Choosing to be a responsible driller by having proper procedures and – equally important – choosing to follow those procedures, is up to owners and operators. To help mitigate the risks of damaging an underground utility, procedures must include the following best practices, at a minimum.
Plan the bore.
Planning the work is critical and must be part of the process for horizontal directional drilling projects. Thorough planning and preparation before beginning work can prevent unforeseen problems. Include the following:
• Determine existing underground facilities
• Obtain right-of-way and geological information
• Map the planned installation
• Consider clearance requirements, vertical and horizontal, of existing facilities
– size of pullback tools
– bend radius of pipe and product
– ability to track the bore
– ability to expose existing utilities
– surface structures for drill placement and setback requirements
Maintain two-way communication.
A drill operator relies entirely on the tracker to provide the feedback needed to successfully drill around obstructions. The tracker relies on the operator to use the information to steer clear of hazards. They must collaborate and be on the same page regarding drilling responsibly and safely. Because the tracker and operator must be able to communicate at all times, having a two-way radio or other form of communication is essential for HDD operations.
Locate, locate, locate, then verify.
Locating procedures should include marking the proposed excavation with white paint (also known as white-lining) before calling for utility locates. Directional drilling jobs cover a long area in one shot. To effectively locate, the locator needs to know exactly where the bore has been planned. In 2018, approximately 71,000 damage events (21% of total) were linked to poor locating practices (CGA). So, even after a locate has been completed, the contractor must observe the area and look for signs of any utilities that may have been missed. Know all the utilities that should be expected for building service and ensure they have all been accounted for. Additionally, utility maps should be referenced to determine which utilities are expected to be in the area and their approximate location. It is important for drillers to have locating equipment available to verify locates.
Find the sewer lines.
To avoid a dangerous situation known as a sewer cross bore, sewer lines must be located using methods such as sewer beacon locators or ground penetrating radar. They must either be exposed and treated like any other facility, or they must be inspected after boring is complete, especially if installing a gas or electric line.
Observe tolerance zones.
Tolerance zones around locates should always be observed. Depending on the state, an 18”-36” tolerance zone is required on each side of the located utility. Only hand digging or soft excavation, such as vacuum excavation, can be used inside the tolerance zone. Consider horizontal and vertical tolerances when drilling near utilities.
6. Expose the line – depths should never be assumed.
Depths are rarely given by locators, but if they are, operators should always assume it is an estimate and should expose the line using a vacuum excavator or hand digging. Accuracies can vary between various locating equipment used. The only sure way to know the exact depth is to expose it. It is not sufficient to expose in only one location to determine the depth of the entire utility. The depth of utilities can change along a line. The utility must be exposed every time, even if it is under concrete and even if the operator thinks he knows the depth.
Note: If the utility cannot be found or is too deep to expose, the facility owner must be contacted to develop an acceptable plan before drilling.
Don’t adopt “just drill deeper” as a rule.
When drilling in a congested area, it is tempting to just go deeper than everything else. This may seem like an easy answer to try to miss everything. However, this is not a perfect solution because utility locators typically cannot locate lines accurately much deeper than 10 feet. So, you may think you are clear, but there may be a utility that was too deep to be detected by the locator. Also, the new utility that you just installed may not be detected next time someone locates utilities in the area.
Setup for success.
Successful drilling depends on setup. HDDs must be set up in a position that will allow the anchors to be driven outside of tolerance zones. Also, a bore path calculator should be used to determine the minimum setback distance and entry pitch needed with the pipe bend radius to be able to bore underneath obstacles directly in front of the drill.
Take additional precautions when drilling parallel.
When drilling parallel to underground utilities, additional precautions must be taken – more frequent potholing/daylighting is needed to verify the location of the utility and more frequent tracking of the drill head is needed to ensure that the tolerance zone is not encroached. Follow local guidelines for tracking and exposing utilities when drilling parallel to an existing utility. If no local guidelines exist, use:
Watch the crossing.
A utility should not be crossed without a spotter, in communication with the operator, watching the crossing, while drilling and backreaming. Utilities can be nicked by a backreamer even if the drill head cleared it.
Consider the backream.
The width of the backreamer must be considered when creating the bore plan. An operator may be far enough outside the tolerance zone while drilling, but the additional width of a backreamer could put it inside the tolerance zone on the pullback. Also, consider that the backream may not pull back directly centered in the pilot bore.
Always track the bore.
The bore must always be tracked through surface tracking or wireline. Even on short bores or if going back into a previous bore hole. The drill string must be pulled back to the drill anytime the ability to track is lost, including when the beacon batteries die or the drill string breaks. While drilling, the drill head must be tracked at least every half to full length of pipe, and more often depending on underground congestion in the area. Each tracking location should be marked and progress should be checked to ensure the bore is staying on the intended path.
Create an “as-built” record.
Contractors should create an “as-built” map to indicate the actual location of the installed product for future reference. Tracking electronics provide the capability of logging the tracker readings which can be logged and saved for each job. This is a good practice for creating maps and for future reference, if needed.
Susan Harmon is Product Safety & Compliance Manager with Ditch Witch/Charles Machine Works. She can be reached at firstname.lastname@example.org.