Limestone quarries and a Portuguese karstic aquifer

In the Alenquer region (35 km north of Lisbon) there occurs an important group of limestone quarries that supply aggregates used in the construction industry across the region. These quarries have been active for more than 60 years and play an important role in the regional social and economic frame.
This region also contains the Ota-Alenquer aquifer, which contributes to the Lisbon region water supply. The public supply water wells are managed by the company Empresa Portuguesa das Águas Livres (EPAL). These wells have legal protection areas, defined by the Portuguese legislation “Portaria nº1187/2010”, which distinguishes three types of protection zones: inner zone, intermediate zone and outer zone.
The intermediate zone contains almost the entire Ota – Alenquer aquifer system outcrop area and the quarry areas.
Since 2005, hydrogeological data has been collected within the Environmental Impact Assessment (EIA) for the Alenquer quarries exploitation plans (Visa Consultores, 2010). This article presents those data in order to provide information about the supposed paradox of groundwater quality versus quarry exploitation.