America’s sewers: finally money goes down the drain

Wastewater collection systems in the United States are in disarray. About 60 percent of the country’s sewers were installed before 1950, and their pipes are deteriorating. Municipalities have deferred preventive maintenance for many reasons, among them diminished federal and state funding and diversion of local tax money to more politically viable — read “visible” — issues.

Sewers have been neglected for one main reason — out of sight, out of mind.

Still, the future of sewers in America looks bright.

Public officials, consulting engineers and management specialists are developing new engineering technologies and building on old ones, borrowing techniques from abroad and applying technologies from other fields to analyze, repair, rehabilitate, relocate, construct and generally bring wastewater collection systems up to snuff.

One of the most popular techniques in use — trenchless technology — has been around for some time, but has only gained momentum in the past five years as pressures mounted to keep sewer rates down. “The technology extends back 15 to 20 years, but it has exploded over the past five years,” says Rich Cunningham, chairman of the Alexandria, Va.-based Water Environment Federation’s collection systems committee. “Availability of capital through federal loans and grants is, at best, flat, if not declining.

“Therefore, there is the implied requirement that cities make sure each dollar is spent in the most effective manner. Cities and agencies that have to comply with U.S. Environmental Protection Agency regulations on one end are facing diminished participation on the federal end. [That means] major increases in sewer charges. So, they have to turn to new technologies.”

Trenchless Technologies Explode

The popularity and increased use of trenchless technology has spawned a structured industry. The formation of the Chicago-based North American Society for Trenchless Technology (NASTT) in 1990 marked the development of a national level organization devoted entirely to the technique. NASTT holds annual conferences and serves as a clearinghouse for information and industry contacts. The Trenchless Technology Center at Louisiana Tech University, Ruston, La., founded in 1989, serves as a research center.

“The sewer industry realizes that trenchless is a true pipeline-problem solver,” says Tony Hooper, senior vice president of marketing and technology for Memphis, Tenn.-based Insitu-form, which has more than 7,000 miles of trenchless experience.

Projects using various types of trenchless technology range from massive undertakings such as Boston’s 7.9 billion Central Artery/Tunnel (CAT), which Massachusetts Highway Department officials call the “largest and most complex highway project ever undertaken in the core of a major American city,” to a repair management program in Dallas, which includes repairing a few feet of sewer line at a time.

Arthur Spruch, a principal of SEA Consultants, Cambridge, Mass., one of the consulting engineering firms working on the CAT project, says designers of sewer systems can learn a great deal from the Boston experience. By the time the project is completed in 2002 or 2003, construction engineers at the Boston CAT will have built or reconstructed 7.5 miles of urban highway — about half of that in tunnels.

New tunnels, including one under Boston Harbor that completes the last link in the U. S. Interstate Highway System, as well as new links to local highways add relocation of miles of sewer, water and other utility lines, are part of the ambitious undertaking.

The project area, located in one of the city’s most congested and environmentally sensitive areas, features buildings more than 150 years old, which city officials and historic preservationists feared would be damaged by vibrations and other detrimental effects associated with open trench construction.

The project also crosses the historic Boston Freedom Trail, which is walked by more than 1 million visitors each year; the Massachusetts Bay Transportation Authority Bus Terminal; and entrances and exits to the Sumner and Callahan tunnels connecting the city to East Boston and Logan Airport. It is adjacent to the Fleet Center, a new sports complex, and North Station, a railroad terminus. Nearby residents demanded that access to these be uninterrupted.

Finally, the Occupational Safety and Health Administration (OSHA) required that the contractor comply with safety regulations such as trench support, exposure of workers to traffic and falling loads and emergency rescue equipment accessibility.

Before beginning, a new method was used to determine the exact horizontal and vertical locations of underground utility lines. Called Subsurface Utility Engineering (SUE), the technique combines geotechnical prospecting, conventional surveying techniques and digital mapping into one service. The approach minimizes the risk of damage to utilities, according to Spruch.

After locating the lines, the contractor used microtunneling to install combined sewer mains, as well as three water mains and gas mains and underground conduits for electric and telephone service. A tunnel boring machine was used to microtunnel through soils, and lasers established a grade line for the operation.

“People never thought it could work,” Spruch says. “But the sewer line was installed in 14 days instead of six weeks with open trenching, and there was no significant shutdown of the street.”

Leslie Tulpin, a project engineer with Bechtel-Parsons Brinkerhoff, a Boston-based joint engineering venture, says Microtunneling means savings. “There is a quick turnaround, and turnaround time is money,” she says. Additionally, open trench cutting requires a bigger trench and a much larger area for workmen, and there is always the potential for hitting utility lines.

Many of Boston’s water and sewer lines are more than 200 years old and made of wood and bricks, Tulpin says. When wooden pilings are exposed to air they deteriorate, and many of the city’s buildings are on wooden pilings or granite blocks without mortar. Thus, excavating near historic structures, such as the Paul Revere House, was not an option.

Additionally, no-dig technology was ideally suited to the city’s sewer and water lines because they are much deeper than those of other utilities. Most experts agree that, based on costs alone, open-trench construction is more cost efficient at shallow depths. But as depth increases, the cost of open trench construction increases much more than the cost of microtunneling until they reach a point where both methods cost the same.

Additionally, besides being narrow, Medford Street is lined with loading docks and parking areas. Disruption in such a commercial area would result in decreased economic activity and lost revenues.

Fixing Up Old Lines

Unlike Boston’s massive concentrated project, sprawling Dallas uses a variety of trenchless technologies as part of its management plan in maintaining the miles of sewer and water systems in the busy downtown area and outlying residential areas.

“It’s basically an aggressive program to take care of backlog fixes,” says Antonio Almeida, deputy director, Dallas Water Utilities. “The old paradigm was ‘If it ain’t broke, don’t fix it,’ but we do have to maintain it.”

The city has a $3 million program to replace and rehabilitate the sanitary sewer system and plans to eventually increase that amount to $10 million without federal funds, according to Almeida.

Funds will come from achieving internal efficiencies and in rate growth, he says. The costs of failing to provide routine maintenance can be staggering. “If you assume a 100-year life for a 4,000-mile system — and that’s not a big one — you would need to spend 1 percent a year, or $40 million, to be able to replace it in 100 years,” says Almeida. “And that’s at today’s price of $100 per foot. Who knows what the price will be 10 years from now?”

A recent contract to replace 42,000 square feet of wastewater collection mains through the city uses trenchless technologies such as cured-in-place, slip lining and point repairs. Despite the explosion, however, new techniques being used in sewer construction and repair are not limited to trenchless technologies.

USING RADAR

Indianapolis obtains rainfall data that is superior by a factor of 20 to 30 to traditional methods by radar. Brian Neilson of the city’s department of public works says Indianapolis was the first city in the country, to install a French-developed technology designed by urban hydrologists to measure rainfall between gauges.

“Rainfall is the engine that drives all Combined Sewer Overflow (CSO), stormwater and sanitary sewer wet weather programs,” he says. The CALAMAR system was used to develop more accurate rainfall distribution for the Lick Creek Sanitary Sewer Evaluation Survey and will refine the calibration of its CSO hydraulic model.

CALAMAR is a French acronym for Calcul de La Mes d’eau a l’Aide du Radar, which simply means Calculating Rainfall with the Aid of Radar. The method relies on a local rain gauge network to calibrate the National Weather Service’s NEXRAD (NEXT generation Radar) images to obtain geographically precise rainfall measurements.

CALAMAR uses three sets of data — NEXRAD radar images of reflectivity, five-minute rain gauge data and a geographic database of the catchment areas — transforming them into geographically correct, absolute rainfall rates.

According to Neilson, the system provides superior knowledge of rainfall at a fraction of the cost of a rain gauge network. “We foresaw a capital cost in rain gauges alone — no telemetry or computers — of more than $1 million for 800 gauges to cover a 200-square-mile county,” he says. “We could get the CALAMAR system for $250,000. Twenty-five rain gauges of CALAMAR are more accurate than 800 regular rain gauges. We may add 10 more CALAMAR gauges just to spotcheck accuracy.”

The system also allows the city to direct limited Infiltration/inflow (I/I) and stormwater removal funds to the area with the greatest needs and allows it to calibrate hydraulic models more accurately.

Sewers Go High-Tech

Like Indianapolis, Oakland, Calif., was concerned about 1/1. The sewer collection system suffered from significant overflow problems during intense but brief storms when flow increased to 20 times the normal amount in some parts of the city. Overflows were caused by 1/1 entering the collection system and insufficient flow capacities of key trunk sewers.

The city uses a PC-based custom software package to manage maintenance. The package features a complete inventory of manholes, cleanouts, lampholes, pipelines and pump stations; tracking of maintenance activities for all collection system components, including physical inspections and closed circuit television inspections; least-cost analysis of alternative pipeline rehabilitation methods for reducing 1/1 based on inspection results; and maintenance activity scheduling.

Through the end of 1994, the city designed and constructed 24 rehabilitation projects and 27 relief pipeline projects, leading to a 74 percent reduction in overflows from previous years during the near-record rainfall season of 1994-1995 when a number of events recorded exceeded the intensity and duration of the design storm event.

When St. Louis wanted to assess the condition of its sewer pipelines and the soil conditions around it, it turned to seismic testing technologies.

Seismic Resonance Testing (SRT), an inexpensive, non-destructive methodology that allows design engineers to identify loose or voided soils around sewers, is an innovative application of the established technology. With it, seismic wave testing is used to determine the subsurface characteristics of the soils surrounding sewers and manholes.

The Metropolitan St. Louis Sewer District (MSD) used SRT when it wanted better subsurface information along three sections of sewer in the city. Assessments included hydraulic conditions, structural analysis of brick and other sewers, corrosion potential analysis and geotechnical information to define soil and groundwater conditions in areas with suspected defects.

Benefits of SRT include:

* Non-destructivity. It requires no trenching or borehole drilling;

* Reproducibility. Unlike boring, which can only produce information once in a given location, results from seismic testing can be duplicated and tested numerous times to verify information or monitor rehabilitation progress;

* Productivity. Since minimal setup is required, an experienced team can test up to one mile of sewer pipe per day. Depending on the depth of the borcholes, a drilling team can drill one or two boreholes a day. Placing a borehole every 200 feet along a one-mile section would require 15 to 25 days of drilling. Seismic testing can perform in-depth investigations at a rate of 600 feet of pipe per day; and

* Cost. The process eliminates the need for excess boreholes, which are costly and provide little useful information. The estimated cost of boreholes placed every 200 fect, including mobilization, is $11 per linear foot of pipe. The cost for seismic testing, which will provide useful information the entire length of the section of pipe, is $10 per linear foot of pipe.

Furthermore, SRT does not require entry other than at manholes. No in-sewer cabling is required. And, SRT produces a continuous profile of the materials between the sewer and the ground surface above the sewer, revealing information about soil densities and relative strength. It can be used to focus further investigations or rehabilitation efforts, such as soil grouting or compaction.

SRT can also help determine the best location for borehole placement, meaning fewer boreholes are required.

There are many more system designs for the future, of course, including the use of parallel-series pumping technologies, development of expandable modular wastewater lift stations, new methods for cleaning sediments in sewers and storage tanks and new designs of wet weather overflow storage and treatment facilities.

And the search for more new methods continues. One Kent, Wash., company, UTILX, is currently seeking partnerships with municipalities to test its new mine horizontal directional drilling system. “We’re looking for people to verify the technology, which is just in its infancy [in the sewer industry],” says John Schissler, manager of municipal applications.

Originally designed for the electric industry and later adopted by the telecommunications and gas industries, directional drilling has been applied successfully to force mains and is now being applied to gravity sewers and low pressure sewers.

Schissler says this type of trenchless technology will be in demand in communities undergoing rehabilitation in areas served by septic tanks and in environmentally sensitive areas such as wetlands.

“The costs are equal to or less than open-cut construction,” he says.

RETHINKING DOGMA

But, while these projects and their use of new technologies are impressive and give a glimpse of what is to come, the sewers of the future will look suspiciously like the sewers of the past unless people change the way they think about sewers.

“We can talk about new types of sewer materials that might be used in the future,” says Ralph Petroff of ADS Environmental Services, Huntsville, Ala. “We can talk about new types of manhole design or sewer rehabilitation techniques or innovative ways of removing I/I or of maximizing storage. But, the single greatest change in the sewers of the future will be the way we think about a city’s largest and most expensive infrastructure asset. So many of our long-held beliefs on sewers are, in fact, backward.

“The conventional solutions of the past are affordable to only a few of the wealthiest cities,” he says. Petroff, who appeared as the keynote speaker at a Sewers of the Future conference sponsored by the WEF, says the new dogma should be based on what Edward Deming called “fact-based management.” Deming, the father of Total Quality Management (TQM), was fond of saying, “In God We Trust — All Others Bring Facts.”

And new techniques used to get the facts about sewer systems have reordered conventional wisdom about how sewers actually behave, according to Petroff.

Citing the long-held theory that sewer systems surcharge because of hydraulic overload, Petroff notes, “our ability to measure the phenomenon of overflow has increased to the point where we can say with confidence that nearly all sewer system surcharging is a result of downstream constrictions rather than actual hydraulic overload.

“This has some profound implications. If sewer systems surcharge because of downstream constrictions, will construction of new relief sewers solve the root cause of the problem? Probably not. Therefore, many storage projects that are constructed are probably not needed. The more appropriate solution would be to bottleneck these downstream constrictions rather than undertake huge and expensive new construction.”

More accurate measurements have led Petroff to other conclusions about sewer system performance, including:

* sewer system performance is more dynamic than previously thought. It constantly changes as blockages and constrictions appear and disappear;

* I/I cannot be managed through construction of storage as previously thought. Measurements show I/I only increases, if nothing is done about it;

* I/I removal does work much better at a much lower cost than most people could have predicted;

* the real asset in a system is the hole in the ground. The pipe is, in many ways, less important because even an old broken pipe can be rehabilitated or transformed into a new pipe; and

* cities that have attempted to do real-time control without a real understanding of how the sewer system actually performs under a wide variety or conditions have encountered problems.

Wastewater collection systems managers must recognize what Petroff calls “irreversible megatreilds” if they are to be successful in managing their operations. (See “Petroff’s Irreversible Megatrends”).

NEW MANAGEMENT SKILLS

Technology is not, however, the only new development in the sewer world. Managers of sewer systems are also developing new management skills and managing differently.

The Miami-Dade Water and Sewer Department (MWSD), the largest water and wastewater utility in the Southeast, turned to program management when it was facing a tight deadline for improvement required by the Florida Department of Environmental Protection and the U.S. EPA.

Program management is not a new technique, but its use by utilities in managing a wastewater improvement program is, says Luis Aguiar, MWSD deputy director.

Aguiar defines program management as a “focused approach led by a team for long-term interrelated projects to achieve specific objectives by a definite date within budget.”

Miami-Dade’s problem fit the profile perfectly. The improvement program it faced included comprehensive sewer system rehabilitation, major force main and pump station improvements and upgrading and expansion of three wastewater treatment plants and effluent disposal facilities. The estimated cost of the improvements is $1 billion, and all projects must be completed in less than 10 years. Seventy percent of the dollar value of the project will be completed in five years.

Program management is useful when a uniform approach is needed for multiple projects and when there is insufficient or inadequately trained in-house resources and a tight schedule and budget, Aguiar says.

“The program manager brings expertise into the equation,” he says. “He has worked on different projects and brings an overall look at what everyone else is doing in the United States. In many small things we were ahead of the game, and the project manager learned from us. But that was on a minor scale. He had the expertise on the big picture. We were constantly reinventing the wheel.”

Typical services performed by the program manager are budget control, scheduling, document control and reporting, planning and project definition, permitting, easements and rights-of-way and development of relevant standards.

Aguiar says his department has completed or has under way more than $400 million worth of improvements. It has met or beaten the scheduled delivery date for all work activities (more than 380 accomplishments) and has not paid any penalties for missed deadlines. One of the key components — installation of the new $60 million force main crossing Biscayne Bay — was completed almost a year ahead of schedule and more than $2 million under budget.

THE REGULATORY FRONT

“One of the hottest areas in collection systems and sewers of the future is on the regulatory front,” says Stephen Jenkins, vice chairman of the WEF’s Collection Systems Committee and director of environment and engineering for San Marcos, Texas.

EPA is studying sanitary sewer overflows and examining separate sewer systems to alleviate problems.

With the program, EPA is taking a comprehensive watershed approach while looking at wastewater and collection systems.

“All issues will be brought together to consider what’s going on as a whole rather than addressing a regulation here and another there,” Jenkins says.

“The objective of a wet weather management program is to provide water quality and environmental quality with recognizable public benefits at costs that are affordable.”

WEF Deputy Director Albert Gray sees EPA making a concerted effort to protect watersheds. Consequently, he says, the agency will treat wastewater management from the perspective of watershed protection.

New technology will be critical in fixing broken pipes, leads, groundwater infiltration and wastewater contamination.

CHANGE IS COMING

“We will have to look at different ways to maintain and construct sewers,” says Marsha Slaughter, deputy director for environmental operations in the Tulsa, Okla., Department of Pubic Works and co-chairwoman of the Sewers of the Future conference held last September in Houston.

“Our basic assumptions will change. There will be more pressurized systems to prevent excess water from coming in. Use of plastics as a liner in construction will increase,” she says.

But, she acknowledges, “the changes will be gradual. It takes a year to disseminate information about new technology.”

Still, sewer systems are no longer the invisible infrastructure. “More communities are doing proper sewer planning because it makes sense,” says Wayne Miles of Camp Dresser & McKee’s (CDM) Raleigh, N.C., office. Miles worked on an enormous sanitary sewer evaluation, rehabilitation and flow equalization project for the Charlotte-Mecklenburg County (N.C.) Utility Department, the purpose of which was to identify improvements necessary to eliminate rainfall, induced overflows as quickly and effectively as possible in an area that encompassed 240 square miles within 13 major drainage basins.

“There’s lots of frustration among the people in the holes because there has been no funding for sewers,” Miles says. “But they are finally getting the recognition they deserve, and I believe national level funding will come. Communities see what happens when there is no money.”

1 We will continue to spend more in the future on wastewater than in the past.

2 The shift from plants to sewers will continue.

3 As the cost o:construction continues to increase, construction and storage solutions for sewers will be the last, not the first, resort.

4 Cities have less money because of ratepayer revolt and reductions in state and federal funding.

5 There is greater competition for fewer funds.

6 The issue of sanitary sewer over-flows, all but invisible five years ago, has become very important to civic and mainstream groups.

7 Congress will be focusing increasing regulatory attention on basic pollution problems.