Natural Resources

Natural Resources Management Group ~ Vegetation Management

Hazardous Trees   |   Herbicide Application   |   Priority Weeds
Recovery Zone   |   Sight Distance   |   T & E Species

The Natural Resources Management Group (NRMG) strives to uphold the diverse environmental responsibilities of ADOT while supporting native ecosystems with stable plant communities. Vegetation Management is arguably the cornerstone of the NRMG. The Integrated Roadside Vegetation Management (IRVM) program is comprised of herbicide treatments, priority weeds, brush control, hazardous tree removal, native plant salvage and revegetation. IRVM is the result of years of evaluation of management practices and a continuous check of current process to achieve the stated objectives. Active management of Arizona’s right of way provides for motorist safety, infrastructure stability and protects ecosystems adjacent to roadways. Right of Ways (ROW) are unique areas within any ecosystem. The artificial impervious layer (pavement) directs precipitation quickly to the closest available soil surface. This moisture allows plants that do not normally exist in drier soil the opportunity to establish and thrive. Often these plants are non-native species that grow to heights higher and densities greater than their native counterparts causing sight distance and safety issues along with infrastructure stability problems. To reduce the negative affects of vegetation along the ROW, the following management actions grouped into continuous projects have been established
Hazardous Trees
	One goal of ADOT Natural Resources Management is to preserve the natural beauty and environmental integrity of our right-of-way while providing a safe and efficient road system. Hazard tree management, within the constraints of the Department's resources, is a necessary part of providing a complete road system. Hazard trees must have two characteristics, a defect and a target. A hazard tree is defined as a tree that has structural defects in the roots, stem, or branches that may cause the tree or tree part to fail, where such failure may cause personal injury or property damage (target). A defect may be caused by an injury or disease. A target is any area that has a high risk of injury to people or property if a tree falls within striking distance of the site.
Herbicide Application
With vast areas of responsibility, both geographically and ecologically, the most efficient way to control vegetation along the ROW is through herbicide application. Often referred to as chemical mowing, herbicides can be used to slow the growth of tall native vegetation, and control non-native species. To follow our bi-modal precipitation pattern, bi-yearly herbicide applications are used to manage annual weed species, noxious weeds, visibility issues and safety features. Integrated Roadside Vegetation Management provides better weed control with less herbicide by:
Application only to the target vegetation              Application at most effective time of growth Using the most effective herbicides Application at minimum effective rates Utilize the latest technology Application by trained personnel Prioritizing targets and applying proactively
Priority Weeds
A weed is any plant that interferes with the management objectives for a given area of land at a given point in time. Any plant growing where it is not wanted may be considered a weed. Criteria used for ADOT Natural Resources to classify vegetation as a weed.
	Does it limit visibility of the roadway?   Is it a potential safety hazard? Is its growth detrimental to maintaining the road Is it a federally or state listed noxious weed?
Recovery Zone
In accordance with the ADOT Design Policy on Clear Zones and the ADOT Roadway Design Guidelines, vegetation growing within 30-45 feet of roadway shoulder white lines must undergo aggressive management in order to meet safety standards.  On roadways with a posted speed limit of 55 MPH, trees having a trunk diameter of 4 inches and greater within 32 feet of the edge stripe will be removed.  On roadways with a posted speed limit of 65 MPH, trees having a trunk diameter of 4 inches and greater within 46 feet of the road's edge stripe will be removed.
Currently, recovery zones along Arizona's state highways and roads are being managed using methods that encourage the establishment of native plant species that suppress the spread of noxious weeds, inhibit fire, reduce soil erosion, stabilize roadsides, and are aesthetically pleasing without compromising traffic operations
Sight Distance
Year-round attention is given to traffic intersections. From private drives to county roads intersecting state highways, visibility of oncoming traffic is important to the safe travel of vehicles entering these intersections. Visibility also applies to other safety features including guardrails, signs, ramps and gore points, driveways, and crossovers that intersect with the main highway thoroughfares. Maintaining a safe travel environment requires a sustained, adequately funded effort. We maintain these areas using a variety of tools.   Chainsaws, brush chippers and cut stump treatments Foliar herbicide applications Boom mowers
T & E Species

The Endangered Species Act (ESA) directs all federal agencies to ensure that any action authorized, funded or carried out by these agencies is not likely to jeopardize the continued existence of a federally listed threatened or endangered species, or result in the destruction or adverse modification of critical habitat for a listed species. This mandate includes regulatory and licensing activities such as the federal registration of pesticides. The objective of this program is to provide protection for endangered species. To achieve this goal ADOT Natural Resources does the following:

Uses sound science to assess the risk of work activity to listed species Attempts to find means to avoid concerns for listed species Consults with the United States Fish and Wildlife Service (USFWS), which then issue biological opinions on the potential for adverse effects on particular species. Implement use limitations that are either specified in USFWS biological opinions or developed from these opinions Develop maps of advoidance locations