Meb Cutlack
The Reporter (Belize)
May 17, 2002

The geological mapping done by AMEC and presented by BEL and Fortis for the Chalillo dam site is so faulty that the Geology and Petroleum Departments in Belmopan, Belize, have demanded that new mapping be done.

A death toll in the thousands is the likely grim reality of an early morning failure of the Chalillo dam, if construction were to go ahead at the present site on the Macal River. The geological mapping done by AMEC and presented by BEL and Fortis for this dam site are so faulty that the Geology and Petroleum Department in Belmopan have demanded that new mapping be done.

If anyone thinks that a death toll of thousands in Cayo is exaggerated, all that they have to do is look at the history of dam failures elsewhere.

A dam failure which has particular significance for Cayo and Belize riverside dwellers is the famous Johnstown Flood which happened in Pennsylvania on May 31, 1889, when a 72 foot wide dam broke in the hills about 24 miles upriver from Johnstown. A wall of water, which was 76 feet high at one point and 23 feet high when it hit Johnstown, roared down the valley into the city. The official death toll was 2,209. The Chalillo dam wall is currently designed to be well over 500 feet wide and 100 feet high, and San Ignacio and Santa Elena are only a few more miles away than Johnstown was from the US dam which failed.

About 13 years ago I was in Cayo staying at Chaa Creek farm above the Macal River when the Burns Avenue Flood hit. Just 12 to 15 hours of rain caused a massive flood along the Macal. The water at Chaa Creek rose 40 feet in two hours, whole trees were uprooted, a horseman trying to cross the river was drowned, floodwaters reached to a few feet below the Hawksworth Bridge and Burns Avenue was flooded throughout most of its length.

And that was from just 15 hours of rain! A full Chalillo dam would represent more than 50 to 100 times the volume of water which descended on Cayo that night.

If the Chalillo dam broke late at night or in the early hours of the morning, a 50 foot high crest of water could hit San Ignacio and Santa Elena while everyone was still in bed. It would most likely flood half way up the Fire Station hill and destroy most of lower San Igancio to the double boulevard, a great deal of Santa Elena, all the river communities above and below the town and quite possibly drown thousands of riverside residents.

This same flood would back-flood up the Mopan probably as far as Clarissa Falls, destroying everything in its way. It would devastate all the communities between Cayo and Belize City and could also cause serious flooding as far north as Crooked Tree.

Neither BEL nor Fortis have done any serious studies of what would happen if the Chalillo dam broke when full. They have just implied that a dam failure is unlikely.

There are companies throughout the world which specialize in producing models and simulated studies created from geological data as to exactly what would happen in a particular dam failure. Neither BEL nor Fortis have seen fit to contract or engage such a company to present a study of a Chalillo dam failure and what it would mean to Belizeans. This, despite the $1,000,000 US which Canadian taxpayers have spent trying unsuccessfully to prove that Chalillo is economically and environmentally sound and despite the $700,000 which the Belize government say they have spent since NEAC “approved” the EIA. In case BEL and Fortis are relying on the rarity of dam failures, let me remind them that in modern China alone dam bursts number in the thousands. By the 1980’s (the latest figures available), 2,976 dams in China had collapsed in recent times, including two large-scale dams [the Shimantan and Banqiao dams]. One hundred and seventeen medium-sized and 2,857 small dams had also collapsed. On average, China witnessed 110 collapses per year, with the worst year being 1973, when 554 dams collapsed. The official death toll (not including the Banqiao and Shimantan) from collapses resulting from dam failures came to 9,937.

The Chinese built Mollejon and who knows who will build Chalillo? Great numbers of the death toll in Honduras from hurricane Mitch were from dam failures, the suddenly released water which swept away villages in their path and drowned hundreds

The potential of a Chalillo dam break might not be so worrying except for the very cavalier attitude the two companies, BEL and Fortis Inc., have over the accuracy of the geology which they presented in their EIA. When it was pointed out to them over a year ago that the geological descriptions of the dam site core samples might not be accurate, they called me and, by inference, the highly respected geologist, Brian Holland, liars. When their claim on there being a granite base and granite bedrock under the dam site was proved totally wrong, they simply changed their story and said that granite was not necessary and that they could build on anything! They also continue to deny the existence of major geological fault lines which occur at and adjacent to the proposed dam site area. AMEC says they have not seen these large faults but, if they are there, they don’t matter!

Their attitude to the possibility of earthquakes is equally dismissive. Their EIA: “The most significant seismic event relative to the Chalillo site that has occurred in the 20th century was an earthquake on June 12, 1912. It was recorded at the Pasadena seismic station and assigned a magnitude of M = 6.8.

The epicentre of the event is approximately 16 km from Chalillo site, in a northerly direction. The depth of this earthquake is not known. The site seismic acceleration associated with this event may have been in the range of 26% g to 42% g, depending on the attenuation formula used, and assuming a focal depth of 33 km. It is not certain whether the assigned magnitude of 6.8 is based on actual seismographic data. In any case, the accuracy and reliability of seismographs available at that time was substantially lower than that of present-day instruments.” (note their attempt to belittle the ancient data to suit themselves)

The EIA goes on: “A relative recent and strong event relevant to the site was of M = 6.3 event on August 9, 1980 at a distance of 122 km from the site at a depth of 22 km. This event may have resulted in a ground acceleration at Chalillo in the range of 5% g to 8% g.” And, “The basic method used in the seismic evaluation (of the Chalillo site) was a statistical approach… This method uses the available historical data and projects them into the future to predict the return period of events of given magnitudes…” Wait a minute! Didn’t they just imply that you could not trust the “accuracy and reliability of seismographs available” from historical data?

I live on a small patch of land 12 to 15 feet or so above the Mopan River a few miles upstream from Branch Mouth where the Macal and Mopan rivers meet. Pretty well the only time the land floods is when a Macal River flood causes a back-flood up the Mopan River. In the Burns Avenue flood, my property was a foot deep in flood water. If the Chalillo dam were to burst in anything like the manner described above, my house and the entire village of Bullet Tree would be wiped out by a massive upriver flood.

Yes, I am worried by the idea of a Chalillo dam failure. I am equally concerned however by the fact that BEL and Fortis Inc. do not consider the lives of thousands of Belizeans to be worth spending a few thousand more dollars to commission a true and independent study of the geology of the Chalillo site and creating a model of the effects of a dam failure.

If the Chalillo dam is to go ahead without these sensible precautionary measures, then Belizeans need to know what, if any, early warning systems would be put in place to notify everyone downstream that a deadly wall of water 50 foot high was approaching at 20 to 30 mph!