“Because concrete is fuel- and fire-resistant, we do a lot of airports. Concrete will take a heavy load and is warranted for use under taxiways and parking garages. Airports tend to evolve; an area used for parking may become a taxiway, which means heavier loads. The need is to design pipe installation in such a way that it anticipates new uses. There are lines in use today where the pipe is over 100 years old–not surprising since concrete grows in strength as it ages. It lasts longer than other lighter materials.” What about the weight challenge presented by concrete? Relates Domenico, “It’s ideal for areas where pipe depth will be rather shallow, yet it can handle burials of 100 feet or more without deflecting or collapsing. Furthermore, not only is RCP strong enough to handle traffic with minimal cover but, since it’s available in gasketed or mortared joints, concrete pipe can be soil-tight and silt-tight. Regardless of how well manufacturers build a product, the operation of the storm line depends on the contractor’s installation, and RCP is the most foolproof product to install. Inspection when laying each section of pipe is not crucial when concrete is used because there is such a large safety factor in design. When you use RCP you get 90% of the strength delivered on the truck. When installing flexible pipe, the bedding and backfill play a larger role in creating the strength of the line.”Domenico also reports that stormwater trends in this highly populated state include putting retention ponds underground. Underground systems present fewer public hazards than open ponds, don’t need mosquito abatement programs, don’t present aesthetic challenges, and don’t compete for surface acreage.Middlesex Trenching Company of Metuchen, NJ, has been doing site-preparation work since 1952 and includes underground retention systems in its repertoire of services. “One of our more recent projects for Adams Bickel Associates involved the site work for Commerce Bank’s regional headquarters 12 miles away in Bridgewater,” explains William Gulya, president. He adds that site preparation for this current project totaled nearly $1 million, with the 107- x 130-ft. retention basin accounting for 30% of the bid.“Basically it’s a series of 48-inch RCP connected with specially fabricated concrete tees. Stormwater is collected through a series of catch basins and manholes from the finished parking lot, then routed into this underground storage facility. When completed, the top of the retention pipes were 5 feet from the surface, which will be used as the major street access to the bank and for parking. We’ve put in all types, but RCP was called for in this one because it was more economical, and we didn’t need to go nearly as deep as we would have with other products.” This also reduced the risk of groundwater intrusion, a factor in this coastal state.With just 12 working days permitted for installation, the 26 concrete tees joining the 15 lines of piping posed a particular challenge to the crew of five because of the awkwardness of slinging them into place. Gulya explains, “We worked closely with Kerr Concrete Pipe to be able to lift them safely and efficiently and put them right into place with a minimum chance of damaging the pipe. Basically we located 3-inch cored holes, about a foot from each end of the tee, and used tapered steel cones that slipped into the holes when the tee was lifted, keeping the tee level. It made installation a piece of cake.” After backfilling to subgrade with 2.5-in. clean stone, it was a matter of paving to grade, and the retention basin was ready for use.Mike Saubert, director of marketing for the American Concrete Pipe Association (ACPA) in Irving, TX, points out, “Stormwater transport and detention has certainly become a more critical topic in the last couple of years as a result of federal legislation and state and local governmental actions. That’s why ACPA, in conjunction with the Illinois Concrete Pipe Association, has issued DASH–Detention and Sewer Hydraulics–software to enable engineers and pipe specifiers to develop stormwater detention systems utilizing precast concrete pipe. We’re also seeing a lot of interest from our membership with stormwater separator systems, which isolate waste from stormwater runoff before transporting that water to processing plants.”Increasingly, local authorities are mandating such systems wherever cars gather in great numbers, whether it’s a local filling station, a shopping mall, or a sports complex. Saubert observes, “It keeps our members busy providing solutions for more efficient stormwater storage and transport. More and more, stormwater is being diverted from sanitary systems because you don’t need to process stormwater at the same level you do human waste. This separation is helping municipal treatment plants have a longer life before growth outpaces original capacity.”He continues, “Precast concrete pipe has benefited tremendously from new technology. Pipe design has changed significantly during the past two decades. For example, our members can design and manufacture products for specific applications and installation requirements. Owners may be able to use a lower strength class of pipe where they have good backfill and good native soil, or if they have very weak soils, they can opt for a higher strength class of concrete pipe to achieve design parameters.”ACPA President John J. Duffy, who has been in the industry since 1974, reports that precast concrete pipe is a $1.4 billion- to $1.6 billion-a-year business, with 75–80% used for stormwater and the remainder for sanitary systems and miscellaneous uses. “The principal advantages of concrete pipe are that it is more durable, comes in a wide assortment of classes, and has a proven service life of over 100 years.”Although there can be a concern about shipping issues, Alan Siebenthaler, director of marketing and quality assurance for the National Precast Concrete Association in Indianapolis, comments, “There are precast concrete plants throughout the country, so shipping costs are not the issue faced by manufacturers of other pipe materials. RCP is readily available. When it comes to pipe product, we’ve found that when you include installation and long-term maintenance, overall project costs tend to lean in our favor. Specifiers and contractors must understand the limitations of all types of pipe. RCP comes in a broad range of sizes and with high compressive strength so is therefore ideal for nearly all applications.” However, Siebenthaler notes, “Reasonable care must be taken with job-site storage, handling, and installation of RCP. Good practices can prevent damage in any type of pipe, reducing the number of discarded pieces and overall costs. During installation, use of the proper equipment and safety procedures will reduce the likelihood of damage and injury while improving installation time. Installers must know the best procedures for installing RCP. This information is usually available from the pipe manufacturers and trade associations.”When Flexibility Is Part of the Equation
“The [biggest] advancement for us in metal pipe has been the development of various new coatings. These coatings allow us to extend the service life and also use [the pipe] in a wider environmental range. Galvanized is still the standard, but both Aluminized Type 2 and polymer precoated are increasing our market share.” Roberts emphasizes, “The idea is to protect the steel, which provides structural superiority and can be fabricated to any size or shape needed. We’re seeing a resurgence in the demand for our products.”Eric Whitney, stormwater treatment products marketing manager for Contech Construction Products in Middletown, OH, agrees. Phil Perry, supervisor of corrugated metal pipe (CMP) for Contech, reports that the company expects $450 million in sales this year. “Storm sewers are a major part of DOTs [Departments of Transportation], municipalities, counties, and a lot of private commercial work. Every shopping center, subdivision, commercial office, warehouse, new school, and new prison has storm sewers.”Whitney points out, “We make steel, aluminum, and lots of different types of corrugated metal pipe with metallic and nonmetallic coating. We try to match the right corrugated product to the customer’s needs. For example, Florida DOT has a design life requirement such that they use a lot of aluminum pipe and Aluminized Steel Type 2, which gives them a long service life in their harsh environments, which includes saltwater intrusion.”Other areas of the country favor the use of polymeric-coated CMP, which can handle low pH and water, while galvanized works well with high-pH conditions. With aluminum, an appropriate corrugation and thickness can be specified to give the pipe the equivalent strength of steel. Perry says, “A 16-gauge corrugated steel may handle up to 75 feet of cover, whereas 16-gauge aluminum may handle only 25 feet, but 90% of the jobs out there involve less than 10 feet of cover, so it’s really a nonevent.“The number-one problem with any pipe product in the marketplace, whether plastic, concrete, steel, or aluminum, is poor installation by the contractor. The primary problem is using poor backfill materials that don’t compact well.” Another problem involves the minimum cover needed. What may suffice for general traffic after construction might not handle heavy equipment during construction, so temporary berming over the pipes during the construction phase helps all products handle the temporary additional load.Whitney notes that raw prices for metal piping vary across the country, with aluminized costing 10–15% more than galvanized, polymer-coated steel 30–40% more, and aluminum 30% above galvanized CMP. “A new product on the market is bell-and-spigot joint for metal pipe. Contractors can install that pipe similar to concrete or HPDE pipe, no wrench work necessary.”Perry adds that one of the evolving markets for metal is underground stormwater storage because the cost-effectiveness and the larger diameters possible with corrugated metal make it an attractive choice. “This is why the City of Champaign, Illinois, chose corrugated metal pipe for a large stormwater storage project requiring 155,000 cubic feet of storage. Contech supplied 9,000 lineal feet of 132-inch-diameter pipe to meet the needs of the project. With diameters of 6 to 144 inches, metal gives the user a wide range of choices when it comes to specifying a stormwater drainage system.”As manufacturers of concrete, plastic, and metal pipe continue to improve the products they offer for stormwater concerns, the ultimate winner is the user, whether private, commercial, industrial, or public.
