In today’s fast-expanding digital ecosystem, the tools that had long comprised a trusted arsenal for transportation engineering are now constrained. Digital workflows and adopting 3D and Building Information Management (BIM) for design, engineering, and production are progressively required to streamline review processes, reduce costs, increase efficiency, and meet customer specifications. 

An important step in selecting pumps is developing the system head curve, which gives the head needed to move various flow rates through a pumped system. The shape of this curve depends on The lift to be provided between tank water levels on the suction and discharge sides of the pump Friction losses through the system. If most of the energy goes to lifting the water, the curves are relatively flat since lift is independent of flow, while if most of the energy is used to overcome friction, the slope will be steep. Simple Case  In the case where the flow moves from one tank to the next with a single pipe, the system head curve is easy to develop and can be done manually, as shown in Fig. 1 below. Fig 1 Real System Real water and wastewater pumping system are more complicated to the extent that it is necessary to use a model such as WaterGEMS to develop these curves. Plus, there will be different curves for different combinations of tank levels and local demands. Fig 2 Dead end system The problem becomes more difficult when pumping into a closed (dead end) system with no tank. In this

If you pick up most water-related journals these days, it seems as if half the papers are devoted to applying some optimization techniques to solve some real problem. However, almost none of these methods actually find their way into water engineering and operations. Why is that? When I was a young engineer, trying to justify my work in this area, I would read what sounded like a great paper in a journal. I’d call the author to hear about their success story when they applied their paper to the real world. The response was usually, “We didn’t actually apply it anywhere. We just developed the algorithm and made up some data to test it.” I realized that while the goal of these studies is ostensibly to solve real-world problems, the real goal is to publish papers which will lead to funding of more research studies. I remember talking with one highly regarded professor who told me that his promotion and tenure are not tied to the usefulness of his work, but to how much research funding he could bring into the university. Why don’t these solutions work in practice? There’s the story of the guy walking down the street one

Flow control valve (FCV) elements are the most abused elements in WaterGEMS/WaterCAD. If I had my way, I would eliminate them as model elements. In the many years I have been working with water and wastewater systems, I can’t recall ever seeing an actual valve that behaves the way that the FCV model element behaves. There are always better ways to model valves that control flow. Before you insert one in a model, you need to ask yourself if you really have a valve that will behave this way. According to the WaterGEMS/WaterCAD help. “FCVs are used to limit the maximum flow rate through the valve from upstream to downstream. FCVs do not limit the minimum flow rate or negative flow rate (flow from the To Pipe to the From Pipe).” If you search for flow control valves on Google or Bing, you won’t see any listed for the large sizes that exist in water and wastewater systems, and perform as described above. That’s because there are better ways to control water systems and disadvantages to using an FCV that the model describes. A model FCV is at least four different components: A flow meter A controller (a PLC) that

One of the more common questions I get is, “What is the target velocity I should achieve when I’m flushing a water main?” As with most questions I’m asked, the initial response is, “It depends. Why are you flushing in the first place?” There are multiple reasons for flushing, including: Removing suspended solids from water mains Responding to customer complaints about dirty water Removing dissolved material from water mains Responding to customer complaints about taste and odor Pulling water with a good residual disinfectant into the area Velocity matters significantly only for the first two items on the list. For the other three, velocity isn’t especially important. The problems with the first two items are caused by the suspension of solids and keeping them suspended in the flow. This depends heavily on the nature of the solids, including specific gravity, size, and cohesiveness. The most common culprits are iron and manganese. They may have carried over from the treatment process or, for iron, they may be a result of corrosion in unlined iron pipe. It may be a temporary problem triggered by a short-term high velocity from a fire or a pipe break. Theoretical sidebar: It is not velocity that

Before any water utility starts working on detailed plans and specifications―which I’ll refer to as “Design” in this blog―for water distribution and wastewater collection system projects, there is a phase that typically involves the word “Planning.” The one consistent aspect of planning is that different utilities use various terms for it, such as capital planning, master planning, preliminary design, comprehensive planning study, basis of design report, or project prioritization, to name a few. In this blog I will try to identify what I think is the best terminology. I generally based my terms on the planning horizon: Master Planning involves using long term population and flow forecasts to lay out major facilities over a fairly long-time horizon. Capital Planning looks at projects needed in the next few years. It includes developing pipe sizing, pump station locations and sizing, tank locations and sizing for the design phase, and cost estimates to evaluate project funding. Master Planning: The Big Picture Master planning (also referred to as comprehensive planning studies) uses 20- to 50-year forecasts to lay out major transmission or interceptor piping, locate pump stations and tanks, and determine implementations timelines. While the pipe and other facility sizing should be reasonable, they

Most of us are familiar with the concept of “triage” in medical emergencies. During large-scale crises, medical staff can only treat a certain number of patients. To prioritize which patients receive treatment first, they apply the principle of “the greatest good for the greatest number,” dividing patients into three groups. Those who will recover without immediate attention and can receive care later. Those who will not survive regardless of how much attention they receive. Those who will only survive with immediate attention. These categories are commonly applied on battlefields and other emergency situations. Fortunately, in the water, wastewater and stormwater industry, we aren’t faced with such life-and-death decisions. However, these principles also can be applied when responding to widespread pipe breaks or flooding. Widespread Pipe Breaks Let’s explore how using triage can help prioritize pipe break response. On most days, there are sufficient utility crews ongoing pipe breaks. But what about those days when there are too many pipes breaks to deal with all at once? The obvious example is earthquakes which can break many pipes simultaneously. During extreme weather events, such as hurricanes or extreme cold, like the Texas freeze a few years ago, can create such an emergency.

“Variable frequency drives (VFDs) are valuable technology, and they always save energy in water and wastewater system pumping.” The first part of that statement is true, and the second part is generally true but not always. There are exceptions that engineers and operators need to be aware of when they are buying and operating pumping systems. A question I frequently pose is: “What is the best speed to run a variable speed pump?” I receive a variety of responses, but the correct one is, “Off.” If you can select a pump that operates at an efficient operating point, allowing it to run near its best efficiency point (BEP), it will outperform a variable speed pump which tends to have fluctuating operating points along the pump efficiency curves (Walski et al., 2001). ApplicationTurning pumps on and off requires storage to meet demand when the pumps are Off. In water systems, pumped flow is often directed to elevated tanks, which allows the tanks to be filled and drained with constant speed pumps. This has the added benefit of turning over the water in the tank improving disinfectant residuals. In wastewater systems, the storage occurs on the suction side of the pump, with

Engineers and scientists love graphs. With one image, they can convey as much information as many pages of text and do it in a way that can be clearly visualized. Nowadays, with software, we can do so much more with graphing, but that’s not always the way it was done. Here is how simple graphs used to look like in the past, drawn on preprinted graph. Straight line y=mx+b Here is a graph you can get from Excel today: Sure, anybody can draw a graph on arithmetic graph paper. But what happens when you have data that cover several orders of magnitude and data aren’t very evenly spaced. You could take the logarithm of each point and plot it that way, but then you would need to continuously convert the data from the log scale to your original values. For example, “the graph says 3.52 but that’s the log of the real value that is 3311”. The key of course is to have graph paper with logarithmic scales. Your graph paper would look like this: The figure shows 3 cycle log-log paper. Straight line y = aXb In Excel the figure could look like this: Sometimes, however, only one axis