Fast-track Water Treatment Design and Construction in the Dominican Republic

Client: National Institute of Water and Sewage of the Dominican Republic
Location: Dominican Republic

In the Dominican Republic, competing uses of water for irrigation, water supply, and hydropower generation have resulted in water shortages in several urban and newly-constructed tourist areas. To provide safe drinking water to the urban service areas of La Romana, San Cristobal, and San Francisco de Macoris, the National Institute of Water and Sewage of the Dominican Republic (INAPA) retained the Biwater/Sinercon Consortium for the Design-Build delivery of three 87,000 m3/d Water Treatment Plants and associated infrastructure. In turn, Biwater U.S.A. retained Hazen and Sawyer to provide engineering design and support in the procurement management services for the project.

Project Outcomes and Benefits

  • 36-month fast track schedule to have facilities designed, installed and placed on-line was met.
  • More than $180 million in loans were secured from the U.S. Export-Import Bank for the national government of the Dominican Republic by the Design-Build Team.
  • Met the strict environmental and water quality criteria established by the World Health Organization.

The San Cristobal Water Treatment Plant receives its water from a surface water source bound by the dam. In order to obtain water for the treatment facility, two existing 2,000-mm concrete raw water pipes were tapped to receive 600-mm piping that would provide water to the WTP.

San Cristobal Plant: Design and subsequent construction of the 87,000 m3/d treatment plant was a challenge due to the size of the site and elevation difference within the site boundaries.

San Cristobal Plant: In order to utilize the natural contours of the land and reduce earthwork, the head works and filter building were located at the top of the site while the remaining facilities were located toward the lower end of the site.

The La Romana Water Treatment Plant obtains its water from the Rio Chavon. The characteristics and elevation of the water within the river change seasonally. During the rainy season river water turbidity can approach 1,000 NTU.

La Romana Water Plant: Several field treatability tests were conducted over the design period in order establish unit process parameters and chemical dosages for treatment.

La Romana Water Plant: The raw water pumping station was constructed approximately 13 meters above the average river water level to ensure the facility would not flood as a result of seasonal changes in the water’s elevation. The seven vertical turbine pumps transmit the raw water through 9.8 kilometer of 750-mm raw water piping to the 87,000 m3/d treatment plant over terrain ranging in elevation from 5 to 70 meters.

Due to funding restrictions, the San Francisco de Macoris water treatment plant had been partially constructed in the late 1980’s. As such, several structures were partially built including the filter building.

As a cost saving measure, Hazen and Sawyer incorporated these buildings into the proposed design. After careful evaluation of the existing structures, a series of remedial action plans were developed to improve the condition of the existing structures. The use of the existing structures required a detailed analysis of the hydraulic conditions through these facilities prior to proceeding with the detail design.

Finished San Cristobal Filter Basin

Finished Hatillo Water Storage Tank

San Cristobal Water Treatment Plant

The project consisted of building three water treatment plants (The Mata Larga Plant, La Romana Plant and the San Cristobal Plant), to serve approximately 500,000 people, each of which is rated at 1 m3/s (23 mgd) capacity. Other supporting infrastructure development included nine water storage tanks, seven pump stations with capacities of up to 91,000 m3/d, and 130 km of ductile iron raw water and transmission mains, ranging in size from 200 to 1,000 mm in diameter.

In order to meet the 36-month fast track schedule to have facilities designed, installed and placed on-line, Hazen and Sawyer issued owner-furnished specifications and assisted during the equipment/materials purchasing process during the initial design phase. The design team concurrently prepared more than 2,000 drawings according to priorities established in the field, to stay ahead of the construction and meet the project schedule. Civil works were designed and constructed first, pending the delivery of U.S. equipment and materials.

Two of the water treatment plants obtain raw water from reservoirs serving hydroelectric dams. River water from the Rio Chavon is pumped to the third plant (La Romana). During the rainy season river water turbidity can approach 1,000 NTU. Hazen and Sawyer conducted field treatability studies to confirm unit process parameters and chemical dosages at all plants.

The basic unit processes are similar at all three plants and include pre-aeration through a triple cascade works, flash mixing of ALUM and polymer, flocculation, sedimentation utilizing settling tubes to enhance performance, dual media filtration (anthracite and sand), filter media cleaning using air scour followed by backwash water, chlorination and on-site storage to meet distribution system water demands.

For more information on this project, or to discuss a similar project in your area, contact

Fernando Chiriboga, Latin America Operations Manager, at fchiriboga@hazenandsawyer.com