Precast and concrete block producers are finding work on roadway noise abatement walls to be a sound investment.

Panel type or block walls are muscling out competing materials like wood, steel and plastic on a national basis, but in doing so quite often are going up against each other in bids. "Precast and masonry represent almost two-thirds of total usage," affirms Bob Armstrong, Highway Noise Team leader, Federal Highway Administration (FHWA) Office of Environment and Planning, in The Wall Journal.

And while private development is a growing market for sound walls - for example, around expanding retail centers in residential neighborhoods - mile for mile, the state and municipal public sector is driving sound wall construction. "Highway noise barrier construction will continue to be a growth area in the U.S.," reports the Transportation Research Board's Committee on Transportation-Related Noise and Vibration, in "Transportation in the New Millennium: State of the Art and Future Directions." "As of 1995 [the most recent year for which sound data are available], the number of linear miles of barriers constructed in the U.S. had tripled over the previous 10 years alone, eclipsing 1,300 linear miles by the end of 1995, [with] no signs that this trend will be significantly altered," committee members reported in January 2000.

Because of this anticipated growth, they add, and the fact that highway noise barriers typically cost approximately $1 million per linear mile, highway noise barrier design must be as efficient and cost-effective as possible. That's why FHWA released, in March 1998, a new, state-of-the-art model for predicting noise impacts in the vicinity of highways: FHWA Traffic Noise Model (TNM), Version 1.0.

"It uses advances in personal computer hardware and software to improve on the accuracy and ease of modeling highway noise, including the effective and cost-efficient design of highway noise barriers," the committee notes. "FHWA is committed to continued TNM improvement and long-term development."

However, in a December 1999 memo, FHWA chided state departments of transportation for not promptly validating TNM. The new model was to be phased in over the two years beginning March 1998, when it would replace the existing FHWA noise prediction model and software. "Little such work has been reported," the memo stated, adding that the Volpe National Transportation Systems Center in Cambridge, Mass., had begun a full validation of the model. As a result of the delay, the final phase-in date was extended to December 31, 2002.

Feds want sound walls The federal government is firmly behind sound wall construction where appropriate. The National Environmental Policy Act (NEPA) of 1969 provides broad authority for evaluating and mitigating adverse environmental effects, including highway traffic noise, while the Federal-Aid Highway Act of 1970 charged FHWA with developing standards for mitigating highway noise. The Noise Control Act of 1972 gave the Environmental Protection Agency (EPA) the authority to establish regulations to control major sources of noise, including transportation vehicles and construction equipment. It also requires EPA to issue noise emission standards for vehicles used in interstate commerce.

Federal funds may be spent on mandatory sound walls for new projects (Type I walls). Also, as articulated in the FHWA's June 1995 document, "Highway Traffic Noise Analysis and Abatement Policy and Guidance," a state may spend federal-aid highway funds for noise abatement along existing routes. These Type II projects are implemented strictly at a state's discretion.

Precast leads Precast is the leading material for highway sound wall construction, edging out concrete masonry, FHWA statistics show. And while block has the edge in California - where the bulk of sound walls are built - precast leads elsewhere in the nation. The Precast/Prestressed Concrete Institute (PCI) reinforces members' market position in current promotional literature: "Whether called upon to satisfy the need to reduce highway traffic sound or minimize undesirable and intrusive views, precast sound wall systems are among today's most economical and remedial systems."

One of the nation's leading concrete sound wall producers, Prestress Engineering Corp. (PEC) of Prairie Grove, Ill., makes sure its own marketing materials are in the hands of government agencies, architects, consulting engineers, and contractors throughout the Midwest and elsewhere. "We have a package that discusses our PCI plant certification, provides actual engineering drawings of how the product goes in the field, stains and color, and salt scaling reports showing how our product performs," notes PEC Vice President of Sales Andy Keenan. "Most agencies ask us to meet certain criteria, such as ASTM and BOCA. We have a package that shows the designer, engineer, consultant, state agency, or whomever else that our walls meet their criteria."

PEC's binder-based presentation kit also includes site locations; abundant photography reproduced on a quality color photocopier; and other brochures tucked into inside-cover pockets. The producer's Web site, www.pre-stress.com, also profiles sound wall projects and other precast applications.

Keenan makes sure PEC has the best marketing presentation he can provide, but that's understandable, as he's the chairman of PCI's Sound Wall Marketing Subcommittee. In February, the group released a new promotional sound wall VHS tape, featuring product benefits and testimonials from state and municipal officials. The tape is free to government agency representatives and residential organizations who request it on their letterhead, and also will be distributed through PCI producer members. Additionally, PCI's subcommittee last month put the finishing touches on a color precast sound wall brochure that emphasizes product from PCI-certified plants.

PEC is geared to conventional precast over hollow core panels, while North American Precast Inc. of Stow, Ohio, produces reflective sound wall using its Spancrete Hollow Core Plank machine. The bed has an Aslar Stone mat producing a finish that typically faces residential areas. The freeway side is rolled with a similar pattern. North American's absorptive sound wall is a wet-cast wall with two faces.

California boosts masonry Although precast has the lion's share of sound walls, concrete block comes up a close second, driven primarily by its traditional, abundant use in California. The Golden State's use of masonry sound walls wins kudos for aesthetic impact that would not be possible with any other construction medium.

"I-680 in Walnut Creek, Calif., has sound walls made of blocks in a combination of colors, textures and sizes," writes Philip Langdon in an August 1997 Atlantic Monthly feature. "The walls start uniformly dark gray at either end and progress to a lighter tone of gray interspersed at random with dark-reddish blocks; then the reddish blocks form two horizontal bands. The pattern changes from one end to the other, giving rhythm to the drive," Langdon notes. In a quote from Caltrans' Arthur Yee, he adds: "Because of all the gray block, these walls were less expensive than the usual earth-tone walls we build."

California was an early adopter. "In 1968 California built what are believed to be the first noise barriers along modern federal highways," Langdon explains. "Walls were erected on Highway 101 in San Francisco and I-680 north of San Jose to shield abutting residential neighborhoods from the sound of heavy traffic. Within four years the federal government followed California's lead, adopting regulations requiring that whenever a state builds, expands, or realigns a federally funded highway, an attempt be made to curtail noise."

Since then, Langdon reports, 41 states have built highway noise barriers, generally with 75 to 90 percent of the cost paid by federal funds. Nineteen of those states voluntarily have built noise barriers along existing highways where no widening or roadway relocation occured.

The Caltrans Highway Design Manual permits block, precast concrete panel (with post or mounted on safety shaped barrier), wood (post and plank or framed plywood), metal (ribbed steel), and composite beam (foam and wire mesh core with stucco exterior). "Other design alternatives may be considered provided that they meet the structural and noise attenuation criteria," the manual states.

"Masonry has proved itself to be the best performer for its cost of any sound wall product Caltrans permits," notes Peter Beard, sales manager of Orco Block Co., Inc., Stanton, Calif. "It's used here far more than anywhere else in the country. From appearance, noise abatement and performance standpoints, masonry wins."

Masonry sound walls provide the ability to have many different designs in different locations throughout the state, Beard adds. "We can even put designs in the walls by varying the masonry units. We can use walls with slump, some walls with split face, some with a combination of both. Many masonry sound walls use a fluted top, which is part of Caltrans' sound reduction design. They can use an attractive product and reduce sound," he says.

Under license, Orco also markets Sound Block, a unit with vertical lines that absorb sound into a cavity or filled septum. Marketed by Connecticut-based Proudfoot Architectural Group, the proprietary product has been used m ost recently at a private development for Sears in Ventura, Calif.

Masonry sound wall erection is more labor-intensive than precast, and the perception persists that lower-cost labor in the West gives block an advantage over precast. Not so, Beard argues: "It has very little to do with labor rates. It's a decision based on quality and price. Our labor is all-union, prevailing rate, very similar to anywhere else in the country."

Instead, a desire to provide an aesthetically pleasing roadway underscores California's heavy use of masonry block. "They definitely put more thought into it, and are more concerned about the aesthetic look along the freeways," Beard explains. "That plays into it because of the multitude of colors and shapes we can give them." That's in addition to masonry walls' serviceability and durability.

"As you drive along, one city will have one look to its sound walls, and another city will have another look," Beard says. "The masonry sound walls are tied into an overall landscape design. Caltrans subs out the design to landscape architects and other designers."

Competing materials Although precast concrete and masonry are the leading materials for sound walls, wood often is thought of first for sound walls. Other competing materials include steel, plastic and recycled products.

The involvement of Illinois' PEC in sound wall production dates back only eight years, Andy Keenan tells Concrete Products. "We were contacted by a gentleman in the cement industry who brought us an article on how the Illinois State Toll Highway Authority was going to build a large amount of sound wall and was planning to use wood, and he wanted to know why. So we got involved early-on in getting concrete as an alternate bid.

"We were really concerned that we were going to be more expensive than wood, so we fought hard for life-cycle costing. With that we could be more expensive in first cost, yet cheaper in terms of durability and service life. When the bids came in, we beat wood hands down. Since then, it's been 100 percent precast on the ISTHA projects."

PEC and other Illinois precasters in this market also benefit from the educational efforts of Precast/Prestressed Producers of Illinois (PPPI)Marketing Director Ed Gregory, who conducts workshops throughout the state and meets with communities to promote the use of concrete. "Wood would be there, plastic and recycled materials would be there, steel and masonry would be there," Keenan says. "But 100 percent of the time, precast would be the choice of the community."

Wood has declined in usage because of durability problems compared to concrete; difficulties in cleaning of graffiti; and the disfavor of use of imported wood from tropical rain forests, which had been the prime source. Wood also suffers because preservatives such as creosote emit volatile organic compounds (VOCs) to the atmosphere.

And while in actual, diluted practice these emissions may be harmless, the perception of danger exists and can be exploited. "We argued that point early on against wood," Keenan says. "Concrete is from Mother Nature. And the stain that we use is purposely VOC-compliant, being water-based and without solvents."

Use of alternate materials may have been boosted with the January 1999 Transportation Research Board-sponsored publication of Noise Barriers Using Recycled-Plastic Lumber (Hag-Elsafi, Elwell, Glath and Hiris). This New York State DOT paper describes use of "lumber" fashioned from recycled plastic extruded into classic lumber sizes, and placed in wood or steel frames. It mentions competitive costs per square meter of $161-194 for plastic lumber with wood frames, and $226-269 with steel frames.

Plastic is making inroads elsewhere. Last year American Insulock Inc. of Vancouver, B.C., submitted a formal proposal to Caltrans to have its proprietary foam block material technology approved for statewide sound wall construction. Along with masonry and precast producers, Insulock was chasing after some$170 million for 58 sound wall projects statewide that were announced August 1999.

The system uses interlocking, self-aligning, dry stacking polyurethane foam blocks that incorporate concrete and steel to form a post-and-beam superstructure. The manufacturer says Insulock replaces conventional load bearing walls - above and below grade - and can be used in conjunction with any interior or exterior finishing materials.

Insulock Sound Walls are set in place approximately eight times faster then conventional masonry walls, system developers claim, noting that a shorter building envelope results in reduced traffic interruption. The light weight of the Insulock block (1.5 lbs.) eliminates the need for heavy scaffolding and other large equipment on site, reducing site clearance requirements, they add.

"Masonry sound walls are 79 percent heavier than the Post & Beam Insulock Wall System, and cast-in place concrete walls are 211 percent heavier," Insulock contends. "This reduced load factor translates to measurable savings in foundation requirements as well as further reducing construction time lines."

In 1991, Caltrans constructed a 300-foot Insulock Sound Wall at the intersection of Ventura Highway and White Oaks. The wall was undamaged by the Northridge earthquake of 1994, the manufacturer reported.

Today's technology helps one building medium grab sales by imitating a competing material. For example, not only does Insulock manufacture plastic block that resembles masonry block, but American Technocrete Corp. makes both Woodcrete, Brickcrete and Fencestone walls, with precast elements resembling those materials. And some very unique sound walls are blossoming in parts of the country. For example, sound walls made of soil growing thousands of plants and flowers, are being promoted by the Green Sound Wall Co. of San Ramon, Calif. One such wall was constructed along Ygnacio Valley Road in Walnut Creek, Calif.