The main problems addressed by Mapocho 42k can be categorized into spatial and social issues. One of the main spatial issues is rooted in the fact that the river, historically central to Santiago’s urban fabric, has been progressively isolated due to large-scale infrastructure projects, including canalization efforts and the expansion of highways. As a result, a variety of barriers such as highway junctions, uninhabited properties and informal settlements, prevent the possibility of experiencing the river, for example by walking along it. These circumstances not only lead to a spatial fragmentation of the riverbanks but also resulted in a “null relationship” of the city to its river, causing a lack of spatial integration into the urban fabric of Santiago. 

The social issues are mainly caused by the heterogeneous structure of the 8 riverbank municipalities, leading to administrative fragmentation. Varying financial, social and topographic conditions complicate the coordination of a collaborative project. Historically, the eastern sector of Santiago, wealthier and more developed, had a greater proportion of green areas, while the western side contained degraded and underutilized spaces, often appropriated for informal activities like sand extraction. Therefore, inhabitants along the urban river stretch have very different opportunities and possibilities to access and experience the river. The resulting spatial injustice is one of the main problems Mapocho 42k has to tackle.

Spatial cohesion was accomplished by introducing a 42 kilometre long ‘spine’, a public space corridor connecting 8 municipalities along the river. It consists of a 10 to 25 m wide ‘intervention strip’, containing a pathway for cycling and walking. The corridor prioritizes connectivity of green spaces, linking them into a cohesive park system. Common design criteria (e.g. a common set of components and elements like urban furniture) ensure to form a uniform character and therefore a common identity and spatial cohesion.

The above-mentioned social issues were tackled by providing a common framework which enables cooperation of all the involved communities of varying backgrounds, and thus overcoming the administrative fragmentation. Furthermore, the implementation of a public space for all enables access for all citizens.

The process of Mapocho 42k started in 2009 as a research seminar at Universidad Católica de Chile’s School of Architecture, led by Sandra Iturriaga, and was later formalized as an applied research project. In 2011, the team of architects won competitive funding of 150 million CLP (~300 000 USD). In 2012, an implementation agreement was made with the Ministry of Housing and Urbanism.

The project was developed in two stages starting in 2013 and 2016. The first stage, the central part of stretch, cost about 4.5 billion CLP (~6.7 million USD) and is about 90 % complete today. In each case, the measures are developed by the private sector which is also responsible for their maintenance for a span of 5 years.

Even though only 90 % of the first and 70 % of the second phase have been implemented to date, Mapocho 42K has significant impact: One of the main achievements is the recovery and consolidation of the southern riverbank as a public promenade. Providing access to public green spaces for citizens from underprivileged communities ensures spatial justice and equal opportunities. In addition, the continuous path along the riverbank enables sustainable mobility, e.g. cycling and walking.

The initiative has connected 8 municipalities with different conditions, counteracting the administrative fragmentation and promoting a sense of social integration. The corridor therefore serves as a physical and social connector.

Unlike other large-scale urban river projects, Mapocho 42K follows a strategy of minimal intervention, ensuring a continuous green corridor rather than isolated green spaces. This approach might also encourage future urban renewal in adjacent areas. The modular system of design components allows for future urban expansion and adaptation over time.

Despite its success, the project has faced challenges in integrating both river banks, mainly due to the presence of highway infrastructure, which has restricted connectivity. In addition, issues such as vandalism and maintenance concerns, have posed difficulties for long-term sustainability and are yet to overcome.