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Understanding bypass pumping for your next coatings rehabilitation project

Discover best practices to manage your bypass pumping operation that will save you time and money

Written By: David Adams

As billions of dollars in federal stimulus money become available to rehabilitate aging infrastructure, municipalities will face issues keeping systems operational during construction. This is often ­­­accomplished through flow diversion or bypass pumping. However, there are often scenarios where a utility cannot simply divert the flow. Rehabilitation of sewers is a great example of where bypass pumping is required.

Bypass pumping is the process of temporarily pumping flow around a section in a pipe or channel that is going to be repaired or replaced. This allows the repair or replacement of a section without spillage and jeopardizing service to customers while work is being performed. While this is commonly used on sewer mains, it can also be used on other systems, such as treatment plants and lift stations    

Pumps commonly are placed upstream from the system, and a temporary pipeline is installed from the pumps to a downstream section. Temporary plugs are also set between these points, allowing the pipe or channel to be removed or repaired. Depending on the number of homes or businesses the line serves, the bypass may range from a few gallons to thousands of gallons per minute.

For coating rehabilitations, bypass pumping is a crucial component of the overall project. This post provides utilities guidance on identifying the correct bypass pumping system, critical factors in the planning process for coating rehabilitations, and best practices for managing your bypass operation.


How to identify the right bypass for your next project

While this process sounds simple, many factors can quickly turn this into a complex decision. The following are some basics that utilities should consider in evaluating all bypass projects. 

  1. Design
    • Calculations of static lift, friction losses, and flow velocity.
    • Bypass pump sizes, capacity, number of each size to be on-site 
    • Size, length, material, location, and method of installation for suction and discharge piping
    • Downstream discharging plan
    • Equipment requirements and customizations— monitoring systems; automatic start/stop systems designed to monitor influent fluid levels and initiate the startup/shutdown of pumps when needed; temperature requirements; manifolds; sewer plugging methods; and special requests
  2. Estimate and determine job scope
  3. Provide submittals and detailed plans; this submittal should include a signed bypass plan from an in-state engineering firm.
  4. Walk-throughs with on-site staff in charge
    • Review logistics; methods of noise control for each pump; landscape barriers; safety regulations; permitting and code requirements; road crossings; power sources, diesel, or electric-driven equipment
  5. Project setup
    • Pumps, piping material type and SRD rating, discharge, suction material, and size.
    • System testing
  6. Project monitoring
    • Sewage spill violations are a serious matter and all precautions should be taken to avoid 
    • Completion and teardown

Planning and executing a temporary sewer bypass can be a large, costly undertaking. Many municipalities lack the resources and laborers required to take on these types of projects and should seek a company specializing in bypass pumping. Often these companies will provide more than equipment rentals and can serve as a subcontractor that handles the design, setup, monitoring, and installation, providing specific application engineering expertise and a complete bypass pumping system. 


Critical factors in planning process for coating rehabilitations

If not done right, mistakes can cause sewage overflows, negative social impact, and environmental damage. A critical factor to consider for a standard rehabilitation is understanding your anticipated flow. Knowing this will allow the engineer to design the most efficient bypass pump system for your project. Not understanding flows and redundancy are common problems with the design process.

When selecting coatings for your project, utilities should analyze and consider certain attributes of the chosen products. Unfortunately, many utilities aren’t aware that the type of lining selected can drastically impact your bypass pumping plan. As described in our April post, not all coatings are created equal about the differences between polymer coatings and linings.

A critical factor, often overlooked, is time. Does your coating system include a concrete underlayment? If so, concrete requires 28 days to cure. That means if your applicator applies the polymer topcoat before this window, you run the risk of failure. Or does your coating system require multiple layers to achieve the thickness needed to repair your asset effectively? Multiple layer systems or those that need a concrete underlayment take time. That time can alter your bypass pumping plan and negatively impact the following aspects of your project:

Cost

Longer cure times and multiple layer systems means you must bypass your flow for that period which can drastically increase your job costs. Your bypass pumping plan may require personnel to maintain the system, manage alarms, backup pumps, 24-hour emergency contacts, city noise ordinances, traffic, and access control, and much more. 

Disruption

Longer cure and multiple layer coating systems can prolong disruption to the daily lives of customers. Bypass rarely happens in remote areas where there is ample space for installation. Often, it occurs in the right-of-way, and daily activities are disrupted. There’s also the potential of noise pollution from generators affecting the surrounding area. Seeking a coating product that offers the fastest return to service is ideal. 

Risk

Bypassing any flow, whether it be water or sewage, inherently involves risk to the utility. A possible sewage spill is always a possibility that would incur environmental contamination and costly clean-up operations. The goal for any lining rehabilitation should be to reduce the amount of bypass required and have your system return to normal operation as soon as possible. 


Best practices for managing your bypass pump operation during application

Although thorough planning is a major factor in your bypass operation’s success, utilities should take precautionary steps to prepare for the worst-case scenarios. You should develop and have readily available a detailed contingency plan that can be executed in the case of an emergency. If bypassing a sewer, a comprehensive sewage spill response plan should be included to protect the environment from contamination and prevent costly clean-up work.

Here are some additional steps to ensure your bypass system operates smoothly during your next project: 

  • Check and test before startup – Fixing issues becomes more difficult once the system goes under live flow. Reduce the risk of problems by checking and testing your systems in advance. This includes checking your pump’s lubricant, fuel levels, suction gauges, discharge pressure gauges,  bypass system piping, and telemetry systems (if using one). Also, including pressure testing in the scope can offer assurance before bypass begins. Attaching spill response kits and emergency response plans/contact lists to every pump while keeping them updated is recommended. 
  • Set up monitoring – An experienced, capable worker should be watching the system regularly. Labor costs could be saved by using a Telemetry to monitor the pumps. The Telemetry will automatically send alerts for problems involving fuel levels, oil pressure, coolant temperature, flow rate, discharge pressure, and more. It is important to specify elevation for your telemetry system, whether it’s a float style or pressure transducer. 
  • Keep the bypass running smoothly – It’s recommended you install drains, air, and gate valves to allow for full control of the bypass. This should be included in any design submittal. This will help contend with blockages and other unforeseen issues.  Have a de-ragging plan for all structure’s pre-bar screens. The build-up rags and debris can negatively impact a smooth bypass.
  • Keep the pump(s) warm – If temperatures go below 32 Fahrenheit, freezing water can crack the volute in the pump, disrupting the bypass. Space heaters, electric blankets, or tents can be used to accomplish this. Daily, each pump should be manually ramped up to the specified RPM to ensure it’s in working order. 

Planning and execution of a temporary bypass pumping can be a large, costly undertaking. You should always consult with a pumping system expert on your specific circumstances, applicable rules and regulations related to your site and your situation. Utilities should evaluate additional considerations if you are using coatings as your trenchless rehabilitation method. All the factors mentioned throughout the post determine if your bypass will be a success.

Are you interested in learning more about this topic? 

Register for our upcoming webinar presented by David Adams

Understanding bypass pumping for your next coatings rehabilitation project

Wednesday, June 30, 2021 | 12:00 – 1:00 PM EST

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