The old dam of the Aulencia is a dam of certainty in the entrepot of Valdemorillo and Colmenarejo. It was built in 1945 to supply the towns of Brunete, Villanueva del Pardillo and other towns in the area such as Villanueva de la Cañada and Quijorna.

Photo 1. Panoramic photo of the Aulencia Dam (Source: Own Development)

The dam is located in a Special Protection Area for Birds (ZEPA), a place of community importance (SCI), and is also part of the Guadarrama Regional Park. In the area there are species such as the otter, the black stork or the badger.

The growing needs of water in the province of Madrid, which have a large population increase at the end of the 60s (from 2,260,000 inhabitants in 1960 to 3,150,000 in 1970) led to the creation of a new reservoir taking advantage of the flow of the Guadarrama River. In 1976 the Valmayor reservoir and the Valmayor

ETAP started to operate, leaving the old Aulencia dam in disuse.

The location of the Valmayor reservoir endangered the Aulencia dam, which is 2 kilometers downstream from the reservoir. From 1976 until the end of the 1990s, the sludge from the ETAP was dumped into the river and retained by the dam, contaminating the swamp with an important environment and turning it into one of the most polluted places in the Community of Madrid. The reservoir glass was filled by sludge occupying approximately 300,000 cubic meters of the reservoir (80% of the reservoir). In times of rain, the water of the dam overflows that drags the remains of the sludge to the channel of the Aulencia.

Photo 2. Profile of the Aulencia Dam (Source: Own Development)

The information collected by the Canal de Isabel II indicates that the Valmayor ETAP it became operational in 1976, but the sludge treatment plant did not do so until 2001.
The unsustainable situation of pressure pollution caused the Park Board to commission the region in 2005 to CEDEX (Center for Public Works Experimentation Studies). “In the report prepared at that time were detected remains of 12 metals (chromium, iron, manganese or cadmium), 74 contaminants (derived from soaps, hydrocarbons, liquids of textile products …) and 31 compounds in the solid waste as sulfur. The report concluded that the materials found in the reservoir corresponded “to sludge residues obtained from the ETAP treatment plant that treats the waters of the Valmayor reservoir, upstream of the reservoir and from the wastewater discharges that are generated by the urban core of Colmenarejo “

Although in recent years “spills” have been paralyzed, the problem persists and several environmental groups have denounced it. However, the Canal de Isabel II, the organism responsible for the exploitation and management of the Valmayor, derives the competences for cleaning the channel of the Audencia river and the provision for the CHT (Tajo Hydrographic Confederation). This public body confirms that it has had its intention to clean the channel, but the technical difficulty to access the Regional Park and the economic cost that allows it, has made both organizations avoid the advance for the recovery of the situation and the natural  landscape

One of the main problems of the mud is the danger that constitutes for the ecosystems of the area, being the fish fauna practically non-existent in the reservoir. In addition, the presence of toxic agents in these sludges made it possible to reuse them in the field of agriculture. Although it is a fact that both seals and lakes have a natural way of filling, it is not common that this clogging occurs as briefly as with sludge of doubtful origin.

This text invites readers to question the moral and ethical considerations of the agencies and authorities that allow this type of problems to the environment. Is it ethical to pour sludge into the river, although the legislation on discharges is not as restrictive as at present? Is it acceptable to pay a penalty for dumping sludge at the site of the construction of a sludge plant because it is more economical? Although in the Spanish Constitution, art.25.1 states: “No one can be convicted or punished for actions or omissions that at the time of occurrence do not constitute a crime, fault or administrative infraction, according to the legislation in force at that time.” Can you demand responsibility from an authority that knew the environmental risk of the problem.

MARIA LUCIA CUEVA DUARTE