Zorrotzaurre is an artificial island generated from the excavation of the Deusto canal in the town of Bilbao, which from the 1960s onwards showed enormous industrial strength, especially thanks to the port activity on both sides of the canal; however, the economic crisis caused its decline, which left it abandoned, reducing the quality of life of those who continued to live there. Today this space is being decontaminated of multiple products: fibrocement, hydrocarbons, heavy metals, lead, nickel, PCB refrigerant liquids, among others, which are already eradicated from two thirds of the island; this area also makes up the first phase of urbanization or Execution Unit 1 (UE 1) of the future urban development project, the most important currently being developed in Bilbao, and which consists of a mixed-use neighborhood connected to the rest of the city. It has taken five years of continuous work by the Junta de Concertación de Zorrotzaurre (JCZ), where work has been carried out on 142,620 square meters, a smaller area than expected according to previous research and estimates. To treat the soil mixture saturated with heavy metals and hydrocarbons, biopiles were used, elongated mountains of this contaminated area to which natural nutrients have been applied, such as bacteria integrated in horse manure capable of literally eating the dirt under the ideal conditions of time and humidity. Two biopiles of 2,285 cubic meters of dirty soil were concentrated at the northern end of the site and another, on the former Cadenas Vicinay site, where another 9,500 cubic meters of contaminated material will be treated in five accumulations. The Zorrotzaurre project is the latest major urban regeneration operation to be launched in Bilbao. It represents a comprehensive and sustainable plan, which recovers a currently degraded area to turn it into a new district of Bilbao, well connected to the rest of the city, with accessible housing, areas of non-polluting business implantation, numerous social and cultural facilities as well as large areas for citizen enjoyment. Below, you can read an article published in the Basque newspaper , where the details of the project and the cleaning up of the land are presented: IN THE MORE THAN OF LAND HAVE BEEN CLEANED UP FINDING – Fibrocement, hydrocarbons, pyrite ashes, heavy metals, lead, nickel, PCB coolants, soil soaked in fuel oil, chemical compounds formed by chlorine, carbon and hydrogens? These are some of the pollutants that have been eradicated from two thirds of Zorrotzaurre Island and the Deusto Canal docks, the area that makes up the first phase of urbanization or Execution Unit 1 (UE 1) of the most important urban development project being developed in Bilbao. It has taken five years of continuous work on the plot by the Zorrotzaurre Joint Venture (JCZ), which has now been completed, pending the completion of the administrative procedures that will give the go-ahead to the Cadenas Vicinay site, the last one in the process of being cleaned up. “Of the 390,000 square meters that hosts the UE 1 we have investigated 180,700 that were suspected to be dirty. Of this amount, just over 38,000 were found to be clean and the rest, 142,620, had to be cleaned,” says Juan Carlos Sinde, manager of the entity responsible for the cleaning work.
A sum of plots similar to 20 fields of San Mames that, curiously, has generated a lower sterilization work than expected, “about 60% less”, says Sinde. This has determined that, in the global computation, a large part of the initial amount of euros that the owners of the plots, as the ones ultimately responsible for financing the decontamination, had committed to the JCZ as the executor of the cleanup, has been returned. Sinde details how “the initial estimate was 10.5 million euros and in the end, the cost was 4.1 million, less than half”. Mind you, the euros advanced between 2015 and 2016 have not been reimbursed to all the owners of the land. “Some plots were almost clean and the money had to be returned, while in others even more contamination than expected was detected,” says the head of the JCZ. There were three groups of contaminants found, almost all of them on the island. The simplest was the twenty or so fuel tanks detected in the subsoil, either directly buried or isolated in basements under the pavilions. They were tanks of fuel oil and gas oil that the companies used for the operation of the machines or as heating for the installations that over time have deteriorated and the fuel has been seeping into the subsoil or soaking the concrete. A second group is made up of the material used to fill holes in the ground when the first industries and pavilions were built in Zorrotzaurre in the 1940s. They were dirty fillers made up of slag and leftover components from heavy industries that were used to cover holes and small valleys, lay the floor screed and then build the pavilions on a flat site. “This previous filling accounts for most of the contamination we have dealt with, since in many cases the companies that set up or inherited the plots were not polluting in their activity”, explains Sinde. This scenario has meant that it has not been necessary to excavate much to remove the layers of dirt. The director of the JCZ emphasizes that “they have been shallow, on average about two meters, since the strata below were also quite impermeable clay and had not been impregnated with contamination”. Finally, the third pollutant was the hydrocarbons associated with some production processes that were not as clean as they should have been. And how was this huge amount of soil and dangerous elements sterilized? Mainly with the process of extracting the material and transferring it to an authorized landfill, although at all times we have tried to minimize shipments and even take advantage of these leftovers to use them as clean landfills on the island itself. This has occurred with mixtures containing low-level waste, which have been pre-treated to reduce their contamination and to be deposited in inert landfills. We have tried to take advantage of everything that can be used. For example, in a floor that was almost half a meter deep.
The JCZ director explains how “we chopped up the first 30 centimeters to separate them and then reuse them in nearby landfills. The remaining 20 centimeters, more in contact with the contaminated soil, were taken to a landfill”. The most comprehensive use has been made at the request of the Basque Government. The biopile formula was chosen to treat the mixture of soil saturated with heavy metals and hydrocarbons. It is a matter of generating elongated mountains of this polluted mixture to which natural nutrients have been applied, such as bacteria integrated in horse manure, capable of literally eating the dirt under the ideal conditions of time and humidity. Two are the areas where action has been taken, in the northern tip where 2,285 cubic meters of dirty soil were concentrated in two biopiles, an amount that would fill 228 dump trucks. The other, on the former Cadenas Vicinay site, where another 9,500 cubic meters of contaminated material will be treated in five piles in October. In addition, sterilizing solutions have had to be sought across borders. This has been the case for the treatment of PCBs, the liquid refrigerant material present in the electrical transformers that some large companies used and which, after they were scrapped, were mixed with the land on which they were built. “The management of this land with PCBs, found in three locations, has been done by transferring them to Holland to be destroyed by incineration, since there is no infrastructure for burning them here,” Sinde concludes.
