DPWH Region I headed by Regional Director Mariano R. Alquiza has been directed by DPWH Secretary Hermogenes E. Ebdane Jr. to strictly monitor the restoration of the 1.128 kilometers stretch reinforced concrete structure viaduct comprising of 76 spans that runs along the seashore beneath the steep slopes of the Patapat mountains in Pagudpud, Ilocos Norte and form part of the Laoag-Allacapan Road Section.
Restoration works of the viaduct is now 90.11% complete. It is being implemented by the DPWH-Philippine Japan Highway Loan-Project Management Office with a contract amount of Php.219,101,258.42 under the Philippine-Japan Friendship Highway Loan.
Scope of work includes the construction of reinforced concrete seawall gravity wall, concrete blocks and other related structures for pier foundation against sea wave action, rehabilitation/restoration of selected damaged spots of the viaduct at spans 57 to 61, the construction of additional slope protection structures in the rockslide areas, removal and disposal of rocks/boulders along the old road and the repair and improvement for catch wall structures.
The viaduct was constructed by Hanil Development Co. Ltd. under the overall management of DPWH-PMO-PJHK and was completed and opened to traffic in October 1986. It piers rest on spread footings founded on outcropping bedrock. In February 1991 a major rockslide occurred above the viaduct after a heavy rainfall and caused a major damage to three spans including the bridge component, however, it was rehabilitated in October 1991. Five years after its completion, super typhoon 'Trining' struck the coast with a maximum wind velocity of 280 kph and passed directly across the viaduct. The Signal number 4 typhoon brought strong sea wave action hit the weathered rock beneath the viaduct footings, causing several pier foundations to be undercut and exposed.
Based on the KEI typhoon damage investigation, typhoon 'Trining' adversely affected 51 of the viaduct's 71 piers. The investigation report categorized four priorities based on the urgency, scale of damage and budget constraints. In 1993 priority-countermeasures were carried out covering only 16 piers out of the 51 piers affected were given a limited fund of PHP20.0 million. Only those piers that were considered in critical condition received rehabilitation work based upon an emergency classification of the damages.
In October 2001 a major rockslide with an estimated volume of 7500 cum occurred during a rain storm causing major damaged to four spans of the existing viaduct from pier 57 to pier 61. Boulders up to 5cm in size weighing up to 300 tons punched through the deck destroying the viaduct's girders and deck slab.