Río Añasco River Training, Añasco, Puerto Rico

Client: Puerto Rico Aqueduct and Sewer Authorithy (PRASA)

Contract Period: 2017-2018 (Project Duration: 6 months)

The Puerto Rico Aqueduct and Sewer Authority operates the Miradero Filter Plant which serves about 64,000 families in Mayagüez, Añasco, Hormigueros, Rincón and Cabo Rojo, including 7 hospitals and 195 schools. Most of its raw water supply comes from a pumped intake located on the south bank of Río Grande de Añasco, a meandering alluvial river. The river course has been actively moving in the vicinity of the PRASA intake, but this movement was greatly accelerat­ed by flood flows from hurricane María during September 2017.

In prior work in this on this river GLM Engineering had predicted the meander migration and cutoff location that occurred upstream of the Miradero intake prior to the hurricane. Following the flood, GLM Engineering flew a drone to obtain post-hurricane information on the migration caused by the flood, identifying the threat of another imminent meander cutoff that would result in the river moving away from the intake, rendering it inoperative. As an emergency measure, GLM recommended making a new upstream meander cutoff to sustain flows in the vicinity of the intake. The firm prepared design drawings and performed construction inspection services for this project. The project was completed in April, 2018 at a cost of $800,000. Within a year the river had has adjusted to its new channel, abandoning and sedimenting the old meander that previously threatened the new cutoff that would divert the river away from the intake.