Project for the Elevating Pipeline: Between borehole RA2 (Cós) and the Montes Reservoir

Municipal Services of Alcobaça

Introduction

This article details the engineering project for the design and dimensioning of the rising main that connects the groundwater intake borehole RA2 in Cós to the Montes Reservoir, located in Casal do Monte, in the municipality of Alcobaça. The project was developed under the guidelines of the Alcobaça Municipal Services, strictly complying with current technical and regulatory standards, namely the General Regulation of Public and Building Water Distribution Systems, Decree-Law No. 207/94 of August 6 and Decree-Law No. 23/95 of August 23.

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Context and Need

The intervention arises from the need to guarantee the efficient and safe transport of water from an underground well approximately 212 meters deep. As the water from the well is characterized as “low mineral content” and of excellent quality, the pipeline infrastructure was designed to preserve these characteristics and ensure a continuous supply to the ground-level reservoir.

The technical challenge involved designing a system capable of overcoming a considerable elevation difference and dealing with a rugged geographical environment, which required specific solutions for protection against transient hydraulic phenomena (water hammer) and management of sections with exposed installation due to the slope of the terrain.

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Summary of the Project Completed

The lifting system was designed based on a flow rate of 30 l/s (108 m³/h) and has the following technical specifications:

• Transportation Infrastructure: Construction of a pipeline approximately 1662 meters long in Ductile Cast Iron (DCF), class C40, with a diameter of 200 mm. Standard Vi type interlocking joints were used to ensure the structural integrity of the network.
• Pumping System: Installation of a 1+1 operating system (one pump in service and another in reserve), using high-performance submersible pumps with a manometric head of 230 m.
• Hydraulic Protection: To protect the pipeline against hydraulic shock, a hydropneumatic reservoir with a bladder (volume of 1500 liters) was installed next to the intake, complemented by a pressure reducing valve to 16 bar.
• Operations and Security Units:
  • Triple-Effect Air Valves: Located at high points for air expulsion under normal conditions and intake/expulsion during filling or emptying.
  • Bottom Drains: Located at low points to allow for cleaning, disinfection, and maintenance operations.
  • Bottoming Blocks: Constructed of concrete in curves and branches to transmit the impulses generated by the water to the ground.
• Special Implementation: In the section between km 0+235.60 and km 0+280.00, the pipeline was installed in an exposed manner, properly anchored with specific blocks, adapting to the terrain morphology.
• Hydraulic Calculation: The dimensioning was verified using HidroCad software, employing the Newton-Raphson iterative model to ensure that flow velocities remain within regulatory limits (between 0.3 m/s and 1.0 m/s), guaranteeing sanitary quality and hydraulic efficiency.

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