Washington cities do have some say on the design of highway noise barriers

Published 12:01 am Monday, November 30, 2009

Connie Trier of Everett writes: Our driving group has been discussing noise barriers. We want to know how much costlier it is to put up scenic barriers as opposed to plain old concrete. A scenic noise barrier has “pictures” on it. In Mount Vernon there are trees, in Everett there are mountains, the new pedestrian overpass on Highway 99 has shells and water patterns, etc.

My opinion is the cost for the forms might be more, but hopefully they can be reused so the cost goes down to almost nothing over time.

Bronlea Mishler, a spokeswoman for the state Department of Transportation, responds: When we are building a project that calls for noise walls, we have a standard price and a standard mold design. The standard design depends on the highway corridor along which it is being installed.

Along I-5, for example, we use a fractured fin pattern of vertical ridges. Along Highway 202 in Redmond, we use a “random board” pattern of alternating raised board shapes. We use the same pattern so we can maintain continuity throughout the highway corridor.

Because these noise walls sometimes cut through cities, some cities have strong feelings about the design. Some cities choose to have communities vote on a design or they’ll pay a local artist to develop a design with the city in mind. Once that happens, we get an estimate to create a mold for that design and ask the city to pay the difference between the cost of our standard design and their preferred design.

This was the case on Highway 202. The price for our normal random board finish is $3.50 per square foot. The three-dimensional tree pattern they asked for was $4 per square foot. The city agreed to pay the difference. We used this pattern for a total of 44,590 square feet.

There are cases where we don’t itemize the cost and we pay for the design. Usually these designs are basic and have very little detail work and are therefore not much more expensive than our standard design.

The manufacturers we use also own the mold design once we ask them to create a mold. This typically means the manufacturer can place a very competitive bid with our contractor crews when we are asking for noise wall cost estimates.

It is cheaper for the manufacturer to recast a pre-existing mold rather than design and create one from scratch. Sometimes, we can also reuse the actual noise wall forms. Fractured fin molds, for example, can be reused up to three times before the mold is no longer effective. Special forms can also be reused.

E-mail Street Smarts at stsmarts@heraldnet.com. Please include your city of residence.