At a time when a drought is spreading throughout Puerto Rico and the water level of the reservoirs has decreased substantially, the executive president of the Aqueduct and Sewer Authority ( AAA ), Doriel Pagán Crespo , indicated today, Monday, that a request for $ 300 million to dredge the reservoirs is pending approval by the Federal Emergency Management Agency (FEMA).
Removing the sedimentation, which accumulated in the reservoirs, would increase the storage capacity of water to supply the population, although administrators and experts debate the most efficient way to do it.
In the case of Carraízo, which practically decreased to a control level (31.50), it was dredged, for the last time, in fiscal year 1998 at a cost of $ 60 million, according to a study by the Office of the Water Plan of the Department of Natural and Environmental Resources (DRNA), in 2004.
The consultants hired by this office observed that Carraízo “has lost a substantial part of the capacity recovered (by dredging) due to the high rates of erosion in the basin and the transport of the sediments to the reservoir ”. Then, they added: "A permanent dredging program in said reservoir will be necessary to maintain its consistent water supply viability, particularly during droughts, as well as an aggressive basin protection program."
The estimate of Carraízo sedimentation is at 45%, according to AAA data. The former AAA executive president, Elí Díaz Atienza, anticipated that he would commission a bathymetric study (of the seabed) in the reservoirs, to have exact sedimentation figures and promote dredging.
Pagán Crespo assured that talks with FEMA are in progress. at an advanced stage, but the allocation of funds has been delayed due to the need for studies and justifications that are convincing for the directors of the federal agency.
“We have been exchanging information, we must do studies. It is not as simple as a pipe that may be exposed and we know the diameter and the damage … We are talking about reservoirs … You have to do studies, wait for the results, do technical analyzes, send them to FEMA, so that FEMA evaluates if they agree; and if not, then we will collect the information again, "said the engineer.
El Nuevo Día learned, from a source related to AAA, that the management of that public corporation originally requested the funds for the dredging as part of the debris removal category of the FEMA Public Assistance program, but there were objections from the federal agency about whether these works should be considered as part of the recovery from Hurricane Maria.
According to the AAA itself, the Reservoirs lost -on average- 10% of capacity due to sedimentation caused by Hurricane Maria. Experts such as former EPA administrator Carl Soderberg estimate that the loss was greater.
Previous AAA administrations discussed three different ways to remove sedimentation from reservoirs: full dredging, installing dredges that allow for monthly cleanings, or simply open the dam gates when there is a lot of precipitation, so that the water currents remove the sedimentation. This last option is promoted by experts such as Gregory Morris, consultant in hydrology and environmental engineering.
Total dredging of the reservoirs is not only costly (some say it requires doubling the AAA budget), but its effect could be short lasting and requires permanent and continuous efforts.
Another problem that dredging represents, according to Morris, is where to locate the rubble, since the dumps are close to their capacity. Hurricane Maria and earthquakes also shortened the useful life of landfills due to the large amount of waste generated.
Morris suggested that the amount of water in reservoirs and the northern aquifer be strengthened by increasing storage capacity by rehabilitation of dozens of wells, which the AAA has.
Pagán commented, in fact, that the activation of wells was one of the measures adopted by the AAA, to try to mitigate the decrease in water levels in the reservoir. That made it possible to supply 3 million gallons of water, he said.
However, Morris observed that 3 million is not enough. "They have to start with 25 million gallons. There is no need for rationing in Puerto Rico. Puerto Rico has a lot of water, a lot of infrastructure. The question is how to manage it, "said the environmental engineer, who has been in Puerto Rico since 1974.
In addition to the problem of sedimentation and erosion of the basins, the AAA estimates that 58% of the water is lost through broken pipes. That translates to 292 million gallons per day, out of the 507 million produced.
AAA's fiscal plan for 2021 includes replacing pipes, displaying tanks, and installing flow meters.