0893-A1

Conservation of Wood Properties in Trees Submerged for 14 Years in Water, Tucurui, Brazil

Joaquim Carlos Gonçalez^[1], Newton Zerbini, Gérard Janin, and Ghislaine M. Bonduelle

Abstract

The rapid construction of the large barrage of the Tucurui (superficies of 3 000 km²) has left trees of the natural forest stands submerged under 30 to 50 m of water. After more than 15 years, efforts were made to recover the submerged trees, which were still standing. A diver took a part of the wood or branches for their identification and the most valuable trees were cut under water. Then, utilizing buoyancy, the trees were gathered together and taken a mill to be sawn. During the work innovative techniques were developed and utilized with the equipped boats: sonar was used to detect the trees and a crane was installed on the boat for extracting the trees. The yield of the team of three people - diver, technician and auxiliary - reaches 20 commercial poles a day.

Technical properties were measured and the results showed no significant differences with those found for unsubmerged trees in literature, the only difference being a slight darkening of the sapwood and heartwood, which had no effect on their use. Deep water is the best way to preserve entire tropical trees and the technological properties of the wood and its appearance. The recovery of the trees is a fruitful commercial and industrial operation considering the value of the trees already utilized and the quantity of trees still left to be exploited.

1 Objectives

The purposes of this work is to pointed first that the EXPLOITATION AND TECHNOLOGICAL CHARACTERISATION OF THE AMAZONIAN TREES, ANGELIM (DINIZIA EXCELSA), CASTANHEIRA (BERTHOLLETIA EXCELSA), MAÇARANDUBA (MANILKARA HUBERI), MERGED DURING 14 YEARS, IN THE BARRAGE AT TUCURUÍ, STATE OF PARÁ, IN THE BRAZIL is possible and the second to pointed out that the merged trees for a long time in the water can feel in good conditions and that may be still a suitable raw material for the wood industry Thus a barrage located at Tucuruí (UHE TUCURUI), state of Pará, Brazil, were constructed for the production of the hydroelectric power in the basin of the Rio Tocantins, 300 km at the south below of the Belém city. A large area, 2 875 km2, corresponding to the basin of the Rio Tocantins and his affluent was submerged. This area was occupied before by the tropical rainforest partly by the "Varzea" and partly by the forest of "Terra Firme"

2 Forestry inventory

The forestry inventory realized before the construction of the barrage was showing the presence of the 551 different species: trees and grasses belonging to 81 families. Between the trees species the most representative of the "Terra Firme" forest were: acapù, mata-mata, breus, ingas, castanheiras, andiroba, maçaranduba, faveiras, louros, and angelims. The conclusions of the inventory of the forest were pointing out that 50% of the trees were important commercially, well known species and accepted in the exterior and interior market for a grand total of: 21,5 millions of cubic meters. The forest harvesting was not totally performed before and during the construction of the UHE TUCURUI barrage. Thus many trees of high value were left under the water, and the tentative to exploit the "merged trees" was undertaken.

3 Technical exploitation

A new technique was developed to exploit the trees utilizing equipped boats, both for technical installations to cut and to carry the logs and also for the residence of the workers. A special engine was designed to find the trees under water using a sonar and to remove the trees by the aid of the divers using a special water proof hydraulic motorized chain saws under oil pressure to cut the trees. Utilizing the "natural buoyancy " of some logs to catch the "Non buoyant" logs, the floating allows to carry the logs to the sawing mill. The volume of the commercial wood exploited were very high and the yield of the harvesting performed by the divers team (20 poles/ day) make the operation fruitful.

4 Sampling the wood and determination of the mechanical properties,.

Figure of the Sampling of the wood

Thus some logs of the 3 species of the main interest, Angelim (Dinizia excelsa), Castanheira (Bertholletia excelsa), Maçaranduba (Manilkara huberi), were chosen at random, in order to study the effect of the time of submersion in the water (14 years) on the technological characteristics of the wood: physical, mechanical properties, and visual aspect of the wood sawn color. All the technological tests were performed under the rules of normative COPANT and the results: Density, Shrinkage (tangential, radial and volumetric), Hardness Janka, MOE, MOR in the green and dry wood conditions were compared to those of the relevant literature for the same species and they did not show noticeable percentage differences. The wood color of the sawn logs shows a lightly darker and redder in the appearance than do the original control wood, but without any incident on the industrial and artisan uses.

5 Results and Discussion

The preservation of the wood mechanical properties of the tropical amazonian trees,Angelim (Dinizia excelsa), Castanheira (Bertholletia excelsa), Maçaranduba (Manilkara huberi), merged during 14 years in the water of TUCURUI barrage in the PARÀ State, Brazil were analysed and are presentated in the tables:

- Table 1 - Wood density of the species Angelim, Castanheira e Maçaranduba, extracted from the barrage of Tucurui (column 1), compared with the litterature (column 2).

(2)Potencial Madeireiro do Grande Carajás - IBDF/LPF, 1983, 134p.; Madeiras Tropicais Brasileiras - IBAMA/LPF, 1997, 151p.

Table 2 -Comparison of the mechanical properties of the wood Angelim, Castanheira e Maçaranduba, Tucuruí (1) compared with the data of the litterature (2) and the % of the differences betwen them.

(2)Potencial Madeireiro do Grande Carajás - IBDF/LPF, 1983, 134p.; Madeiras Tropicais Brasileiras - IBAMA/LPF, 1997, 151p.

*V - wet (Saturated); *S - Dry (12% humidity) MOR - Module of Rupture; MOE - Module of Elasticity

Differences in %: 1-2 / 1 *100, i.e. ((value of the wood of Tucurui - value of the litterature) / value of the wood of Tucurui expressed in %))

The values of the wood properties merged in TUCURUI compared with normal wood are quite the same for alls the characteristics we have studied.

The % of the differences observed are very low between them after 14 years under the water.

6 Conclusion

Looking at the data found in the litterature we can consider that the immersion in the water cannot modify the behavior of the wood. The colour only can shows a ligth darkening of the wood that cannot be worry for the industrial use of the wood

These results confirm that, also for a long time: 14 years, the water is the best treatment to preserve the properties of the entire tropical wood trees. We have to notice that the harvesting technique under water brings news "pioneering" techniques and can be applied at every time during the year, with and without rains, no pathways to be created to exploit the forest, without heavy equipments. Considering the results both for the commercially value and for the good conservation of the tropical trees under water we can expect that the diver’s harvesting method would be yet used for a long period of the working time in the barrages like UHE TUCURUI in the state of Pará, in the Brazil.

Carte du Brésil et des ses Etats - Brazil map and its states.

Localisation de "Usina Hidrelétrica de Tucuruí", Etat du Pará, Brésil. - Location of the TUCURUI hydroelectric plant in PARÁ STATE, BRAZIL.