Other agencies prefer to provide some type of housing (e.g., PVC conduit) for placing the probe, while others choose to secure the probe by tightly packing sand or using sealant around it.
The general rule for the diameter of the hole is to use the diameter of the sensing probe plus 1/8-inch (3.2 mm).
The optimum depth and placement of the probes depends on the type of detection required (see Chapter 4 and Appendix L) and the size of the probes.
After the preinstallation activities (described earlier in this chapter) have been completed, installation usually follows the step-by-step procedures discussed below.
A 5-ft (1.5-m) length of extra cable should be left at the pull box.
The cables should be identified by lane or by probe designation.
After securing the work zone with appropriate barricades, cones, etc., to divert traffic from the area, the first step is to layout and mark the detection area with spray paint or chalk markers to match the construction plans.