DIRT Report

Horizontal Directional Drilling (HDD)

• When horizontal directional drilling (HDD) is the equipment type, excavators (including engineering) are the leading source of damage reports, locating is the leading root cause group identified, and telecommunications (including cable TV) is the leading type of work performed.
• Many damages involving HDD are facility operators, or their subcontractors, hitting each other and/or themselves.
• HDD projects can be expected to increase in future years due to increased infrastructure spending.

In this section, we take a closer look at damages associated with horizontal directional drilling (HDD), a selection for “type of excavation equipment” in DIRT. For this subsection of data, total reports entered (9,054) was used for analysis. There is little difference in percentage calculations between total event and unique event totals, especially when “unknowns” are filtered out.

HDD is often used as an alternative to open trenching for installing buried facilities. It requires an entry and exit pit, but these are often in an unpaved area that can be more easily restored. By avoiding cutting pavement, restoration issues such as unsightly patches, uneven settlement, water infiltration and freeze-thaw cycles leading to cracks, etc. are avoided. When used under roadways, it can minimize traffic disruption. HDD is also often used to cross under water bodies, wetlands, railroads and other sensitive areas where traditional excavation is impractical or environmentally harmful. However, the downside with HDD is that unless potholing is performed, there is no visual verification that the drill path has successfully crossed existing buried facilities with no contact. Additionally, if the drill does damage another buried facility, some time may pass before it is realized.

Figure 25 shows the event sources for this dataset. Excavator/engineering is the largest contributor.

Figure 25

Figure 26 shows the root cause groups for this dataset. In contrast to the full dataset, no locate request becomes a much smaller slice.

Figure 26

Figure 27 further shows the root cause groups for the leading types of facility damaged when HDD is used.

FFigure 27

For each facility type depicted within the Excavation Practices root cause group, failure to pothole and/or maintain clearance are the leading individual root causes. Within the Locating Practices root cause group, the leading individual root causes indicate locator error (not marked and marked inaccurately). At this level of granularity, we find reports with a root cause from the Miscellaneous group associated with sewer/water as the damaged facility. Most of those involved sewer, with previous damage as the leading individual root cause.

Table 20 shows the facility damaged by types of work for the leading contributing combinations. The 6,081 total reports are 95% of the reports where parameters are “known.”

Table 20—Report totals for facility damaged and work performed with HDD as equipment

Table 20 shows that Telecom/CATV is the leading type of work for all facility damaged types. The top “known” excavator types for the entire dataset of 9,054 records were contractor (95%) and utility (4%). Most of the contractors involved were likely working for the affected utility (ex: a subcontractor for a gas operator installing gas mains or services). This likely explains the very small percentage of damages caused by no locate request: The facility operators impress the importance of 811 notification upon their subcontractors and in-house crews. This analysis emphasizes that most of the damages around horizontal directional drilling involve facility operators damaging each other and themselves, largely due to locating and excavation practice root causes.

The use of HDD for telecommunications/cable TV work will likely increase in the coming years as a result of the Infrastructure Investment and Jobs Act of 2021.  As discussed above, Locator Error is the leading root cause associated with HDD and telecom/CATV work. Locator Error can be considered a general “catch-all” root cause that masks deeper root causes such as bad maps, tracer wire and abandoned facility issues. Choosing Locator Error as a root cause is preferable to choosing “unknown.”^[1]