It is wise to keep a stock of compatible replacement materials on hand to repair damage from impact or vandalism. Consideration should be given to keeping replacement materials where they can weather to match installed barriers, such as for pressure-treated timber components. Also, if color is added to concrete panels during manufacture, it is desirable to make future replacement panels in the same operation.
The control of graffiti remains a problem in some urban areas. There are some antigraffiti surface treatments available, but they are generally costly. Power washing and repainting are current options.
Plantings should be tolerant of roadside environments and require little or no maintenance. Access must be provided to both sides of the barrier for mowing, general maintenance, etc. Sometimes this may require backside access from city streets, or overlap openings along the length of the barrier. In some cases, arrangements can be made with abutting property owners to maintain the area behind the barrier. If the noise barrier is over 5 ft (1.5 m) high, the right-of-way fence can usually be eliminated.
Some block masonry noise walls and retaining wall combinations made of 2000- to 3000-lb/in[13] [14] [15] [16] [17] [18] [19] [20] (14- to 21-MPa) dry cast units have exhibited extensive disintegration after 3 to 5 years. This disintegration is caused by salt spray from winter driving traffic during removal of snow and ice from the roadways. Testing of blocks removed from barriers showed similar disintegration and chloride ion content on the front and back or fill side. Application of treatments to seal only the front or exposed surfaces will not be effective for the back surfaces. Sealing the surfaces must be repeated and becomes a costly maintenance item. Work is underway to evaluate high — strength (5000-lb/in2) (35 MPa) dry cast blocks that should reduce susceptibility to chloride contaminants.
