The highway section “Razdrto-Vipava” is located on an unstable slope that is built on Eocene flysch covered with several 10-m-thick layers of limestone rubble with lenses and with the remnants of clay and rubble weathered and disintegrated flysch rocks. This paper deals with the conditions of a deep excavation between profile P288 and P294 at a depth of 32 m in the fossil scree of limestone rubble with an average depth of 30 m. During the construction, a creep slope of the total region to a depth of 30 m at an average speed of 1cm/year was activated. The area of the ranged creep slopes extends approximately 650 m above the highway route all over to the Nanos mountains that are above it. To secure the remainder of the 10 m depth of the excavation in an unstable slope, in 2008 three reinforced-concrete (RC) drainage caissons, 8 m in diameter, were completed, and a deep-drainage system with drilled drainage at a depth of 20 to 30 m below the original surface slopes was introduced. With a stability analyses we demonstrated for the performed actions an improvement in the stability of the conditions by approximately 5%, with respect to the initial state (F = 1.05). The caissons were equipped for observation of the horizontal movement with vertical inclinometers and strain gauges in the concrete and the steel reinforcement, and the GPS stations for monitoring the movements in the global coordinate system. The measurement results after the implementation of the rehabilitation show that the remediation was carried out successfully.