With Water and Wastewater Systems in a State of Decay, Engineers Must Have Options
By Suad Cisic, P.E., John Harris, P.E., and Fred Muncy, P.E.
It is time to prepare for future infrastructure needs now and an increasingly critical area is horizontal infrastructure – roads, bridges and most especially water and wastewater pipes. Leaks, bursting pipes and public health scares are now the norm as water infrastructure has declined. In the United States, the 2017 ASCE Infrastructure Report Card gave wastewater infrastructure a D+ grade, with drinking water earning a D. According to the American Water Works Association, an estimated $1T is necessary to maintain and expand drinking water service to meet demands over the next 25 years, while the Environmental Protection Agency (EPA) estimates that the nation’s wastewater treatment facilities will need $271B over the next 20 years to meet the Clean Water Act’s water quality objectives.
The issue isn’t limited to the United States, however. From November 2011 to February 2018, the city of London’s water pipes burst and leaked more than 36,000 times as the result of Victorian era-pipes that are just now being replaced. In Japan, much of the current water infrastructure was constructed during a period of rapid economic growth in the 1960s and as a result, approximately 38,000 kilometers of the nation’s water pipes have passed the statutory 40-year use life. This has contributed to more than 1,000 pipeline ruptures in the public water system and about 5,000 cave-in accidents annually.
An aging system and ever-increasing demands have put a strain on horizontal infrastructure. Many agencies recognize the need for programmatic replacement. Perhaps most problematic are cast iron pipes – these are susceptible to movement soil and pressure – and as our water systems expand, service outages with frequent start-stop can be rough on pipes, causing more wear and tear. It is estimated that by 2020, the average age of the more than 1.6 million miles of water and sewer pipes in the U.S. will hit 45 years old. Currently, cast iron, steel and other traditional materials make up nearly two-thirds of the municipal pipes in horizontal water infrastructure.
Horizontal Infrastructure Challenges
A key issue in horizontal infrastructure is simply the fact that when drinking and wastewater systems were originally designed, not a lot of thought was given to future replacements. The water and wastewater industry has roughly two-thirds of its assets in the ground and one-third “inside the fence” – reservoirs, treatment facilities or pumping stations. So, most assets are hidden and access to lines has become a major challenge when updating horizontal infrastructure. Throughout the years, development and utilities have encroached on pipelines. For example, it is quite common for fiber optic cables to be laid shallowly, making it challenging to access and repair or replace pipes. Narrow easements straddling property lines have also made access difficult. In addition, engineers must also try to plan for the least amount of disruption possible to continuous service and access to surrounding areas.
When considering horizontal infrastructure upgrades, there are only two choices: replace or rehab. Replacement is certainly more valuable over time in most cases. Pipe replacement costs can be approximately the same as rehab, but the benefit is that replacement can begin up to a new 100-year lifecycle, rather than adding approximately 25 years to an existing lifecycle through rehab.
Trends & New Methodologies
As we take on the challenge of updating horizontal infrastructure, new trends and methodologies are appearing that will help to facilitate the pipeline replacement. Government agencies typically employ one of three methods for horizontal infrastructure improvements: in-house replacement (typically used in straightforward water distribution or wastewater collection projects), design-bid-build with contractors and consultants (typically used in more complicated, high-traffic areas or challenging soil conditions) and design-build projects (also used in more complicated, high-traffic areas or challenging soil conditions).
To effectively mitigate the risks associated with horizontal infrastructure needs, evaluation and planning are key. Today, we have innovative technologies that will help. Light Detection and Ranging (LiDAR) profiling can analyze the shape and condition of a pipeline. Unmanned aerial vehicles (UAVs) and robots can also be particularly useful when it comes to horizontal infrastructure and detecting leaks. These inspection vehicles can provide access to areas not easily reached by teams and can be deployed within the pipe itself. Some crawling drones even have the ability to cut pipes, weld seams and more. We are seeing more and more flying drones being used in confined spaces, like sewer tunnels and large-diameter pipes with air gaps. High-resolution and infrared cameras, as well as LEDs, are housed within protective barriers to allow the UAV to roll and bounce off obstacles to capture live footage and help engineers identify issues and determine the best course of action.
Big data is also becoming increasingly important in guiding pipeline replacements. We are combining artificial intelligence with machine learning with historic data on utility pipe breaks and information on environmental factors, including flow rate, soil chemistry and temperature, to identify which pipes may be at an elevated risk for failure. With the cost for replacing a single mile of pipeline typically being in the millions, big data helps us make well-informed decisions on what needs to be replaced and when.
Once the need for replacement has been determined, there are several new and emerging methodologies that can be particularly effective. Horizontal directional drilling (HDD) is a trenchless boring method that borrows from the oil drilling industry. This surface-to-surface method does not require excavation of an entry/launch shaft or exit/reception shaft and is known to reduce environmental impacts as HDD techniques require less earth disturbance, usually limited to the entry and exit points. It can also shorten planning, permitting and installation schedules and has been successfully used to install pipelines through environmentally-sensitive areas, long crossings and delineated corridor obstructions.
Another increasingly-popular trenchless boring method, microtunneling, involves using a remote-controlled tunneling machine, typically with a laser-guided boring system. Microtunneling comes at a higher upfront cost than HHD, but is extremely precise, with an accuracy of +/1 10mm. This technique can be used with all types of materials, including various soils, sand, clay and even rock. The benefits here include the accuracy, reliability and lower maintenance for pipelines post-installation.
In looking to the future, we are also exploring alternative materials for pipelines themselves that not only improve durability but also provide longer life expectancy. It’s more and more common for plastic pipes to be installed. PVC pipes are corrosion-resistant and light, making them easy to transport and handle. CPVC is similar to PVC, but its makeup allows it to withstand a wider range of temperatures. PEX (cross-linked polyethylene) pipes are the newest type of pipe material, but the benefits are clear – the material is extremely flexible and unlike PVC or copper pipes, it doesn’t require elbow joints.
Real World Replacement
Modernizing horizontal infrastructure across the globe is a massive undertaking and one that will not be done overnight. At Michael Baker International, we have worked with Fairfax Water for more than 20 years on pipeline replacements, evolving replacement methodologies and incorporating emerging trends into everyday actions.
A key takeaway for our team is that collaboration across specialties is critical to overall success. To successfully and continually upgrade Virginia’s horizontal infrastructure, our Water practice has incorporated colleagues across surveying, corrosion engineering, planning, construction management, design engineering (electrical, mechanical), stormwater (erosion/sediment control), park planning/landscaping and traffic control planning. Collaboration and adaptability are critical in developing innovative solutions as we all work to improve our water systems for future generations.
Suad Cisic, P.E., National Water Practice Lead; John Harris, P.E., Water Department Manager; and Fred Muncy, P.E., Regional Water Practice Lead, all at Michael Baker International.