Contractors and operators are quite familiar with installing all sorts of utility lines using HDD. Sewer lines, though? For many, this is uncharted territory. However, there are a lot of opportunities in this particular area, with potentially more to come. Why? A lot of big cities are utilizing incredibly old sewer systems, while small towns are often plagued by septic systems with tanks that are ecologically risky. That means that municipalities across the country are (or soon will be) in desperate need of upgrades to their sewer systems.
At one point, HDD wasn't even considered a viable method for sewer installation. Now, HDD sewer jobs are much more common and, in many instances, preferable. Read on to find out why and get a sense of the benefits and challenges you'll face with HDD sewer line installation projects and more.
Why is HDD Better for Sewer Jobs Now?
Sewer line maintenance and installation are usually dictated by the budget of a city's governing body. On the other hand, homeowners typically handle their own septic systems while complying with local laws and regulations. For a long time, the cost of HDD was simply too high — especially when compared to traditional open-cut installation methods — because of the specialized directional drill rig equipment. Additionally, HDD was not thought to be accurate enough for certain installations.
Now? HDD sewer jobs are often more cost-effective than open-cut methods. It started with pressure pipeline systems for sewage conveyance, but at this point, there are a variety of different applications for horizontal directional drilling. Gravity sewer installations are particularly common. There are numerous reasons for this shift, including:
- Advancements in tooling and electronics have made them more efficient, accurate and affordable.
- Contractors have more experience in dealing with challenging soil conditions.
- The sewer industry embraced HDPE, PVC and other sewer line materials that are necessary for HDD.
- The inspectors and designers who plan out sewer systems are more aware of the potential advantages (and limitations) of HDD.
Regardless of the reasoning, the shift has meant a gradual increase in HDD sewer projects over time.
What Types of HDD Sewer Projects Exist?
As mentioned, when it comes to horizontal directional drilling, gravity sewer installations are probably the most prevalent. However, an all-terrain sewer (ATS) is another type of system that can be installed with HDD. There are some differences in how these operate and what that means for their installation process.
Simply put, most sewers are gravity sewers. These systems:
- Utilize changes in elevation to move wastewater and sewage from one area to another.
- Are different from force main and vacuum sewers, but they may be used in conjunction with these systems.
- Can lead to a pump station and possibly to a force main or outfall sewer.
- Can be difficult to install using HDD, depending on the grade requirements.
As the name implies, these sewer systems can be installed in any terrain. ATS systems are often used to convert septics to new sewers, a process that requires a significant amount of underground pipe. ATS systems:
- Could be the only way to update a city's wastewater infrastructure if the soil conditions involve clay, silt, sand or rock; HDD rock bits can aid in this process.
- Utilize a grinder pump station, buried tank and displacement pump to push wastewater to a force main or treatment plant.
- Can be installed one house at a time, making short-length HDD a perfect method of installation.
What are the Benefits of Using HDD for Sewers?
When sewer lines need to be installed, there are a lot of factors to consider. Some are specific to a locality, such as homes, roads and restaurants, while others are related to the environment or terrain, including landscapes and other utility lines. However, these things tend to make HDD sewer installations the perfect solution. Benefits include the following:
- HDD is more affordable than it has ever been, making it a great financial choice for governing bodies on strict budgets.
- The environmental impact is minimal and less invasive — there's a lower risk of water contamination than with open-cut installations, and the natural land is barely disturbed.
- Homes, yards and businesses see little-to-no negative impacts.
- Since HDD can be used for even portions of a new sewer line, it's not necessary to use open-cut methods to install a pumping station.
- Above-ground obstructions can prevent traditional installation methods altogether, meaning a trenchless, underground solution is imperative.
- Total project time is often shorter because HDD requires less planning, fewer pieces of equipment and a smaller overall workforce.
- HDD isn't likely to disturb traffic or create a public nuisance.
- HDD can handle sewer projects that involve curved streets and long distances between utility holes.
What Challenges or Drawbacks Exist for HDD Sewer Projects?
While HDD sewer pipe installations work well for a wide range of situations, as always, it's important to weigh every aspect of a project before taking it on — that includes potential problems. Consider the following factors:
- When using a walk-over locator, projects that require drilling deeper than 50' can have a weaker signal strength, making accurate location more difficult.
- Certain job sites may not have enough workspace to perform HDD due to obstructions or structures where the borehole would need to be.
- Changes in ground conditions along the bore path can make it difficult to maintain grade.
Things to Keep in Mind for Any HDD Sewer Job
Whether you've already accepted a project or you're still deciding if it's a good idea to take on the challenge, you'll want to keep these considerations in mind:
- Horizontal directional drilling is not right for every gravity sewer project, even when all parties might prefer it — it depends on the location, design of the sewer system and ground conditions, all of which could make or break the whole operation.
- Drilling fluid management is crucial to any HDD sewer job because you must be able to remove cuttings.
- Note any changing geological conditions that may arise on the bore path.
- Sewer pipeline installation requires precision and clear communication between contractors and drill rig operators.
- These jobs require a high level of expertise, even with shorter bores, so the contractor needs to do proper research — this includes consulting with other HDD professionals about sewer jobs, studying the location's soil and understanding how the sewer system will work.
- Patience is key.
- When in doubt, stick to the plan defined by the contractor, designer and city inspector.
Take On the Challenge with Melfred Borzall
Even with all the possible benefits, HDD sewer jobs are always a challenge. And if you know Melfred Borzall, you know we're up to the task. So, if you're thinking about pulling pipe for a sewer line installation, get a puller and reamer that are ready for your rig.
If you're looking for a custom solution, we've got you covered there, too. We manufacture custom reamers for on-grade sewer bores, working directly with the contractor to design a reamer that meets their sewer job's requirements and conditions. Typically, the reamer will not cut much bigger than the OD of the sewer pipe being installed. The normal rule of thumb is for the bore hole to be 1.5x the diameter of the product pipe. But, with an on-grade sewer, it may only be cutting an inch or two more than the pipe OD. Feel free to contact us if you have any questions or want to know more about what we can offer your operation!