The Monterroso River (Rio Monterroso or Arroyo Monterroso) is a seasonal river that flows from the Sierra Bermeja mountains[1] to Estepona, Andalusia, Spain, where it empties into the Mediterranean Sea.[2] It remains dry through the average summer weather and flows during the winter rainy season depending on the amount of rain.[3]
The river was originally culverted on the coast of Estepona in the 1960s for use as the paseo maritimo.[4] However, a much larger culvert was constructed in the 1970s.[5] It runs underground in the city of Estepona, beginning at Calle Monterroso.[6]
On January 12, 1973,[7] the dossiers were signed to construct the modern rectangular Monterroso Culvert. Construction started in April 1973 and ended in June 1974.[8] It took 14 months (430 d) to complete. The name of the work was "Embovedado del arroyo Monterroso" and the construction company was Construcciones Civiles, S. A.[9][10]
The culvert is located directly under Av. Juan Carlos I, the main road in Estepona.[11] The outfall of the culvert is located on the southern end of the Av. Juan Carlos I. The river culvert was constructed to form the Av. Juan Carlos I. The culvert is 1.16 kilometres (0.72 mi) in length, has a span of 11 metres (36 ft) and a rise of 2.61 metres (8.6 ft).[12]
The construction of the Monterroso river culvert had a base budget of 55,105,234 Pesetas, The bid price on March 29, 1973, was 51,247,869 Pesetas.[9]
On October 11, 1986, the separate 1960s culvert that the Monterroso river flowed through via the newer culvert collapsed.[13] A sewage treatment truck was engulfed, but the operator managed to get out in time. The collapse created a 700 square metre sinkhole and sparked the construction of the rest of the culvert to engulf the original location of the collapsed bridge maintaining the shape and size of the original box culvert in 1987.[citation needed]
As of 2015, there were plans to build a river park along the banks of a portion of the Monterroso river in Estepona.[14]
In 2017, the plans to build the river park lacked authorization and were never instated; however, a beautification project was conducted.[15]
Inside the River Monterroso culvert, the Arroyo de Juan Benítez flows in via another culvert which is also over a kilometre in length.[16] In 2018, plans to resize a portion of the culvert were successfully completed.[17][18]
The resizing was conducted by Constructions y Excavations Manzano[19] and cost 5 million euros ($6 million) to conduct.[20]