ROAD CONSTRUCTION & MAINTENANCE

A Guide to Reducing  Water Quality Impacts  Potential Water Quality Problems Critical Areas and Issues Assessing Existing Conditions Making Improvements     Funding and Technical Assistance

 POTENTIAL WATER QUALITY PROBLEMS

Road construction, road maintenance and vehicle traffic can increase concentrations of sediment, nutrients, oils and grease, and heavy metals.  Also if the road is constructed parallel to a riparian area, as is often the case in mountainous terrain, shade species may be eliminated resulting in higher water temperatures.

Increased sediment concentrations in waterbodies can impact fisheries and other aquatic life. This may include less successful spawning activity, a change in the macro-invertebrate populations, and a change in the aquatic plant community.  

Increased nutrient concentrations can cause over fertilization of waterbodies creating a condition known as eutrophication.  This situation, which is often more serious in lakes than streams, results in excessive algal growth.  When the algae die and decompose, oxygen is depleted.  Depending on the extent of the oxygen depletion, a fish kill may result.  Increased nutrient levels can also impact water supplies that are used for human consumption. Elevated nitrate levels can interfere with the blood's ability to carry oxygen.  This can be a serious problem for infants and the elderly.  

Oils and grease as well as heavy metals can harm aquatic life and in some cases cause human health problems.

Increased water temperatures can impact temperature sensitive species such as trout.  Increased temperatures can also reduce the dissolved oxygen holding capacity of water.

CRITICAL AREAS AND ISSUES

The closer the road construction activity is to a surface waterbody, the greater the chance for a water quality impact.  While this is a general rule of thumb, it is possible that areas close to water may not have an impact and areas removed from water may have a significant impact.  

When identifying critical areas, it is important to consider: proximity to water, soil type; topography; drainage patterns; and precipitation patterns. Situations that are likely to have a negative impact on water quality include: road construction in riparian areas; road construction on steep slopes; and road construction without proper layout, shoulder stabilization, culverts and bridges.  With proper planning, many of these potential impacts can be mitigated.

A number of management tools can be used to protect water quality.  They are outlined in the 'Making Improvements' section below.   However, before improvements can be planned existing conditions should be assessed.

ASSESSING EXISTING CONDITIONS

If road construction is being considered, there is a potential to have a negative impact on water quality if any of the following exist:

• Surface waterbodies are located adjacent to the road or drainage patterns carry runoff from the road to nearby surface waterbodies.
• The road is located in moderate to steep terrain.
• There will be a need to operate construction/maintenance equipment in riparian areas.

MAKING IMPROVEMENTS

Improvements, often called Best Management Practices (BMPs), fall into two broad categories: structural or management. Good planning often requires both types of BMPs.

There are many kinds of structural BMPs including: culverts; bridges; rip-rap; straw bale dikes; sediment traps; etc.  Depending on complexity, a structural BMP may require a detailed engineering drawing.  In other cases, existing drawings can be utilized or modified to fit a given situation. 

Management BMPs include: carefully planning the road layout; leaving buffer strips along riparian areas; minimizing stream crossings; seasonal road closures; etc.     

Excellent sources of information for planning specific BMPs include:

• EPA's 'Controlling NPS Pollution From Roads and Bridges'
• EPA's 'Erosion, Sediment, and Runoff Control for Roads and Highways'
• EPA's 'Management Measure for Road, Highway, and Bridge Runoff Systems'
• EPA's 'Management Measures for Forestry' (the road section)
• National Forest Service's Road Construction and Maintenance Specifications

Preplanning construction activities to reduce water quality impacts is very important. The following will generally be included in a good plan:

• Construct roads a safe distance from a waterbody.
• Minimize the number of stream crossings.
• Carefully design stream crossings with bridges, culverts, rip-rap, etc.
• Construct stream crossings during periods of low streamflow. 
• Fit upland roads to the topography using culverts, waterbars, stabilized slopes, etc.
• Route road runoff to a filter strip and not directly into a waterbody.
• Provide energy dissipaters (bales, rocks, logs, etc.) to reduce the erosive force of runoff.
• Carefully locate, and properly reclaim, borrow pits and gravel sources.
• Seed or otherwise stabilize disturbed areas as soon as possible.
• Complete road construction prior to the main runoff season to minimize exposure of unfinished roads to heavy runoff. 

FUNDING AND TECHNICAL ASSISTANCE

Section 319 funds maybe available from DEQ to assist with conservation practices relating to private road construction and maintenance. Applicants for these funds must show that a water quality problem exists and that the proposed practices will improve the problem.  Interested parties should apply through their local conservation district.   For assistance with issues relating to public roads the appropriate city, county, state or federal highway department should be contacted. 

The Internet also contains a wealth of information including the following sites:

• National Evaluation of Water Quality Issues for Highway Planning
• National Highway Runoff Water-Quality Data and Methodology Synthesis

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