Improvement of the Route 1-Route 28 Road Junction, Antofagasta Region

PROYECTO

Improvement of the Route 1-Route 28 Road Junction, Antofagasta Region

PROJECT DESCRIPTION

General Background

This project was a comprehensive solution designed to improve the Route 1 (Republica de Croacia Avenue) intersection with Route 28, the southern access to the city of Antofagasta.
The road junction, formed by Route 28 and 1 meeting, allows access to the city of Antofagasta from the south, through Route 28. It is therefore of vital importance to the city. For this reason, it was necessary to improve the operational level of the junction, allowing for safer operation for road users of the mentioned routes as well as for the general public.

Situation before the works

The set up of the existing junction did not allow for fluid flow of traffic and caused considerable congestion which was increased by the construction of the second carriageway in Route 28. This affected traffic with speed decreases and an increased risk of accidents in the area.

Description of the works

The principal aim of the works considered for this project was the improvement of operational conditions at the Croacia junction so that the entry of vehicles from the south of the city of Antofagasta and the traffic from south to north of the city could interact fluidly. This was to protect the safety of all users, and also to make it more convenient for pedestrians and cyclists in the sector.
The project was about accomplishing the improvement of the Route 1/Route 28 intersection in the Cajón sector, an area situated 6km south of the centre of Antofagasta. It involved the definition and development of a new geometry for the road junction over an approximate length of 1.5 km considering the length of both stretches of road.

Location
Antofagasta District, Region II
Initial contract amount
$ 6,451,724,471. – including VAT
Final contract amount
$ 6,187,411,059 -including VAT
Time frame
22.12.2017 to 29.09.2019

GEOMETRIC DESIGN

Proposed Solution

This solution meant rebuilding Croacia Avenue as a one-way street with 2 lanes and giving it a pavement and cycle path on the west side as well as incorporating a bay for a bus stop. The accesses to parking on sections 1 and 2, roughly at the 350 dm point, were to be redesigned. From the 361 dm point, both the cyclepath and the pavement had different altimetry in order to maintain the existing wall which separated the road from the pavement.
Croacia Avenue from south to north (section 7) is separate from the east bound section with the option to merge onto Route 28 to the east (Section 4) or to continue north and join the section coming from the east and going northbound.
Section 4 is separate from Section 5 (Avenue Croatia north to south), so it is possible to continue towards the east to Route 28 or turn around to return north along section 12.
Section 3 begins at the junction with Route 28 towards the west, turning north, or one can take Section 6 which joins the existing loop, then cross section 3 to join section 5 to continue south. For access to the Minera Escondida mining company facilities, braking lanes were designed as well as an acceleration lane to exit.
Section 8 detaches from Section 4 with a turn lane to turn left with a stopping area to access the Minera Escondida facilities. Another U-turn option was generated between sections 3 and 4 (Section 13) allowing drivers to continue eastbound on Route 28. (Section 4)
Section 10 detaches from Section 3 for access to Cerro Paranal Avenue
It is worth mentioning that Section 9 was merged with Section 6 because of the resurfacing of the existing road.

Cross section

The cross section is constant along the two main projected sections and can be adjusted to the connectivity needs with the rest of the road network, as required.

Drainage

The drainage project initially involved the review and analysis of the city of Antofagasta’s Rainwater Master Plan which was drawn up by AC Ingenieros Consultores Ltda. in 2003. This plan has all the important parameters for the development of the drainage network in the city.

Paving Project

The design of the paving structure was made to last 20 years given the category and importance of the road. The paving was made up of three asphalt layers (C.A.R, BINDER and BASE ASFALTICA) on a granular base, the characteristics of which were presented above.

Lighting Project

Originally, the road lighting projected for the entire project was to be through high pressure sodium vapour lamps (HPS). The 250W versions with a power factor of 0.93 were to be used and installed on single arm lamp posts on the sidewalks using the same type of setup. Double arm lamp posts were to be installed on the central reservation, generally conical tubular metal posts with a functional height of 12m. These posts were to be equally spaced between 35 and 50 metres apart. The cables were to be underground.
In accordance with what was set out in the base bid, the Contractor checked and took into consideration the changes that could occur in the project design, in particular responsibility for new Photometric Calculations and the technology of new lamps. Following this evaluation, a new lighting project was devised.
The number of posts to be installed in the junction was increased after a photometric recalculation. This took into account the change from HPS to LED lighting as well as the distance between posts that was needed to provide the required brightness to this type of area.

Landscaping Project

The landscaping proposal consolidated the southern access to the city of Antofagasta, through the following design components:
The replanting and relocating of the existing palm trees at the junction and the incorporation of Canary Island date palm trees.

Green Areas Irrigation Project

The project bid, which was presented to the Illustrious Municipality of Antofagasta, considered the modification of the irrigation system, with the understanding that once the works were finished, it would be handed over to the municipality for its maintenance.

Road Safety Project

The projected signs basically corresponded to Regulatory, Warning and Informational types, taking into account the characteristics and the message to be delivered, in the sector in which they would be placed.
To summarise, the road signal and safety project included the following elements:
- Regulatory, Warning and Informational Signs
- Horizontal and vertical demarcation
- Crash barriers
- Pedestrian railings
- Rumble Strips

Traffic Lights
- The geometric redesign of the road junction included the modification of existing facilities due to the geometric changes. The intersection on República de Croacia Avenue and Route 28 had to have traffic lights installed in order to allow for safe south to north movement across the Avenue faced with the traffic flow from Route 28. Furthermore it is relevant to consider that these sections allow for a high volume of traffic to enter and exit the city of Antofagasta from the south. This includes both light and heavy vehicles.

VALUE
PROPOSITION

The consulting work was focused on supervision of the contractor’s tasks related to the ‘re-thinking’ of the works. This included the determination of the volume calculations, making comparisons with the projected project budget and the situation on the ground, and informing the Fiscal Inspection of the modifications that needed to be added to the contract (particularly the excavations and the works to restore the affected Military Stadium. All of this was arranged according to the bidding terms with the appropriate personnel, both for topographical and laboratory control and for construction aspects all of which allowed the works to progress and to be finished without any nonconformities that would affect the quality of work. Furthermore it was all arranged in accordance with the administrative terms of the contract.