The Havana City Sewer System Siphon: Engineering Beneath the Bay

In the bustling city of Havana, a remarkable engineering marvel lies hidden beneath the bay—a siphon that plays a crucial role in the city’s sewer system. This underground infrastructure serves as a vital link, facilitating the efficient and safe conveyance of wastewater. In this article, we will delve into the intricacies of the siphon under the bay, exploring its design, construction, functionality, and the impact it has on the sanitation infrastructure of Havana.

The Need for an Advanced Sewer System

As Havana grew and urbanized, the need for an advanced sewer system became evident. The increasing population and urban development posed significant challenges in managing wastewater effectively. Prior to the implementation of the siphon, wastewater management in the city faced numerous challenges, leading to sanitation issues and health concerns. At the beginning of the 1830s, General Tacón ordered the layout and construction of sewers for the drainage of the streets since the houses lacked receptacles to absorb the water that had been used for domestic and personal uses, being forced to pour it into the streets in violation of government regulations. But this system did not give results because they did not have the necessary dimensions and were built by partial sections. The neighborhoods furthest from the city center had open ditches on the sides of the streets, only covered in the most important streets such as Calzada del Cerro and Calzada de Jesús del Monte.

This system had the drawback that, in addition to collecting sewage, they also received rainwater, so that in the rainy season, these gutters overflowed onto the streets, sidewalks, and lower floors of houses. This caused the city to be characterized by its bad smell, the dirt of the streets and the polluted waters of the bay. At the end of the Spanish-Cuban-American War in 1899, the government created the Office of the Chief Engineer of Public Works of the City of Havana, which drew up a general plan of the existing sewers, determining that their total length was about 58 km and proceeded to its general cleaning. The siphon under the bay emerged as a solution to address the city’s sanitation requirements while considering the unique geographical constraints of the bay area.

Design

The design and construction of the siphon under the bay required meticulous planning and engineering expertise. From the year 1899, the maps of the city were completed and the necessary studies, such as to account for the depth of the bay, water pressure, and the need to maintain a continuous flow of wastewater, were carried out for the projection of the new sewer system, which made it possible to prepare the Specifications that served as the basis for the auction that took place on January 10, 1902.

Extensive studies were conducted to determine the optimal route and depth for the siphon, because one of the conditions established that sewage could not be discharged into the bay or the coast at any point where it was exposed to being washed ashore, near built-up areas.

The engineer Samuel M. Gray, an American specialist in sewage matters, was commissioned to design the new sewage system. This system consisted of gathering the sewage in La Punta, taking it across the bay through concrete tubes to an intake well, from which it would rise by means of pumps to the main discharge sewer to the point of discharge into the ocean, one kilometer east of Castillo del Morro, 147 m from the coast and 10.70 m deep. The project involved the installation of large-diameter pipes that would carry the wastewater under the water body. The design considered factors such as water pressure, tidal fluctuations, and maintenance requirements. To achieve the efficiency of the system, four pumping stations were built along the route.

Construction of the Siphon

The construction of the Havana City Sewer System Siphon involved precise planning and engineering expertise. Construction works on the sewerage system began on June 29, 1908, and were completed on August 26, 1914, under the direction of chief engineers David E. Mc Comb (1908-1912), José Manuel Babé (1912) and Alberto M. Brosius (1912-1914). A total of 294.3 km (179 miles) of sewers and 149.6 km (91 miles) of drains were built. The siphon under the bay consisted of a concrete tunnel 2.13 m (7 feet) in diameter, which was constructed from coves made on both sides of the bay entrance. The ground consisted of silt, sand, and more compact mud until reaching the rock, which was found at depths of 20 m (66 feet) on the Havana side, 15 m (49 feet) at Casablanca, and approximately 40 m (131 feet) in the center of the bay channel. The construction of the tunnel under the bay took place uninterruptedly from May 1st, 1911, until April 19, 1912.

The compressed air method and protective steel shell were used, with air pressure reaching 2.7 kg/cm² (38.40 psi) at the lowest points. As the protective shell advanced, the tunnel was protected with wooden trusses before receiving a final lining of 30 cm (12 inches) thick concrete. The protective shell, consisting of three steel sheets, had a diameter of 3.20 m (10.5 feet) and two doors – one at the top and one at the bottom. Eight jacks on a cylinder pushed the protective shell. Workers had to be relieved every six hours when the pressure exceeded 2 kg/cm² (28.45 psi). To facilitate pipe cleaning, a smaller conduit was built at the bottom of the 2.13 m (7 feet) section. The discharge pipeline into the sea was constructed using 1.50 m (5 feet) diameter pipes, 50 mm (2 inches) thick, placed in a trench and covered with concrete. The cost of the sewerage system was 9,851,160.37 pesos.

Functionality and Operation

The siphon operates based on the principle of gravity and differential pressure. It utilizes the difference in elevation between the source of wastewater and the discharge point to create a flow that minimizes the need for mechanical pumps. By carefully designing the gradient and ensuring appropriate pipe sizing, the siphon under the bay effectively transports wastewater from one side of the bay to the other, seamlessly connecting it with the rest of the city’s sewer network.

Challenges and Engineering Solutions

Constructing a siphon under a bay presents various engineering challenges. The depth of the bay and the potential impact of tidal movements require robust engineering solutions. The engineers implemented measures to safeguard the siphon from the corrosive effects of saltwater and to prevent sedimentation or blockages that could impede the flow. Careful monitoring systems and regular inspections help ensure the ongoing efficiency and functionality of the siphon.

Maintenance and Future Considerations

Regular maintenance and inspection of the siphon are crucial to its long-term operation. This includes clearing potential blockages, monitoring structural integrity, and addressing any necessary repairs. As Havana continues to develop and urbanize, future considerations may involve upgrading the siphon’s capacity or implementing advanced monitoring systems to enhance its efficiency and adapt to changing demands.

Conclusion

The siphon under the bay stands as a remarkable engineering feat, enabling the efficient and reliable transportation of wastewater in Havana. Its design, construction, and operation exemplify the ingenuity and expertise of the engineers involved. This hidden marvel plays a crucial role in maintaining the city’s sanitation infrastructure and preserving the environmental well-being of the bay. The siphon serves as a testament to Havana’s commitment to modernizing its sewer system and ensuring a clean and sustainable future.

Frequently Asked Questions (FAQs)

Q1: How deep is the siphon under the bay? 
The siphon was excavated 30 m from the surface of the water.

Q2: Does the siphon operate continuously? 
Yes, it does. 

Q3: What measures are in place to prevent blockages in the siphon? 
To facilitate pipe cleaning, a smaller conduit was built at the bottom of the 2.13 m (7 feet) section siphon.

Q4: How long is the Havana City Sewer System Siphon? 
The siphon is 375 m (1,230 feet) long.

Q5: What materials are used in the construction of the siphon? 
The tunnel of the siphon was constructed using concrete.

In this article, we have explored the siphon under the bay, a remarkable engineering marvel that plays a crucial role in Havana’s sewer system. Its design, functionality, and impact highlight the city’s commitment to efficient wastewater management and environmental preservation. The siphon stands as a testament to the engineering expertise and innovation employed in overcoming the challenges of transporting wastewater beneath the bay.

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