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	T H E M O S T A D V A N C E D N A M E I N D R A I N A G E S Y S T E M S.
N-12 and N-12 HC Pipe
The high-performance future of engineered drainage

The new standard in drainage pipe
Every day for more than 30 years, Advanced Drainage Systems corrugated high-density polyethylene (HDPE) pipe has been building it's reputation for economy, durability, and superior performance in gravity-flow drainage application. During the 1970's and 1980's, ADS single wall pipe became the preferred product for agricultural, mining, turf/recreation and residential drainage markets.
N-12 Pipe (100-1050mm)
The hydraulic capabilities of the product were significantly improved in 1987 when ADS introduced the first HDPE pipe to combine an annular corrugated exterior for strength with a smooth inner wall for maximum flow capacity. Named for its excellent Manning's "n" rating of 0.012, N-12 pipe was designed specifically for storm sewers, highways, airports, and other engineered construction. Through extensive field and university testing, ADS engineers were able to refine the corrugated wall design for successfully large diameters without compromising the pipe's excellent strength-to-weight ratio. Its performance and economy have led to rapid acceptance by contractors and engineers.
N-12 ProLink Ultra Pipe (300-1050mm)
In 1997, ADS incorporated a flush gasketed integral socket joint into each section of the popular storm sewer sizes of N-12 pipe. This design eliminates the need for separate couplings and the excavation of socket holes in the trench. The joint is silt-tight, and it's quick and easy installation has led to instant acceptance by contractors.
N-12 HC Pipe (1050-1500mm)
Soon after the introduction of N-12 pipe, ADS engineers began a major program to develop an alternative wall profile that would provide superior strength, stiffness and production efficiencies. An 8-Year old development and testing program produced a revolutionary pipe design called N-12 HC. The pipe features smooth inner and outer walls, and a unique "honeycomb" wall section using closely spaced circular ribs that brace the pipe circumferentially for added ring stiffness and structural strength. Soil loading tests at Utah State University indicate that NC-12 HC pipe may have the most stable wall profile ever manufactured for large diameter flexible pipe.
Applications
All products can be specified for highway drainage, culverts, cross drains, storm sewers, landfills, and other public and private construction.

Technology creates a superior pipe material

Gone are the days when plastic pipe was specified only for cost reasons. Advances in polymer science and structural design have created a product that has actually outperformed and outlasted concrete and metal pipe while maintaining its installed cost advantage. By any measure, ADS N-12 and N-12 HC pipe compare favourable to conventional materials.

Structural Strength

As a flexible conduit, HDPE pipe withstands vertical pressure by transferring most of the load into the surrounding soil. N-12 and N-12 HC pipe will support H-25 live loads with 200mm minimum cover* and E-80 loads under 600mm cover. Maximum cover will very with design conditions, but can usually be specified up to 20m. In controlled tests, N-12 pipe has performed well as fill heights of more than 30m, and N-12 HC pipe has withstood soil pressures equivalent to 54m of cover before significant deformation occurred.

Durability

High density polyethylene is an extremely tough material that can easily withstand the normal impacts involved in transporting and installation. It is highly resistant to chemical attack and is unaffected by soils or effluents with pH ranges from 1.5 to 14.

HDPE's density and molecular structure result in excellent resistance to abrasion. Polyethylene pipe shows less than 20% of the material loss of concrete pipe in abrasive environments, and is often specified for harsh mine slurries as a slip liner for deteriorated culverts.

Hydraulic efficiency

The smooth interior of N-12 pipe provides superior flow characteristics. Tests on various sizes of N-12 pipe show Manning's "n" values ranging from 0.010 to 0.013. (It should be that "n" values tend to increase with slower velocities and larger pipe sizes.) The chart below indicates that N-12 pipe values are basically the same as those yielded on previous tests of reinforced concrete pipe. On the other hand, the "n" ratings for corrugated metal pipe are considerably higher, and are predicted on the pipe running full to develop the spiral flow.

Light weight

HDPE pipe is up to 30 times lighter than concrete pipe, making it far easier to transport and handle. On-site labour and equipment requirements are reduced, with a corresponding reduction in the potential risk of injury.

Fast installation

Six metre lengths mean fewer joints. Silt or water-tight connections are quick and easy with gasketed integral socket couplers. The pipe cuts easily and does not need to be bevelled for jointing. In typical trench depths of 2-3m, contractors report installation rates ranging from 360m per day of 375-600mm pipe to 120m per day of 1200mm pipe.

The lowest installed cost of any drainage pipe

The material cost of HDPE is extremely competitive with concrete and corrugated metal. When installation costs are factored in, the savings start to multiply.

Polyethylene's light weight cuts transport charges. More pipe per load means fewer deliveries.
Fewer people are needed for on-site loading and handling.
Heavy equipment requirements are reduced.
Six metre lengths are easy to handle and require fewer joints.

A recent survey if Departments of Transportation revealed that reductions in installed cost for HDPE pipe were 12 to 38 percent compared to concrete, and 5 to 28 percent versus corrugated steel.

A choice of joining systems

N-12 ProLink Ultra pipe with a built-in integral socket is the ultimate time-saver for installation of long straight storm sewer lines.
Hinged split couplers and fabricated fittings provide cost effective connections for normal drainage installations. ADS can fabricate virtually any fitting as long as it meets engineering standards.
Pro Link moulded HDPE couplers are another source of installation savings. Just align the pipe sections, lubricate the spigot, and push together. Double socket couplers are offered in 300mm through 600mm diameters, and single socket styles are factory welded on 750mm through to 1500mm pipe. Two levels of joint security are available.

N-12 Pro Link ST pipe provides a silt-tight joint for normal storm sewer and culvert applications
N-12 Pro Link WT Pipe is a pressure-tested coupler that provides water tight connections, meeting a full 10,8 pdi in accordance with ASTM D3212

Series 35 Thermo-moulded PVC sewer fittings meet the requirements of ASTM D3212 Selection includes couplers, tees, wyes, elbows, caps and adapters, each fitted with an O-ring seal. The fittings connect not only corrugated HDPE pipe, but also PVC, concrete and other materials.
All moulded couplers are designed to permit up to 3º of directional deflection with no loss of joint integrity or flow capacity. In rare instances, this allows the pipe to be lain of a curvilinear track when necessary to avoid underground obstacles or to parallel curves in roadways and ramps.

Installation recommendations

Proper installation is perhaps the major determinant of long-term performances of any drainage pipe, and the basic procedures and precautions for corrugated polyethylene are in fact quite similar to those for concrete and metal pipe.

N-12 and N-12 HC pipe are flexible conduits which transfer live and dead loads to the surrounding soil. particular care is therefore required in bedding, backfilling and compaction, and in the selection of backfill material. Class I, II, or III soils may be used for backfill, and should be compacted to at least 90% Standard Proctor Density.

Instructions for underground installation of plastic drainage pipe are contained in ASTM D2321. AASHTO Section 30 is recommended for highway applications. Specific instructions for N-12 and N-12 HC pipe are detailed in ADS Product Note 3.15, "installing N-12 Storm, Sewer and Culvert Pipe".

Solving drainage problems across the nation
PennDOT deep Burial study
	In 1987, the Pennsylvania Department of Transportation initiated what is believed to be the most ambitious research project ever attempted by the plastic pipe industry. A total of 175m of 600mm corrugated HDPE pipe (both standard single wall and N-12) were buried at depths exceeding 20m in an embankment under interstate 279 near Pittsburgh. Researchers from the University of Massachusetts administered the test, which sought to determine the performance limits of HDPE pipes under extreme loads.
<pic>	Electronic and hydraulic systems have been monitoring many aspects of pipe performance, including wall strain, deflection, soil pressure and soil strain. The results to date are impressive. Despite the tremendous soil load, the total of pipe deflection and circumferential shortening is just 4.3%, and has remained constant since the second year of the test. No cracking of any kind was observed in the N-12 pipe at any depth. The research has already led to improvements in coupling design and technical refinements in pipe manufacturing. PennDOT officials view the pipe's performance under these severe soil pressures as very positive, particularly since a sample of concrete pipe failed rather quickly under 20m in the same embankment. The study results have led PennDOT and other state transportation agencies to conclude that existing maximum fill height requirements for HDPE pipe are conservative and may be increased under certain project design conditions.
Missouri test proves value of soil compaction
	Missouri's first installation of large diameter polyethylene pipe provided a dramatic illustration of the effect of soil compaction on pipe performance. Two 15m cross drains using 1050mm N-12 HC pipe were installed approximately 2.7km apart. In both locations, a coarse grained gravel was used for embedment and backfill.
<pic>	In the first installation, the material around the pipe was mechanically compacted in 150mm lifts. No mechanical compaction was employed in the second installation. The maximum cover in both cases was 300mm, including the pavement. Immediately after complete of the work, vertical pipe deflection was measured. The numbers were conclusive: 1.2% maximum deflection in the compacted trench and 4.5% in the non-compacted trench. While the higher deflection reading was still well within the performance limits of polyethylene pipe, Missouri Highway and Transport officials planned to monitor the two sites to determine any longer term performance variations between the two installation procedures.
Neighbourhood storm sewer project installs easily
	After 25 years of persistent flooding, the residents of the Lakeview subdivision of Madison Township, Ohio, applied for state public improvement funds to install a modern storm drainage system. Of all the materials bid, only the HDPE system fell within the funding limit.
	The installation included 1525m of ADS N-12 pipe (300-900mm) and was accomplished well within the deadline and the limited budget. Since then, flooding complaints have been non-existent, despite a 100-year rain event in 1993. Five years later, ADS co-operated in an internal inspection by an independent pipe cleaning company using a remotely controlled television camera. Three hours of video tape revealed no abnormalities with the 730m of sewer line inspected - no damage, no misaligned joints, no changes in line and grade. Since the Lakeview installation, Madison Township has specified N012 pipe on several other large drainage projects. Officials point to HDPE's ease of handling, and believe that it performs as well or better than the concrete and metal pipe used previously. Lakeview was also the first HDPE sewer installation for the contractor, who cites several advantages of the lighter weight pipe: Use of smaller equipment which made it easier to negotiate the narrow right-of-ways with numerous trees, less risk of damaging the streets, the 10 loads of polyethylene versus the 29 loads if the pipes were concrete, and the ability to unloads and move the N-12 pipe by hand.
One-way culverts feature custom fabrications
	The 1989 earthquake which devastated San Francisco also damaged a set of seven bituminous metal corrugated culverts in Monterey County. These had been fitted with tidal flood gates to prevent salt water on the west from intruding into inland grazing areas, while at the same time allowing a freshwater creek to flow westward into the estuary.
	In late 1995, the culverts were replaced with 1200mm N-12 HC pipe, New aluminum tidal gates were designed and assembled on the west end of the pipes, while 600mm tall risers fabricated with 1050mm N-12 HC pipe were installed on the inlet ends of the culverts to handle fresh water spill-over during simultaneous high tides and storm flooding. The installation followed design practice recommended by ADS engineers. The culverts were bedded in gravel with three foot spacing between them, and the pipe ends were supported on concrete pads rather than being cantilevered. After repaving and removal of the coffer dams, the road was reopened, and within a few weeks the flooded farmlands were drained of the accumulated sea water.
New coupling design allows curvilinear installation
	Municipal engineers often find it necessary to route trenches around utility structures of some other buried obstacle. And highway engineers prefer to maintain a constant distance between the pavement edge and roadside drainage lines which means the pipe should be able to parallel bends in the roadway fairly precisely. ADS recognised these needs in the design of the new Por Link socket couplers for 300mm through 1200mm N-12 pipe. Each coupler permit up to 3º of directional deflection with no loss of joint integrity or flow capacity. All of the new socket-style fabricated fittings also have this capability. Drainage projects can thus benefit from a number of cost saving-options. One example is the Mon-Fayette extension of the Pennsylvania Turnpike, built to connect Pittsburgh and Morgantown, WV. The mountainous terrain dictated severe curvature in many sections of the highway and access ramps. Concrete and coated metal pipe were originally specified for drainage, but the alternate N-12 pipe was chosen for its ease of installation and its ability to follow roadway curves without shortening the 6m lengths or installing more costly angled fittings. The deflection allowed by the socket couples was sufficient to lay the pipe on the prescribed curvilinear track.
Tomorrow's drainage system products available everywhere today.
As time takes its toll on the service life of installed concrete and metal pipe, N-12 and N-12 HC pipes are fast becoming the preferred choice for gravity flow drainage applications. In addition to its proven performance and economy, ADS HDPE pipe has the same widespread availability as traditional pipe materials.
Use the ADS N-12 Prolink Ultra twinwall system to make next project installation easier.
Superior integral sealing socket on 300mm to 1500mm range. Pre-fitted seal to suit most site requirements. Full range of fittings and chambers. Cost-effective. Available in sizes from 100mm to 1500mm.

*For further information regarding ADS products in the United Kingdom contact:*
01430 423020	North England & Scotland	T H E M O S T A D V A N C E D N A M E I N D R A I N A G E S Y S T E M S.
01295 770394	Midlands, Wales and South England