PROJECT SUMMARY

When the city of Rehoboth Beach sought bids on a 914 m (3,000 ft) ocean outfall pipeline crossing to release treated effluent into the ocean, the HDD Company proposed a two-million dollar idea. By pushing a 762 mm (30 in) Permalok casing nearly half the total distance from its shore-based rig, the HDD company would significantly reduce the time a marine contractor was required on the project (by nearly half). These savings would be passed onto the municipality.

This plan called for the HDD Group to drill and forward-ream the borehole to 1067 mm (42 in), and push the casing out approximately 365.8 m (1,200 ft). Then, the directional drill would guided through the casing to complete the crossing, emerging through the seabed. The marine contractor would be tasked with pulling the casing the remainder of the distance.

KEY CHALLENGES

The design proposal indicated the geography was entirely sand. However, at the 228.6 m (750 ft) mark, the HDD Company encountered cobble – which was unforeseen by engineers and the HDD Company. This caused the casing to bundle up on a large bolder. As a result, the initial hole had to be abandoned. The HDD Company promptly proceeded to drill a second hole, adjusting to compensate for cobble.

Despite the unanticipated setback, the HDD Group completed the project on time, while still coming near two million dollars under budget.

SERVICES PROVIDED

HORIZONTAL DIRECTIONAL DRILLING (HDD)