Coupla tidbits:
re: dredging/maintenance of the presas
The Presa de Tavera has never been dredged to the best of my knowledge. That 1979 date I believe is when the dam was completed, just in time for Hurricane David. Loss of reservoir capacity due to sedimentation is a serious issue here though for some reason they don't include sediment traps in the design. A fine example can be had by visiting the Presa de Blanco west of Bonao. Completed in the mid 90s, it was turned into a gravel pit by Hurricane Georges a few years later with perhaps 20% (swag) of its design capacity.
The maintenance issue for the major presas here is one that truly scares me. Assuming that the quality of construction has been equal to that found in the United States, on average an impoundment structure (dam and related parts) will require a major maintenance/reconstruction every 30-50 years. The cost to undertake reconstuction is commonly many times the initial cost of construction. Some Dominican examples courtesy of INDRHI cost vs. rebuild cost:
Presa de Maguaca - RD$ 1.9 million vs. RD$ 129.9 million (2002)
Presa de Chacuey - RD$ 1.9 million vs. RD$ 42.0 million (1993)
These two presas are little ones. The cost to rebuild a major structure like that for the Presa de Tavera will be significant. In the US it is becoming common to write the anticipated expenses of reconstruction into the operating costs of the facility, one reason why an increasing number of smaller scale hydroelectric facilities are being removed as unprofitable. This is not the case in the RD. Surely they wouldn't neglect necessary maintenance for lack of funds? Personally I wouldn't build anything of value in the floodplain downstream of any of the major dams here.
re: logging data at the Presa de Tavera
It is common practice to maintain a facility status log at hydroelectric facilities which should include water data such as impoundment elevation and water flows to the turbines to generate power as well as any excess water being discharged. I know that the emergency operations plan for the Presa de Tavera calls for impoundment elevation to be measured every ten minutes, presumably more often than whatever time period would or sould be a norm. I can't speak for what actually was done and in any case would be highly suspicious of any data that was released to the public.
re: drawdown of water levels during hurricane season
Schedule of mandated water levels for the Presa de Tavera has it being drawn down to 320 msnm during hurricane season, defined as between June 15th and Oct 15th. The presa may be maintained full at 327.5 msnm from Nov 30th to June 1st with the remaining dates being used to slowly raise or lower the level. I would not be surprised in the least were it that these levels were disregarded. The arrival of Olga outside the season when the presa was (theoretically at least) drawn down in anticipation of high water events did make for a more challenging than normal operational situation but one would reasonably expect that those entrusted with the task would be capable. I've not seen news that the dam operators in Puerto Rico, which was run over by the same storm, had to resort to such drastic measures to maintain the integrity of their structures.
re: water discharge prior to TS Olga
In the coverage of this issue on the Saturday evening television program of journalist Huchi Lora, he stated that the initial discharge from the Presa de Tavera to prepare for the incoming storm was 100 m3/sec. He didn't attribute this number but Sr. Lora is one of the few public figures in the RD that I trust to at least try to be accurate. Considering that incoming flows from the Yaque del Norte and Bao watersheds were at an elevated flow prior to the arrival of Olga , this represents a nominal drawdown at best if not simply an attempt to maintain levels at or near full.
re: since I'm already annoyed....
Two new hydroelectric projects getting underway, Palomino and Las Placetas. Both are being built in supposedly biologically protected areas (national park) without a peep. Both are being built with borrowed money. Both were justified by questionable data. Why the heck are they starting two new projects when the Presa de Gualgui stands near abandoned, half completed? Whatever happend to all the money that was invested in starting the Presa de Hondo Valle project, which has since disappeared from the planning boards? The work on the Presa de Gualgui and the Presa de Hondo Valle were done on borrowed funds as well, for which the country is now paying interest.
"Hey. All we have to do is say 'free electricity' and we can do whatever we damn well please."
Sorry...my bias showing there
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