 1973;)
Ozone (O3)
Ozone is a colorless and odorless and chemically reactive gas which at ground level can be a very harmful air pollutant. Upper atmosphere ozone occurs naturally and forms a protective layer that shields the surface from the sun's harmful ultraviolet rays. Ozone at ground level is considered "bad ozone" and is emitted from automobiles, power plants, industrial boilers, refineries and other chemical process plants.
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