Rehablilitación de la presa Txarrota ,Zarátamo,Bizkaia

The “Txarrota” reservoir is located in the municipality of Zarátamo (Vizcaya) on the Txarrota stream, which flows into the Ibaizabal river. Txarrota is a gravity dam with a triangular profile witch  dimensions are  15 m high 72.5 meters length  .The dam was built in the 60s to supply the neighbourhood  This dam, both in terms of its dimensions and its danger of flooding, in an eventual break, belongs to the highest category in terms of danger-(A)

Currently, is no longer used for water supply and in March 2014 the dam loses almost all the water due to a break in its bottom valves.

In order to decided what to solve this situation, the council responsible of the dam, study the different alternatives for the adequacy of the dam to the applicable regulations Due to the cost and budget necessary to recover and maintain the reservoir activity and because the dam is no longer useful, the council decided to promote a contest for THE DEMOLITION OF THE DAM

To participate in this contest, we created a team with a civil engineer, a biologist, a geologist , a forester and a landscape architect, expert in Soil and Water Bioengineering techniques

We carried out an analysis of the possibilities and risks involved in the demolition, both from an environmental and a safety point of view.From recovery the river functionality, the total demolition of the dam was a priori the solution .However the characteristics of the small basin , the seasonality and circumstances of this stream ( buried in most of its route ) indicate that the environmental benefits should be  very low , compared with the environmental cost that  such demolition provokes in terms of rubble, elimination  of accumulated sludge, acoustic pollution ..

We concluded that, from an environmental and safety point of view, the most convenient option was to maintain the wall of the dam, and our team present a proposal that guarantees safety, creates the smallest possible inconvenient and improves the environmental and landscape aspects making of the area an important point for biodiversity and for the approach to nature by the inhabitants of Zarátamo

The proposal, is summarized in the following points:

 1-To  solve the declassification of the dam so the level of the water do never exceeds the 5 m height , so we decided to open the wall with a long perforation that is enough to permit the pass of the Q500 Water

2-The sludge of the vessel is stabilized and restored using traditional techniques and Soil and Water  bioengineering

3-Biodiversity is promoted by the creation of two lagoons maintaining the character of a wetland and favouring the presence of fauna,

4- We propose a recreational and social use in the area

We won the contest with the proposal  THE NO DEMOLITION OF THE TXARROTA DAM AND THE SUBSEQUENT REHABILITATION

The project was elaborated in 2015 , the administrative authorizations in 2016 and the work finished mars 2017