Restoring Vital Water Capacity: The Loíza Lake (Carraízo) Dredging Project

The Loíza (Carraízo) Reservoir is the lifeline of the San Juan Metropolitan Area, supplying drinking water to hundreds of thousands of families. Over the years, sedimentation has steadily reduced its storage capacity—from its original 27 million cubic meters to just 15 million. Without intervention, the region faced growing risks to its water security. The last major dredging, performed in 1997–1998, removed 6 million cubic meters of sediment, but decades of new deposits erased those gains. By 2023, it was clear: a large-scale effort was needed to restore capacity and safeguard the region’s drinking water supply.

A Mission to Restore Capacity
In February 2023, the Puerto Rico Aqueduct and Sewer Authority (PRASA), through Great Lakes Dredge and Dock Company, contracted ECR Engineering to provide engineering design and permitting support for critical infrastructure at the reservoir’s three containment areas. ECR’s role focused on designing permanent improvements, managing overflow systems, and stabilizing containment structures—while the dredging contractor carried out the massive sediment removal effort.

Early Challenges and Key Solutions
One of the project’s complexities was the design-build environment, where dredging operations advanced while engineering and permitting tasks were under development. A decisive engineering moment came with the design of a 40-foot-high structural steel weir box. This temporary structure, essential for decanting water from containment areas, faced significant buoyancy and overturning forces from high water levels. ECR Engineering developed an innovative structural reinforcement design, ensuring stability, safety, and uninterrupted dredging operations.

Technical Approach
ECR Engineering designed:

• Earthwork cut and fill plans to restore and elevate the containment dikes.
• Permanent reinforced concrete overflow spillways to safely manage stormwater and return decanted water to the reservoir.
• Drainage improvements to prevent ponding after dredging.
• Contractor staging areas with earthen crane pads, boat ramps, and temporary utilities for operational efficiency.
• The temporary structural steel weir box that made dredging operations feasible under challenging conditions.

Lasting Impact
Upon completion in October 2025, the project will directly benefit 171,387 families by restoring critical water storage capacity for the San Juan metropolitan area. By combining dredging operations with permanent infrastructure improvements, the Loíza Lake project ensures both immediate water security and long-term resilience for Puerto Rico’s most populated region.